Description: PostGIS is an extension to the PostgreSQL object-relational database system which allows GIS (Geographic Information Systems) objects to be stored in the database. PostGIS includes support for GiST-based R-Tree spatial indexes, and functions for analysis and processing of GIS objects. This is the manual for version 2.0.1 This work is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Feel free to use this material any way you like, but we ask that you attribute credit to the PostGIS Project and wherever possible, a link back to http://www.postgis.org.

# PostGIS 2.0.1 Manual

Abstract

PostGIS is an extension to the PostgreSQL object-relational database system which allows GIS (Geographic Information Systems) objects to be stored in the database. PostGIS includes support for GiST-based R-Tree spatial indexes, and functions for analysis and processing of GIS objects.

This is the manual for version 2.0.1

This work is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Feel free to use this material any way you like, but we ask that you attribute credit to the PostGIS Project and wherever possible, a link back to http://www.postgis.org.

## Chapter 1. Introduction

PostGIS was developed by Refractions Research Inc, as a spatial database technology research project. Refractions is a GIS and database consulting company in Victoria, British Columbia, Canada, specializing in data integration and custom software development. We plan on supporting and developing PostGIS to support a range of important GIS functionality, including full OpenGIS support, advanced topological constructs (coverages, surfaces, networks), desktop user interface tools for viewing and editing GIS data, and web-based access tools.

PostGIS is an incubation project of the OSGeo Foundation. PostGIS is being continually improved and funded by many FOSS4G Developers as well as corporations all over the world that gain great benefit from its functionality and versatility.

## 1.1. Project Steering Committee

The PostGIS Project Steering Committee (PSC) coordinates the general direction, release cycles, documentation, and outreach efforts for the PostGIS project. In addition the PSC provides general user support, accepts and approves patches from the general PostGIS community and votes on miscellaneous issues involving PostGIS such as developer commit access, new PSC members or significant API changes.

Mark Cave-Ayland

  Coordinates bug fixing and maintenance effort, alignment of PostGIS with PostgreSQL releases, spatial index selectivity and binding, loader/dumper, and Shapefile GUI Loader, integration of new and new function enhancements.

Chris Hodgson

  General development, site and buildbot maintenance, OSGeo incubation management

Regina Obe

  Documentation, general user support on PostGIS newsgroup, windows production and experimental builds, X3D support, Tiger Geocoder Support, management functions, and smoke testing new functionality or major code changes.

Paul Ramsey (Chair)

  Co-founder of PostGIS project. General bug fixing, geography support, geography and geometry index support (2D, 3D, nD index and anything spatial index), underlying geometry internal structures, GEOS functionality integration and alignment with GEOS releases, loader/dumper, and Shapefile GUI loader.

Sandro Santilli

  Bug fixes and maintenance and integration of new GEOS functionality and alignment with GEOS releases, Topology support, and Raster framework and low level api functions.

## 1.2. Contributors Past and Present

Kevin Neufeld

  Prior PSC Member. Documentation and documentation support tools, advanced user support on PostGIS newsgroup, and PostGIS maintenance function enhancements.

Dave Blasby

  The original developer/Co-founder of PostGIS. Dave wrote the server side objects, index bindings, and many of the server side analytical functions.

Jeff Lounsbury

  Original development of the Shape file loader/dumper. Current PostGIS Project Owner representative.

Olivier Courtin

  Input output XML (KML,GML)/GeoJSON functions, 3D support and bug fixes.

Mark Leslie

  Ongoing maintenance and development of core functions. Enhanced curve support. Shapefile GUI loader.

Pierre Racine

  Raster overall architecture, prototyping, programming support

Nicklas Avén

  Distance function enhancements (including 3D distance and relationship functions) and additions, Windows testing, and general user support

Jorge Arévalo

  Raster development, GDAL driver support, loader

Bborie Park

  Raster development

Mateusz Loskot

  Raster loader, low level raster api functions

David Zwarg

  Raster development

Other contributors: Individuals

  In alphabetical order: Alex Bodnaru, Alex Mayrhofer, Andrea Peri, Andreas Forø Tollefsen, Andreas Neumann, Anne Ghisla, Barbara Phillipot, Ben Jubb, Bernhard Reiter, Brian Hamlin, Bruce Rindahl, Bruno Wolff III, Bryce L. Nordgren, Carl Anderson, Charlie Savage, Dane Springmeyer, David Skea, David Techer, Eduin Carrillo, Even Rouault, Frank Warmerdam, George Silva, Gerald Fenoy, Gino Lucrezi, Guillaume Lelarge, IIDA Tetsushi, Ingvild Nystuen, Jeff Adams, Jose Carlos Martinez Llari, Kashif Rasul, Klaus Foerster, Kris Jurka, Leo Hsu, Loic Dachary, Luca S. Percich, Maria Arias de Reyna, Mark Sondheim, Markus Schaber, Maxime Guillaud, Maxime van Noppen, Michael Fuhr, Nikita Shulga, Norman Vine, Rafal Magda, Ralph Mason, Richard Greenwood, Silvio Grosso, Steffen Macke, Stephen Frost, Tom van Tilburg, Vincent Picavet

Other contributors: Corporate Sponsors

  These are corporate entities that have contributed developer time, hosting, or direct monetary funding to the PostGIS project

  In alphabetical order: Arrival 3D, Associazione Italiana per l'Informazione Geografica Libera (GFOSS.it), AusVet, Avencia, Azavea, Cadcorp, CampToCamp, City of Boston (DND), Clever Elephant Solutions, Cooperativa Alveo, Deimos Space, Faunalia, Geographic Data BC, Hunter Systems Group, Lidwala Consulting Engineers, LisaSoft, Logical Tracking & Tracing International AG, Michigan Tech Research Institute, Norwegian Forest and Landscape Institute, OpenGeo, OSGeo, Oslandia, Paragon Corporation, R3 GIS,, Refractions Research, Regione Toscana-SIGTA, Safe Software, Sirius Corporation plc, Stadt Uster, UC Davis Center for Vectorborne Diseases, University of Laval, U.S Department of State (HIU), Vizzuality, Zonar Systems

Crowd Funding Campaigns

  Crowd funding campaigns are campaigns we run to get badly wanted features funded that can service a large number of people. Each campaign is specifically focused on a particular feature or set of features. Each sponsor chips in a small fraction of the needed funding and with enough people/organizations contributing, we have the funds to pay for the work that will help many. If you have an idea for a feature you think many others would be willing to co-fund, please post to the PostGIS newsgroup your thoughts and together we can make it happen.

  PostGIS 2.0.0 was the first release we tried this strategy. We used PledgeBank and we got two successful campaigns out of it.

  postgistopology - 10 plus sponsors each contributed $250 USD to build toTopoGeometry function and beef up topology support in 2.0.0. It happened.

  postgis64windows - 20 someodd sponsors each contributed $100 USD to pay for the work needed to work out PostGIS 64-bit on windows issues. It happened. We now have a 64-bit beta release for PostGIS 2.0.0 and a final one planned for release that will be available on PostgreSQL stack builder.

Important Support Libraries

  The GEOS geometry operations library, and the algorithmic work of Martin Davis in making it all work, ongoing maintenance and support of Mateusz Loskot, Sandro Santilli (strk), Paul Ramsey and others.

  The GDAL Geospatial Data Abstraction Library, by Frank Warmerdam and others is used to power much of the raster functionality introduced in PostGIS 2.0.0. In kind, improvements needed in GDAL to support PostGIS are contributed back to the GDAL project.

  The Proj4 cartographic projection library, and the work of Gerald Evenden and Frank Warmerdam in creating and maintaining it.

  Last but not least, the PostgreSQL DBMS, The giant that PostGIS stands on. Much of the speed and flexibility of PostGIS would not be possible without the extensibility, great query planner, GIST index, and plethora of SQL features provided by PostgreSQL.

## 1.3. More Information

- The latest software, documentation and news items are available at the PostGIS web site, http://www.postgis.org.

- More information about the GEOS geometry operations library is available at http://trac.osgeo.org/geos/.

- More information about the Proj4 reprojection library is available at http://trac.osgeo.org/proj/.

- More information about the PostgreSQL database server is available at the PostgreSQL main site http://www.postgresql.org.

- More information about GiST indexing is available at the PostgreSQL GiST development site, http://www.sai.msu.su/~megera/postgres/gist/.

- More information about MapServer internet map server is available at http://mapserver.org.

- The "Simple Features for Specification for SQL" is available at the OpenGIS Consortium web site: http://www.opengeospatial.org/.

## Chapter 2. Installation

This chapter details the steps required to install PostGIS.

## 2.1. Short Version

The raster support is currently optional, but installed by default. For installing using the PostgreSQL 9.1+ extensions model it is required. Please refer to Section 2.4.3, “Building PostGIS Extensions and Deploying them” if you are using PostgreSQL 9.1+.

All the .sql files once installed will be installed in share/contrib/postgis-2.0.1 folder of your PostgreSQL install

The `postgis_comments.sql`, `raster_comments.sql`, `topology_comments.sql` generate quick help tips for each function that can be accessed via pgAdmin III or psql. In psql with a command of the form e.g.`\dd ST_SetPoint`

    tar xvfz postgis-2.0.1.tar.gz
    cd postgis-2.0.1
    ./configure --with-raster --with-topology --with-gui
    make
    make install
    createdb yourdatabase
    createlang plpgsql yourdatabase
    psql -d yourdatabase -f postgis.sql
    psql -d yourdatabase -f postgis_comments.sql
    psql -d yourdatabase -f spatial_ref_sys.sql
    psql -d yourdatabase -f rtpostgis.sql
    psql -d yourdatabase -f raster_comments.sql
    psql -d yourdatabase -f topology/topology.sql
    psql -d yourdatabase -f doc/topology_comments.sql

topology_comments.sql since its an optional feature is not installed by make install or make comments install. However if you do a `make comments` or `make topology_comments.sql`, it will be generated in the docs folder

The rest of this chapter goes into detail each of the above installation steps.

## 2.2. Requirements

PostGIS has the following requirements for building and usage:

Required

- PostgreSQL 8.4 or higher. A complete installation of PostgreSQL (including server headers) is required. PostgreSQL is available from http://www.postgresql.org .

  For a full PostgreSQL / PostGIS support matrix and PostGIS/GEOS support matrix refer to http://trac.osgeo.org/postgis/wiki/UsersWikiPostgreSQLPostGIS

- GNU C compiler (`gcc`). Some other ANSI C compilers can be used to compile PostGIS, but we find far fewer problems when compiling with `gcc`.

- GNU Make (`gmake` or `make`). For many systems, GNU `make` is the default version of make. Check the version by invoking `make -v`. Other versions of `make` may not process the PostGIS `Makefile` properly.

- Proj4 reprojection library, version 4.6.0 or greater. The Proj4 library is used to provide coordinate reprojection support within PostGIS. Proj4 is available for download from http://trac.osgeo.org/proj/ .

- GEOS geometry library, version 3.2.2 or greater, but GEOS 3.3.2+ is recommended. Without GEOS 3.3, you will be missing some major enhancements with handling of topological exceptions and improvements to geometry validation and making geometries valid such as ST_ValidDetail and ST_MakeValid. GEOS 3.3.2+ is also required for topology support. GEOS is available for download from http://trac.osgeo.org/geos/ and 3.3+ is backward-compatible with older versions so fairly safe to upgrade.

- LibXML2, version 2.5.x or higher. LibXML2 is currently used in some imports functions (ST_GeomFromGML and ST_GeomFromKML). LibXML2 is available for download from http://xmlsoft.org/downloads.html.

- JSON-C, version 0.9 or higher. JSON-C is currently used to import GeoJSON via the function ST_GeomFromGeoJson. JSON-C is available for download from http://oss.metaparadigm.com/json-c/.

- GDAL, version 1.6 or higher (1.9 or higher is preferable since some things will not work well with lower versions). This is needed for raster support and will be required in final release of PostGIS 2.0. http://trac.osgeo.org/gdal/wiki/DownloadSource.

Optional

- GTK (requires GTK+2.0) to compile the shp2pgsql-gui shape file loader. http://www.gtk.org/ .

- CUnit (`CUnit`). This is needed for regression testing. http://cunit.sourceforge.net/

- Apache Ant (`ant`) is required for building any of the drivers under the `java` directory. Ant is available from http://ant.apache.org .

- DocBook (`xsltproc`) is required for building the documentation. Docbook is available from http://www.docbook.org/ .

- DBLatex (`dblatex`) is required for building the documentation in PDF format. DBLatex is available from http://dblatex.sourceforge.net/ .

- ImageMagick (`convert`) is required to generate the images used in the documentation. ImageMagick is available from http://www.imagemagick.org/ .

## 2.3. Getting the Source

Retrieve the PostGIS source archive from the downloads website http://www.postgis.org/download/postgis-2.0.1.tar.gz

    wget http://www.postgis.org/download/postgis-2.0.1.tar.gz
    tar -xvzf postgis-2.0.1.tar.gz

This will create a directory called `postgis-2.0.1` in the current working directory.

Alternatively, checkout the source from the svn repository http://svn.osgeo.org/postgis/trunk/ .

    svn checkout http://svn.osgeo.org/postgis/trunk/ postgis-2.0.1

Change into the newly created `postgis-2.0.1` directory to continue the installation.

## 2.4. Installation

Many OS systems now include pre-built packages for PostgreSQL/PostGIS. In many cases compilation is only necessary if you want the most bleeding edge versions or you are a package maintainer. This section includes general compilation instructions, if you are compiling for Windows etc or another OS, you may find additional more detailed help at PostGIS User contributed compile/install guides and PostGIS Dev Wiki. If you are a windows user, you can get stable builds via Stackbuilder or PostGIS Windows download site We also have very bleeding-edge windows experimental builds that are built usually once or twice a week or whenever anything exciting happens. You can use these to experiment with the in progress releases of PostGIS

The PostGIS module is an extension to the PostgreSQL backend server. As such, PostGIS 2.0.1 requires full PostgreSQL server headers access in order to compile. It can be built against PostgreSQL versions 8.4 or higher. Earlier versions of PostgreSQL are not supported.

Refer to the PostgreSQL installation guides if you haven't already installed PostgreSQL. http://www.postgresql.org .

For GEOS functionality, when you install PostgresSQL you may need to explicitly link PostgreSQL against the standard C++ library:
    LDFLAGS=-lstdc++ ./configure [YOUR OPTIONS HERE]
This is a workaround for bogus C++ exceptions interaction with older development tools. If you experience weird problems (backend unexpectedly closed or similar things) try this trick. This will require recompiling your PostgreSQL from scratch, of course.

The following steps outline the configuration and compilation of the PostGIS source. They are written for Linux users and will not work on Windows or Mac.

### 2.4.1. Configuration

As with most linux installations, the first step is to generate the Makefile that will be used to build the source code. This is done by running the shell script

./configure

With no additional parameters, this command will attempt to automatically locate the required components and libraries needed to build the PostGIS source code on your system. Although this is the most common usage of ./configure, the script accepts several parameters for those who have the required libraries and programs in non-standard locations.

The following list shows only the most commonly used parameters. For a complete list, use the --help or --help=short parameters.

--prefix=PREFIX

  This is the location the PostGIS libraries and SQL scripts will be installed to. By default, this location is the same as the detected PostgreSQL installation.

  This parameter is currently broken, as the package will only install into the PostgreSQL installation directory. Visit http://trac.osgeo.org/postgis/ticket/635 to track this bug.

--with-pgconfig=FILE

  PostgreSQL provides a utility called pg_config to enable extensions like PostGIS to locate the PostgreSQL installation directory. Use this parameter (--with-pgconfig=/path/to/pg_config) to manually specify a particular PostgreSQL installation that PostGIS will build against.

--with-gdalconfig=FILE

  GDAL, a required library, provides functionality needed for raster support gdal-config to enable software installations to locate the GDAL installation directory. Use this parameter (--with-gdalconfig=/path/to/gdal-config) to manually specify a particular GDAL installation that PostGIS will build against.

--with-geosconfig=FILE

  GEOS, a required geometry library, provides a utility called geos-config to enable software installations to locate the GEOS installation directory. Use this parameter (--with-geosconfig=/path/to/geos-config) to manually specify a particular GEOS installation that PostGIS will build against.

--with-xml2config=FILE

  LibXML is the library required for doing GeomFromKML/GML processes. It normally is found if you have libxml installed, but if not or you want a specific version used, you'll need to point PostGIS at a specific `xml2-config` confi file to enable software installations to locate the LibXML installation directory. Use this parameter (>--with-xml2config=/path/to/xml2-config) to manually specify a particular LibXML installation that PostGIS will build against.

--with-projdir=DIR

  Proj4 is a reprojection library required by PostGIS. Use this parameter (--with-projdir=/path/to/projdir) to manually specify a particular Proj4 installation directory that PostGIS will build against.

--with-libiconv=DIR

  Directory where iconv is installed.

--with-jsondir=DIR

  JSON-C is an MIT-licensed JSON library required by PostGIS ST_GeomFromJSON support. Use this parameter (--with-jsondir=/path/to/jsondir) to manually specify a particular JSON-C installation directory that PostGIS will build against.

--with-gui

  Compile the data import GUI (requires GTK+2.0). This will create shp2pgsql-gui graphical interface to shp2pgsql.

--with-raster

  Compile with raster support. This will build rtpostgis-2.0.1 library and rtpostgis.sql file. This may not be required in final release as plan is to build in raster support by default.

--with-topology

  Compile with topology support. This will build the topology.sql file. There is no corresponding library as all logic needed for topology is in postgis-2.0.1 library.

--with-gettext=no

  By default PostGIS will try to detect gettext support and compile with it, however if you run into incompatibility issues that cause breakage of loader, you can disable it entirely with this command. Refer to ticket http://trac.osgeo.org/postgis/ticket/748 for an example issue solved by configuring with this. NOTE: that you aren't missing much by turning this off. This is used for international help/label support for the GUI loader which is not yet documented and still experimental.

If you obtained PostGIS from the SVN repository , the first step is really to run the script ./autogen.sh This script will generate the configure script that in turn is used to customize the installation of PostGIS. If you instead obtained PostGIS as a tarball, running ./autogen.sh is not necessary as configure has already been generated.

### 2.4.2. Building

Once the Makefile has been generated, building PostGIS is as simple as running

make

The last line of the output should be "`PostGIS was built successfully. Ready to install.`"

As of PostGIS v1.4.0, all the functions have comments generated from the documentation. If you wish to install these comments into your spatial databases later, run the command which requires docbook. The postgis_comments.sql and other package comments files raster_comments.sql, topology_comments.sql are also packaged in the tar.gz distribution in the doc folder so no need to make comments if installing from the tar ball.

make comments

Introduced in PostGIS 2.0. This generates html cheat sheets suitable for quick reference or for student handouts. This requires xsltproc to build and will generate 4 files in doc folder `topology_cheatsheet.html`, `tiger_geocoder_cheatsheet.html`, `raster_cheatsheet.html`, `postgis_cheatsheet.html`

You can download some pre-built ones available in html and pdf from PostGIS / PostgreSQL Study Guides

make cheatsheets

### 2.4.3. Building PostGIS Extensions and Deploying them

The PostGIS extensions are built and installed automatically if you are using PostgreSQL 9.1+.

If you are building from source repository, you need to build the function descriptions first. These get built if you have docbook installed. You can also manually build with the statement:

    make comments

Building the comments is not necessary if you are building from a release tar ball since these are packaged pre-built with the tar ball already.

If you are building against PostgreSQL 9.1, the extensions should automatically build as part of the make install process. You can if needed build from the extensions folders or copy files if you need them on a different server.

    cd extensions
    cd postgis
    make clean
    make
    make install
    cd ..
    cd postgis_topology
    make clean
    make
    make install

The extension files will always be the same for the same version of PostGIS regardless of OS, so it is fine to copy over the extension files from one OS to another as long as you have the PostGIS binaries already installed on your servers.

If you want to install the extensions manually on a separate server different from your development, You need to copy the following files from the extensions folder into the `PostgreSQL / share / extension` folder of your PostgreSQL install as well as the needed binaries for regular PostGIS if you don't have them already on the server.

- These are the control files that denote information such as the version of the extension to install if not specified. `postgis.control, postgis_topology.control`.

- All the files in the /sql folder of each extension. Note that these need to be copied to the root of the PostgreSQL share/extension folder `extensions/postgis/sql/*.sql`, `extensions/postgis_topology/sql/*.sql`

Once you do that, you should see `postgis`, `postgis_topology` as available extensions in PgAdmin -> extensions.

If you are using psql, you can verify that the extensions are installed by running this query:

    SELECT name, default_version,installed_version
    FROM pg_available_extensions WHERE name LIKE 'postgis%' ;
          name       | default_version | installed_version
    -----------------+-----------------+-------------------
    postgis          | 2.0.1     | 2.0.1
    postgis_topology | 2.0.1      |

If you have the extension installed in the database you are querying, you'll see mention in the `installed_version` column. If you get no records back, it means you don't have postgis extensions installed on the server at all. PgAdmin III 1.14+ will also provide this information in the `extensions` section of the database browser tree and will even allow upgrade or uninstall by right-clicking.

If you have the extensions available, you can install postgis extension in your database of choice by either using pgAdmin extension interface or running these sql commands:

    CREATE EXTENSION postgis;
    CREATE EXTENSION postgis_topology;

Extension tables `spatial_ref_sys`, `layer`, `topology` can not be explicitly backed up. They can only be backed up when the respective `postgis` or `postgis_topology` extension is backed up, which only seems to happen when you backup the whole database. As of PostGIS 2.0.1, only srid records not packaged with PostGIS are backed up when the database is backed up so don't go around changing srids we package and expect your changes to be there. Put in a ticket if you find an issue. The structures of extension tables are never backed up since they are created with `CREATE EXTENSION` and assumed to be the same for a given version of an extension. These behaviors are built into the current PostgreSQL extension model, so nothing we can do about it.

If you installed 2.0.1, without using our wonderful extension system, you can change it to be extension based by first upgrading to the latest micro version running the upgrade scripts: `postgis_upgrade_20_minor.sql`,`raster_upgrade_20_minor.sql`,`topology_upgrade_20_minor.sql`.

If you installed postgis without raster support, you'll need to install raster support first (using the full `rtpostgis.sql`

Then you can run teh below commands to package the functions in their respective extension.

    CREATE EXTENSION postgis FROM unpackaged;
    CREATE EXTENSION postgis_topology FROM unpackaged;

### 2.4.4. Testing

If you wish to test the PostGIS build, run

make check

The above command will run through various checks and regression tests using the generated library against an actual PostgreSQL database.

If you configured PostGIS using non-standard PostgreSQL, GEOS, or Proj4 locations, you may need to add their library locations to the LD_LIBRARY_PATH environment variable.

Currently, the make check relies on the `PATH` and `PGPORT` environment variables when performing the checks - it does not use the PostgreSQL version that may have been specified using the configuration parameter --with-pgconfig. So make sure to modify your PATH to match the detected PostgreSQL installation during configuration or be prepared to deal with the impending headaches.

If successful, the output of the test should be similar to the following:

         CUnit - A Unit testing framework for C - Version 2.1-0
    	 http://cunit.sourceforge.net/

    Suite: print_suite
      Test: test_lwprint_default_format ... passed
      Test: test_lwprint_format_orders ... passed
      Test: test_lwprint_optional_format ... passed
      Test: test_lwprint_oddball_formats ... passed
      Test: test_lwprint_bad_formats ... passed
    Suite: Misc Suite
      Test: test_misc_force_2d ... passed
      Test: test_misc_simplify ... passed
      Test: test_misc_count_vertices ... passed
      Test: test_misc_area ... passed
      Test: test_misc_wkb ... passed
    Suite: PointArray Suite
      Test: test_ptarray_append_point ... passed
      Test: test_ptarray_append_ptarray ... passed
    Suite: PostGIS Computational Geometry Suite
      Test: test_lw_segment_side ... passed
      Test: test_lw_segment_intersects ... passed
      Test: test_lwline_crossing_short_lines ... passed
      Test: test_lwline_crossing_long_lines ... passed
      Test: test_lwline_crossing_bugs ... passed
      Test: test_lwpoint_set_ordinate ... passed
      Test: test_lwpoint_get_ordinate ... passed
      Test: test_point_interpolate ... passed
      Test: test_lwline_clip ... passed
      Test: test_lwline_clip_big ... passed
      Test: test_lwmline_clip ... passed
      Test: test_geohash_point ... passed
      Test: test_geohash_precision ... passed
      Test: test_geohash ... passed
      Test: test_isclosed ... passed
    Suite: PostGIS Measures Suite
      Test: test_mindistance2d_tolerance ... passed
      Test: test_rect_tree_contains_point ... passed
      Test: test_rect_tree_intersects_tree ... passed
      Test: test_lwgeom_segmentize2d ... passed
    Suite: WKT Out Suite
      Test: test_wkt_out_point ... passed
      Test: test_wkt_out_linestring ... passed
      Test: test_wkt_out_polygon ... passed
      Test: test_wkt_out_multipoint ... passed
      Test: test_wkt_out_multilinestring ... passed
    :
    :
    --Run Summary: Type      Total     Ran  Passed  Failed
                   suites       17      17     n/a       0
                   tests       143     143     143       0
                   asserts    1228    1228    1228       0

    Creating spatial db postgis_reg
     Postgis 2.0.0SVN - 2011-01-11 15:33:37
       GEOS: 3.3.0-CAPI-1.7.0
       PROJ: Rel. 4.6.1, 21 August 2008

    Running tests

     loader/Point.............. ok
     loader/PointM.............. ok
     loader/PointZ.............. ok
     loader/MultiPoint.............. ok
     loader/MultiPointM.............. ok
     loader/MultiPointZ.............. ok
     loader/Arc.............. ok
     loader/ArcM.............. ok
     loader/ArcZ.......... ok
     loader/Polygon.............. ok
     loader/PolygonM.............. ok
     loader/PolygonZ.............. ok
     regress. ok
     regress_index. ok
     regress_index_nulls. ok
     lwgeom_regress. ok
     regress_lrs. ok
     removepoint. ok
     setpoint. ok
     simplify. ok
     snaptogrid. ok
     affine. ok
     measures. ok
     long_xact. ok
     ctors. ok
     sql-mm-serialize. ok
     sql-mm-circularstring. ok
     sql-mm-compoundcurve. ok
     sql-mm-curvepoly. ok
     sql-mm-general. ok
     sql-mm-multicurve. ok
     sql-mm-multisurface. ok
     polyhedralsurface. ok
     out_geometry. ok
     out_geography. ok
     in_gml. ok
     in_kml. ok
     iscollection. ok
     regress_ogc. ok
     regress_ogc_cover. ok
     regress_ogc_prep. ok
     regress_bdpoly. ok
     regress_proj. ok
     dump. ok
     dumppoints. ok
     wmsservers_new. ok
     tickets. ok
     remove_repeated_points. ok
     split. ok
     relatematch. ok
     regress_buffer_params. ok
     hausdorff. ok
     clean. ok
     sharedpaths. ok
     snap. ok

    Run tests: 55
    Failed: 0

### 2.4.5. Installation

To install PostGIS, type

make install

This will copy the PostGIS installation files into their appropriate subdirectory specified by the --prefix configuration parameter. In particular:

- The loader and dumper binaries are installed in `[prefix]/bin`.

- The SQL files, such as `postgis.sql`, are installed in `[prefix]/share/contrib`.

- The PostGIS libraries are installed in `[prefix]/lib`.

If you previously ran the make comments command to generate the `postgis_comments.sql`, `raster_comments.sql` file, install the sql file by running

make comments-install

`postgis_comments.sql`, `raster_comments.sql`, `topology_comments.sql` was separated from the typical build and installation targets since with it comes the extra dependency of xsltproc.

## 2.5. Create a spatially-enabled database on PostgreSQL lower than 9.1

The first step in creating a PostGIS database is to create a simple PostgreSQL database.

createdb [yourdatabase]

Many of the PostGIS functions are written in the PL/pgSQL procedural language. As such, the next step to create a PostGIS database is to enable the PL/pgSQL language in your new database. This is accomplish by the command below command. For PostgreSQL 8.4+, this is generally already installed

createlang plpgsql [yourdatabase]

Now load the PostGIS object and function definitions into your database by loading the `postgis.sql` definitions file (located in `[prefix]/share/contrib` as specified during the configuration step).

psql -d [yourdatabase] -f postgis.sql

For a complete set of EPSG coordinate system definition identifiers, you can also load the `spatial_ref_sys.sql` definitions file and populate the `spatial_ref_sys` table. This will permit you to perform ST_Transform() operations on geometries.

psql -d [yourdatabase] -f spatial_ref_sys.sql

If you wish to add comments to the PostGIS functions, the final step is to load the `postgis_comments.sql` into your spatial database. The comments can be viewed by simply typing \dd [function_name] from a psql terminal window.

psql -d [yourdatabase] -f postgis_comments.sql

Install raster support

psql -d [yourdatabase] -f rtpostgis.sql

Install raster support comments. This will provide quick help info for each raster function using psql or PgAdmin or any other PostgreSQL tool that can show function comments

psql -d [yourdatabase] -f raster_comments.sql

Install topology support

psql -d [yourdatabase] -f topology/topology.sql

Install topology support comments. This will provide quick help info for each topology function / type using psql or PgAdmin or any other PostgreSQL tool that can show function comments

psql -d [yourdatabase] -f topology/topology_comments.sql

If you plan to restore an old backup from prior versions in this new db, run:

psql -d [yourdatabase] -f legacy.sql

There is an alternative `legacy_minimal.sql` you can run instead which will install barebones needed to recover tables and work with apps like MapServer and GeoServer. If you have views that use things like distance / length etc, you'll need the full blown `legacy.sql`

You can later run `uninstall_legacy.sql` to get rid of the deprecated functions after you are done with restoring and cleanup.

## 2.6. Creating a spatial database using EXTENSIONS

If you are using PostgreSQL 9.1+ and have compiled and installed the extensions/ postgis modules, you can create a spatial database the new way.

createdb [yourdatabase]

The core postgis extension installs PostGIS geometry, geography, raster, spatial_ref_sys and all the functions and comments with a simple:

    CREATE EXTENSION postgis;

command.

psql -d [yourdatabase] -c "CREATE EXTENSION postgis;"

Topology is packaged as a separate extension and installable with command:

psql -d [yourdatabase] -c "CREATE EXTENSION postgis_topology;"

If you plan to restore an old backup from prior versions in this new db, run:

psql -d [yourdatabase] -f legacy.sql

You can later run `uninstall_legacy.sql` to get rid of the deprecated functions after you are done with restoring and cleanup.

## 2.7. Installing, Upgrading Tiger Geocoder and loading data

The Tiger geocoder does not get installed / upgraded with the core PostGIS scripts because it is only of regional use. In fact nothing located in the extras folder is installed by default with the regular PostGIS install / upgrade. Extras like Tiger geocoder may also not be packaged in your PostGIS distribution, but will always be available in the postgis-2.0.1.tar.gz file. The instructions provided here are also available in the `extras/tiger_geocoder/tiger_2010/README`

If you are on Windows and you don't have tar installed, you can use http://www.7-zip.org/ to unzip the PostGIS tarball.

### 2.7.1. Tiger Geocoder Enabling your PostGIS database

First install PostGIS using the prior instructions.

If you don't have an extras folder, download http://www.postgis.org/download/postgis-2.0.1.tar.gz

tar xvfz postgis-2.0.1.tar.gz

cd postgis-2.0.1/extras/tiger_geocoder/tiger_2010

Edit the `tiger_loader.sql` to the paths of your executables server etc.

If you are installing Tiger geocoder for the first time edit either the `create_geocode.bat` script If you are on windows or the `create_geocode.sh` if you are on Linux/Unix/Mac OSX with your PostgreSQL specific settings and run the corresponding script from the commandline. If you don't edit this file, it will just contain common case locations of items. You can edit the generated script after the fact when you run the Loader_Generate_Script command.

Verify that you now have a `tiger` schema in your database and that it is part of your database search_path. If it is not, add it with a command something along the line of:

    ALTER DATABASE geocoder SET search_path=public, tiger;

The normalizing address functionality works more or less without any data except for tricky addresses. Run this test and verify things look like this:

    SELECT pprint_addy(normalize_address('202 East Fremont Street, Las Vegas, Nevada 89101')) As pretty_address;
    pretty_address
    ---------------------------------------
    202 E Fremont St, Las Vegas, NV 89101

### 2.7.2. Upgrading your Tiger Geocoder Install

If you have Tiger Geocoder packaged with 2.0 already installed, you can upgrade the functions at any time even from an interim tar ball if there are fixes you badly need.

If you don't have an extras folder, download http://www.postgis.org/download/postgis-2.0.1.tar.gz

tar xvfz postgis-2.0.1.tar.gz

cd postgis-2.0.1/extras/tiger_geocoder/tiger_2010

Locate the `upgrade_geocoder.bat` script If you are on windows or the `upgrade_geocoder.sh` if you are on Linux/Unix/Mac OSX. Edit the file to have your postgis database credientials and run then corresponding script from the commandline.

### 2.7.3. Loading Tiger Data

The instructions for loading data are available in a more detailed form in the `extras/tiger_geocoder/tiger_2010/README`. This just includes the general steps.

The load process downloads data from the census website for the respective states requested, extracts the files, and then loads each state into its own separate set of state tables. Each state table inherits from the tables defined in `tiger` schema so that its sufficient to just query those tables to access all the data and drop a set of state tables at any time using the Drop_State_Tables_Generate_Script if you need to reload a state or just don't need a state anymore.

In order to be able to load data you'll need the following tools:

- A tool to unzip the zip files from census website.

  For Unix like systems: `unzip` executable which is usually already installed on most Unix like platforms.

  For Windows, 7-zip which is a free compress/uncompress tool you can download from http://www.7-zip.org/

- `shp2pgsql` commandline which is installed by default when you install PostGIS.

- `wget` which is a web grabber tool usually installed on most Unix/Linux systems.

  If you are on windows, you can get pre-compiled binaries from http://gnuwin32.sourceforge.net/packages/wget.htm

To load data refer to Loader_Generate_Script to generate a data load script for your platform for the states you desire. Note that you can install these piecemeal. You don't have to load all the states you want all at once. You can load them as you need them.

After the states you desire have been loaded, make sure to run the:

    SELECT install_missing_indexes();

as described in Install_Missing_Indexes.

To test that things are working as they should, try to run a geocode on an address in your state using Geocode

## 2.8. Create a spatially-enabled database from a template

Some packaged distributions of PostGIS (in particular the Win32 installers for PostGIS >= 1.1.5) load the PostGIS functions into a template database called `template_postgis`. If the `template_postgis` database exists in your PostgreSQL installation then it is possible for users and/or applications to create spatially-enabled databases using a single command. Note that in both cases, the database user must have been granted the privilege to create new databases.

From the shell:

    # createdb -T template_postgis my_spatial_db

From SQL:

    postgres=# CREATE DATABASE my_spatial_db TEMPLATE=template_postgis

## 2.9. Upgrading

Upgrading existing spatial databases can be tricky as it requires replacement or introduction of new PostGIS object definitions.

Unfortunately not all definitions can be easily replaced in a live database, so sometimes your best bet is a dump/reload process.

PostGIS provides a SOFT UPGRADE procedure for minor or bugfix releases, and a HARD UPGRADE procedure for major releases.

Before attempting to upgrade PostGIS, it is always worth to backup your data. If you use the -Fc flag to pg_dump you will always be able to restore the dump with a HARD UPGRADE.

### 2.9.1. Soft upgrade

If you installed your database using extensions, you'll need to upgrade using the extension model as well. If you installed using the old sql script way, then you should upgrade using the sql script way. Please refer to the appropriate.

#### 2.9.1.1. Soft Upgrade Pre 9.1+ or without extensions

This section applies only to those who installed PostGIS not using extensions. If you have extensions and try to upgrade with this approach you'll get messages like:

    can't drop ... because postgis extension depends on it

After compiling you should find several `postgis_upgrade*.sql` files. Install the one for your version of PostGIS. For example `postgis_upgrade_13_to_15.sql` should be used if you are upgrading from PostGIS 1.3 to 1.5. If you are moving from PostGIS 1.* to PostGIS 2.* or from PostGIS 2.* prior to r7409, you need to do a HARD UPGRADE.

    psql -f postgis_upgrade_20_minor.sql -d your_spatial_database

The same procedure applies to raster and topology extensions, with upgrade files named `rtpostgis_upgrade*.sql` and `topology_upgrade*.sql` respectively. If you need them:

    psql -f rtpostgis_upgrade_20_minor.sql -d your_spatial_database

    psql -f topology_upgrade_20_minor.sql -d your_spatial_database

If you can't find the `postgis_upgrade*.sql` specific for upgrading your version you are using a version too early for a soft upgrade and need to do a HARD UPGRADE.

The PostGIS_Full_Version function should inform you about the need to run this kind of upgrade using a "procs need upgrade" message.

#### 2.9.1.2. Soft Upgrade 9.1+ using extensions

If you originally installed PostGIS with extensions, then you need to upgrade using extensions as well. Doing a minor upgrade with extensions, is fairly painless.

    ALTER EXTENSION postgis UPDATE TO "2.0.1";
    ALTER EXTENSION postgis_topology UPDATE TO "2.0.1";

If you get an error notice something like:

    No migration path defined for ... to 2.0.1

Then you'll need to backup your database, create a fresh one as described in Section 2.6, “Creating a spatial database using EXTENSIONS” and then restore your backup on top of this new database. You might get a message that `postgis extension` already installed which you can safely ignore.

If you installed PostGIS originally without a version specified, you can often skip the reinstallation of postgis extension before restoring since the backup just has `CREATE EXTENSION postgis` and thus picks up the newest latest version during restore. .

### 2.9.2. Hard upgrade

By HARD UPGRADE we mean full dump/reload of postgis-enabled databases. You need a HARD UPGRADE when PostGIS objects' internal storage changes or when SOFT UPGRADE is not possible. The Release Notes appendix reports for each version whether you need a dump/reload (HARD UPGRADE) to upgrade.

The dump/reload process is assisted by the postgis_restore.pl script which takes care of skipping from the dump all definitions which belong to PostGIS (including old ones), allowing you to restore your schemas and data into a database with PostGIS installed without getting duplicate symbol errors or bringing forward deprecated objects.

Supplementary instructions for windows users are available at Windows Hard upgrade.

The Procedure is as follows:

1. Create a "custom-format" dump of the database you want to upgrade (let's call it `olddb`) include binary blobs (-b) and verbose (-v) output. The user can be the owner of the db, need not be postgres super account.

       pg_dump -h localhost -p 5432 -U postgres -Fc -b -v -f "/somepath/olddb.backup" olddb

2. Do a fresh install of PostGIS in a new database -- we'll refer to this database as `newdb`. Please refer to Section 2.5, “Create a spatially-enabled database on PostgreSQL lower than 9.1” and Section 2.6, “Creating a spatial database using EXTENSIONS” for instructions on how to do this.

   The spatial_ref_sys entries found in your dump will be restored, but they will not override existing ones in spatial_ref_sys. This is to ensure that fixes in the official set will be properly propagated to restored databases. If for any reason you really want your own overrides of standard entries just don't load the spatial_ref_sys.sql file when creating the new db.

   If your database is really old or you know you've been using long deprecated functions in your views and functions, you might need to load `legacy.sql` for all your functions and views etc. to properly come back. Only do this if _really_ needed. Consider upgrading your views and functions before dumping instead, if possible. The deprecated functions can be later removed by loading `uninstall_legacy.sql`.

3. Restore your backup into your fresh `newdb` database using postgis_restore.pl. Unexpected errors, if any, will be printed to the standard error stream by psql. Keep a log of those.

       perl utils/postgis_restore.pl "/somepath/olddb.backup" | psql -h localhost -p 5432 -U postgres newdb 2> errors.txt

Errors may arise in the following cases:

1. Some of your views or functions make use of deprecated PostGIS objects. In order to fix this you may try loading `legacy.sql` script prior to restore or you'll have to restore to a version of PostGIS which still contains those objects and try a migration again after porting your code. If the `legacy.sql` way works for you, don't forget to fix your code to stop using deprecated functions and drop them loading `uninstall_legacy.sql`.

2. Some custom records of spatial_ref_sys in dump file have an invalid SRID value. Valid SRID values are bigger than 0 and smaller than 999000. Values in the 999000.999999 range are reserved for internal use while values > 999999 can't be used at all. All your custom records with invalid SRIDs will be retained, with those > 999999 moved into the reserved range, but the spatial_ref_sys table would loose a check constraint guarding for that invariant to hold and possibly also its primary key ( when multiple invalid SRIDS get converted to the same reserved SRID value ).

   In order to fix this you should copy your custom SRS to a SRID with a valid value (maybe in the 910000..910999 range), convert all your tables to the new srid (see UpdateGeometrySRID), delete the invalid entry from spatial_ref_sys and re-construct the check(s) with:

       ALTER TABLE spatial_ref_sys ADD CONSTRAINT spatial_ref_sys_srid_check check (srid > 0 AND srid < 999000 );

       ALTER TABLE spatial_ref_sys ADD PRIMARY KEY(srid));

## 2.10. Common Problems

There are several things to check when your installation or upgrade doesn't go as you expected.

1. Check that you have installed PostgreSQL 8.4 or newer, and that you are compiling against the same version of the PostgreSQL source as the version of PostgreSQL that is running. Mix-ups can occur when your (Linux) distribution has already installed PostgreSQL, or you have otherwise installed PostgreSQL before and forgotten about it. PostGIS will only work with PostgreSQL 8.4 or newer, and strange, unexpected error messages will result if you use an older version. To check the version of PostgreSQL which is running, connect to the database using psql and run this query:

       SELECT version();

   If you are running an RPM based distribution, you can check for the existence of pre-installed packages using the rpm command as follows: rpm -qa | grep postgresql

2. If your upgrade fails, make sure you are restoring into a database that already has PostGIS installed.

       SELECT postgis_full_version();

Also check that configure has correctly detected the location and version of PostgreSQL, the Proj4 library and the GEOS library.

1. The output from configure is used to generate the `postgis_config.h` file. Check that the `POSTGIS_PGSQL_VERSION`, `POSTGIS_PROJ_VERSION` and `POSTGIS_GEOS_VERSION` variables have been set correctly.

## 2.11. JDBC

The JDBC extensions provide Java objects corresponding to the internal PostGIS types. These objects can be used to write Java clients which query the PostGIS database and draw or do calculations on the GIS data in PostGIS.

1. Enter the `java/jdbc` sub-directory of the PostGIS distribution.

2. Run the `ant` command. Copy the `postgis.jar` file to wherever you keep your java libraries.

The JDBC extensions require a PostgreSQL JDBC driver to be present in the current CLASSPATH during the build process. If the PostgreSQL JDBC driver is located elsewhere, you may pass the location of the JDBC driver JAR separately using the -D parameter like this:

    # ant -Dclasspath=/path/to/postgresql-jdbc.jar

PostgreSQL JDBC drivers can be downloaded from http://jdbc.postgresql.org .

## 2.12. Loader/Dumper

The data loader and dumper are built and installed automatically as part of the PostGIS build. To build and install them manually:

    # cd postgis-2.0.1/loader
    # make
    # make install

The loader is called `shp2pgsql` and converts ESRI Shape files into SQL suitable for loading in PostGIS/PostgreSQL. The dumper is called `pgsql2shp` and converts PostGIS tables (or queries) into ESRI Shape files. For more verbose documentation, see the online help, and the manual pages.

## Chapter 3. PostGIS Frequently Asked Questions

3.1. My applications and desktop tools worked with PostGIS 1.5,but they don't work with PostGIS 2.0. How do I fix this?
3.2. I'm running PostgreSQL 9.0 and I can no longer read/view geometries in OpenJump, Safe FME, and some other tools?
3.3. I tried to use PgAdmin to view my geometry column and it is blank, what gives?
3.4. What kind of geometric objects can I store?
3.5. I'm all confused. Which data store should I use geometry or geography?
3.6. I have more intense questions about geography, such as how big of a geographic region can I stuff in a geography column and still get reasonable answers. Are there limitations such as poles, everything in the field must fit in a hemisphere (like SQL Server 2008 has), speed etc?
3.7. How do I insert a GIS object into the database?
3.8. How do I construct a spatial query?
3.9. How do I speed up spatial queries on large tables?
3.10. Why aren't PostgreSQL R-Tree indexes supported?
3.11. Why should I use the AddGeometryColumn() function and all the other OpenGIS stuff?
3.12. What is the best way to find all objects within a radius of another object?
3.13. How do I perform a coordinate reprojection as part of a query?
3.14. I did an ST_AsEWKT and ST_AsText on my rather large geometry and it returned blank field. What gives?
3.15. When I do an ST_Intersects, it says my two geometries don't intersect when I KNOW THEY DO. What gives?
3.16. I am releasing software that uses PostGIS, does that mean my software has to be licensed using the GPL like PostGIS? Will I have to publish all my code if I use PostGIS?

3.1. | My applications and desktop tools worked with PostGIS 1.5,but they don't work with PostGIS 2.0. How do I fix this?
| A lot of deprecated functions were removed from the PostGIS code base in PostGIS 2.0. This has affected applications in addition to third-party tools such as Geoserver, MapServer, QuantumGIS, and OpenJump to name a few. There are a couple of ways to resolve this. For the third-party apps, you can try to upgrade to the latest versions of these which have many of these issues fixed. For your own code, you can change your code to not use the functions removed. Most of these functions are non ST_ aliases of ST_Union, ST_Length etc. and as a last resort, install the whole of `legacy.sql` or just the portions of `legacy.sql` you need. The `legacy.sql` file is located in the same folder as postgis.sql. You can install this file after you have installed postgis.sql and spatial_ref_sys.sql to get back all the 200 some-odd old functions we removed.
3.2. | I'm running PostgreSQL 9.0 and I can no longer read/view geometries in OpenJump, Safe FME, and some other tools?
| In PostgreSQL 9.0+, the default encoding for bytea data has been changed to hex and older JDBC drivers still assume escape format. This has affected some applications such as Java applications using older JDBC drivers or .NET applications that use the older npgsql driver that expect the old behavior of ST_AsBinary. There are two approaches to getting this to work again. You can upgrade your JDBC driver to the latest PostgreSQL 9.0 version which you can get from http://jdbc.postgresql.org/download.html If you are running a .NET app, you can use Npgsql 2.0.11 or higher which you can download from http://pgfoundry.org/frs/?group_id=1000140 and as described on Francisco Figueiredo's NpgSQL 2.0.11 released blog entry If upgrading your PostgreSQL driver is not an option, then you can set the default back to the old behavior with the following change:
    ALTER DATABASE mypostgisdb SET bytea_output='escape';
3.3. | I tried to use PgAdmin to view my geometry column and it is blank, what gives?
| PgAdmin doesn't show anything for large geometries. The best ways to verify you do have data in your geometry columns are?
    -- this should return no records if all your geom fields are filled in
    SELECT somefield FROM mytable WHERE geom IS NULL;
    -- To tell just how large your geometry is do a query of the form
    --which will tell you the most number of points you have in any of your geometry columns
    SELECT MAX(ST_NPoints(geom)) FROM sometable;
3.4. | What kind of geometric objects can I store?
| You can store point, line, polygon, multipoint, multiline, multipolygon, and geometrycollections. In PostGIS 2.0 and above you can also store TINS and Polyhedral Surfaces in the basic geometry type. These are specified in the Open GIS Well Known Text Format (with XYZ,XYM,XYZM extensions). There are three data types currently supported. The standard OGC geometry data type which uses a planar coordinate system for measurement, the geography data type which uses a geodetic coordinate system (not OGC, but you'll find a similar type in Microsoft SQL Server 2008+). Only WGS 84 long lat (SRID:4326) is supported by the geography data type. The newest family member of the PostGIS spatial type family is raster for storing and analyzing raster data. Raster has its very own FAQ. Refer to Chapter 10, PostGIS Raster Frequently Asked Questions and Chapter 9, Raster Reference for more details.
3.5. | I'm all confused. Which data store should I use geometry or geography?
| Short Answer: geography is a new data type that supports long range distances measurements, but most computations on it are currently slower than they are on geometry. If you use geography -- you don't need to learn much about planar coordinate systems. Geography is generally best if all you care about is measuring distances and lengths and you have data from all over the world. Geometry data type is an older data type that has many more functions supporting it, enjoys greater support from third party tools, and operations on it are generally faster -- sometimes as much as 10 fold faster for larger geometries. Geometry is best if you are pretty comfortable with spatial reference systems or you are dealing with localized data where all your data fits in a single spatial reference system (SRID), or you need to do a lot of spatial processing. Note: It is fairly easy to do one-off conversions between the two types to gain the benefits of each. Refer to Section 13.10, “PostGIS Function Support Matrix” to see what is currently supported and what is not. Long Answer: Refer to our more lengthy discussion in the Section 4.2.2, “When to use Geography Data type over Geometry data type” and function type matrix.
3.6. | I have more intense questions about geography, such as how big of a geographic region can I stuff in a geography column and still get reasonable answers. Are there limitations such as poles, everything in the field must fit in a hemisphere (like SQL Server 2008 has), speed etc?
| Your questions are too deep and complex to be adequately answered in this section. Please refer to our Section 4.2.3, “Geography Advanced FAQ”.
3.7. | How do I insert a GIS object into the database?
| First, you need to create a table with a column of type "geometry" or "geography" to hold your GIS data. Storing geography type data is a little different than storing geometry. Refer to Section 4.2.1, “Geography Basics” for details on storing geography. For geometry: Connect to your database with `psql` and try the following SQL:
    CREATE TABLE gtest ( ID int4, NAME varchar(20) );
    SELECT AddGeometryColumn('', 'gtest','geom',-1,'LINESTRING',2);
If the geometry column addition fails, you probably have not loaded the PostGIS functions and objects into this database. See the Section 2.4, “Installation”. Then, you can insert a geometry into the table using a SQL insert statement. The GIS object itself is formatted using the OpenGIS Consortium "well-known text" format:
    INSERT INTO gtest (ID, NAME, GEOM)
    VALUES (
      1,
      'First Geometry',
      ST_GeomFromText('LINESTRING(2 3,4 5,6 5,7 8)', -1)
    );
For more information about other GIS objects, see the object reference. To view your GIS data in the table:
    SELECT id, name, ST_AsText(geom) AS geom FROM gtest;
The return value should look something like this:
     id | name           | geom
    ----+----------------+-----------------------------
      1 | First Geometry | LINESTRING(2 3,4 5,6 5,7 8)
    (1 row)
3.8. | How do I construct a spatial query?
| The same way you construct any other database query, as an SQL combination of return values, functions, and boolean tests. For spatial queries, there are two issues that are important to keep in mind while constructing your query: is there a spatial index you can make use of; and, are you doing expensive calculations on a large number of geometries. In general, you will want to use the "intersects operator" (&&) which tests whether the bounding boxes of features intersect. The reason the && operator is useful is because if a spatial index is available to speed up the test, the && operator will make use of this. This can make queries much much faster. You will also make use of spatial functions, such as Distance(), ST_Intersects(), ST_Contains() and ST_Within(), among others, to narrow down the results of your search. Most spatial queries include both an indexed test and a spatial function test. The index test serves to limit the number of return tuples to only tuples that might meet the condition of interest. The spatial functions are then use to test the condition exactly.
    SELECT id, the_geom
    FROM thetable
    WHERE
      ST_Contains(the_geom,'POLYGON((0 0, 0 10, 10 10, 10 0, 0 0))');
3.9. | How do I speed up spatial queries on large tables?
| Fast queries on large tables is the raison d'etre of spatial databases (along with transaction support) so having a good index is important. To build a spatial index on a table with a `geometry` column, use the "CREATE INDEX" function as follows:
    CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometrycolumn] );
The "USING GIST" option tells the server to use a GiST (Generalized Search Tree) index.
GiST indexes are assumed to be lossy. Lossy indexes uses a proxy object (in the spatial case, a bounding box) for building the index.
You should also ensure that the PostgreSQL query planner has enough information about your index to make rational decisions about when to use it. To do this, you have to "gather statistics" on your geometry tables. For PostgreSQL 8.0.x and greater, just run the VACUUM ANALYZE command. For PostgreSQL 7.4.x and below, run the SELECT UPDATE_GEOMETRY_STATS() command.
3.10. | Why aren't PostgreSQL R-Tree indexes supported?
| Early versions of PostGIS used the PostgreSQL R-Tree indexes. However, PostgreSQL R-Trees have been completely discarded since version 0.6, and spatial indexing is provided with an R-Tree-over-GiST scheme. Our tests have shown search speed for native R-Tree and GiST to be comparable. Native PostgreSQL R-Trees have two limitations which make them undesirable for use with GIS features (note that these limitations are due to the current PostgreSQL native R-Tree implementation, not the R-Tree concept in general): R-Tree indexes in PostgreSQL cannot handle features which are larger than 8K in size. GiST indexes can, using the "lossy" trick of substituting the bounding box for the feature itself. R-Tree indexes in PostgreSQL are not "null safe", so building an index on a geometry column which contains null geometries will fail.
3.11. | Why should I use the `AddGeometryColumn()` function and all the other OpenGIS stuff?
| If you do not want to use the OpenGIS support functions, you do not have to. Simply create tables as in older versions, defining your geometry columns in the CREATE statement. All your geometries will have SRIDs of -1, and the OpenGIS meta-data tables will not be filled in properly. However, this will cause most applications based on PostGIS to fail, and it is generally suggested that you do use `AddGeometryColumn()` to create geometry tables. MapServer is one application which makes use of the `geometry_columns` meta-data. Specifically, MapServer can use the SRID of the geometry column to do on-the-fly reprojection of features into the correct map projection.
3.12. | What is the best way to find all objects within a radius of another object?
| To use the database most efficiently, it is best to do radius queries which combine the radius test with a bounding box test: the bounding box test uses the spatial index, giving fast access to a subset of data which the radius test is then applied to. The `ST_DWithin(geometry, geometry, distance)` function is a handy way of performing an indexed distance search. It works by creating a search rectangle large enough to enclose the distance radius, then performing an exact distance search on the indexed subset of results. For example, to find all objects with 100 meters of POINT(1000 1000) the following query would work well:
    SELECT * FROM geotable
    WHERE ST_DWithin(geocolumn, 'POINT(1000 1000)', 100.0);
3.13. | How do I perform a coordinate reprojection as part of a query?
| To perform a reprojection, both the source and destination coordinate systems must be defined in the SPATIAL_REF_SYS table, and the geometries being reprojected must already have an SRID set on them. Once that is done, a reprojection is as simple as referring to the desired destination SRID. The below projects a geometry to NAD 83 long lat. The below will only work if the srid of the_geom is not -1 (not undefined spatial ref)
    SELECT ST_Transform(the_geom,4269) FROM geotable;
3.14. | I did an ST_AsEWKT and ST_AsText on my rather large geometry and it returned blank field. What gives?
| You are probably using PgAdmin or some other tool that doesn't output large text. If your geometry is big enough, it will appear blank in these tools. Use PSQL if you really need to see it or output it in WKT.
    				--To check number of geometries are really blank
    				SELECT count(gid) FROM geotable WHERE the_geom IS NULL;
3.15. | When I do an ST_Intersects, it says my two geometries don't intersect when I KNOW THEY DO. What gives?
| This generally happens in two common cases. Your geometry is invalid -- check ST_IsValid or you are assuming they intersect because ST_AsText truncates the numbers and you have lots of decimals after it is not showing you.
3.16. | I am releasing software that uses PostGIS, does that mean my software has to be licensed using the GPL like PostGIS? Will I have to publish all my code if I use PostGIS?
| Almost certainly not. As an example, consider Oracle database running on Linux. Linux is GPL, Oracle is not, does Oracle running on Linux have to be distributed using the GPL? No. So your software can use a PostgreSQL/PostGIS database as much as it wants and be under any license you like. The only exception would be if you made changes to the PostGIS source code, and distributed your changed version of PostGIS. In that case you would have to share the code of your changed PostGIS (but not the code of applications running on top of it). Even in this limited case, you would still only have to distribute source code to people you distributed binaries to. The GPL does not require that you publish your source code, only that you share it with people you give binaries to.

## Chapter 4. Using PostGIS: Data Management and Queries

## 4.1. GIS Objects

The GIS objects supported by PostGIS are a superset of the "Simple Features" defined by the OpenGIS Consortium (OGC). As of version 0.9, PostGIS supports all the objects and functions specified in the OGC "Simple Features for SQL" specification.

PostGIS extends the standard with support for 3DZ,3DM and 4D coordinates.

### 4.1.1. OpenGIS WKB and WKT

The OpenGIS specification defines two standard ways of expressing spatial objects: the Well-Known Text (WKT) form and the Well-Known Binary (WKB) form. Both WKT and WKB include information about the type of the object and the coordinates which form the object.

Examples of the text representations (WKT) of the spatial objects of the features are as follows:

- POINT(0 0)

- LINESTRING(0 0,1 1,1 2)

- POLYGON((0 0,4 0,4 4,0 4,0 0),(1 1, 2 1, 2 2, 1 2,1 1))

- MULTIPOINT(0 0,1 2)

- MULTILINESTRING((0 0,1 1,1 2),(2 3,3 2,5 4))

- MULTIPOLYGON(((0 0,4 0,4 4,0 4,0 0),(1 1,2 1,2 2,1 2,1 1)), ((-1 -1,-1 -2,-2 -2,-2 -1,-1 -1)))

- GEOMETRYCOLLECTION(POINT(2 3),LINESTRING(2 3,3 4))

The OpenGIS specification also requires that the internal storage format of spatial objects include a spatial referencing system identifier (SRID). The SRID is required when creating spatial objects for insertion into the database.

Input/Output of these formats are available using the following interfaces:

    bytea WKB = ST_AsBinary(geometry);
    text WKT = ST_AsText(geometry);
    geometry = ST_GeomFromWKB(bytea WKB, SRID);
    geometry = ST_GeometryFromText(text WKT, SRID);

For example, a valid insert statement to create and insert an OGC spatial object would be:

    INSERT INTO geotable ( the_geom, the_name )
      VALUES ( ST_GeomFromText('POINT(-126.4 45.32)', 312), 'A Place');

### 4.1.2. PostGIS EWKB, EWKT and Canonical Forms

OGC formats only support 2d geometries, and the associated SRID is *never* embedded in the input/output representations.

PostGIS extended formats are currently superset of OGC one (every valid WKB/WKT is a valid EWKB/EWKT) but this might vary in the future, specifically if OGC comes out with a new format conflicting with our extensions. Thus you SHOULD NOT rely on this feature!

PostGIS EWKB/EWKT add 3dm,3dz,4d coordinates support and embedded SRID information.

Examples of the text representations (EWKT) of the extended spatial objects of the features are as follows. The * ones are new in this version of PostGIS:

- POINT(0 0 0) -- XYZ

- SRID=32632;POINT(0 0) -- XY with SRID

- POINTM(0 0 0) -- XYM

- POINT(0 0 0 0) -- XYZM

- SRID=4326;MULTIPOINTM(0 0 0,1 2 1) -- XYM with SRID

- MULTILINESTRING((0 0 0,1 1 0,1 2 1),(2 3 1,3 2 1,5 4 1))

- POLYGON((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0))

- MULTIPOLYGON(((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0)),((-1 -1 0,-1 -2 0,-2 -2 0,-2 -1 0,-1 -1 0)))

- GEOMETRYCOLLECTIONM( POINTM(2 3 9), LINESTRINGM(2 3 4, 3 4 5) )

- MULTICURVE( (0 0, 5 5), CIRCULARSTRING(4 0, 4 4, 8 4) )

- POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )

- TRIANGLE ((0 0, 0 9, 9 0, 0 0))

- TIN( ((0 0 0, 0 0 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 0 0 0)) )

Input/Output of these formats are available using the following interfaces:

    bytea EWKB = ST_AsEWKB(geometry);
    text EWKT = ST_AsEWKT(geometry);
    geometry = ST_GeomFromEWKB(bytea EWKB);
    geometry = ST_GeomFromEWKT(text EWKT);

For example, a valid insert statement to create and insert a PostGIS spatial object would be:

    INSERT INTO geotable ( the_geom, the_name )
      VALUES ( ST_GeomFromEWKT('SRID=312;POINTM(-126.4 45.32 15)'), 'A Place' )

The "canonical forms" of a PostgreSQL type are the representations you get with a simple query (without any function call) and the one which is guaranteed to be accepted with a simple insert, update or copy. For the postgis 'geometry' type these are:

    - Output
      - binary: EWKB
    	ascii: HEXEWKB (EWKB in hex form)
    - Input
      - binary: EWKB
    	ascii: HEXEWKB|EWKT

For example this statement reads EWKT and returns HEXEWKB in the process of canonical ascii input/output:

    =# SELECT 'SRID=4;POINT(0 0)'::geometry;

    geometry
    ----------------------------------------------------
    01010000200400000000000000000000000000000000000000
    (1 row)

### 4.1.3. SQL-MM Part 3

The SQL Multimedia Applications Spatial specification extends the simple features for SQL spec by defining a number of circularly interpolated curves.

The SQL-MM definitions include 3dm, 3dz and 4d coordinates, but do not allow the embedding of SRID information.

The well-known text extensions are not yet fully supported. Examples of some simple curved geometries are shown below:

- CIRCULARSTRING(0 0, 1 1, 1 0)

  CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0)

  The CIRCULARSTRING is the basic curve type, similar to a LINESTRING in the linear world. A single segment required three points, the start and end points (first and third) and any other point on the arc. The exception to this is for a closed circle, where the start and end points are the same. In this case the second point MUST be the center of the arc, ie the opposite side of the circle. To chain arcs together, the last point of the previous arc becomes the first point of the next arc, just like in LINESTRING. This means that a valid circular string must have an odd number of points greated than 1.

- COMPOUNDCURVE(CIRCULARSTRING(0 0, 1 1, 1 0),(1 0, 0 1))

  A compound curve is a single, continuous curve that has both curved (circular) segments and linear segments. That means that in addition to having well-formed components, the end point of every component (except the last) must be coincident with the start point of the following component.

- CURVEPOLYGON(CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0),(1 1, 3 3, 3 1, 1 1))

  Example compound curve in a curve polygon: CURVEPOLYGON(COMPOUNDCURVE(CIRCULARSTRING(0 0,2 0, 2 1, 2 3, 4 3),(4 3, 4 5, 1 4, 0 0)), CIRCULARSTRING(1.7 1, 1.4 0.4, 1.6 0.4, 1.6 0.5, 1.7 1) )

  A CURVEPOLYGON is just like a polygon, with an outer ring and zero or more inner rings. The difference is that a ring can take the form of a circular string, linear string or compound string.

  As of PostGIS 1.4 PostGIS supports compound curves in a curve polygon.

- MULTICURVE((0 0, 5 5),CIRCULARSTRING(4 0, 4 4, 8 4))

  The MULTICURVE is a collection of curves, which can include linear strings, circular strings or compound strings.

- MULTISURFACE(CURVEPOLYGON(CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0),(1 1, 3 3, 3 1, 1 1)),((10 10, 14 12, 11 10, 10 10),(11 11, 11.5 11, 11 11.5, 11 11)))

  This is a collection of surfaces, which can be (linear) polygons or curve polygons.

PostGIS prior to 1.4 does not support compound curves in a curve polygon, but PostGIS 1.4 and above do support the use of Compound Curves in a Curve Polygon.

All floating point comparisons within the SQL-MM implementation are performed to a specified tolerance, currently 1E-8.

## 4.2. PostGIS Geography Type

The geography type provides native support for spatial features represented on "geographic" coordinates (sometimes called "geodetic" coordinates, or "lat/lon", or "lon/lat"). Geographic coordinates are spherical coordinates expressed in angular units (degrees).

The basis for the PostGIS geometry type is a plane. The shortest path between two points on the plane is a straight line. That means calculations on geometries (areas, distances, lengths, intersections, etc) can be calculated using cartesian mathematics and straight line vectors.

The basis for the PostGIS geographic type is a sphere. The shortest path between two points on the sphere is a great circle arc. That means that calculations on geographies (areas, distances, lengths, intersections, etc) must be calculated on the sphere, using more complicated mathematics. For more accurate measurements, the calculations must take the actual spheroidal shape of the world into account, and the mathematics becomes very complicated indeed.

Because the underlying mathematics is much more complicated, there are fewer functions defined for the geography type than for the geometry type. Over time, as new algorithms are added, the capabilities of the geography type will expand.

One restriction is that it only supports WGS 84 long lat (SRID:4326). It uses a new data type called geography. None of the GEOS functions support this new type. As a workaround one can convert back and forth between geometry and geography types.

The new geography type uses the PostgreSQL 8.3+ typmod definition format so that a table with a geography field can be added in a single step. All the standard OGC formats except for curves are supported.

### 4.2.1. Geography Basics

The geography type only supports the simplest of simple features. Standard geometry type data will autocast to geography if it is of SRID 4326. You can also use the EWKT and EWKB conventions to insert data.

- POINT: Creating a table with 2d point geometry:

      CREATE TABLE testgeog(gid serial PRIMARY KEY, the_geog geography(POINT,4326) );

  Creating a table with z coordinate point

      CREATE TABLE testgeog(gid serial PRIMARY KEY, the_geog geography(POINTZ,4326) );

- LINESTRING

- POLYGON

- MULTIPOINT

- MULTILINESTRING

- MULTIPOLYGON

- GEOMETRYCOLLECTION

The new geography fields don't get registered in the `geometry_columns`. They get registered in a new view called geography_columns which is a view against the system catalogs so is always automatically kept up to date without need for an AddGeom... like function.

Now, check the "geography_columns" view and see that your table is listed.

You can create a new table with a GEOGRAPHY column using the CREATE TABLE syntax. Unlike GEOMETRY, there is no need to run a separate AddGeometryColumns() process to register the column in metadata.

    CREATE TABLE global_points (
        id SERIAL PRIMARY KEY,
        name VARCHAR(64),
        location GEOGRAPHY(POINT,4326)
      );

Note that the location column has type GEOGRAPHY and that geography type supports two optional modifier: a type modifier that restricts the kind of shapes and dimensions allowed in the column; an SRID modifier that restricts the coordinate reference identifier to a particular number.

Allowable values for the type modifier are: POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON. The modifier also supports dimensionality restrictions through suffixes: Z, M and ZM. So, for example a modifier of 'LINESTRINGM' would only allow line strings with three dimensions in, and would treat the third dimension as a measure. Similarly, 'POINTZM' would expect four dimensional data.

The SRID modifier is currently of limited use: only 4326 (WGS84) is allowed as a value. If you do not specify an SRID, the a value 0 (undefined spheroid) will be used, and all calculations will proceed using WGS84 anyways.

In the future, alternate SRIDs will allow calculations on spheroids other than WGS84.

Once you have created your table, you can see it in the GEOGRAPHY_COLUMNS table:

    -- See the contents of the metadata view
    SELECT * FROM geography_columns;

You can insert data into the table the same as you would if it was using a GEOMETRY column:

    -- Add some data into the test table
    INSERT INTO global_points (name, location) VALUES ('Town', ST_GeographyFromText('SRID=4326;POINT(-110 30)') );
    INSERT INTO global_points (name, location) VALUES ('Forest', ST_GeographyFromText('SRID=4326;POINT(-109 29)') );
    INSERT INTO global_points (name, location) VALUES ('London', ST_GeographyFromText('SRID=4326;POINT(0 49)') );

Creating an index works the same as GEOMETRY. PostGIS will note that the column type is GEOGRAPHY and create an appropriate sphere-based index instead of the usual planar index used for GEOMETRY.

    -- Index the test table with a spherical index
      CREATE INDEX global_points_gix ON global_points USING GIST ( location );

Query and measurement functions use units of meters. So distance parameters should be expressed in meters, and return values should be expected in meters (or square meters for areas).

    -- Show a distance query and note, London is outside the 1000km tolerance
      SELECT name FROM global_points WHERE ST_DWithin(location, ST_GeographyFromText('SRID=4326;POINT(-110 29)'), 1000000);

You can see the power of GEOGRAPHY in action by calculating the how close a plane flying from Seattle to London (LINESTRING(-122.33 47.606, 0.0 51.5)) comes to Reykjavik (POINT(-21.96 64.15)).

    -- Distance calculation using GEOGRAPHY (122.2km)
      SELECT ST_Distance('LINESTRING(-122.33 47.606, 0.0 51.5)'::geography, 'POINT(-21.96 64.15)':: geography);

    -- Distance calculation using GEOMETRY (13.3 "degrees")
      SELECT ST_Distance('LINESTRING(-122.33 47.606, 0.0 51.5)'::geometry, 'POINT(-21.96 64.15)':: geometry);

The GEOGRAPHY type calculates the true shortest distance over the sphere between Reykjavik and the great circle flight path between Seattle and London.

Great Circle mapper The GEOMETRY type calculates a meaningless cartesian distance between Reykjavik and the straight line path from Seattle to London plotted on a flat map of the world. The nominal units of the result might be called "degrees", but the result doesn't correspond to any true angular difference between the points, so even calling them "degrees" is inaccurate.

### 4.2.2. When to use Geography Data type over Geometry data type

The new GEOGRAPHY type allows you to store data in longitude/latitude coordinates, but at a cost: there are fewer functions defined on GEOGRAPHY than there are on GEOMETRY; those functions that are defined take more CPU time to execute.

The type you choose should be conditioned on the expected working area of the application you are building. Will your data span the globe or a large continental area, or is it local to a state, county or municipality?

- If your data is contained in a small area, you might find that choosing an appropriate projection and using GEOMETRY is the best solution, in terms of performance and functionality available.

- If your data is global or covers a continental region, you may find that GEOGRAPHY allows you to build a system without having to worry about projection details. You store your data in longitude/latitude, and use the functions that have been defined on GEOGRAPHY.

- If you don't understand projections, and you don't want to learn about them, and you're prepared to accept the limitations in functionality available in GEOGRAPHY, then it might be easier for you to use GEOGRAPHY than GEOMETRY. Simply load your data up as longitude/latitude and go from there.

Refer to Section 13.10, “PostGIS Function Support Matrix” for compare between what is supported for Geography vs. Geometry. For a brief listing and description of Geography functions, refer to Section 13.3, “PostGIS Geography Support Functions”

### 4.2.3. Geography Advanced FAQ

4.2.3.1. Do you calculate on the sphere or the spheroid?
4.2.3.2. What about the date-line and the poles?
4.2.3.3. What is the longest arc you can process?
4.2.3.4. Why is it so slow to calculate the area of Europe / Russia / insert big geographic region here ?

4.2.3.1. | Do you calculate on the sphere or the spheroid?
| By default, all distance and area calculations are done on the spheroid. You should find that the results of calculations in local areas match up will with local planar results in good local projections. Over larger areas, the spheroidal calculations will be more accurate than any calculation done on a projected plane. All the geography functions have the option of using a sphere calculation, by setting a final boolean parameter to 'FALSE'. This will somewhat speed up calculations, particularly for cases where the geometries are very simple.
4.2.3.2. | What about the date-line and the poles?
| All the calculations have no conception of date-line or poles, the coordinates are spherical (longitude/latitude) so a shape that crosses the dateline is, from a calculation point of view, no different from any other shape.
4.2.3.3. | What is the longest arc you can process?
| We use great circle arcs as the "interpolation line" between two points. That means any two points are actually joined up two ways, depending on which direction you travel along the great circle. All our code assumes that the points are joined by the *shorter* of the two paths along the great circle. As a consequence, shapes that have arcs of more than 180 degrees will not be correctly modelled.
4.2.3.4. | Why is it so slow to calculate the area of Europe / Russia / insert big geographic region here ?
| Because the polygon is so darned huge! Big areas are bad for two reasons: their bounds are huge, so the index tends to pull the feature no matter what query you run; the number of vertices is huge, and tests (distance, containment) have to traverse the vertex list at least once and sometimes N times (with N being the number of vertices in the other candidate feature). As with GEOMETRY, we recommend that when you have very large polygons, but are doing queries in small areas, you "denormalize" your geometric data into smaller chunks so that the index can effectively subquery parts of the object and so queries don't have to pull out the whole object every time. Just because you *can* store all of Europe in one polygon doesn't mean you *should*.

## 4.3. Using OpenGIS Standards

The OpenGIS "Simple Features Specification for SQL" defines standard GIS object types, the functions required to manipulate them, and a set of meta-data tables. In order to ensure that meta-data remain consistent, operations such as creating and removing a spatial column are carried out through special procedures defined by OpenGIS.

There are two OpenGIS meta-data tables: `SPATIAL_REF_SYS` and `GEOMETRY_COLUMNS`. The `SPATIAL_REF_SYS` table holds the numeric IDs and textual descriptions of coordinate systems used in the spatial database.

### 4.3.1. The SPATIAL_REF_SYS Table and Spatial Reference Systems

The spatial_ref_sys table is a PostGIS included and OGC compliant database table that lists over 3000 known spatial reference systems and details needed to transform/reproject between them.

Although the PostGIS spatial_ref_sys table contains over 3000 of the more commonly used spatial reference system definitions that can be handled by the proj library, it does not contain all known to man and you can even define your own custom projection if you are familiar with proj4 constructs. Keep in mind that most spatial reference systems are regional and have no meaning when used outside of the bounds they were intended for.

An excellent resource for finding spatial reference systems not defined in the core set is http://spatialreference.org/

Some of the more commonly used spatial reference systems are: 4326 - WGS 84 Long Lat, 4269 - NAD 83 Long Lat, 3395 - WGS 84 World Mercator, 2163 - US National Atlas Equal Area, Spatial reference systems for each NAD 83, WGS 84 UTM zone - UTM zones are one of the most ideal for measurement, but only cover 6-degree regions.

Various US state plane spatial reference systems (meter or feet based) - usually one or 2 exists per US state. Most of the meter ones are in the core set, but many of the feet based ones or ESRI created ones you will need to pull from spatialreference.org.

For details on determining which UTM zone to use for your area of interest, check out the utmzone PostGIS plpgsql helper function.

The `SPATIAL_REF_SYS` table definition is as follows:

    CREATE TABLE spatial_ref_sys (
      srid       INTEGER NOT NULL PRIMARY KEY,
      auth_name  VARCHAR(256),
      auth_srid  INTEGER,
      srtext     VARCHAR(2048),
      proj4text  VARCHAR(2048)
    )

The `SPATIAL_REF_SYS` columns are as follows:

SRID

  An integer value that uniquely identifies the Spatial Referencing System (SRS) within the database.

AUTH_NAME

  The name of the standard or standards body that is being cited for this reference system. For example, "EPSG" would be a valid `AUTH_NAME`.

AUTH_SRID

  The ID of the Spatial Reference System as defined by the Authority cited in the `AUTH_NAME`. In the case of EPSG, this is where the EPSG projection code would go.

SRTEXT

  The Well-Known Text representation of the Spatial Reference System. An example of a WKT SRS representation is:

      PROJCS["NAD83 / UTM Zone 10N",
        GEOGCS["NAD83",
      	DATUM["North_American_Datum_1983",
      	  SPHEROID["GRS 1980",6378137,298.257222101]
      	],
      	PRIMEM["Greenwich",0],
      	UNIT["degree",0.0174532925199433]
        ],
        PROJECTION["Transverse_Mercator"],
        PARAMETER["latitude_of_origin",0],
        PARAMETER["central_meridian",-123],
        PARAMETER["scale_factor",0.9996],
        PARAMETER["false_easting",500000],
        PARAMETER["false_northing",0],
        UNIT["metre",1]
      ]

  For a listing of EPSG projection codes and their corresponding WKT representations, see http://www.opengeospatial.org/. For a discussion of WKT in general, see the OpenGIS "Coordinate Transformation Services Implementation Specification" at http://www.opengeospatial.org/standards. For information on the European Petroleum Survey Group (EPSG) and their database of spatial reference systems, see http://www.epsg.org.

PROJ4TEXT

  PostGIS uses the Proj4 library to provide coordinate transformation capabilities. The `PROJ4TEXT` column contains the Proj4 coordinate definition string for a particular SRID. For example:

      +proj=utm +zone=10 +ellps=clrk66 +datum=NAD27 +units=m

  For more information about, see the Proj4 web site at http://trac.osgeo.org/proj/. The `spatial_ref_sys.sql` file contains both `SRTEXT` and `PROJ4TEXT` definitions for all EPSG projections.

### 4.3.2. The GEOMETRY_COLUMNS VIEW

In versions of PostGIS prior to 2.0.0, geometry_columns was a table that could be directly edited, and sometimes got out of synch with the actual definition of the geometry columns. In PostGIS 2.0.0, `GEOMETRY_COLUMNS` became a view with the same front-facing structure as prior versions, but reading from database system catalogs Its structure is as follows:

    \d geometry_columns

                 View "public.geometry_columns"
          Column       |          Type          | Modifiers
    -------------------+------------------------+-----------
     f_table_catalog   | character varying(256) |
     f_table_schema    | character varying(256) |
     f_table_name      | character varying(256) |
     f_geometry_column | character varying(256) |
     coord_dimension   | integer                |
     srid              | integer                |
     type              | character varying(30)  |

The column meanings have not changed from prior versions and are:

F_TABLE_CATALOG, F_TABLE_SCHEMA, F_TABLE_NAME

  The fully qualified name of the feature table containing the geometry column. Note that the terms "catalog" and "schema" are Oracle-ish. There is not PostgreSQL analogue of "catalog" so that column is left blank -- for "schema" the PostgreSQL schema name is used (`public` is the default).

F_GEOMETRY_COLUMN

  The name of the geometry column in the feature table.

COORD_DIMENSION

  The spatial dimension (2, 3 or 4 dimensional) of the column.

SRID

  The ID of the spatial reference system used for the coordinate geometry in this table. It is a foreign key reference to the `SPATIAL_REF_SYS`.

TYPE

  The type of the spatial object. To restrict the spatial column to a single type, use one of: POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, GEOMETRYCOLLECTION or corresponding XYM versions POINTM, LINESTRINGM, POLYGONM, MULTIPOINTM, MULTILINESTRINGM, MULTIPOLYGONM, GEOMETRYCOLLECTIONM. For heterogeneous (mixed-type) collections, you can use "GEOMETRY" as the type.

  This attribute is (probably) not part of the OpenGIS specification, but is required for ensuring type homogeneity.

### 4.3.3. Creating a Spatial Table

Creating a table with spatial data, can be done in one step. As shown in the following example which creates a roads table with a 2D linestring geometry column in WGS84 long lat

    CREATE TABLE ROADS ( ID int4
    	  	, ROAD_NAME varchar(25), geom geometry(LINESTRING,4326) );

We can add additional columns using standard ALTER TABLE command as we do in this next example where we add a 3-D linestring.

    ALTER TABLE roads ADD COLUMN geom2 geometry(LINESTRINGZ,4326);

For backwards compability, you can still create a spatial table in two stages using the management functions.

- Create a normal non-spatial table.

  For example: CREATE TABLE ROADS ( ID int4, ROAD_NAME varchar(25) )

- Add a spatial column to the table using the OpenGIS "AddGeometryColumn" function. Refer to AddGeometryColumn for more details.

  The syntax is:

      AddGeometryColumn(
        <schema_name>,
        <table_name>,
        <column_name>,
        <srid>,
        <type>,
        <dimension>
      )

  Or, using current schema:

      AddGeometryColumn(
        <table_name>,
        <column_name>,
        <srid>,
        <type>,
        <dimension>
      )

  Example1: SELECT AddGeometryColumn('public', 'roads', 'geom', 423, 'LINESTRING', 2)

  Example2: SELECT AddGeometryColumn( 'roads', 'geom', 423, 'LINESTRING', 2)

Here is an example of SQL used to create a table and add a spatial column (assuming that an SRID of 128 exists already):

    CREATE TABLE parks (
      park_id    INTEGER,
      park_name  VARCHAR,
      park_date  DATE,
      park_type  VARCHAR
    );
    SELECT AddGeometryColumn('parks', 'park_geom', 128, 'MULTIPOLYGON', 2 );

Here is another example, using the generic "geometry" type and the undefined SRID value of 0:

    CREATE TABLE roads (
      road_id INTEGER,
      road_name VARCHAR
    );
    SELECT AddGeometryColumn( 'roads', 'roads_geom', 0, 'GEOMETRY', 3 );

### 4.3.4. Manually Registering Geometry Columns in geometry_columns

The AddGeometryColumn() approach creates a geometry column and also registers the new column in the geometry_columns table. If your software utilizes geometry_columns, then any geometry columns you need to query by must be registered in this view. Starting with PoastGIS 2.0, geometry_columns is no longer editable and all geometry columns are autoregistered.

However they may be registered as a generic geometry column if the column was not defined as a specific type during creation.

Two of the cases where this may happen, but you can't use AddGeometryColumn, is in the case of SQL Views and bulk inserts. For these cases, you can correct the registration in the geometry_columns table by constraining the column. Note in PostGIS 2.0+ if your column is typmod based, the creation process would register it correctly, so no need to do anything.

    --Lets say you have a view created like this
    CREATE VIEW  public.vwmytablemercator AS
    	SELECT gid, ST_Transform(geom,3395) As geom, f_name
    	FROM public.mytable;

    -- For it to register correctly in PostGIS 2.0+
    -- You need to cast the geometry
    --
    DROP VIEW public.vwmytablemercator;
    CREATE VIEW  public.vwmytablemercator AS
    	SELECT gid, ST_Transform(geom,3395)::geometry(3395) As geom, f_name
    	FROM public.mytable;

    -- If you know the geometry type for sure is a 2D POLYGON then you could do
    DROP VIEW public.vwmytablemercator;
    CREATE VIEW  public.vwmytablemercator AS
    	SELECT gid, ST_Transform(geom,3395)::geometry(Polygon, 3395) As geom, f_name
    	FROM public.mytable;

    --Lets say you created a derivative table by doing a bulk insert
    SELECT poi.gid, poi.geom, citybounds.city_name
    INTO myschema.my_special_pois
    FROM poi INNER JOIN citybounds ON ST_Intersects(citybounds.geom, poi.geom);

    --Create 2d index on new table
    CREATE INDEX idx_myschema_myspecialpois_geom_gist
      ON myschema.my_special_pois USING gist(geom);

    -- If your points are 3D points or 3M points,
    -- then you might want to create an nd index instead of a 2d index
    -- like so
    CREATE INDEX my_special_pois_geom_gist_nd
    	ON my_special_pois USING gist(geom gist_geometry_ops_nd);

    --To manually register this new table's geometry column in geometry_columns
    -- Note that this approach will work for both PostGIS 2.0+ and PostGIS 1.4+
    -- For PostGIS 2.0 it will also change the underlying structure of the table to
    -- to make the column typmod based.
    -- For PostGIS prior to 2.0, this technique can also be used to register views
    SELECT populate_geometry_columns('myschema.my_special_pois'::regclass);

    --If you are using PostGIS 2.0 and for whatever reason, you
    -- you need the old constraint based definition behavior
    -- (such as case of inherited tables where all children do not have the same type and srid)
    -- set new optional  use_typmod argument to false
    SELECT populate_geometry_columns('myschema.my_special_pois'::regclass, false);

Although the old-constraint based method is still supported, a constraint-based geomentry column used directly in a view, will not register correctly in geometry_columns, as will a typmod one. In this example we define a column using typmod and another using constraints.

    CREATE TABLE pois_ny(gid SERIAL PRIMARY KEY
       , poi_name text, cat varchar(20)
       , geom geometry(POINT,4326) );
    SELECT AddGeometryColumn('pois_ny', 'geom_2160', 2160, 'POINT', 2, false);

If we run in psql

    \d pois_ny;

We observe they are defined differently -- one is typmod, one is constraint

                                      Table "public.pois_ny"
      Column   |         Type          |                       Modifiers

    -----------+-----------------------+------------------------------------------------------
     gid       | integer               | not null default nextval('pois_ny_gid_seq'::regclass)
     poi_name  | text                  |
     cat       | character varying(20) |
     geom      | geometry(Point,4326)  |
     geom_2160 | geometry              |
    Indexes:
        "pois_ny_pkey" PRIMARY KEY, btree (gid)
    Check constraints:
        "enforce_dims_geom_2160" CHECK (st_ndims(geom_2160) = 2)
        "enforce_geotype_geom_2160" CHECK (geometrytype(geom_2160) = 'POINT'::text
            OR geom_2160 IS NULL)
        "enforce_srid_geom_2160" CHECK (st_srid(geom_2160) = 2160)

In geometry_columns, they both register correctly

    SELECT f_table_name, f_geometry_column, srid, type
    	FROM geometry_columns
    	WHERE f_table_name = 'pois_ny';

    f_table_name | f_geometry_column | srid | type
    -------------+-------------------+------+-------
    pois_ny      | geom              | 4326 | POINT
    pois_ny      | geom_2160         | 2160 | POINT

However -- if we were to create a view like this

    CREATE VIEW vw_pois_ny_parks AS
    SELECT *
      FROM pois_ny
      WHERE cat='park';

    SELECT f_table_name, f_geometry_column, srid, type
    	FROM geometry_columns
    	WHERE f_table_name = 'vw_pois_ny_parks';

The typmod based geom view column registers correctly, but the constraint based one does not.

       f_table_name   | f_geometry_column | srid |   type
    ------------------+-------------------+------+----------
     vw_pois_ny_parks | geom              | 4326 | POINT
     vw_pois_ny_parks | geom_2160         |    0 | GEOMETRY

This may change in future versions of PostGIS, but for now To force the constraint based view column to register correctly, we need to do this:

    DROP VIEW vw_pois_ny_parks;
    CREATE VIEW vw_pois_ny_parks AS
    SELECT gid, poi_name, cat
      , geom
      , geom_2160::geometry(POINT,2160) As geom_2160
      FROM pois_ny
      WHERE cat='park';
    SELECT f_table_name, f_geometry_column, srid, type
    	FROM geometry_columns
    	WHERE f_table_name = 'vw_pois_ny_parks';

       f_table_name   | f_geometry_column | srid | type
    ------------------+-------------------+------+-------
     vw_pois_ny_parks | geom              | 4326 | POINT
     vw_pois_ny_parks | geom_2160         | 2160 | POINT

### 4.3.5. Ensuring OpenGIS compliancy of geometries

PostGIS is compliant with the Open Geospatial Consortium’s (OGC) OpenGIS Specifications. As such, many PostGIS methods require, or more accurately, assume that geometries that are operated on are both simple and valid. For example, it does not make sense to calculate the area of a polygon that has a hole defined outside of the polygon, or to construct a polygon from a non-simple boundary line.

According to the OGC Specifications, a simple geometry is one that has no anomalous geometric points, such as self intersection or self tangency and primarily refers to 0 or 1-dimensional geometries (i.e. `[MULTI]POINT, [MULTI]LINESTRING`). Geometry validity, on the other hand, primarily refers to 2-dimensional geometries (i.e. `[MULTI]POLYGON)` and defines the set of assertions that characterizes a valid polygon. The description of each geometric class includes specific conditions that further detail geometric simplicity and validity.

A `POINT` is inheritably simple as a 0-dimensional geometry object.

`MULTIPOINT`s are simple if no two coordinates (`POINT`s) are equal (have identical coordinate values).

A `LINESTRING` is simple if it does not pass through the same `POINT` twice (except for the endpoints, in which case it is referred to as a linear ring and additionally considered closed).

(a) | (b)
(c) | (d)

(a) and (c) are simple `LINESTRING`s, (b) and (d) are not.

A `MULTILINESTRING` is simple only if all of its elements are simple and the only intersection between any two elements occurs at `POINT`s that are on the boundaries of both elements.

(e) | (f) | (g)

(e) and (f) are simple `MULTILINESTRING`s, (g) is not.

By definition, a `POLYGON` is always simple. It is valid if no two rings in the boundary (made up of an exterior ring and interior rings) cross. The boundary of a `POLYGON` may intersect at a `POINT` but only as a tangent (i.e. not on a line). A `POLYGON` may not have cut lines or spikes and the interior rings must be contained entirely within the exterior ring.

(h) | (i) | (j)
(k) | (l) | (m)

(h) and (i) are valid `POLYGON`s, (j-m) cannot be represented as single `POLYGON`s, but (j) and (m) could be represented as a valid `MULTIPOLYGON`.

A `MULTIPOLYGON` is valid if and only if all of its elements are valid and the interiors of no two elements intersect. The boundaries of any two elements may touch, but only at a finite number of `POINT`s.

(n) | (o) | (p)

(n) and (o) are not valid `MULTIPOLYGON`s. (p), however, is valid.

Most of the functions implemented by the GEOS library rely on the assumption that your geometries are valid as specified by the OpenGIS Simple Feature Specification. To check simplicity or validity of geometries you can use the ST_IsSimple() and ST_IsValid()

    -- Typically, it doesn't make sense to check
    -- for validity on linear features since it will always return TRUE.
    -- But in this example, PostGIS extends the definition of the OGC IsValid
    -- by returning false if a LineString has less than 2 *distinct* vertices.
    gisdb=# SELECT
       ST_IsValid('LINESTRING(0 0, 1 1)'),
       ST_IsValid('LINESTRING(0 0, 0 0, 0 0)');

     st_isvalid | st_isvalid
    ------------+-----------
          t     |     f

By default, PostGIS does not apply this validity check on geometry input, because testing for validity needs lots of CPU time for complex geometries, especially polygons. If you do not trust your data sources, you can manually enforce such a check to your tables by adding a check constraint:

    ALTER TABLE mytable
      ADD CONSTRAINT geometry_valid_check
    	CHECK (ST_IsValid(the_geom));

If you encounter any strange error messages such as "GEOS Intersection() threw an error!" or "JTS Intersection() threw an error!" when calling PostGIS functions with valid input geometries, you likely found an error in either PostGIS or one of the libraries it uses, and you should contact the PostGIS developers. The same is true if a PostGIS function returns an invalid geometry for valid input.

Strictly compliant OGC geometries cannot have Z or M values. The ST_IsValid() function won't consider higher dimensioned geometries invalid! Invocations of AddGeometryColumn() will add a constraint checking geometry dimensions, so it is enough to specify 2 there.

### 4.3.6. Dimensionally Extended 9 Intersection Model (DE-9IM)

It is sometimes the case that the typical spatial predicates (ST_Contains, ST_Crosses, ST_Intersects, ST_Touches, ...) are insufficient in and of themselves to adequately provide that desired spatial filter.

For example, consider a linear dataset representing a road network. It may be the task of a GIS analyst to identify all road segments that cross each other, not at a point, but on a line, perhaps invalidating some business rule. In this case, ST_Crosses does not adequately provide the necessary spatial filter since, for linear features, it returns `true` only where they cross at a point. One two-step solution might be to first perform the actual intersection (ST_Intersection) of pairs of road segments that spatially intersect (ST_Intersects), and then compare the intersection's ST_GeometryType with '`LINESTRING`' (properly dealing with cases that return `GEOMETRYCOLLECTION`s of `[MULTI]POINT`s, `[MULTI]LINESTRING`s, etc.). A more elegant / faster solution may indeed be desirable.

A second [theoretical] example may be that of a GIS analyst trying to locate all wharfs or docks that intersect a lake's boundary on a line and where only one end of the wharf is up on shore. In other words, where a wharf is within, but not completely within a lake, intersecting the boundary of a lake on a line, and where the wharf's endpoints are both completely within and on the boundary of the lake. The analyst may need to use a combination of spatial predicates to isolate the sought after features: ST_Contains(lake, wharf) = TRUE ST_ContainsProperly(lake, wharf) = FALSE ST_GeometryType(ST_Intersection(wharf, lake)) = 'LINESTRING' ST_NumGeometries(ST_Multi(ST_Intersection(ST_Boundary(wharf), ST_Boundary(lake)))) = 1 ... (needless to say, this could get quite complicated)

So enters the Dimensionally Extended 9 Intersection Model, or DE-9IM for short.

#### 4.3.6.1. Theory

According to the OpenGIS Simple Features Implementation Specification for SQL, "the basic approach to comparing two geometries is to make pair-wise tests of the intersections between the Interiors, Boundaries and Exteriors of the two geometries and to classify the relationship between the two geometries based on the entries in the resulting 'intersection' matrix."

Boundary

  The boundary of a geometry is the set of geometries of the next lower dimension. For `POINT`s, which have a dimension of 0, the boundary is the empty set. The boundary of a `LINESTRING` are the two endpoints. For `POLYGON`s, the boundary is the linework that make up the exterior and interior rings.

Interior

  The interior of a geometry are those points of a geometry that are left when the boundary is removed. For `POINT`s, the interior is the `POINT` itself. The interior of a `LINESTRING` are the set of real points between the endpoints. For `POLYGON`s, the interior is the areal surface inside the polygon.

Exterior

  The exterior of a geometry is the universe, an areal surface, not on the interior or boundary of the geometry.

Given geometry a, where the I(a), B(a), and E(a) are the Interior, Boundary, and Exterior of a, the mathematical representation of the matrix is:

| Interior | Boundary | Exterior
--- | --- | --- | ---
Interior | <mml:math> <mml:mrow> <mml:mtext>dim( I(a)</mml:mtext> <mml:mo>∩</mml:mo> <mml:mtext>I(b) )</mml:mtext> </mml:mrow> </mml:math> | <mml:math> <mml:mrow> <mml:mtext>dim( I(a)</mml:mtext> <mml:mo>∩</mml:mo> <mml:mtext>B(b) )</mml:mtext> </mml:mrow> </mml:math> | <mml:math> <mml:mrow> <mml:mtext>dim( I(a)</mml:mtext> <mml:mo>∩</mml:mo> <mml:mtext>E(b) )</mml:mtext> </mml:mrow> </mml:math>
Boundary | <mml:math> <mml:mrow> <mml:mtext>dim( B(a)</mml:mtext> <mml:mo>∩</mml:mo> <mml:mtext>I(b) )</mml:mtext> </mml:mrow> </mml:math> | <mml:math> <mml:mrow> <mml:mtext>dim( B(a)</mml:mtext> <mml:mo>∩</mml:mo> <mml:mtext>B(b) )</mml:mtext> </mml:mrow> </mml:math> | <mml:math> <mml:mrow> <mml:mtext>dim( B(a)</mml:mtext> <mml:mo>∩</mml:mo> <mml:mtext>E(b) )</mml:mtext> </mml:mrow> </mml:math>
Exterior | <mml:math> <mml:mrow> <mml:mtext>dim( E(a)</mml:mtext> <mml:mo>∩</mml:mo> <mml:mtext>I(b) )</mml:mtext> </mml:mrow> </mml:math> | <mml:math> <mml:mrow> <mml:mtext>dim( E(a)</mml:mtext> <mml:mo>∩</mml:mo> <mml:mtext>B(b) )</mml:mtext> </mml:mrow> </mml:math> | <mml:math> <mml:mrow> <mml:mtext>dim( E(a)</mml:mtext> <mml:mo>∩</mml:mo> <mml:mtext>E(b) )</mml:mtext> </mml:mrow> </mml:math>

Where dim(a) is the dimension of a as specified by ST_Dimension but has the domain of `{0,1,2,T,F,*}`

- `0` => point

- `1` => line

- `2` => area

- `T` => `{0,1,2}`

- `F` => empty set

- `*` => don't care

Visually, for two overlapping polygonal geometries, this looks like:

| Interior | Boundary | Exterior
--- | --- | --- | ---
Interior | dim(...) = 2 | dim(...) = 1 | dim(...) = 2
Boundary | dim(...) = 1 | dim(...) = 0 | dim(...) = 1
Exterior | dim(...) = 2 | dim(...) = 1 | dim(...) = 2

Read from left to right and from top to bottom, the dimensional matrix is represented, '212101212'.

A relate matrix that would therefore represent our first example of two lines that intersect on a line would be: '1*1***1**'

    -- Identify road segments that cross on a line
    SELECT a.id
    FROM roads a, roads b
    WHERE a.id != b.id
    AND a.geom && b.geom
    AND ST_Relate(a.geom, b.geom, '1*1***1**');

A relate matrix that represents the second example of wharfs partly on the lake's shoreline would be '102101FF2'

    -- Identify wharfs partly on a lake's shoreline
    SELECT a.lake_id, b.wharf_id
    FROM lakes a, wharfs b
    WHERE a.geom && b.geom
    AND ST_Relate(a.geom, b.geom, '102101FF2');

For more information or reading, see:

- OpenGIS Simple Features Implementation Specification for SQL (version 1.1, section 2.1.13.2)

- Dimensionally Extended Nine-Intersection Model (DE-9IM) by Christian Strobl

- GeoTools: Point Set Theory and the DE-9IM Matrix

- Encyclopedia of GIS By Hui Xiong

## 4.4. Loading GIS Data

Once you have created a spatial table, you are ready to upload GIS data to the database. Currently, there are two ways to get data into a PostGIS/PostgreSQL database: using formatted SQL statements or using the Shape file loader/dumper.

### 4.4.1. Using SQL

If you can convert your data to a text representation, then using formatted SQL might be the easiest way to get your data into PostGIS. As with Oracle and other SQL databases, data can be bulk loaded by piping a large text file full of SQL "INSERT" statements into the SQL terminal monitor.

A data upload file (`roads.sql` for example) might look like this:

    BEGIN;
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (1,ST_GeomFromText('LINESTRING(191232 243118,191108 243242)',-1),'Jeff Rd');
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (2,ST_GeomFromText('LINESTRING(189141 244158,189265 244817)',-1),'Geordie Rd');
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (3,ST_GeomFromText('LINESTRING(192783 228138,192612 229814)',-1),'Paul St');
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (4,ST_GeomFromText('LINESTRING(189412 252431,189631 259122)',-1),'Graeme Ave');
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (5,ST_GeomFromText('LINESTRING(190131 224148,190871 228134)',-1),'Phil Tce');
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (6,ST_GeomFromText('LINESTRING(198231 263418,198213 268322)',-1),'Dave Cres');
    COMMIT;

The data file can be piped into PostgreSQL very easily using the "psql" SQL terminal monitor:

    psql -d [database] -f roads.sql

### 4.4.2. Using the Loader

The `shp2pgsql` data loader converts ESRI Shape files into SQL suitable for insertion into a PostGIS/PostgreSQL database either in geometry or geography format. The loader has several operating modes distinguished by command line flags:

In addition to the shp2pgsql command-line loader, there is an `shp2pgsql-gui` graphical interface with most of the options as the command-line loader, but may be easier to use for one-off non-scripted loading or if you are new to PostGIS. It can also be configured as a plugin to PgAdminIII.

(c|a|d|p) These are mutually exclusive options:

  -c

    Creates a new table and populates it from the shapefile. This is the default mode.

  -a

    Appends data from the Shape file into the database table. Note that to use this option to load multiple files, the files must have the same attributes and same data types.

  -d

    Drops the database table before creating a new table with the data in the Shape file.

  -p

    Only produces the table creation SQL code, without adding any actual data. This can be used if you need to completely separate the table creation and data loading steps.

-?

  Display help screen.

-D

  Use the PostgreSQL "dump" format for the output data. This can be combined with -a, -c and -d. It is much faster to load than the default "insert" SQL format. Use this for very large data sets.

-s [<FROM_SRID%gt;:]<SRID>

  Creates and populates the geometry tables with the specified SRID. Optionally specifies that the input shapefile uses the given FROM_SRID, in which case the geometries will be reprojected to the target SRID. FROM_SRID cannot be specified with -D.

-k

  Keep identifiers' case (column, schema and attributes). Note that attributes in Shapefile are all UPPERCASE.

-i

  Coerce all integers to standard 32-bit integers, do not create 64-bit bigints, even if the DBF header signature appears to warrant it.

-I

  Create a GiST index on the geometry column.

-S

  Generate simple geometries instead of MULTI geometries. Will only succeed if all the geometries are actually single (I.E. a MULTIPOLYGON with a single shell, or or a MULTIPOINT with a single vertex).

-t <dimensionality>

  Force the output geometry to have the specified dimensionality. Use the following strings to indicate the dimensionality: 2D, 3DZ, 3DM, 4D.

  If the input has fewer dimensions that specified, the output will have those dimensions filled in with zeroes. If the input has more dimensions that specified, the unwanted dimensions will be stripped.

-w

  Output WKT format, instead of WKB. Note that this can introduce coordinate drifts due to loss of precision.

-e

  Execute each statement on its own, without using a transaction. This allows loading of the majority of good data when there are some bad geometries that generate errors. Note that this cannot be used with the -D flag as the "dump" format always uses a transaction.

-W <encoding>

  Specify encoding of the input data (dbf file). When used, all attributes of the dbf are converted from the specified encoding to UTF8. The resulting SQL output will contain a `SET CLIENT_ENCODING to UTF8` command, so that the backend will be able to reconvert from UTF8 to whatever encoding the database is configured to use internally.

-N <policy>

  NULL geometries handling policy (insert*,skip,abort)

-n

  -n Only import DBF file. If your data has no corresponding shapefile, it will automatically switch to this mode and load just the dbf. So setting this flag is only needed if you have a full shapefile set, and you only want the attribute data and no geometry.

-G

  Use geography type instead of geometry (requires lon/lat data) in WGS84 long lat (SRID=4326)

-T <tablespace>

  Specify the tablespace for the new table. Indexes will still use the default tablespace unless the -X parameter is also used. The PostgreSQL documentation has a good description on when to use custom tablespaces.

-X <tablespace>

  Specify the tablespace for the new table's indexes. This applies to the primary key index, and the GIST spatial index if -I is also used.

An example session using the loader to create an input file and uploading it might look like this:

    # shp2pgsql -c -D -s 4269 -i -I shaperoads.shp myschema.roadstable > roads.sql
    # psql -d roadsdb -f roads.sql

A conversion and upload can be done all in one step using UNIX pipes:

    # shp2pgsql shaperoads.shp myschema.roadstable | psql -d roadsdb

## 4.5. Retrieving GIS Data

Data can be extracted from the database using either SQL or the Shape file loader/dumper. In the section on SQL we will discuss some of the operators available to do comparisons and queries on spatial tables.

### 4.5.1. Using SQL

The most straightforward means of pulling data out of the database is to use a SQL select query to reduce the number of RECORDS and COLUMNS returned and dump the resulting columns into a parsable text file:

    db=# SELECT road_id, ST_AsText(road_geom) AS geom, road_name FROM roads;

    road_id | geom                                    | road_name
    --------+-----------------------------------------+-----------
    	  1 | LINESTRING(191232 243118,191108 243242) | Jeff Rd
    	  2 | LINESTRING(189141 244158,189265 244817) | Geordie Rd
    	  3 | LINESTRING(192783 228138,192612 229814) | Paul St
    	  4 | LINESTRING(189412 252431,189631 259122) | Graeme Ave
    	  5 | LINESTRING(190131 224148,190871 228134) | Phil Tce
    	  6 | LINESTRING(198231 263418,198213 268322) | Dave Cres
    	  7 | LINESTRING(218421 284121,224123 241231) | Chris Way
    (6 rows)

However, there will be times when some kind of restriction is necessary to cut down the number of fields returned. In the case of attribute-based restrictions, just use the same SQL syntax as normal with a non-spatial table. In the case of spatial restrictions, the following operators are available/useful:

&&

  This operator tells whether the bounding box of one geometry intersects the bounding box of another.

ST_OrderingEquals

  This tests whether two geometries are geometrically identical. For example, if 'POLYGON((0 0,1 1,1 0,0 0))' is the same as 'POLYGON((0 0,1 1,1 0,0 0))' (it is).

=

  This operator is a little more naive, it only tests whether the bounding boxes of two geometries are the same.

Next, you can use these operators in queries. Note that when specifying geometries and boxes on the SQL command line, you must explicitly turn the string representations into geometries by using the "ST_GeomFromText()" function. The 312 is a fictitious spatial reference system that matches our data. So, for example:

    SELECT road_id, road_name
      FROM roads
      WHERE ST_OrderingEquals(roads_geom , ST_GeomFromText('LINESTRING(191232 243118,191108 243242)',312) ) ;

The above query would return the single record from the "ROADS_GEOM" table in which the geometry was equal to that value.

When using the "&&" operator, you can specify either a BOX3D as the comparison feature or a GEOMETRY. When you specify a GEOMETRY, however, its bounding box will be used for the comparison.

    SELECT road_id, road_name
    FROM roads
    WHERE roads_geom && ST_GeomFromText('POLYGON((...))',312);

The above query will use the bounding box of the polygon for comparison purposes.

The most common spatial query will probably be a "frame-based" query, used by client software, like data browsers and web mappers, to grab a "map frame" worth of data for display. Using a "BOX3D" object for the frame, such a query looks like this:

    SELECT ST_AsText(roads_geom) AS geom
    FROM roads
    WHERE
      roads_geom && ST_MakeEnvelope(191232, 243117,191232, 243119,312);

Note the use of the SRID 312, to specify the projection of the envelope.

### 4.5.2. Using the Dumper

The `pgsql2shp` table dumper connects directly to the database and converts a table (possibly defined by a query) into a shape file. The basic syntax is:

    pgsql2shp [<options>] <database> [<schema>.]<table>

    pgsql2shp [<options>] <database> <query>

The commandline options are:

-f <filename>

  Write the output to a particular filename.

-h <host>

  The database host to connect to.

-p <port>

  The port to connect to on the database host.

-P <password>

  The password to use when connecting to the database.

-u <user>

  The username to use when connecting to the database.

-g <geometry column>

  In the case of tables with multiple geometry columns, the geometry column to use when writing the shape file.

-b

  Use a binary cursor. This will make the operation faster, but will not work if any NON-geometry attribute in the table lacks a cast to text.

-r

  Raw mode. Do not drop the `gid` field, or escape column names.

-d

  For backward compatibility: write a 3-dimensional shape file when dumping from old (pre-1.0.0) postgis databases (the default is to write a 2-dimensional shape file in that case). Starting from postgis-1.0.0+, dimensions are fully encoded.

-m `filename`

  Remap identifiers to ten character names. The content of the file is lines of two symbols separated by a single white space and no trailing or leading space: VERYLONGSYMBOL SHORTONE ANOTHERVERYLONGSYMBOL SHORTER etc.

## 4.6. Building Indexes

Indexes are what make using a spatial database for large data sets possible. Without indexing, any search for a feature would require a "sequential scan" of every record in the database. Indexing speeds up searching by organizing the data into a search tree which can be quickly traversed to find a particular record. PostgreSQL supports three kinds of indexes by default: B-Tree indexes, R-Tree indexes, and GiST indexes.

- B-Trees are used for data which can be sorted along one axis; for example, numbers, letters, dates. GIS data cannot be rationally sorted along one axis (which is greater, (0,0) or (0,1) or (1,0)?) so B-Tree indexing is of no use for us.

- R-Trees break up data into rectangles, and sub-rectangles, and sub-sub rectangles, etc. R-Trees are used by some spatial databases to index GIS data, but the PostgreSQL R-Tree implementation is not as robust as the GiST implementation.

- GiST (Generalized Search Trees) indexes break up data into "things to one side", "things which overlap", "things which are inside" and can be used on a wide range of data-types, including GIS data. PostGIS uses an R-Tree index implemented on top of GiST to index GIS data.

### 4.6.1. GiST Indexes

GiST stands for "Generalized Search Tree" and is a generic form of indexing. In addition to GIS indexing, GiST is used to speed up searches on all kinds of irregular data structures (integer arrays, spectral data, etc) which are not amenable to normal B-Tree indexing.

Once a GIS data table exceeds a few thousand rows, you will want to build an index to speed up spatial searches of the data (unless all your searches are based on attributes, in which case you'll want to build a normal index on the attribute fields).

The syntax for building a GiST index on a "geometry" column is as follows:

    CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometryfield] );

The above syntax will always build a 2D-index. To get the an n-dimensional index supported in PostGIS 2.0+ for the geometry type, you can create one using this syntax

    CREATE INDEX [indexname] ON [tablename] USING GIST ([geometryfield] gist_geometry_ops_nd);

Building a spatial index is a computationally intensive exercise: on tables of around 1 million rows, on a 300MHz Solaris machine, we have found building a GiST index takes about 1 hour. After building an index, it is important to force PostgreSQL to collect table statistics, which are used to optimize query plans:

    VACUUM ANALYZE [table_name] [(column_name)];
    -- This is only needed for PostgreSQL 7.4 installations and below
    SELECT UPDATE_GEOMETRY_STATS([table_name], [column_name]);

GiST indexes have two advantages over R-Tree indexes in PostgreSQL. Firstly, GiST indexes are "null safe", meaning they can index columns which include null values. Secondly, GiST indexes support the concept of "lossiness" which is important when dealing with GIS objects larger than the PostgreSQL 8K page size. Lossiness allows PostgreSQL to store only the "important" part of an object in an index -- in the case of GIS objects, just the bounding box. GIS objects larger than 8K will cause R-Tree indexes to fail in the process of being built.

### 4.6.2. Using Indexes

Ordinarily, indexes invisibly speed up data access: once the index is built, the query planner transparently decides when to use index information to speed up a query plan. Unfortunately, the PostgreSQL query planner does not optimize the use of GiST indexes well, so sometimes searches which should use a spatial index instead default to a sequence scan of the whole table.

If you find your spatial indexes are not being used (or your attribute indexes, for that matter) there are a couple things you can do:

- Firstly, make sure statistics are gathered about the number and distributions of values in a table, to provide the query planner with better information to make decisions around index usage. For PostgreSQL 7.4 installations and below this is done by running update_geometry_stats([table_name, column_name]) (compute distribution) and VACUUM ANALYZE [table_name] [column_name] (compute number of values). Starting with PostgreSQL 8.0 running VACUUM ANALYZE will do both operations. You should regularly vacuum your databases anyways -- many PostgreSQL DBAs have VACUUM run as an off-peak cron job on a regular basis.

- If vacuuming does not work, you can force the planner to use the index information by using the SET ENABLE_SEQSCAN=OFF command. You should only use this command sparingly, and only on spatially indexed queries: generally speaking, the planner knows better than you do about when to use normal B-Tree indexes. Once you have run your query, you should consider setting `ENABLE_SEQSCAN` back on, so that other queries will utilize the planner as normal.

  As of version 0.6, it should not be necessary to force the planner to use the index with `ENABLE_SEQSCAN`.

- If you find the planner wrong about the cost of sequential vs index scans try reducing the value of random_page_cost in postgresql.conf or using SET random_page_cost=#. Default value for the parameter is 4, try setting it to 1 or 2. Decrementing the value makes the planner more inclined of using Index scans.

## 4.7. Complex Queries

The raison d'etre of spatial database functionality is performing queries inside the database which would ordinarily require desktop GIS functionality. Using PostGIS effectively requires knowing what spatial functions are available, and ensuring that appropriate indexes are in place to provide good performance. The SRID of 312 used in these examples is purely for demonstration. You should be using a REAL SRID listed in the the spatial_ref_sys table and one that matches the projection of your data. If your data has no spatial reference system specified, you should be THINKING very thoughtfully why it doesn't and maybe it should. If your reason is because you are modeling something that doesn't have a geographic spatial reference system defined such as the internals of a molecule or a good location on Mars to transport the human race in the event of a nuclear holocaust, then simply leave out the SRID or make one up and insert it in the `spatial_ref_sys` table.

### 4.7.1. Taking Advantage of Indexes

When constructing a query it is important to remember that only the bounding-box-based operators such as && can take advantage of the GiST spatial index. Functions such as `ST_Distance()` cannot use the index to optimize their operation. For example, the following query would be quite slow on a large table:

    SELECT the_geom
    FROM geom_table
    WHERE ST_Distance(the_geom, ST_GeomFromText('POINT(100000 200000)', 312)) < 100

This query is selecting all the geometries in geom_table which are within 100 units of the point (100000, 200000). It will be slow because it is calculating the distance between each point in the table and our specified point, ie. one `ST_Distance()` calculation for each row in the table. We can avoid this by using the && operator to reduce the number of distance calculations required:

    SELECT the_geom
    FROM geom_table
    WHERE ST_DWithin(the_geom,  ST_MakeEnvelope(90900, 190900, 100100, 200100,312), 100)

This query selects the same geometries, but it does it in a more efficient way. Assuming there is a GiST index on the_geom, the query planner will recognize that it can use the index to reduce the number of rows before calculating the result of the `ST_distance()` function. Notice that the `ST_MakeEnvelope` geometry which is used in the && operation is a 200 unit square box centered on the original point - this is our "query box". The && operator uses the index to quickly reduce the result set down to only those geometries which have bounding boxes that overlap the "query box". Assuming that our query box is much smaller than the extents of the entire geometry table, this will drastically reduce the number of distance calculations that need to be done.

| Change in Behavior
As of PostGIS 1.3.0, most of the Geometry Relationship Functions, with the notable exceptions of ST_Disjoint and ST_Relate, include implicit bounding box overlap operators.

### 4.7.2. Examples of Spatial SQL

The examples in this section will make use of two tables, a table of linear roads, and a table of polygonal municipality boundaries. The table definitions for the `bc_roads` table is:

    Column      | Type              | Description
    ------------+-------------------+-------------------
    gid         | integer           | Unique ID
    name        | character varying | Road Name
    the_geom    | geometry          | Location Geometry (Linestring)

The table definition for the `bc_municipality` table is:

    Column     | Type              | Description
    -----------+-------------------+-------------------
    gid        | integer           | Unique ID
    code       | integer           | Unique ID
    name       | character varying | City / Town Name
    the_geom   | geometry          | Location Geometry (Polygon)

4.7.2.1. What is the total length of all roads, expressed in kilometers?
4.7.2.2. How large is the city of Prince George, in hectares?
4.7.2.3. What is the largest municipality in the province, by area?
4.7.2.4. What is the length of roads fully contained within each municipality?
4.7.2.5. Create a new table with all the roads within the city of Prince George.
4.7.2.6. What is the length in kilometers of "Douglas St" in Victoria?
4.7.2.7. What is the largest municipality polygon that has a hole?

4.7.2.1. | What is the total length of all roads, expressed in kilometers?
| You can answer this question with a very simple piece of SQL:
    SELECT sum(ST_Length(the_geom))/1000 AS km_roads FROM bc_roads;

    km_roads
    ------------------
    70842.1243039643
    (1 row)
4.7.2.2. | How large is the city of Prince George, in hectares?
| This query combines an attribute condition (on the municipality name) with a spatial calculation (of the area):
    SELECT
      ST_Area(the_geom)/10000 AS hectares
    FROM bc_municipality
    WHERE name = 'PRINCE GEORGE';

    hectares
    ------------------
    32657.9103824927
    (1 row)
4.7.2.3. | What is the largest municipality in the province, by area?
| This query brings a spatial measurement into the query condition. There are several ways of approaching this problem, but the most efficient is below:
    SELECT
      name,
      ST_Area(the_geom)/10000 AS hectares
    FROM
      bc_municipality
    ORDER BY hectares DESC
    LIMIT 1;

    name           | hectares
    ---------------+-----------------
    TUMBLER RIDGE  | 155020.02556131
    (1 row)
Note that in order to answer this query we have to calculate the area of every polygon. If we were doing this a lot it would make sense to add an area column to the table that we could separately index for performance. By ordering the results in a descending direction, and them using the PostgreSQL "LIMIT" command we can easily pick off the largest value without using an aggregate function like max().
4.7.2.4. | What is the length of roads fully contained within each municipality?
| This is an example of a "spatial join", because we are bringing together data from two tables (doing a join) but using a spatial interaction condition ("contained") as the join condition rather than the usual relational approach of joining on a common key:
    SELECT
      m.name,
      sum(ST_Length(r.the_geom))/1000 as roads_km
    FROM
      bc_roads AS r,
      bc_municipality AS m
    WHERE
      ST_Contains(m.the_geom,r.the_geom)
    GROUP BY m.name
    ORDER BY roads_km;

    name                        | roads_km
    ----------------------------+------------------
    SURREY                      | 1539.47553551242
    VANCOUVER                   | 1450.33093486576
    LANGLEY DISTRICT            | 833.793392535662
    BURNABY                     | 773.769091404338
    PRINCE GEORGE               | 694.37554369147
    ...
This query takes a while, because every road in the table is summarized into the final result (about 250K roads for our particular example table). For smaller overlays (several thousand records on several hundred) the response can be very fast.
4.7.2.5. | Create a new table with all the roads within the city of Prince George.
| This is an example of an "overlay", which takes in two tables and outputs a new table that consists of spatially clipped or cut resultants. Unlike the "spatial join" demonstrated above, this query actually creates new geometries. An overlay is like a turbo-charged spatial join, and is useful for more exact analysis work:
    CREATE TABLE pg_roads as
    SELECT
      ST_Intersection(r.the_geom, m.the_geom) AS intersection_geom,
      ST_Length(r.the_geom) AS rd_orig_length,
      r.*
    FROM
      bc_roads AS r,
      bc_municipality AS m
    WHERE  m.name = 'PRINCE GEORGE' AND ST_Intersects(r.the_geom, m.the_geom);
4.7.2.6. | What is the length in kilometers of "Douglas St" in Victoria?
    SELECT
      sum(ST_Length(r.the_geom))/1000 AS kilometers
    FROM
      bc_roads r,
      bc_municipality m
    WHERE  r.name = 'Douglas St' AND m.name = 'VICTORIA'
    	AND ST_Contains(m.the_geom, r.the_geom) ;

    kilometers
    ------------------
    4.89151904172838
    (1 row)
4.7.2.7. | What is the largest municipality polygon that has a hole?
    SELECT gid, name, ST_Area(the_geom) AS area
    FROM bc_municipality
    WHERE ST_NRings(the_geom) > 1
    ORDER BY area DESC LIMIT 1;

    gid  | name         | area
    -----+--------------+------------------
    12   | SPALLUMCHEEN | 257374619.430216
    (1 row)

## Chapter 5. Raster Data Management, Queries, and Applications

## 5.1. Loading and Creating Rasters

For most use cases, you will create PostGIS rasters by loading existing raster files using the packaged `raster2pgsql` raster loader.

### 5.1.1. Using raster2pgsql to load rasters

The `raster2pgsql` is a raster loader executable that loads GDAL supported raster formats into sql suitable for loading into a PostGIS raster table. It is capable of loading folders of raster files as well as creating overviews of rasters.

Since the raster2pgsql is compiled as part of PostGIS most often (unless you compile your own GDAL library), the raster types supported by the executable will be the same as those compiled in the GDAL dependency library. To get a list of raster types your particular raster2pgsql supports use the `-G` switch. These should be the same as those provided by your PostGIS install documented here ST_GDALDrivers if you are using the same gdal library for both.

The older version of this tool was a python script. The executable has replaced the python script. If you still find the need for the Python script Examples of the python one can be found at GDAL PostGIS Raster Driver Usage. Please note that the raster2pgsql python script may not work with future versions of PostGIS raster and is no longer supported.

When creating overviews of a specific factor from a set of rasters that are aligned, it is possible for the overviews to not align. Visit http://trac.osgeo.org/postgis/ticket/1764 for an example where the overviews do not align.

EXAMPLE USAGE:

    raster2pgsql raster_options_go_here raster_file someschema.sometable > out.sql

-?

  Display help screen. Help will also display if you don't pass in any arguments.

-G

  Print the supported raster formats.

(c|a|d) These are mutually exclusive options:

  -c

    Create new table and populate it with raster(s), this is the default mode

  -a

    Append raster(s) to an existing table.

  -d

    Drop table, create new one and populate it with raster(s)

Raster processing: Applying constraints for proper registering in raster catalogs

  -C

    Apply raster constraints -- srid, pixelsize etc. to ensure raster is properly registered in `raster_columns` view.

  -x

    Disable setting the max extent constraint. Only applied if -C flag is also used.

  -r

    Set the regular blocking constraint. Only applied if -C flag is also used.

Raster processing: Optional parameters used to manipulate input raster dataset

  -s <SRID>

    Assign output raster with specified SRID.

  -b BAND

    Index (1-based) of band to extract from raster. For more than one band index, separate with comma (,). If unspecified, all bands of raster will be extracted.

  -t TILE_SIZE

    Cut raster into tiles to be inserted one per table row. `TILE_SIZE` is expressed as WIDTHxHEIGHT.

  -R, --register

    Register the raster as a filesystem (out-db) raster.

    Only the metadata of the raster and path location to the raster is stored in the database (not the pixels).

  -l `OVERVIEW_FACTOR`

    -l `overview factor` Create overview of the raster. For more than one factor, separate with comma(,). Overview table name follows the pattern o_`overview factor`_`table`. Created overview is stored in the database and is not affected by -R. Note that your generated sql file will contain both the main table and overview tables.

Optional parameters used to manipulate database objects

  -q

    Wrap PostgreSQL identifiers in quotes

  -f COLUMN

    Specify name of destination raster column, default is 'rast'

  -F

    Add a column with the name of the file

  -I

    Create a GiST index on the raster column.

  -M

    Vacuum analyze the raster table.

  -T `tablespace`

    Specify the tablespace for the new table. Note that indices (including the primary key) will still use the default tablespace unless the -X flag is also used.

  -Y

    Use copy statements instead of insert statements.

-e

  Execute each statement individually, do not use a transaction.

-E ENDIAN

  Control endianness of generated binary output of raster; specify 0 for XDR and 1 for NDR (default); only NDR output is supported now

-V `version`

  Specify version of output format. Default is 0. Only 0 is supported at this time.

An example session using the loader to create an input file and uploading it chunked in 100x100 tiles might look like this:

You can leave the schema name out e.g `demelevation` instead of `public.demelevation` and the raster table will be created in the default schema of the database or user

    raster2pgsql -s 4236 -I -C -M *.tif -F -t 100x100 public.demelevation > elev.sql
    psql -d gisdb -f elev.sql

A conversion and upload can be done all in one step using UNIX pipes:

    raster2pgsql -s 4236 -I -C -M *.tif -F -t 100x100 public.demelevation | psql -d gisdb

Load rasters Massachusetts state plane meters aerial tiles into a schema called `aerial` and create a full view, 2 and 4 level overview tables, use copy mode for inserting (no intermediary file just straight to db), and -e don't force everything in a transaction (good if you want to see data in tables right away without waiting). Break up the rasters into 128x128 pixel tiles and apply raster constraints. Use copy mode instead of table insert. (-F) Include a field called filename to hold the name of the file the tiles were cut from.

    raster2pgsql -I -C -e -Y -F -s 26986 -t 128x128  -l 2,4 bostonaerials2008/*.jpg aerials.boston | psql -U postgres -d gisdb -h localhost -p 5432

    --get a list of raster types supported:
    raster2pgsql -G

The -G commands outputs a list something like

    Available GDAL raster formats:
      Virtual Raster
      GeoTIFF
      National Imagery Transmission Format
      Raster Product Format TOC format
      ECRG TOC format
      Erdas Imagine Images (.img)
      CEOS SAR Image
      CEOS Image
      JAXA PALSAR Product Reader (Level 1.1/1.5)
      Ground-based SAR Applications Testbed File Format (.gff)
      ELAS
      Arc/Info Binary Grid
      Arc/Info ASCII Grid
      GRASS ASCII Grid
      SDTS Raster
      DTED Elevation Raster
      Portable Network Graphics
      JPEG JFIF
      In Memory Raster
      Japanese DEM (.mem)
      Graphics Interchange Format (.gif)
      Graphics Interchange Format (.gif)
      Envisat Image Format
      Maptech BSB Nautical Charts
      X11 PixMap Format
      MS Windows Device Independent Bitmap
      SPOT DIMAP
      AirSAR Polarimetric Image
      RadarSat 2 XML Product
      PCIDSK Database File
      PCRaster Raster File
      ILWIS Raster Map
      SGI Image File Format 1.0
      SRTMHGT File Format
      Leveller heightfield
      Terragen heightfield
      USGS Astrogeology ISIS cube (Version 3)
      USGS Astrogeology ISIS cube (Version 2)
      NASA Planetary Data System
      EarthWatch .TIL
      ERMapper .ers Labelled
      NOAA Polar Orbiter Level 1b Data Set
      FIT Image
      GRIdded Binary (.grb)
      Raster Matrix Format
      EUMETSAT Archive native (.nat)
      Idrisi Raster A.1
      Intergraph Raster
      Golden Software ASCII Grid (.grd)
      Golden Software Binary Grid (.grd)
      Golden Software 7 Binary Grid (.grd)
      COSAR Annotated Binary Matrix (TerraSAR-X)
      TerraSAR-X Product
      DRDC COASP SAR Processor Raster
      R Object Data Store
      Portable Pixmap Format (netpbm)
      USGS DOQ (Old Style)
      USGS DOQ (New Style)
      ENVI .hdr Labelled
      ESRI .hdr Labelled
      Generic Binary (.hdr Labelled)
      PCI .aux Labelled
      Vexcel MFF Raster
      Vexcel MFF2 (HKV) Raster
      Fuji BAS Scanner Image
      GSC Geogrid
      EOSAT FAST Format
      VTP .bt (Binary Terrain) 1.3 Format
      Erdas .LAN/.GIS
      Convair PolGASP
      Image Data and Analysis
      NLAPS Data Format
      Erdas Imagine Raw
      DIPEx
      FARSITE v.4 Landscape File (.lcp)
      NOAA Vertical Datum .GTX
      NADCON .los/.las Datum Grid Shift
      NTv2 Datum Grid Shift
      ACE2
      Snow Data Assimilation System
      Swedish Grid RIK (.rik)
      USGS Optional ASCII DEM (and CDED)
      GeoSoft Grid Exchange Format
      Northwood Numeric Grid Format .grd/.tab
      Northwood Classified Grid Format .grc/.tab
      ARC Digitized Raster Graphics
      Standard Raster Product (ASRP/USRP)
      Magellan topo (.blx)
      SAGA GIS Binary Grid (.sdat)
      Kml Super Overlay
      ASCII Gridded XYZ
      HF2/HFZ heightfield raster
      OziExplorer Image File
      USGS LULC Composite Theme Grid
      Arc/Info Export E00 GRID
      ZMap Plus Grid
      NOAA NGS Geoid Height Grids

### 5.1.2. Creating rasters using PostGIS raster functions

On many occasions, you'll want to create rasters and raster tables right in the database. There are a plethora of functions to do that. The general steps to follow.

1. Create a table with a raster column to hold the new raster records which can be accomplished with:

       CREATE TABLE myrasters(rid serial primary key, rast raster);

2. There are many functions to help with that goal. If you are creating rasters not as a derivative of other rasters, you will want to start with: ST_MakeEmptyRaster, followed by ST_AddBand

   You can also create rasters from geometries. To achieve that you'll want to use ST_AsRaster perhaps accompanied with other functions such as ST_Union or ST_MapAlgebraFct or any of the family of other map algebra functions.

   There are even many more options for creating new raster tables from existing tables. For example you can create a raster table in a different projection from an existing one using ST_Transform

3. Once you are done populating your table initially, you'll want to create a spatial index on the raster column with something like:

       CREATE INDEX myrasters_rast_st_convexhull_idx ON myrasters USING gist( ST_ConvexHull(rast) );

   Note the use of ST_ConvexHull since most raster operators are based on the convex hull of the rasters.

   Pre-2.0 versions of PostGIS raster were based on the envelop rather than the convex hull. For teh spatial idnexes to work properly you'll need to drop those and replace with convex hull based index.

4. Apply raster constraints using AddRasterConstraints

## 5.2. Raster Catalogs

There are two raster catalog views that come packaged with PostGIS. Both views utilize information embedded in the constraints of the raster tables. As a result the catalog views are always consistent with the raster data in the tables since the constraints are enforced.

1. `raster_columns` this view catalogs all the raster table columns in your database.

2. `raster_overviews` this view catalogs all the raster table columns in your database that serve as overviews for a finer grained table. Tables of this type are generated when you use the `-l` switch during load.

### 5.2.1. Raster Columns Catalog

The `raster_columns` is a catalog of all raster table columns in your database that are of type raster. It is a view utilizing the constraints on the tables so the information is always consistent even if you restore one raster table from a backup of another database. The following columns exist in the `raster_columns` catalog.

If you created your tables not with the loader or forgot to specify the `-C` flag during load, you can enforce the constraints after the fact using AddRasterConstraints so that the `raster_columns` catalog registers the common information about your raster tiles.

- `r_table_catalog` The database the table is in. This will always read the current database.

- `r_table_schema` The database schema the raster table belongs to.

- `r_table_name` raster table

- `r_raster_column` the column in the `r_table_name` table that is of type raster. There is nothing in PostGIS preventing you from having multiple raster columns per table so its possible to have a raster table listed multiple times with a different raster column for each.

- `srid` The spatial reference identifier of the raster. Should be an entry in the Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems”.

- `scale_x` The scaling between geometric spatial coordinates and pixel. This is only available if all tiles in the raster column have the same `scale_x` and this constraint is applied. Refer to ST_ScaleX for more details.

- `scale_y` The scaling between geometric spatial coordinates and pixel. This is only available if all tiles in the raster column have the same `scale_y` and the `scale_y` constraint is applied. Refer to ST_ScaleY for more details.

- `blocksize_x` The width (number of pixels across) of each raster tile . Refer to ST_Width for more details.

- `blocksize_y` The width (number of pixels down) of each raster tile . Refer to ST_Height for more details.

- `same_alignment` A boolean that is true if all the raster tiles have the same alignment . Refer to ST_SameAlignment for more details.

- `regular_blocking` This is a true/false constraint flag set on the table to denote that the tiles do not overlap, are of the same alignment, pixel size, srid etc. It is not really validated but just taken as a given so should be used for informational. In the future we plan to properly constrain this so that this inforamtion is guaranteed to be right when it returns `true`

- `num_bands` The number of bands in each tile of your raster set. This is the same information as what is provided by ST_NumBands

- `pixel_types` An array defining the pixel type for each band. You will have the same number of elements in this array as you have number of bands. The pixel_types are one of the following defined in ST_BandPixelType.

- `nodata_values` An array of double precision numbers denoting the `nodata_value` for each band. You will have the same number of elements in this array as you have number of bands. These numbers define the pixel value for each band that should be ignored for most operations. This is similar information provided by ST_BandNoDataValue.

- `extent` This is the extent of all the raster rows in your raster set. If you plan to load more data that will change the extent of the set, you'll want to run the DropRasterConstraints function before load and then reapply constraints with AddRasterConstraints after load.

### 5.2.2. Raster Overviews

`raster_overviews` catalogs information about raster table columns used for overviews and additional information about them that is useful to know when utilizing overviews. Overview tables are cataloged in both `raster_columns` and `raster_overviews` because they are rasters in their own right but also serve an additional special purpose of being a lower resolution caricature of a higher resolution table. These are generated along-side the main raster table when you use the `-l` switch in raster loading.

Overview tables contain the same constraints as other raster tables as well as additional informational only constraints specific to overviews.

The information in `raster_overviews` does not duplicate the information in `raster_columns`. If you need the information about an overview table present in `raster_columns` you can join the `raster_overviews` and `raster_columns` together to get the full set of information you need.

Two main reasons for overviews are:

1. Low resolution representation of the core tables commonly used for fast mapping zoom-out.

2. Computations are generally faster to do on them than their higher resolution parents because there are fewer records and each pixel covers more territory. Though the computations are not as accurate as the high-res tables they support, they can be sufficient in many rule-of-thumb computations.

The `raster_overviews` catalog contains the following columns of information.

- `o_table_catalog` The database the overview table is in. This will always read the current database.

- `o_table_schema` The database schema the overview raster table belongs to.

- `o_table_name` raster overview table name

- `o_raster_column` the raster column in the overview table.

- `r_table_catalog` The database the raster table that this overview services is in. This will always read the current database.

- `r_table_schema` The database schema the raster table that this overview services belongs to.

- `r_table_name` raster table that this overview services.

- `r_raster_column` the raster column that this overview column services.

- `overview_factor` - this is the pyramid level of the overview table. The higher the number the lower the resolution of the table. raster2pgsql if given a folder of images, will compute overview of each image file and load separately. Level 1 is assumed and always the original file. Level 2 is will have each tile represent 4 of the original. So for example if you have a folder of 5000x5000 pixel image files that you chose to chunk 125x125, for each image file your base table will have (5000*5000)/(125*125) records = 1600, your (l=2) `o_2` table will have ceiling(1600/Power(2,2)) = 400 rows, your (l=3) `o_3` will have ceiling(1600/Power(2,3) ) = 200 rows. If your pixels aren't divisible by the size of your tiles, you'll get some scrap tiles (tiles not completely filled). Note that each overview tile generated by raster2pgsql has the same number of pixels as its parent, but is of a lower resolution where each pixel of it represents (Power(2,overview_factor) pixels of the original).

## 5.3. Building Custom Applications with PostGIS Raster

The fact that PostGIS raster provides you with SQL functions to render rasters in known image formats gives you a lot of optoins for rendering them. For example you can use OpenOffice / LibreOffice for rendering as demonstrated in Rendering PostGIS Raster graphics with LibreOffice Base Reports. In addition you can use a wide variety of languages as demonstrated in this section.

### 5.3.1. PHP Example Outputting using ST_AsPNG in concert with other raster functions

In this section, we'll demonstrate how to use the PHP PostgreSQL driver and the ST_AsGDALRaster family of functions to output band 1,2,3 of a raster to a PHP request stream that can then be embedded in an img src html tag.

The sample query demonstrates how to combine a whole bunch of raster functions together to grab all tiles that intersect a particular wgs 84 bounding box and then unions with ST_Union the intersecting tiles together returning all bands, transforms to user specified projection using ST_Transform, and then outputs the results as a png using ST_AsPNG.

You would call the below using

    http://mywebserver/test_raster.php?srid=2249

to get the raster image in Massachusetts state plane feet.

    <?php
    /** contents of test_raster.php **/
    $conn_str ='dbname=mydb host=localhost port=5432 user=myuser password=mypwd';
    $dbconn = pg_connect($conn_str);
    header('Content-Type: image/png');
    /**If a particular projection was requested use it otherwise use mass state plane meters **/
    if (!empty( $_REQUEST['srid'] ) && is_numeric( $_REQUEST['srid']) ){
    		$input_srid = intval($_REQUEST['srid']);
    }
    else { $input_srid = 26986; }
    /** The set bytea_output may be needed for PostgreSQL 9.0+, but not for 8.4 **/
    $sql = "set bytea_output='escape';
    SELECT ST_AsPNG(ST_Transform(
    			ST_AddBand(ST_Union(rast,1), ARRAY[ST_Union(rast,2),ST_Union(rast,3)])
    				,$input_srid) ) As new_rast
     FROM aerials.boston
    	WHERE
    	 ST_Intersects(rast, ST_Transform(ST_MakeEnvelope(-71.1217, 42.227, -71.1210, 42.218,4326),26986) )";
    $result = pg_query($sql);
    $row = pg_fetch_row($result);
    pg_free_result($result);
    if ($row === false) return;
    echo pg_unescape_bytea($row[0]);
    ?>

### 5.3.2. ASP.NET C# Example Outputting using ST_AsPNG in concert with other raster functions

In this section, we'll demonstrate how to use Npgsql PostgreSQL .NET driver and the ST_AsGDALRaster family of functions to output band 1,2,3 of a raster to a PHP request stream that can then be embedded in an img src html tag.

You will need the npgsql .NET PostgreSQL driver for this exercise which you can get the latest of from http://npgsql.projects.postgresql.org/. Just download the latest and drop into your ASP.NET bin folder and you'll be good to go.

The sample query demonstrates how to combine a whole bunch of raster functions together to grab all tiles that intersect a particular wgs 84 bounding box and then unions with ST_Union the intersecting tiles together returning all bands, transforms to user specified projection using ST_Transform, and then outputs the results as a png using ST_AsPNG.

This is same example as Section 5.3.1, “PHP Example Outputting using ST_AsPNG in concert with other raster functions” except implemented in C#.

You would call the below using

    http://mywebserver/TestRaster.ashx?srid=2249

to get the raster image in Massachusetts state plane feet.

     -- web.config connection string section --
    <connectionStrings>
        <add name="DSN"
            connectionString="server=localhost;database=mydb;Port=5432;User Id=myuser;password=mypwd"/>
    </connectionStrings>

    // Code for TestRaster.ashx
    <%@ WebHandler Language="C#" Class="TestRaster" %>
    using System;
    using System.Data;
    using System.Web;
    using Npgsql;

    public class TestRaster : IHttpHandler
    {
    	public void ProcessRequest(HttpContext context)
    	{

    		context.Response.ContentType = "image/png";
    		context.Response.BinaryWrite(GetResults(context));

    	}

    	public bool IsReusable {
    		get { return false; }
    	}

    	public byte[] GetResults(HttpContext context)
    	{
    		byte[] result = null;
    		NpgsqlCommand command;
    		string sql = null;
    		int input_srid = 26986;
            try {
    		    using (NpgsqlConnection conn = new NpgsqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["DSN"].ConnectionString)) {
    			    conn.Open();

                    if (context.Request["srid"] != null)
                    {
                        input_srid = Convert.ToInt32(context.Request["srid"]);
                    }
                    sql = @"SELECT ST_AsPNG(
                                ST_Transform(
    			                ST_AddBand(
                                    ST_Union(rast,1), ARRAY[ST_Union(rast,2),ST_Union(rast,3)])
    				                    ,:input_srid) ) As new_rast
                            FROM aerials.boston
    	                        WHERE
    	                            ST_Intersects(rast,
                                        ST_Transform(ST_MakeEnvelope(-71.1217, 42.227, -71.1210, 42.218,4326),26986) )";
    			    command = new NpgsqlCommand(sql, conn);
                    command.Parameters.Add(new NpgsqlParameter("input_srid", input_srid));

    			    result = (byte[]) command.ExecuteScalar();
                    conn.Close();
    			}

    		}
            catch (Exception ex)
            {
                result = null;
                context.Response.Write(ex.Message.Trim());
            }
    		return result;
    	}
    }

### 5.3.3. Java console app that outputs raster query as Image file

This is a simple java console app that takes a query that returns one image and outputs to specified file.

You can download the latest PostgreSQL JDBC drivers from http://jdbc.postgresql.org/download.html

You can compile the following code using a command something like:

    set env CLASSPATH .:..\postgresql-9.0-801.jdbc4.jar
    javac SaveQueryImage.java
    jar cfm SaveQueryImage.jar Manifest.txt *.class

And call it from the command-line with something like

    java -jar SaveQueryImage.jar "SELECT ST_AsPNG(ST_AsRaster(ST_Buffer(ST_Point(1,5),10, 'quad_segs=2'),150, 150, '8BUI',100));" "test.png"

     -- Manifest.txt --
    Class-Path: postgresql-9.0-801.jdbc4.jar
    Main-Class: SaveQueryImage

    // Code for SaveQueryImage.java
    import java.sql.Connection;
    import java.sql.SQLException;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.io.*;

    public class SaveQueryImage {
      public static void main(String[] argv) {
          System.out.println("Checking if Driver is registered with DriverManager.");

          try {
            //java.sql.DriverManager.registerDriver (new org.postgresql.Driver());
            Class.forName("org.postgresql.Driver");
          }
          catch (ClassNotFoundException cnfe) {
            System.out.println("Couldn't find the driver!");
            cnfe.printStackTrace();
            System.exit(1);
          }

          Connection conn = null;

          try {
            conn = DriverManager.getConnection("jdbc:postgresql://localhost:5432/mydb","myuser", "mypwd");
            conn.setAutoCommit(false);

            PreparedStatement sGetImg = conn.prepareStatement(argv[0]);

            ResultSet rs = sGetImg.executeQuery();

    		FileOutputStream fout;
    		try
    		{
    			rs.next();
    			/** Output to file name requested by user **/
    			fout = new FileOutputStream(new File(argv[1]) );
    			fout.write(rs.getBytes(1));
    			fout.close();
    		}
    		catch(Exception e)
    		{
    			System.out.println("Can't create file");
    			e.printStackTrace();
    		}

            rs.close();
    		sGetImg.close();
            conn.close();
          }
          catch (SQLException se) {
            System.out.println("Couldn't connect: print out a stack trace and exit.");
            se.printStackTrace();
            System.exit(1);
          }
      }
    }

### 5.3.4. Use PLPython to dump out images via SQL

This is a plpython stored function that creates a file in the server directory for each record.

    //plpython postgresql stored proc.  Requires you have plpython installed
    CREATE OR REPLACE FUNCTION write_file (param_bytes bytea, param_filepath text)
    RETURNS text
    AS $$
    f = open(param_filepath, 'wb+')
    f.write(param_bytes)
    return param_filepath
    $$ LANGUAGE plpythonu;

    --write out 5 images to the PostgreSQL server in varying sizes
    -- note the postgresql daemon account needs to have write access to folder
    -- this echos back the file names created;
     SELECT write_file(ST_AsPNG(
    	ST_AsRaster(ST_Buffer(ST_Point(1,5),j*5, 'quad_segs=2'),150*j, 150*j, '8BUI',100)),
    	 'C:/temp/slices'|| j || '.png')
    	 FROM generate_series(1,5) As j;

         write_file
    ---------------------
     C:/temp/slices1.png
     C:/temp/slices2.png
     C:/temp/slices3.png
     C:/temp/slices4.png
     C:/temp/slices5.png

### 5.3.5. Outputting Rasters with PSQL

Sadly PSQL doesn't have easy to use built-in functionality for outputting binaries. This is a bit of a hack and based on one of the suggestions outlined in Clever Trick Challenge -- Outputting bytea with psql that piggy backs on PostgreSQL somewhat legacy large object support. To use first launch your psql commandline connected to your database.

Unlike the python approach, this approach creates the file on your local computer.

    SELECT oid, lowrite(lo_open(oid, 131072), png) As num_bytes
     FROM
     ( VALUES (lo_create(0),
       ST_AsPNG( (SELECT rast FROM aerials.boston WHERE rid=1) )
      ) ) As v(oid,png);
    -- you'll get an output something like --
       oid   | num_bytes
    ---------+-----------
     2630819 |     74860

    -- next note the oid and do this replacing the c:/test.png to file path location
    -- on your local computer
     \lo_export 2630819 'C:/temp/aerial_samp.png'

    -- this deletes the file from large object storage on db
    SELECT lo_unlink(2630819);

## Chapter 6. Using PostGIS Geometry: Building Applications

## 6.1. Using MapServer

The Minnesota MapServer is an internet web-mapping server which conforms to the OpenGIS Web Mapping Server specification.

- The MapServer homepage is at http://mapserver.org.

- The OpenGIS Web Map Specification is at http://www.opengeospatial.org/standards/wms.

### 6.1.1. Basic Usage

To use PostGIS with MapServer, you will need to know about how to configure MapServer, which is beyond the scope of this documentation. This section will cover specific PostGIS issues and configuration details.

To use PostGIS with MapServer, you will need:

- Version 0.6 or newer of PostGIS.

- Version 3.5 or newer of MapServer.

MapServer accesses PostGIS/PostgreSQL data like any other PostgreSQL client -- using the `libpq` interface. This means that MapServer can be installed on any machine with network access to the PostGIS server, and use PostGIS as a source of data. The faster the connection between the systems, the better.

1. Compile and install MapServer, with whatever options you desire, including the "--with-postgis" configuration option.

2. In your MapServer map file, add a PostGIS layer. For example:

       LAYER
         CONNECTIONTYPE postgis
         NAME "widehighways"
         # Connect to a remote spatial database
         CONNECTION "user=dbuser dbname=gisdatabase host=bigserver"
         PROCESSING "CLOSE_CONNECTION=DEFER"
         # Get the lines from the 'geom' column of the 'roads' table
         DATA "geom from roads using srid=4326 using unique gid"
         STATUS ON
         TYPE LINE
         # Of the lines in the extents, only render the wide highways
         FILTER "type = 'highway' and numlanes >= 4"
         CLASS
           # Make the superhighways brighter and 2 pixels wide
           EXPRESSION ([numlanes] >= 6)
           STYLE
             COLOR 255 22 22
             WIDTH 2
           END
         END
         CLASS
           # All the rest are darker and only 1 pixel wide
           EXPRESSION ([numlanes] < 6)
           STYLE
             COLOR 205 92 82
           END
         END
       END

   In the example above, the PostGIS-specific directives are as follows:

   CONNECTIONTYPE

     For PostGIS layers, this is always "postgis".

   CONNECTION

     The database connection is governed by the a 'connection string' which is a standard set of keys and values like this (with the default values in <>):

     user=<username> password=<password> dbname=<username> hostname=<server> port=<5432>

     An empty connection string is still valid, and any of the key/value pairs can be omitted. At a minimum you will generally supply the database name and username to connect with.

   DATA

     The form of this parameter is "<geocolumn> from <tablename> using srid=<srid> using unique <primary key>" where the column is the spatial column to be rendered to the map, the SRID is SRID used by the column and the primary key is the table primary key (or any other uniquely-valued column with an index).

     You can omit the "using srid" and "using unique" clauses and MapServer will automatically determine the correct values if possible, but at the cost of running a few extra queries on the server for each map draw.

   PROCESSING

     Putting in a CLOSE_CONNECTION=DEFER if you have multiple layers reuses existing connections instead of closing them. This improves speed. Refer to for MapServer PostGIS Performance Tips for a more detailed explanation.

   FILTER

     The filter must be a valid SQL string corresponding to the logic normally following the "WHERE" keyword in a SQL query. So, for example, to render only roads with 6 or more lanes, use a filter of "num_lanes >= 6".

3. In your spatial database, ensure you have spatial (GiST) indexes built for any the layers you will be drawing.

       CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometrycolumn] );

4. If you will be querying your layers using MapServer you will also need to use the "using unique" clause in your DATA statement.

   MapServer requires unique identifiers for each spatial record when doing queries, and the PostGIS module of MapServer uses the unique value you specify in order to provide these unique identifiers. Using the table primary key is the best practice.

### 6.1.2. Frequently Asked Questions

6.1.2.1. When I use an EXPRESSION in my map file, the condition never returns as true, even though I know the values exist in my table.
6.1.2.2. The FILTER I use for my Shape files is not working for my PostGIS table of the same data.
6.1.2.3. My PostGIS layer draws much slower than my Shape file layer, is this normal?
6.1.2.4. My PostGIS layer draws fine, but queries are really slow. What is wrong?
6.1.2.5. Can I use "geography" columns (new in PostGIS 1.5) as a source for MapServer layers?

6.1.2.1. | When I use an `EXPRESSION` in my map file, the condition never returns as true, even though I know the values exist in my table.
| Unlike shape files, PostGIS field names have to be referenced in EXPRESSIONS using lower case.
    EXPRESSION ([numlanes] >= 6)
6.1.2.2. | The FILTER I use for my Shape files is not working for my PostGIS table of the same data.
| Unlike shape files, filters for PostGIS layers use SQL syntax (they are appended to the SQL statement the PostGIS connector generates for drawing layers in MapServer).
    FILTER "type = 'highway' and numlanes >= 4"
6.1.2.3. | My PostGIS layer draws much slower than my Shape file layer, is this normal?
| In general, the more features you are drawing into a given map, the more likely it is that PostGIS will be slower than Shape files. For maps with relatively few features (100s), PostGIS will often be faster. For maps with high feature density (1000s), PostGIS will always be slower. If you are finding substantial draw performance problems, it is possible that you have not built a spatial index on your table.
    postgis# CREATE INDEX geotable_gix ON geotable USING GIST ( geocolumn );
    postgis# VACUUM ANALYZE;
6.1.2.4. | My PostGIS layer draws fine, but queries are really slow. What is wrong?
| For queries to be fast, you must have a unique key for your spatial table and you must have an index on that unique key. You can specify what unique key for mapserver to use with the `USING UNIQUE` clause in your `DATA` line:
    DATA "geom FROM geotable USING UNIQUE gid"
6.1.2.5. | Can I use "geography" columns (new in PostGIS 1.5) as a source for MapServer layers?
| Yes! MapServer understands geography columns as being the same as geometry columns, but always using an SRID of 4326. Just make sure to include a "using srid=4326" clause in your `DATA` statement. Everything else works exactly the same as with geometry.
    DATA "geog FROM geogtable USING SRID=4326 USING UNIQUE gid"

### 6.1.3. Advanced Usage

The `USING` pseudo-SQL clause is used to add some information to help mapserver understand the results of more complex queries. More specifically, when either a view or a subselect is used as the source table (the thing to the right of "FROM" in a `DATA` definition) it is more difficult for mapserver to automatically determine a unique identifier for each row and also the SRID for the table. The `USING` clause can provide mapserver with these two pieces of information as follows:

    DATA "geom FROM (
      SELECT
        table1.geom AS geom,
        table1.gid AS gid,
        table2.data AS data
      FROM table1
      LEFT JOIN table2
      ON table1.id = table2.id
    ) AS new_table USING UNIQUE gid USING SRID=4326"

USING UNIQUE <uniqueid>

  MapServer requires a unique id for each row in order to identify the row when doing map queries. Normally it identifies the primary key from the system tables. However, views and subselects don't automatically have an known unique column. If you want to use MapServer's query functionality, you need to ensure your view or subselect includes a uniquely valued column, and declare it with `USING UNIQUE`. For example, you could explicitly select nee of the table's primary key values for this purpose, or any other column which is guaranteed to be unique for the result set.

  "Querying a Map" is the action of clicking on a map to ask for information about the map features in that location. Don't confuse "map queries" with the SQL query in a `DATA` definition.

USING SRID=<srid>

  PostGIS needs to know which spatial referencing system is being used by the geometries in order to return the correct data back to MapServer. Normally it is possible to find this information in the "geometry_columns" table in the PostGIS database, however, this is not possible for tables which are created on the fly such as subselects and views. So the `USING SRID=` option allows the correct SRID to be specified in the `DATA` definition.

### 6.1.4. Examples

Lets start with a simple example and work our way up. Consider the following MapServer layer definition:

    LAYER
      CONNECTIONTYPE postgis
      NAME "roads"
      CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
      DATA "geom from roads"
      STATUS ON
      TYPE LINE
      CLASS
        STYLE
          COLOR 0 0 0
        END
      END
    END

This layer will display all the road geometries in the roads table as black lines.

Now lets say we want to show only the highways until we get zoomed in to at least a 1:100000 scale - the next two layers will achieve this effect:

    LAYER
      CONNECTIONTYPE postgis
      CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
      PROCESSING "CLOSE_CONNECTION=DEFER"
      DATA "geom from roads"
      MINSCALE 100000
      STATUS ON
      TYPE LINE
      FILTER "road_type = 'highway'"
      CLASS
        COLOR 0 0 0
      END
    END
    LAYER
      CONNECTIONTYPE postgis
      CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
      PROCESSING "CLOSE_CONNECTION=DEFER"
      DATA "geom from roads"
      MAXSCALE 100000
      STATUS ON
      TYPE LINE
      CLASSITEM road_type
      CLASS
        EXPRESSION "highway"
        STYLE
          WIDTH 2
          COLOR 255 0 0
        END
      END
      CLASS
        STYLE
          COLOR 0 0 0
        END
      END
    END

The first layer is used when the scale is greater than 1:100000, and displays only the roads of type "highway" as black lines. The `FILTER` option causes only roads of type "highway" to be displayed.

The second layer is used when the scale is less than 1:100000, and will display highways as double-thick red lines, and other roads as regular black lines.

So, we have done a couple of interesting things using only MapServer functionality, but our `DATA` SQL statement has remained simple. Suppose that the name of the road is stored in another table (for whatever reason) and we need to do a join to get it and label our roads.

    LAYER
      CONNECTIONTYPE postgis
      CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
      DATA "geom FROM (SELECT roads.gid AS gid, roads.geom AS geom,
            road_names.name as name FROM roads LEFT JOIN road_names ON
            roads.road_name_id = road_names.road_name_id)
            AS named_roads USING UNIQUE gid USING SRID=4326"
      MAXSCALE 20000
      STATUS ON
      TYPE ANNOTATION
      LABELITEM name
      CLASS
        LABEL
          ANGLE auto
          SIZE 8
          COLOR 0 192 0
          TYPE truetype
          FONT arial
        END
      END
    END

This annotation layer adds green labels to all the roads when the scale gets down to 1:20000 or less. It also demonstrates how to use an SQL join in a `DATA` definition.

## 6.2. Java Clients (JDBC)

Java clients can access PostGIS "geometry" objects in the PostgreSQL database either directly as text representations or using the JDBC extension objects bundled with PostGIS. In order to use the extension objects, the "postgis.jar" file must be in your CLASSPATH along with the "postgresql.jar" JDBC driver package.

    import java.sql.*;
    import java.util.*;
    import java.lang.*;
    import org.postgis.*;

    public class JavaGIS {

    public static void main(String[] args) {

      java.sql.Connection conn;

      try {
        /*
        * Load the JDBC driver and establish a connection.
        */
        Class.forName("org.postgresql.Driver");
        String url = "jdbc:postgresql://localhost:5432/database";
        conn = DriverManager.getConnection(url, "postgres", "");
        /*
        * Add the geometry types to the connection. Note that you
        * must cast the connection to the pgsql-specific connection
        * implementation before calling the addDataType() method.
        */
        ((org.postgresql.PGConnection)conn).addDataType("geometry",Class.forName("org.postgis.PGgeometry"));
        ((org.postgresql.PGConnection)conn).addDataType("box3d",Class.forName("org.postgis.PGbox3d"));
        /*
        * Create a statement and execute a select query.
        */
        Statement s = conn.createStatement();
        ResultSet r = s.executeQuery("select geom,id from geomtable");
        while( r.next() ) {
          /*
          * Retrieve the geometry as an object then cast it to the geometry type.
          * Print things out.
          */
          PGgeometry geom = (PGgeometry)r.getObject(1);
          int id = r.getInt(2);
          System.out.println("Row " + id + ":");
          System.out.println(geom.toString());
        }
        s.close();
        conn.close();
      }
    catch( Exception e ) {
      e.printStackTrace();
      }
    }
    }

The "PGgeometry" object is a wrapper object which contains a specific topological geometry object (subclasses of the abstract class "Geometry") depending on the type: Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon.

    PGgeometry geom = (PGgeometry)r.getObject(1);
    if( geom.getType() == Geometry.POLYGON ) {
      Polygon pl = (Polygon)geom.getGeometry();
      for( int r = 0; r < pl.numRings(); r++) {
        LinearRing rng = pl.getRing(r);
        System.out.println("Ring: " + r);
        for( int p = 0; p < rng.numPoints(); p++ ) {
          Point pt = rng.getPoint(p);
          System.out.println("Point: " + p);
          System.out.println(pt.toString());
        }
      }
    }

The JavaDoc for the extension objects provides a reference for the various data accessor functions in the geometric objects.

## 6.3. C Clients (libpq)

...

### 6.3.1. Text Cursors

...

### 6.3.2. Binary Cursors

...

## Chapter 7. Performance tips

## 7.1. Small tables of large geometries

### 7.1.1. Problem description

Current PostgreSQL versions (including 8.0) suffer from a query optimizer weakness regarding TOAST tables. TOAST tables are a kind of "extension room" used to store large (in the sense of data size) values that do not fit into normal data pages (like long texts, images or complex geometries with lots of vertices), see the PostgreSQL Documentation for TOAST for more information).

The problem appears if you happen to have a table with rather large geometries, but not too much rows of them (like a table containing the boundaries of all European countries in high resolution). Then the table itself is small, but it uses lots of TOAST space. In our example case, the table itself had about 80 rows and used only 3 data pages, but the TOAST table used 8225 pages.

Now issue a query where you use the geometry operator && to search for a bounding box that matches only very few of those rows. Now the query optimizer sees that the table has only 3 pages and 80 rows. He estimates that a sequential scan on such a small table is much faster than using an index. And so he decides to ignore the GIST index. Usually, this estimation is correct. But in our case, the && operator has to fetch every geometry from disk to compare the bounding boxes, thus reading all TOAST pages, too.

To see whether your suffer from this bug, use the "EXPLAIN ANALYZE" postgresql command. For more information and the technical details, you can read the thread on the postgres performance mailing list: http://archives.postgresql.org/pgsql-performance/2005-02/msg00030.php

### 7.1.2. Workarounds

The PostgreSQL people are trying to solve this issue by making the query estimation TOAST-aware. For now, here are two workarounds:

The first workaround is to force the query planner to use the index. Send "SET enable_seqscan TO off;" to the server before issuing the query. This basically forces the query planner to avoid sequential scans whenever possible. So it uses the GIST index as usual. But this flag has to be set on every connection, and it causes the query planner to make misestimations in other cases, so you should "SET enable_seqscan TO on;" after the query.

The second workaround is to make the sequential scan as fast as the query planner thinks. This can be achieved by creating an additional column that "caches" the bbox, and matching against this. In our example, the commands are like:

    SELECT AddGeometryColumn('myschema','mytable','bbox','4326','GEOMETRY','2');
    UPDATE mytable SET bbox = ST_Envelope(ST_Force_2d(the_geom));

Now change your query to use the && operator against bbox instead of geom_column, like:

    SELECT geom_column
    FROM mytable
    WHERE bbox && ST_SetSRID('BOX3D(0 0,1 1)'::box3d,4326);

Of course, if you change or add rows to mytable, you have to keep the bbox "in sync". The most transparent way to do this would be triggers, but you also can modify your application to keep the bbox column current or run the UPDATE query above after every modification.

## 7.2. CLUSTERing on geometry indices

For tables that are mostly read-only, and where a single index is used for the majority of queries, PostgreSQL offers the CLUSTER command. This command physically reorders all the data rows in the same order as the index criteria, yielding two performance advantages: First, for index range scans, the number of seeks on the data table is drastically reduced. Second, if your working set concentrates to some small intervals on the indices, you have a more efficient caching because the data rows are spread along fewer data pages. (Feel invited to read the CLUSTER command documentation from the PostgreSQL manual at this point.)

However, currently PostgreSQL does not allow clustering on PostGIS GIST indices because GIST indices simply ignores NULL values, you get an error message like:

    lwgeom=# CLUSTER my_geom_index ON my_table;
    ERROR: cannot cluster when index access method does not handle null values
    HINT: You may be able to work around this by marking column "the_geom" NOT NULL.

As the HINT message tells you, one can work around this deficiency by adding a "not null" constraint to the table:

    lwgeom=# ALTER TABLE my_table ALTER COLUMN the_geom SET not null;
    ALTER TABLE

Of course, this will not work if you in fact need NULL values in your geometry column. Additionally, you must use the above method to add the constraint, using a CHECK constraint like "ALTER TABLE blubb ADD CHECK (geometry is not null);" will not work.

## 7.3. Avoiding dimension conversion

Sometimes, you happen to have 3D or 4D data in your table, but always access it using OpenGIS compliant ST_AsText() or ST_AsBinary() functions that only output 2D geometries. They do this by internally calling the ST_Force_2d() function, which introduces a significant overhead for large geometries. To avoid this overhead, it may be feasible to pre-drop those additional dimensions once and forever:

    UPDATE mytable SET the_geom = ST_Force_2d(the_geom);
    VACUUM FULL ANALYZE mytable;

Note that if you added your geometry column using AddGeometryColumn() there'll be a constraint on geometry dimension. To bypass it you will need to drop the constraint. Remember to update the entry in the geometry_columns table and recreate the constraint afterwards.

In case of large tables, it may be wise to divide this UPDATE into smaller portions by constraining the UPDATE to a part of the table via a WHERE clause and your primary key or another feasible criteria, and running a simple "VACUUM;" between your UPDATEs. This drastically reduces the need for temporary disk space. Additionally, if you have mixed dimension geometries, restricting the UPDATE by "WHERE dimension(the_geom)>2" skips re-writing of geometries that already are in 2D.

## 7.4. Tuning your configuration

These tips are taken from Kevin Neufeld's presentation "Tips for the PostGIS Power User" at the FOSS4G 2007 conference. Depending on your use of PostGIS (for example, static data and complex analysis vs frequently updated data and lots of users) these changes can provide significant speedups to your queries.

For a more tips (and better formatting), the original presentation is at http://2007.foss4g.org/presentations/view.php?abstract_id=117.

### 7.4.1. Startup

These settings are configured in postgresql.conf:

checkpoint_segments

- Maximum number of log file segments between automatic WAL checkpoints (each segment is normally 16MB); default is 3

- Set to at least 10 or 30 for databases with heavy write activity, or more for large database loads. Another article on the topic worth reading Greg Smith: Checkpoint and Background writer

- Possibly store the xlog on a separate disk device

constraint_exclusion

- Default: off (prior to PostgreSQL 8.4 and for PostgreSQL 8.4+ is set to partition)

- This is generally used for table partitioning. If you are running PostgreSQL versions below 8.4, set to "on" to ensure the query planner will optimize as desired. As of PostgreSQL 8.4, the default for this is set to "partition" which is ideal for PostgreSQL 8.4 and above since it will force the planner to only analyze tables for constraint consideration if they are in an inherited hierarchy and not pay the planner penalty otherwise.

shared_buffers

- Default: ~32MB

- Set to about 1/3 to 3/4 of available RAM

### 7.4.2. Runtime

work_mem (the memory used for sort operations and complex queries)

- Default: 1MB

- Adjust up for large dbs, complex queries, lots of RAM

- Adjust down for many concurrent users or low RAM.

- If you have lots of RAM and few developers:

                          SET work_mem TO 1200000;

maintenance_work_mem (used for VACUUM, CREATE INDEX, etc.)

- Default: 16MB

- Generally too low - ties up I/O, locks objects while swapping memory

- Recommend 32MB to 256MB on production servers w/lots of RAM, but depends on the # of concurrent users. If you have lots of RAM and few developers:

                          SET maintainence_work_mem TO 1200000;

## Chapter 8. PostGIS Reference

The functions given below are the ones which a user of PostGIS is likely to need. There are other functions which are required support functions to the PostGIS objects which are not of use to a general user.

PostGIS has begun a transition from the existing naming convention to an SQL-MM-centric convention. As a result, most of the functions that you know and love have been renamed using the standard spatial type (ST) prefix. Previous functions are still available, though are not listed in this document where updated functions are equivalent. The non ST_ functions not listed in this documentation are deprecated and will be removed in a future release so STOP USING THEM.

## 8.1. PostgreSQL PostGIS Geometry/Geography/Box Types

Abstract

This section lists the PostgreSQL data types installed by PostGIS. Note we describe the casting behavior of these which is very important especially when designing your own functions.

A Cast is when one type is coerced into another type. PostgreSQL is unique from most databases in that it allows you to define casting behavior for custom types and the functions used for casting. A cast can be specified as automatic in which case, you do not have to do a CAST(myfoo As otherfootype) or myfoo::otherfootype if you are feeding it to a function that only works with otherfootype and there is an automatic cast in place for it.

The danger of relying on automatic cast behavior is when you have an overloaded function say one that takes a box2d and one that takes a box3d but no geometry. What happens is that both functions are equally good to use with geometry since geometry has an autocast for both -- so you end up with an ambiguous function error. To force PostgreSQL to choose, you do a CAST(mygeom As box3d) or mygeom::box3d.

At least as of PostgreSQL 8.3 - Everything can be CAST to text (presumably because of the magical unknown type), so no defined CASTS for that need to be present for you to CAST an object to text.

## Name

box2d — A box composed of x min, ymin, xmax, ymax. Often used to return the 2d enclosing box of a geometry.

## Description

box2d is a spatial data type used to represent the enclosing box of a geometry or set of geometries. ST_Extent in earlier versions prior to PostGIS 1.4 would return a box2d.

## Name

box3d — A box composed of x min, ymin, zmin, xmax, ymax, zmax. Often used to return the 3d extent of a geometry or collection of geometries.

## Description

box3d is a postgis spatial data type used to represent the enclosing box of a geometry or set of geometries. ST_3DExtent returns a box3d object.

## Casting Behavior

This section lists the automatic as well as explicit casts allowed for this data type

Cast To | Behavior
box | automatic
box2d | automatic
geometry | automatic

## Name

geometry — Planar spatial data type.

## Description

geometry is a fundamental postgis spatial data type used to represent a feature in the Euclidean coordinate system.

## Casting Behavior

This section lists the automatic as well as explicit casts allowed for this data type

Cast To | Behavior
box | automatic
box2d | automatic
box3d | automatic
bytea | automatic
geography | automatic
text | automatic

## See Also

Section 4.1, “GIS Objects”

## Name

geometry_dump — A spatial datatype with two fields - geom (holding a geometry object) and path[] (a 1-d array holding the position of the geometry within the dumped object.)

## Description

geometry_dump is a compound data type consisting of a geometry object referenced by the .geom field and path[] a 1-dimensional integer array (starting at 1 e.g. path[1] to get first element) array that defines the navigation path within the dumped geometry to find this element. It is used by the ST_Dump* family of functions as an output type to explode a more complex geometry into its constituent parts and location of parts.

## See Also

Section 13.5, “PostGIS Geometry / Geography / Raster Dump Functions”

## Name

geography — Ellipsoidal spatial data type.

## Description

geography is a spatial data type used to represent a feature in the round-earth coordinate system.

## Casting Behavior

This section lists the automatic as well as explicit casts allowed for this data type

Cast To | Behavior
geometry | explicit

## See Also

Section 13.3, “PostGIS Geography Support Functions”, Section 4.2, “PostGIS Geography Type”

## 8.2. Management Functions

## Name

AddGeometryColumn — Adds a geometry column to an existing table of attributes. By default uses type modifier to define rather than constraints. Pass in false for use_typmod to get old check constraint based behavior

## Synopsis

`text AddGeometryColumn(`varchar table_name, varchar column_name, integer srid, varchar type, integer dimension, boolean use_typmod=true`)`;

`text AddGeometryColumn(`varchar schema_name, varchar table_name, varchar column_name, integer srid, varchar type, integer dimension, boolean use_typmod=true`)`;

`text AddGeometryColumn(`varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name, integer srid, varchar type, integer dimension, boolean use_typmod=true`)`;

## Description

Adds a geometry column to an existing table of attributes. The `schema_name` is the name of the table schema. The `srid` must be an integer value reference to an entry in the SPATIAL_REF_SYS table. The `type` must be a string corresponding to the geometry type, eg, 'POLYGON' or 'MULTILINESTRING' . An error is thrown if the schemaname doesn't exist (or not visible in the current search_path) or the specified SRID, geometry type, or dimension is invalid.

Changed: 2.0.0 This function no longer updates geometry_columns since geometry_columns is a view that reads from system catalogs. It by default also does not create constraints, but instead uses the built in type modifier behavior of PostgreSQL. So for example building a wgs84 POINT column with this function is now equivalent to: `ALTER TABLE some_table ADD COLUMN geom geometry(Point,4326);` Changed: 2.0.0 If you require the old behavior of constraints use the default `use_typmod`, but set it to false.

Changed: 2.0.0 Views can no longer be manually registered in geometry_columns, however views built against geometry typmod tables geometries and used without wrapper functions will register themselves correctly because they inherit the typmod behavior of their parent table column. Views that use geometry functions that output other geometries will need to be cast to typmod geometries for these view geometry columns to be registered correctly in geometry_columns. Refer to Section 4.3.4, “Manually Registering Geometry Columns in geometry_columns”.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Enhanced: 2.0.0 use_typmod argument introduced. Defaults to creating typmod geometry column instead of constraint-based.

## Examples

    -- Create schema to hold data
    CREATE SCHEMA my_schema;
    -- Create a new simple PostgreSQL table
    CREATE TABLE my_schema.my_spatial_table (id serial);

    -- Describing the table shows a simple table with a single "id" column.
    postgis=# \d my_schema.my_spatial_table
    							 Table "my_schema.my_spatial_table"
     Column |  Type   |                                Modifiers
    --------+---------+-------------------------------------------------------------------------
     id     | integer | not null default nextval('my_schema.my_spatial_table_id_seq'::regclass)

    -- Add a spatial column to the table
    SELECT AddGeometryColumn ('my_schema','my_spatial_table','geom',4326,'POINT',2);

    -- Add a point using the old constraint based behavior
    SELECT AddGeometryColumn ('my_schema','my_spatial_table','geom_c',4326,'POINT',2, false);

    --Add a curvepolygon using old constraint behavior
    SELECT AddGeometryColumn ('my_schema','my_spatial_table','geomcp_c',4326,'CURVEPOLYGON',2, false);

    -- Describe the table again reveals the addition of a new geometry columns.
    \d my_schema.my_spatial_table
                                addgeometrycolumn
    -------------------------------------------------------------------------
     my_schema.my_spatial_table.geomcp_c SRID:4326 TYPE:CURVEPOLYGON DIMS:2
    (1 row)

                                        Table "my_schema.my_spatial_table"
      Column  |         Type         |                                Modifiers
    ----------+----------------------+-------------------------------------------------------------------------
     id       | integer              | not null default nextval('my_schema.my_spatial_table_id_seq'::regclass)
     geom     | geometry(Point,4326) |
     geom_c   | geometry             |
     geomcp_c | geometry             |
    Check constraints:
        "enforce_dims_geom_c" CHECK (st_ndims(geom_c) = 2)
        "enforce_dims_geomcp_c" CHECK (st_ndims(geomcp_c) = 2)
        "enforce_geotype_geom_c" CHECK (geometrytype(geom_c) = 'POINT'::text OR geom_c IS NULL)
        "enforce_geotype_geomcp_c" CHECK (geometrytype(geomcp_c) = 'CURVEPOLYGON'::text OR geomcp_c IS NULL)
        "enforce_srid_geom_c" CHECK (st_srid(geom_c) = 4326)
        "enforce_srid_geomcp_c" CHECK (st_srid(geomcp_c) = 4326)

    -- geometry_columns view also registers the new columns --
    SELECT f_geometry_column As col_name, type, srid, coord_dimension As ndims
        FROM geometry_columns
        WHERE f_table_name = 'my_spatial_table' AND f_table_schema = 'my_schema';

     col_name |     type     | srid | ndims
    ----------+--------------+------+-------
     geom     | Point        | 4326 |     2
     geom_c   | Point        | 4326 |     2
     geomcp_c | CurvePolygon | 4326 |     2

## See Also

DropGeometryColumn, DropGeometryTable, Section 4.3.2, “The GEOMETRY_COLUMNS VIEW”, Section 4.3.4, “Manually Registering Geometry Columns in geometry_columns”

## Name

DropGeometryColumn — Removes a geometry column from a spatial table.

## Synopsis

`text DropGeometryColumn(`varchar table_name, varchar column_name`)`;

`text DropGeometryColumn(`varchar schema_name, varchar table_name, varchar column_name`)`;

`text DropGeometryColumn(`varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name`)`;

## Description

Removes a geometry column from a spatial table. Note that schema_name will need to match the f_table_schema field of the table's row in the geometry_columns table.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Changed: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a view against the system catalogs, you can drop a geometry column like any other table column using `ALTER TABLE`

## Examples

    			SELECT DropGeometryColumn ('my_schema','my_spatial_table','geom');
    			----RESULT output ---
    			                  dropgeometrycolumn
    ------------------------------------------------------
     my_schema.my_spatial_table.geom effectively removed.

    -- In PostGIS 2.0+ the above is also equivalent to the standard
    -- the standard alter table.  Both will deregister from geometry_columns
    ALTER TABLE my_schema.my_spatial_table DROP column geom;

## See Also

AddGeometryColumn, DropGeometryTable, Section 4.3.2, “The GEOMETRY_COLUMNS VIEW”

## Name

DropGeometryTable — Drops a table and all its references in geometry_columns.

## Synopsis

`boolean DropGeometryTable(`varchar table_name`)`;

`boolean DropGeometryTable(`varchar schema_name, varchar table_name`)`;

`boolean DropGeometryTable(`varchar catalog_name, varchar schema_name, varchar table_name`)`;

## Description

Drops a table and all its references in geometry_columns. Note: uses current_schema() on schema-aware pgsql installations if schema is not provided.

Changed: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a view against the system catalogs, you can drop a table with geometry columns like any other table using `DROP TABLE`

## Examples

    SELECT DropGeometryTable ('my_schema','my_spatial_table');
    ----RESULT output ---
    my_schema.my_spatial_table dropped.

    -- The above is now equivalent to --
    DROP TABLE my_schema.my_spatial_table;

## See Also

AddGeometryColumn, DropGeometryColumn, Section 4.3.2, “The GEOMETRY_COLUMNS VIEW”

## Name

PostGIS_Full_Version — Reports full postgis version and build configuration infos.

## Synopsis

`text PostGIS_Full_Version(``)`;

## Description

Reports full postgis version and build configuration infos. Also informs about synchronization between libraries and scripts suggesting upgrades as needed.

## Examples

    SELECT PostGIS_Full_Version();
    							   postgis_full_version
    ----------------------------------------------------------------------------------
     POSTGIS="1.3.3" GEOS="3.1.0-CAPI-1.5.0" PROJ="Rel. 4.4.9, 29 Oct 2004" USE_STATS
    (1 row)

## See Also

Section 2.9, “Upgrading”, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version, PostGIS_Version

## Name

PostGIS_GEOS_Version — Returns the version number of the GEOS library.

## Synopsis

`text PostGIS_GEOS_Version(``)`;

## Description

Returns the version number of the GEOS library, or `NULL` if GEOS support is not enabled.

## Examples

    SELECT PostGIS_GEOS_Version();
     postgis_geos_version
    ----------------------
     3.1.0-CAPI-1.5.0
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version, PostGIS_Version

## Name

PostGIS_LibXML_Version — Returns the version number of the libxml2 library.

## Synopsis

`text PostGIS_LibXML_Version(``)`;

## Description

Returns the version number of the LibXML2 library.

Availability: 1.5

## Examples

    SELECT PostGIS_LibXML_Version();
     postgis_libxml_version
    ----------------------
     2.7.6
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_Lib_Version, PostGIS_PROJ_Version, PostGIS_GEOS_Version, PostGIS_Version

## Name

PostGIS_Lib_Build_Date — Returns build date of the PostGIS library.

## Synopsis

`text PostGIS_Lib_Build_Date(``)`;

## Description

Returns build date of the PostGIS library.

## Examples

    SELECT PostGIS_Lib_Build_Date();
     postgis_lib_build_date
    ------------------------
     2008-06-21 17:53:21
    (1 row)

## Name

PostGIS_Lib_Version — Returns the version number of the PostGIS library.

## Synopsis

`text PostGIS_Lib_Version(``)`;

## Description

Returns the version number of the PostGIS library.

## Examples

    SELECT PostGIS_Lib_Version();
     postgis_lib_version
    ---------------------
     1.3.3
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version, PostGIS_Version

## Name

PostGIS_PROJ_Version — Returns the version number of the PROJ4 library.

## Synopsis

`text PostGIS_PROJ_Version(``)`;

## Description

Returns the version number of the PROJ4 library, or `NULL` if PROJ4 support is not enabled.

## Examples

    SELECT PostGIS_PROJ_Version();
      postgis_proj_version
    -------------------------
     Rel. 4.4.9, 29 Oct 2004
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_Version

## Name

PostGIS_Scripts_Build_Date — Returns build date of the PostGIS scripts.

## Synopsis

`text PostGIS_Scripts_Build_Date(``)`;

## Description

Returns build date of the PostGIS scripts.

Availability: 1.0.0RC1

## Examples

    SELECT PostGIS_Scripts_Build_Date();
      postgis_scripts_build_date
    -------------------------
     2007-08-18 09:09:26
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_Version

## Name

PostGIS_Scripts_Installed — Returns version of the postgis scripts installed in this database.

## Synopsis

`text PostGIS_Scripts_Installed(``)`;

## Description

Returns version of the postgis scripts installed in this database.

If the output of this function doesn't match the output of PostGIS_Scripts_Released you probably missed to properly upgrade an existing database. See the Upgrading section for more info.

Availability: 0.9.0

## Examples

    SELECT PostGIS_Scripts_Installed();
      postgis_scripts_installed
    -------------------------
     1.5.0SVN
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_Scripts_Released, PostGIS_Version

## Name

PostGIS_Scripts_Released — Returns the version number of the postgis.sql script released with the installed postgis lib.

## Synopsis

`text PostGIS_Scripts_Released(``)`;

## Description

Returns the version number of the postgis.sql script released with the installed postgis lib.

Starting with version 1.1.0 this function returns the same value of PostGIS_Lib_Version. Kept for backward compatibility.

Availability: 0.9.0

## Examples

    SELECT PostGIS_Scripts_Released();
      postgis_scripts_released
    -------------------------
     1.3.4SVN
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_Scripts_Installed, PostGIS_Lib_Version

## Name

PostGIS_Version — Returns PostGIS version number and compile-time options.

## Synopsis

`text PostGIS_Version(``)`;

## Description

Returns PostGIS version number and compile-time options.

## Examples

    SELECT PostGIS_Version();
    			postgis_version
    ---------------------------------------
     1.3 USE_GEOS=1 USE_PROJ=1 USE_STATS=1
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version

## Name

Populate_Geometry_Columns — Ensures geometry columns are defined with type modifiers or have appropriate spatial constraints This ensures they will be registered correctly in `geometry_columns` view. By default will convert all geometry columns with no type modifier to ones with type modifiers. To get old behavior set `use_typmod=false`

## Synopsis

`text Populate_Geometry_Columns(`boolean use_typmod=true`)`;

`int Populate_Geometry_Columns(`oid relation_oid, boolean use_typmod=true`)`;

## Description

Ensures geometry columns have appropriate type modifiers or spatial constraints to ensure they are registered correctly in `geometry_columns` table.

For backwards compatibility and for spatial needs such as tble inheritance where each child table may have different geometry type, the old check constraint behavior is still supported. If you need the old behavior, you need to pass in the new optional argument as false `use_typmod=false`. When this is done geometry columns will be created with no type modifiers but will have 3 constraints defined. In particular, this means that every geometry column belonging to a table has at least three constraints:

- `enforce_dims_the_geom` - ensures every geometry has the same dimension (see ST_NDims)

- `enforce_geotype_the_geom` - ensures every geometry is of the same type (see GeometryType)

- `enforce_srid_the_geom` - ensures every geometry is in the same projection (see ST_SRID)

If a table `oid` is provided, this function tries to determine the srid, dimension, and geometry type of all geometry columns in the table, adding constraints as necessary. If successful, an appropriate row is inserted into the geometry_columns table, otherwise, the exception is caught and an error notice is raised describing the problem.

If the `oid` of a view is provided, as with a table oid, this function tries to determine the srid, dimension, and type of all the geometries in the view, inserting appropriate entries into the `geometry_columns` table, but nothing is done to enforce constraints.

The parameterless variant is a simple wrapper for the parameterized variant that first truncates and repopulates the geometry_columns table for every spatial table and view in the database, adding spatial constraints to tables where appropriate. It returns a summary of the number of geometry columns detected in the database and the number that were inserted into the `geometry_columns` table. The parameterized version simply returns the number of rows inserted into the `geometry_columns` table.

Availability: 1.4.0

Changed: 2.0.0 By default, now uses type modifiers instead of check constraints to constrain geometry types. You can still use check constraint behavior instead by using the new `use_typmod` and setting it to false.

Enhanced: 2.0.0 `use_typmod` optional argument was introduced that allows controlling if columns are created with typmodifiers or with check constraints.

## Examples

    CREATE TABLE public.myspatial_table(gid serial, geom geometry);
    INSERT INTO myspatial_table(geom) VALUES(ST_GeomFromText('LINESTRING(1 2, 3 4)',4326) );
    -- This will now use typ modifiers.  For this to work, there must exist data
    SELECT Populate_Geometry_Columns('public.myspatial_table'::regclass);

    populate_geometry_columns
    --------------------------
                            1

    \d myspatial_table

                                       Table "public.myspatial_table"
     Column |           Type            |                           Modifiers
    --------+---------------------------+---------------------------------------------------------------
     gid    | integer                   | not null default nextval('myspatial_table_gid_seq'::regclass)
     geom   | geometry(LineString,4326) |

    -- This will change the geometry columns to use constraints if they are not typmod or have constraints already.
    --For this to work, there must exist data
    CREATE TABLE public.myspatial_table_cs(gid serial, geom geometry);
    INSERT INTO myspatial_table_cs(geom) VALUES(ST_GeomFromText('LINESTRING(1 2, 3 4)',4326) );
    SELECT Populate_Geometry_Columns('public.myspatial_table_cs'::regclass, false);
    populate_geometry_columns
    --------------------------
                            1
    \d myspatial_table_cs

                              Table "public.myspatial_table_cs"
     Column |   Type   |                            Modifiers
    --------+----------+------------------------------------------------------------------
     gid    | integer  | not null default nextval('myspatial_table_cs_gid_seq'::regclass)
     geom   | geometry |
    Check constraints:
        "enforce_dims_geom" CHECK (st_ndims(geom) = 2)
        "enforce_geotype_geom" CHECK (geometrytype(geom) = 'LINESTRING'::text OR geom IS NULL)
        "enforce_srid_geom" CHECK (st_srid(geom) = 4326)

## Name

UpdateGeometrySRID — Updates the SRID of all features in a geometry column, geometry_columns metadata and srid table constraint

## Synopsis

`text UpdateGeometrySRID(`varchar table_name, varchar column_name, integer srid`)`;

`text UpdateGeometrySRID(`varchar schema_name, varchar table_name, varchar column_name, integer srid`)`;

`text UpdateGeometrySRID(`varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name, integer srid`)`;

## Description

Updates the SRID of all features in a geometry column, updating constraints and reference in geometry_columns. Note: uses current_schema() on schema-aware pgsql installations if schema is not provided.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## See Also

ST_SetSRID

## 8.3. Geometry Constructors

## Name

ST_BdPolyFromText — Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Known text representation.

## Synopsis

`geometry ST_BdPolyFromText(`text WKT, integer srid`)`;

## Description

Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Known text representation.

Throws an error if WKT is not a MULTILINESTRING. Throws an error if output is a MULTIPOLYGON; use ST_BdMPolyFromText in that case, or see ST_BuildArea() for a postgis-specific approach.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

Availability: 1.1.0 - requires GEOS >= 2.1.0.

## Examples

    Forthcoming

## See Also

ST_BuildArea, ST_BdMPolyFromText

## Name

ST_BdMPolyFromText — Construct a MultiPolygon given an arbitrary collection of closed linestrings as a MultiLineString text representation Well-Known text representation.

## Synopsis

`geometry ST_BdMPolyFromText(`text WKT, integer srid`)`;

## Description

Construct a Polygon given an arbitrary collection of closed linestrings, polygons, MultiLineStrings as Well-Known text representation.

Throws an error if WKT is not a MULTILINESTRING. Forces MULTIPOLYGON output even when result is really only composed by a single POLYGON; use ST_BdPolyFromText if you're sure a single POLYGON will result from operation, or see ST_BuildArea() for a postgis-specific approach.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

Availability: 1.1.0 - requires GEOS >= 2.1.0.

## Examples

    Forthcoming

## See Also

ST_BuildArea, ST_BdPolyFromText

## Name

ST_GeogFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).

## Synopsis

`geography ST_GeogFromText(`text EWKT`)`;

## Description

Returns a geography object from the well-known text or extended well-known representation. SRID 4326 is assumed. This is an alias for ST_GeographyFromText. Points are always expressed in long lat form.

## Examples

    --- converting lon lat coords to geography
    ALTER TABLE sometable ADD COLUMN geog geography(POINT,4326);
    UPDATE sometable SET geog = ST_GeogFromText('SRID=4326;POINT(' || lon || ' ' || lat || ')');

## See Also

ST_AsText, ST_GeographyFromText

## Name

ST_GeographyFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).

## Synopsis

`geography ST_GeographyFromText(`text EWKT`)`;

## Description

Returns a geography object from the well-known text representation. SRID 4326 is assumed.

## See Also

ST_GeogFromText, ST_AsText

## Name

ST_GeogFromWKB — Creates a geography instance from a Well-Known Binary geometry representation (WKB) or extended Well Known Binary (EWKB).

## Synopsis

`geography ST_GeogFromWKB(`bytea geom`)`;

## Description

The `ST_GeogFromWKB` function, takes a well-known binary representation (WKB) of a geometry or PostGIS Extended WKB and creates an instance of the appropriate geography type. This function plays the role of the Geometry Factory in SQL.

If SRID is not specified, it defaults to 4326 (WGS 84 long lat).

This method supports Circular Strings and Curves

## Examples

    --Although bytea rep contains single \, these need to be escaped when inserting into a table
    SELECT ST_AsText(
    ST_GeogFromWKB(E'\\001\\002\\000\\000\\000\\002\\000\\000\\000\\037\\205\\353Q\\270~\\\\\\300\\323Mb\\020X\\231C@\\020X9\\264\\310~\\\\\\300)\\\\\\217\\302\\365\\230C@')
    );
    					  st_astext
    ------------------------------------------------------
     LINESTRING(-113.98 39.198,-113.981 39.195)
    (1 row)

## See Also

ST_GeogFromText, ST_AsBinary

## Name

ST_GeomCollFromText — Makes a collection Geometry from collection WKT with the given SRID. If SRID is not give, it defaults to -1.

## Synopsis

`geometry ST_GeomCollFromText(`text WKT, integer srid`)`;

`geometry ST_GeomCollFromText(`text WKT`)`;

## Description

Makes a collection Geometry from the Well-Known-Text (WKT) representation with the given SRID. If SRID is not give, it defaults to -1.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a GEOMETRYCOLLECTION

If you are absolutely sure all your WKT geometries are collections, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification.

## Examples

    SELECT ST_GeomCollFromText('GEOMETRYCOLLECTION(POINT(1 2),LINESTRING(1 2, 3 4))');

## See Also

ST_GeomFromText, ST_SRID

## Name

ST_GeomFromEWKB — Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).

## Synopsis

`geometry ST_GeomFromEWKB(`bytea EWKB`)`;

## Description

Constructs a PostGIS ST_Geometry object from the OGC Extended Well-Known binary (EWKT) representation.

The EWKB format is not an OGC standard, but a PostGIS specific format that includes the spatial reference system (SRID) identifier

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

line string binary rep 0f LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932) in NAD 83 long lat (4269).

NOTE: Even though byte arrays are delimited with \ and may have ', we need to escape both out with \ and '' if standard_conforming_strings is off. So it does not look exactly like its AsEWKB representation.

    SELECT ST_GeomFromEWKB(E'\\001\\002\\000\\000 \\255\\020\\000\\000\\003\\000\\000\\000\\344J=
    \\013B\\312Q\\300n\\303(\\010\\036!E@''\\277E''K
    \\312Q\\300\\366{b\\235*!E@\\225|\\354.P\\312Q
    \\300p\\231\\323e1!E@');

In PostgreSQL 9.1+ - standard_conforming_strings is set to on by default, where as in past versions it was set to on. You can change defaults as needed for a single query or at the database or server level. Below is how you would do it with standard_conforming_strings = on. In this case we escape the ' with standard ansi ', but slashes are not escaped

    	    set standard_conforming_strings = on;
    SELECT ST_GeomFromEWKB('\001\002\000\000 \255\020\000\000\003\000\000\000\344J=\012\013B
        \312Q\300n\303(\010\036!E@''\277E''K\012\312Q\300\366{b\235*!E@\225|\354.P\312Q\012\300p\231\323e1')

## See Also

ST_AsBinary, ST_AsEWKB, ST_GeomFromWKB

## Name

ST_GeomFromEWKT — Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).

## Synopsis

`geometry ST_GeomFromEWKT(`text EWKT`)`;

## Description

Constructs a PostGIS ST_Geometry object from the OGC Extended Well-Known text (EWKT) representation.

The EWKT format is not an OGC standard, but an PostGIS specific format that includes the spatial reference system (SRID) identifier

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_GeomFromEWKT('SRID=4269;LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)');
    SELECT ST_GeomFromEWKT('SRID=4269;MULTILINESTRING((-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932))');

    SELECT ST_GeomFromEWKT('SRID=4269;POINT(-71.064544 42.28787)');

    SELECT ST_GeomFromEWKT('SRID=4269;POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
    -71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');

    SELECT ST_GeomFromEWKT('SRID=4269;MULTIPOLYGON(((-71.1031880899493 42.3152774590236,
    -71.1031627617667 42.3152960829043,-71.102923838298 42.3149156848307,
    -71.1023097974109 42.3151969047397,-71.1019285062273 42.3147384934248,
    -71.102505233663 42.3144722937587,-71.10277487471 42.3141658254797,
    -71.103113945163 42.3142739188902,-71.10324876416 42.31402489987,
    -71.1033002961013 42.3140393340215,-71.1033488797549 42.3139495090772,
    -71.103396240451 42.3138632439557,-71.1041521907712 42.3141153348029,
    -71.1041411411543 42.3141545014533,-71.1041287795912 42.3142114839058,
    -71.1041188134329 42.3142693656241,-71.1041112482575 42.3143272556118,
    -71.1041072845732 42.3143851580048,-71.1041057218871 42.3144430686681,
    -71.1041065602059 42.3145009876017,-71.1041097995362 42.3145589148055,
    -71.1041166403905 42.3146168544148,-71.1041258822717 42.3146748022936,
    -71.1041375307579 42.3147318674446,-71.1041492906949 42.3147711126569,
    -71.1041598612795 42.314808571739,-71.1042515013869 42.3151287620809,
    -71.1041173835118 42.3150739481917,-71.1040809891419 42.3151344119048,
    -71.1040438678912 42.3151191367447,-71.1040194562988 42.3151832057859,
    -71.1038734225584 42.3151140942995,-71.1038446938243 42.3151006300338,
    -71.1038315271889 42.315094347535,-71.1037393329282 42.315054824985,
    -71.1035447555574 42.3152608696313,-71.1033436658644 42.3151648370544,
    -71.1032580383161 42.3152269126061,-71.103223066939 42.3152517403219,
    -71.1031880899493 42.3152774590236)),
    ((-71.1043632495873 42.315113108546,-71.1043583974082 42.3151211109857,
    -71.1043443253471 42.3150676015829,-71.1043850704575 42.3150793250568,-71.1043632495873 42.315113108546)))');

    --3d circular string
    SELECT ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)');

    --Polyhedral Surface example
    SELECT ST_GeomFromEWKT('POLYHEDRALSURFACE(
    	((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    	((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
    	((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    	((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    	((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
    	((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
    )');

## See Also

ST_AsEWKT, ST_GeomFromText, ST_GeomFromEWKT

## Name

ST_GeometryFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText

## Synopsis

`geometry ST_GeometryFromText(`text WKT`)`;

`geometry ST_GeometryFromText(`text WKT, integer srid`)`;

## Description

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.40

## See Also

ST_GeomFromText

## Name

ST_GeomFromGML — Takes as input GML representation of geometry and outputs a PostGIS geometry object

## Synopsis

`geometry ST_GeomFromGML(`text geomgml`)`;

`geometry ST_GeomFromGML(`text geomgml, integer srid`)`;

## Description

Constructs a PostGIS ST_Geometry object from the OGC GML representation.

ST_GeomFromGML works only for GML Geometry fragments. It throws an error if you try to use it on a whole GML document.

OGC GML versions supported:

- GML 3.2.1 Namespace

- GML 3.1.1 Simple Features profile SF-2 (with GML 3.1.0 and 3.0.0 backward compatibility)

- GML 2.1.2

OGC GML standards, cf: http://www.opengeospatial.org/standards/gml:

Availability: 1.5, requires libxml2 1.6+

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

Enhanced: 2.0.0 default srid optional parameter added.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

GML allow mixed dimensions (2D and 3D inside the same MultiGeometry for instance). As PostGIS geometries don't, ST_GeomFromGML convert the whole geometry to 2D if a missing Z dimension is found once.

GML support mixed SRS inside the same MultiGeometry. As PostGIS geometries don't, ST_GeomFromGML, in this case, reproject all subgeometries to the SRS root node. If no srsName attribute available for the GML root node, the function throw an error.

ST_GeomFromGML function is not pedantic about an explicit GML namespace. You could avoid to mention it explicitly for common usages. But you need it if you want to use XLink feature inside GML.

ST_GeomFromGML function not support SQL/MM curves geometries.

## Examples - A single geometry with srsName

    SELECT ST_GeomFromGML('
    		<gml:LineString srsName="EPSG:4269">
    			<gml:coordinates>
    				-71.16028,42.258729 -71.160837,42.259112 -71.161143,42.25932
    			</gml:coordinates>
    		</gml:LineString>');

## Examples - XLink usage

    SELECT ST_GeomFromGML('
    		<gml:LineString xmlns:gml="http://www.opengis.net/gml"
    				xmlns:xlink="http://www.w3.org/1999/xlink"
    				srsName="urn:ogc:def:crs:EPSG::4269">
    			<gml:pointProperty>
    				<gml:Point gml:id="p1"><gml:pos>42.258729 -71.16028</gml:pos></gml:Point>
    			</gml:pointProperty>
    			<gml:pos>42.259112 -71.160837</gml:pos>
    			<gml:pointProperty>
    				<gml:Point xlink:type="simple" xlink:href="#p1"/>
    			</gml:pointProperty>
    		</gml:LineString>'););

## Examples - Polyhedral Surface

    SELECT ST_AsEWKT(ST_GeomFromGML('
    <gml:PolyhedralSurface>
    <gml:polygonPatches>
      <gml:PolygonPatch>
        <gml:exterior>
          <gml:LinearRing><gml:posList srsDimension="3">0 0 0 0 0 1 0 1 1 0 1 0 0 0 0</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
      <gml:PolygonPatch>
        <gml:exterior>
        	<gml:LinearRing><gml:posList srsDimension="3">0 0 0 0 1 0 1 1 0 1 0 0 0 0 0</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
      <gml:PolygonPatch>
        <gml:exterior>
        	<gml:LinearRing><gml:posList srsDimension="3">0 0 0 1 0 0 1 0 1 0 0 1 0 0 0</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
      <gml:PolygonPatch>
        <gml:exterior>
        	<gml:LinearRing><gml:posList srsDimension="3">1 1 0 1 1 1 1 0 1 1 0 0 1 1 0</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
      <gml:PolygonPatch>
        <gml:exterior>
        	<gml:LinearRing><gml:posList srsDimension="3">0 1 0 0 1 1 1 1 1 1 1 0 0 1 0</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
      <gml:PolygonPatch>
        <gml:exterior>
        	<gml:LinearRing><gml:posList srsDimension="3">0 0 1 1 0 1 1 1 1 0 1 1 0 0 1</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
    </gml:polygonPatches>
    </gml:PolyhedralSurface>'));

    -- result --
     POLYHEDRALSURFACE(((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
     ((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
     ((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
     ((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
     ((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
     ((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1)))

## See Also

Section 2.4.1, “Configuration”, ST_AsGML, ST_GMLToSQL

## Name

ST_GeomFromGeoJSON — Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object

## Synopsis

`geometry ST_GeomFromGeoJSON(`text geomjson`)`;

## Description

Constructs a PostGIS geometry object from the GeoJSON representation.

ST_GeomFromGeoJSON works only for JSON Geometry fragments. It throws an error if you try to use it on a whole JSON document.

Availability: 2.0.0 requires - JSON-C >= 0.9

If you do not have JSON-C enabled, support you will get an error notice instead of seeing an output. To enable JSON-C, run configure --with-jsondir=/path/to/json-c. See Section 2.4.1, “Configuration” for details.

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsText(ST_GeomFromGeoJSON('{"type":"Point","coordinates":[-48.23456,20.12345]}')) As wkt;
    wkt
    ------
    POINT(-48.23456 20.12345)

    -- a 3D linestring
    SELECT ST_AsText(ST_GeomFromGeoJSON('{"type":"LineString","coordinates":[[1,2,3],[4,5,6],[7,8,9]]}')) As wkt;

    wkt
    -------------------
    LINESTRING(1 2,4 5,7 8)

## See Also

ST_AsText, ST_AsGeoJSON, Section 2.4.1, “Configuration”

## Name

ST_GeomFromKML — Takes as input KML representation of geometry and outputs a PostGIS geometry object

## Synopsis

`geometry ST_GeomFromKML(`text geomkml`)`;

## Description

Constructs a PostGIS ST_Geometry object from the OGC KML representation.

ST_GeomFromKML works only for KML Geometry fragments. It throws an error if you try to use it on a whole KML document.

OGC KML versions supported:

- KML 2.2.0 Namespace

OGC KML standards, cf: http://www.opengeospatial.org/standards/kml:

Availability: 1.5,libxml2 2.6+

This function supports 3d and will not drop the z-index.

ST_GeomFromKML function not support SQL/MM curves geometries.

## Examples - A single geometry with srsName

    SELECT ST_GeomFromKML('
    		<LineString>
    			<coordinates>-71.1663,42.2614
    				-71.1667,42.2616</coordinates>
    		</LineString>');

## See Also

Section 2.4.1, “Configuration”, ST_AsKML

## Name

ST_GMLToSQL — Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML

## Synopsis

`geometry ST_GMLToSQL(`text geomgml`)`;

`geometry ST_GMLToSQL(`text geomgml, integer srid`)`;

## Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.50 (except for curves support).

Availability: 1.5, requires libxml2 1.6+

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

Enhanced: 2.0.0 default srid optional parameter added.

## See Also

Section 2.4.1, “Configuration”, ST_GeomFromGML, ST_AsGML

## Name

ST_GeomFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT).

## Synopsis

`geometry ST_GeomFromText(`text WKT`)`;

`geometry ST_GeomFromText(`text WKT, integer srid`)`;

## Description

Constructs a PostGIS ST_Geometry object from the OGC Well-Known text representation.

There are 2 variants of ST_GeomFromText function, the first takes no SRID and returns a geometry with no defined spatial reference system. The second takes a spatial reference id as the second argument and returns an ST_Geometry that includes this srid as part of its meta-data. The srid must be defined in the spatial_ref_sys table.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2 - option SRID is from the conformance suite.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.40

This method supports Circular Strings and Curves

Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards. This should now be written as ST_GeomFromText('GEOMETRYCOLLECTION EMPTY')

## Examples

    SELECT ST_GeomFromText('LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)');
    SELECT ST_GeomFromText('LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)',4269);

    SELECT ST_GeomFromText('MULTILINESTRING((-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932))');

    SELECT ST_GeomFromText('POINT(-71.064544 42.28787)');

    SELECT ST_GeomFromText('POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
    -71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');

    SELECT ST_GeomFromText('MULTIPOLYGON(((-71.1031880899493 42.3152774590236,
    -71.1031627617667 42.3152960829043,-71.102923838298 42.3149156848307,
    -71.1023097974109 42.3151969047397,-71.1019285062273 42.3147384934248,
    -71.102505233663 42.3144722937587,-71.10277487471 42.3141658254797,
    -71.103113945163 42.3142739188902,-71.10324876416 42.31402489987,
    -71.1033002961013 42.3140393340215,-71.1033488797549 42.3139495090772,
    -71.103396240451 42.3138632439557,-71.1041521907712 42.3141153348029,
    -71.1041411411543 42.3141545014533,-71.1041287795912 42.3142114839058,
    -71.1041188134329 42.3142693656241,-71.1041112482575 42.3143272556118,
    -71.1041072845732 42.3143851580048,-71.1041057218871 42.3144430686681,
    -71.1041065602059 42.3145009876017,-71.1041097995362 42.3145589148055,
    -71.1041166403905 42.3146168544148,-71.1041258822717 42.3146748022936,
    -71.1041375307579 42.3147318674446,-71.1041492906949 42.3147711126569,
    -71.1041598612795 42.314808571739,-71.1042515013869 42.3151287620809,
    -71.1041173835118 42.3150739481917,-71.1040809891419 42.3151344119048,
    -71.1040438678912 42.3151191367447,-71.1040194562988 42.3151832057859,
    -71.1038734225584 42.3151140942995,-71.1038446938243 42.3151006300338,
    -71.1038315271889 42.315094347535,-71.1037393329282 42.315054824985,
    -71.1035447555574 42.3152608696313,-71.1033436658644 42.3151648370544,
    -71.1032580383161 42.3152269126061,-71.103223066939 42.3152517403219,
    -71.1031880899493 42.3152774590236)),
    ((-71.1043632495873 42.315113108546,-71.1043583974082 42.3151211109857,
    -71.1043443253471 42.3150676015829,-71.1043850704575 42.3150793250568,-71.1043632495873 42.315113108546)))',4326);

    SELECT ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)');

## See Also

ST_GeomFromEWKT, ST_GeomFromWKB, ST_SRID

## Name

ST_GeomFromWKB — Creates a geometry instance from a Well-Known Binary geometry representation (WKB) and optional SRID.

## Synopsis

`geometry ST_GeomFromWKB(`bytea geom`)`;

`geometry ST_GeomFromWKB(`bytea geom, integer srid`)`;

## Description

The `ST_GeomFromWKB` function, takes a well-known binary representation of a geometry and a Spatial Reference System ID (`SRID`) and creates an instance of the appropriate geometry type. This function plays the role of the Geometry Factory in SQL. This is an alternate name for ST_WKBToSQL.

If SRID is not specified, it defaults to -1 (Unknown).

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.7.2 - the optional SRID is from the conformance suite

This method implements the SQL/MM specification. SQL-MM 3: 5.1.41

This method supports Circular Strings and Curves

## Examples

    --Although bytea rep contains single \, these need to be escaped when inserting into a table
    		-- unless standard_conforming_strings is set to on.
    SELECT ST_AsEWKT(
    ST_GeomFromWKB(E'\\001\\002\\000\\000\\000\\002\\000\\000\\000\\037\\205\\353Q\\270~\\\\\\300\\323Mb\\020X\\231C@\\020X9\\264\\310~\\\\\\300)\\\\\\217\\302\\365\\230C@',4326)
    );
    					  st_asewkt
    ------------------------------------------------------
     SRID=4326;LINESTRING(-113.98 39.198,-113.981 39.195)
    (1 row)

    SELECT
      ST_AsText(
    	ST_GeomFromWKB(
    	  ST_AsEWKB('POINT(2 5)'::geometry)
    	)
      );
     st_astext
    ------------
     POINT(2 5)
    (1 row)

## See Also

ST_WKBToSQL, ST_AsBinary, ST_GeomFromEWKB

## Name

ST_LineFromMultiPoint — Creates a LineString from a MultiPoint geometry.

## Synopsis

`geometry ST_LineFromMultiPoint(`geometry aMultiPoint`)`;

## Description

Creates a LineString from a MultiPoint geometry.

This function supports 3d and will not drop the z-index.

## Examples

    --Create a 3d line string from a 3d multipoint
    SELECT ST_AsEWKT(ST_LineFromMultiPoint(ST_GeomFromEWKT('MULTIPOINT(1 2 3, 4 5 6, 7 8 9)')));
    --result--
    LINESTRING(1 2 3,4 5 6,7 8 9)

## See Also

ST_AsEWKT, ST_Collect, ST_MakeLine

## Name

ST_LineFromText — Makes a Geometry from WKT representation with the given SRID. If SRID is not given, it defaults to -1.

## Synopsis

`geometry ST_LineFromText(`text WKT`)`;

`geometry ST_LineFromText(`text WKT, integer srid`)`;

## Description

Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1. If WKT passed in is not a LINESTRING, then null is returned.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite.

If you know all your geometries are LINESTRINGS, its more efficient to just use ST_GeomFromText. This just calls ST_GeomFromText and adds additional validation that it returns a linestring.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.8

## Examples

    SELECT ST_LineFromText('LINESTRING(1 2, 3 4)') AS aline, ST_LineFromText('POINT(1 2)') AS null_return;
    aline                            | null_return
    ------------------------------------------------
    010200000002000000000000000000F ... | t

## See Also

ST_GeomFromText

## Name

ST_LineFromWKB — Makes a `LINESTRING` from WKB with the given SRID

## Synopsis

`geometry ST_LineFromWKB(`bytea WKB`)`;

`geometry ST_LineFromWKB(`bytea WKB, integer srid`)`;

## Description

The `ST_LineFromWKB` function, takes a well-known binary representation of geometry and a Spatial Reference System ID (`SRID`) and creates an instance of the appropriate geometry type - in this case, a `LINESTRING` geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to -1. `NULL` is returned if the input `bytea` does not represent a `LINESTRING`.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite.

If you know all your geometries are `LINESTRING`s, its more efficient to just use ST_GeomFromWKB. This function just calls ST_GeomFromWKB and adds additional validation that it returns a linestring.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.9

## Examples

    SELECT ST_LineFromWKB(ST_AsBinary(ST_GeomFromText('LINESTRING(1 2, 3 4)'))) AS aline,
    		ST_LineFromWKB(ST_AsBinary(ST_GeomFromText('POINT(1 2)'))) IS NULL AS null_return;
    aline                            | null_return
    ------------------------------------------------
    010200000002000000000000000000F ... | t

## See Also

ST_GeomFromWKB, ST_LinestringFromWKB

## Name

ST_LinestringFromWKB — Makes a geometry from WKB with the given SRID.

## Synopsis

`geometry ST_LinestringFromWKB(`bytea WKB`)`;

`geometry ST_LinestringFromWKB(`bytea WKB, integer srid`)`;

## Description

The `ST_LinestringFromWKB` function, takes a well-known binary representation of geometry and a Spatial Reference System ID (`SRID`) and creates an instance of the appropriate geometry type - in this case, a `LINESTRING` geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to -1. `NULL` is returned if the input `bytea` does not represent a `LINESTRING` geometry. This an alias for ST_LineFromWKB.

OGC SPEC 3.2.6.2 - optional SRID is from the conformance suite.

If you know all your geometries are `LINESTRING`s, it's more efficient to just use ST_GeomFromWKB. This function just calls ST_GeomFromWKB and adds additional validation that it returns a `LINESTRING`.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.9

## Examples

    SELECT
      ST_LineStringFromWKB(
    	ST_AsBinary(ST_GeomFromText('LINESTRING(1 2, 3 4)'))
      ) AS aline,
      ST_LinestringFromWKB(
    	ST_AsBinary(ST_GeomFromText('POINT(1 2)'))
      ) IS NULL AS null_return;
       aline                            | null_return
    ------------------------------------------------
    010200000002000000000000000000F ... | t

## See Also

ST_GeomFromWKB, ST_LineFromWKB

## Name

ST_MakeBox2D — Creates a BOX2D defined by the given point geometries.

## Synopsis

`box2d ST_MakeBox2D(`geometry pointLowLeft, geometry pointUpRight`)`;

## Description

Creates a BOX2D defined by the given point geometries. This is useful for doing range queries

## Examples

    --Return all features that fall reside or partly reside in a US national atlas coordinate bounding box
    --It is assumed here that the geometries are stored with SRID = 2163 (US National atlas equal area)
    SELECT feature_id, feature_name, the_geom
    FROM features
    WHERE the_geom && ST_SetSRID(ST_MakeBox2D(ST_Point(-989502.1875, 528439.5625),
    	ST_Point(-987121.375 ,529933.1875)),2163)

## See Also

ST_MakePoint, ST_Point, ST_SetSRID, ST_SRID

## Name

ST_3DMakeBox — Creates a BOX3D defined by the given 3d point geometries.

## Synopsis

`box3d ST_3DMakeBox(`geometry point3DLowLeftBottom, geometry point3DUpRightTop`)`;

## Description

Creates a BOX3D defined by the given 2 3D point geometries.

This function supports 3d and will not drop the z-index.

Changed: 2.0.0 In prior versions this used to be called ST_MakeBox3D

## Examples

    SELECT ST_3DMakeBox(ST_MakePoint(-989502.1875, 528439.5625, 10),
    	ST_MakePoint(-987121.375 ,529933.1875, 10)) As abb3d

    --bb3d--
    --------
    BOX3D(-989502.1875 528439.5625 10,-987121.375 529933.1875 10)

## See Also

ST_MakePoint, ST_SetSRID, ST_SRID

## Name

ST_MakeLine — Creates a Linestring from point or line geometries.

## Synopsis

`geometry ST_MakeLine(`geometry set geoms`)`;

`geometry ST_MakeLine(`geometry geom1, geometry geom2`)`;

`geometry ST_MakeLine(`geometry[] geoms_array`)`;

## Description

ST_MakeLine comes in 3 forms: a spatial aggregate that takes rows of point-or-line geometries and returns a line string, a function that takes an array of point-or-lines, and a regular function that takes two point-or-line geometries. You might want to use a subselect to order points before feeding them to the aggregate version of this function.

When adding line components a common node is removed from the output.

This function supports 3d and will not drop the z-index.

Availability: 1.4.0 - ST_MakeLine(geomarray) was introduced. ST_MakeLine aggregate functions was enhanced to handle more points faster.

Availability: 2.0.0 - Support for linestring input elements was introduced

## Examples: Spatial Aggregate version

This example takes a sequence of GPS points and creates one record for each gps travel where the geometry field is a line string composed of the gps points in the order of the travel.

    -- For pre-PostgreSQL 9.0 - this usually works,
    -- but the planner may on occasion choose not to respect the order of the subquery
    SELECT gps.gps_track, ST_MakeLine(gps.the_geom) As newgeom
    	FROM (SELECT gps_track,gps_time, the_geom
    			FROM gps_points ORDER BY gps_track, gps_time) As gps
    	GROUP BY gps.gps_track;

    -- If you are using PostgreSQL 9.0+
    -- (you can use the new ORDER BY support for aggregates)
    -- this is a guaranteed way to get a correctly ordered linestring
    -- Your order by part can order by more than one column if needed
    SELECT gps.gps_track, ST_MakeLine(gps.the_geom ORDER BY gps_time) As newgeom
    	FROM gps_points As gps
    	GROUP BY gps.gps_track;

## Examples: Non-Spatial Aggregate version

First example is a simple one off line string composed of 2 points. The second formulates line strings from 2 points a user draws. The third is a one-off that joins 2 3d points to create a line in 3d space.

    SELECT ST_AsText(ST_MakeLine(ST_MakePoint(1,2), ST_MakePoint(3,4)));
    	  st_astext
    ---------------------
     LINESTRING(1 2,3 4)

    SELECT userpoints.id, ST_MakeLine(startpoint, endpoint) As drawn_line
    	FROM userpoints ;

    SELECT ST_AsEWKT(ST_MakeLine(ST_MakePoint(1,2,3), ST_MakePoint(3,4,5)));
    		st_asewkt
    -------------------------
     LINESTRING(1 2 3,3 4 5)

## Examples: Using Array version

    SELECT ST_MakeLine(ARRAY(SELECT ST_Centroid(the_geom) FROM visit_locations ORDER BY visit_time));

    --Making a 3d line with 3 3-d points
    SELECT ST_AsEWKT(ST_MakeLine(ARRAY[ST_MakePoint(1,2,3),
    				ST_MakePoint(3,4,5), ST_MakePoint(6,6,6)]));
    		st_asewkt
    -------------------------
    LINESTRING(1 2 3,3 4 5,6 6 6)

## See Also

ST_AsEWKT, ST_AsText, ST_GeomFromText, ST_MakePoint

## Name

ST_MakeEnvelope — Creates a rectangular Polygon formed from the given minimums and maximums. Input values must be in SRS specified by the SRID.

## Synopsis

`geometry ST_MakeEnvelope(`double precision xmin, double precision ymin, double precision xmax, double precision ymax, integer srid=unknown`)`;

## Description

Creates a rectangular Polygon formed from the minima and maxima. by the given shell. Input values must be in SRS specified by the SRID. If no SRID is specified the unknown spatial reference system is assumed

Availability: 1.5

Enhanced: 2.0: Ability to specify an envelope without specifying an SRID was introduced.

## Example: Building a bounding box polygon

    SELECT ST_AsText(ST_MakeEnvelope(10, 10, 11, 11, 4326));

    st_asewkt
    -----------
    POLYGON((10 10, 10 11, 11 11, 11 10, 10 10))

## See Also

ST_MakePoint, ST_MakeLine, ST_MakePolygon

## Name

ST_MakePolygon — Creates a Polygon formed by the given shell. Input geometries must be closed LINESTRINGS.

## Synopsis

`geometry ST_MakePolygon(`geometry linestring`)`;

`geometry ST_MakePolygon(`geometry outerlinestring, geometry[] interiorlinestrings`)`;

## Description

Creates a Polygon formed by the given shell. Input geometries must be closed LINESTRINGS. Comes in 2 variants.

Variant 1: takes one closed linestring.

Variant 2: Creates a Polygon formed by the given shell and array of holes. You can construct a geometry array using ST_Accum or the PostgreSQL ARRAY[] and ARRAY() constructs. Input geometries must be closed LINESTRINGS.

This function will not accept a MULTILINESTRING. Use ST_LineMerge or ST_Dump to generate line strings.

This function supports 3d and will not drop the z-index.

## Examples: Single closed LINESTRING

    --2d line
    SELECT ST_MakePolygon(ST_GeomFromText('LINESTRING(75.15 29.53,77 29,77.6 29.5, 75.15 29.53)'));
    --If linestring is not closed
    --you can add the start point to close it
    SELECT ST_MakePolygon(ST_AddPoint(foo.open_line, ST_StartPoint(foo.open_line)))
    FROM (
    SELECT ST_GeomFromText('LINESTRING(75.15 29.53,77 29,77.6 29.5)') As open_line) As foo;

    --3d closed line
    SELECT ST_MakePolygon(ST_GeomFromText('LINESTRING(75.15 29.53 1,77 29 1,77.6 29.5 1, 75.15 29.53 1)'));

    st_asewkt
    -----------
    POLYGON((75.15 29.53 1,77 29 1,77.6 29.5 1,75.15 29.53 1))

    --measured line --
    SELECT ST_MakePolygon(ST_GeomFromText('LINESTRINGM(75.15 29.53 1,77 29 1,77.6 29.5 2, 75.15 29.53 2)'));

    st_asewkt
    ----------
    POLYGONM((75.15 29.53 1,77 29 1,77.6 29.5 2,75.15 29.53 2))

## Examples: Outter shell with inner shells

Build a donut with an ant hole

    SELECT ST_MakePolygon(
    		ST_ExteriorRing(ST_Buffer(foo.line,10)),
    	ARRAY[ST_Translate(foo.line,1,1),
    		ST_ExteriorRing(ST_Buffer(ST_MakePoint(20,20),1)) ]
    	)
    FROM
    	(SELECT ST_ExteriorRing(ST_Buffer(ST_MakePoint(10,10),10,10))
    		As line )
    		As foo;

Build province boundaries with holes representing lakes in the province from a set of province polygons/multipolygons and water line strings this is an example of using PostGIS ST_Accum

The use of CASE because feeding a null array into ST_MakePolygon results in NULL

the use of left join to guarantee we get all provinces back even if they have no lakes

    	SELECT p.gid, p.province_name,
    		CASE WHEN
    			ST_Accum(w.the_geom) IS NULL THEN p.the_geom
    		ELSE  ST_MakePolygon(ST_LineMerge(ST_Boundary(p.the_geom)), ST_Accum(w.the_geom)) END
    	FROM
    		provinces p LEFT JOIN waterlines w
    			ON (ST_Within(w.the_geom, p.the_geom) AND ST_IsClosed(w.the_geom))
    	GROUP BY p.gid, p.province_name, p.the_geom;

    	--Same example above but utilizing a correlated subquery
    	--and PostgreSQL built-in ARRAY() function that converts a row set to an array

    	SELECT p.gid,  p.province_name, CASE WHEN
    		EXISTS(SELECT w.the_geom
    			FROM waterlines w
    			WHERE ST_Within(w.the_geom, p.the_geom)
    			AND ST_IsClosed(w.the_geom))
    		THEN
    		ST_MakePolygon(ST_LineMerge(ST_Boundary(p.the_geom)),
    			ARRAY(SELECT w.the_geom
    				FROM waterlines w
    				WHERE ST_Within(w.the_geom, p.the_geom)
    				AND ST_IsClosed(w.the_geom)))
    		ELSE p.the_geom END As the_geom
    	FROM
    		provinces p;

## See Also

ST_Accum, ST_AddPoint, ST_GeometryType, ST_IsClosed, ST_LineMerge, ST_BuildArea

## Name

ST_MakePoint — Creates a 2D,3DZ or 4D point geometry.

## Synopsis

`geometry ST_MakePoint(`double precision x, double precision y`)`;

`geometry ST_MakePoint(`double precision x, double precision y, double precision z`)`;

`geometry ST_MakePoint(`double precision x, double precision y, double precision z, double precision m`)`;

## Description

Creates a 2D,3DZ or 4D point geometry (geometry with measure). `ST_MakePoint` while not being OGC compliant is generally faster and more precise than ST_GeomFromText and ST_PointFromText. It is also easier to use if you have raw coordinates rather than WKT.

Note x is longitude and y is latitude

Use ST_MakePointM if you need to make a point with x,y,m.

This function supports 3d and will not drop the z-index.

## Examples

    --Return point with unknown SRID
    SELECT ST_MakePoint(-71.1043443253471, 42.3150676015829);

    --Return point marked as WGS 84 long lat
    SELECT ST_SetSRID(ST_MakePoint(-71.1043443253471, 42.3150676015829),4326);

    --Return a 3D point (e.g. has altitude)
    SELECT ST_MakePoint(1, 2,1.5);

    --Get z of point
    SELECT ST_Z(ST_MakePoint(1, 2,1.5));
    result
    -------
    1.5

## See Also

ST_GeomFromText, ST_PointFromText, ST_SetSRID, ST_MakePointM

## Name

ST_MakePointM — Creates a point geometry with an x y and m coordinate.

## Synopsis

`geometry ST_MakePointM(`float x, float y, float m`)`;

## Description

Creates a point with x, y and measure coordinates.

Note x is longitude and y is latitude.

## Examples

We use ST_AsEWKT in these examples to show the text representation instead of ST_AsText because ST_AsText does not support returning M.

    --Return EWKT representation of point with unknown SRID
    SELECT ST_AsEWKT(ST_MakePointM(-71.1043443253471, 42.3150676015829, 10));

    --result
    				   st_asewkt
    -----------------------------------------------
     POINTM(-71.1043443253471 42.3150676015829 10)

    --Return EWKT representation of point with measure marked as WGS 84 long lat
    SELECT ST_AsEWKT(ST_SetSRID(ST_MakePointM(-71.1043443253471, 42.3150676015829,10),4326));

    						st_asewkt
    ---------------------------------------------------------
    SRID=4326;POINTM(-71.1043443253471 42.3150676015829 10)

    --Return a 3d point (e.g. has altitude)
    SELECT ST_MakePoint(1, 2,1.5);

    --Get m of point
    SELECT ST_M(ST_MakePointM(-71.1043443253471, 42.3150676015829,10));
    result
    -------
    10

## See Also

ST_AsEWKT, ST_MakePoint, ST_SetSRID

## Name

ST_MLineFromText — Return a specified ST_MultiLineString value from WKT representation.

## Synopsis

`geometry ST_MLineFromText(`text WKT, integer srid`)`;

`geometry ST_MLineFromText(`text WKT`)`;

## Description

Makes a Geometry from Well-Known-Text (WKT) with the given SRID. If SRID is not give, it defaults to -1.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a MULTILINESTRING

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification.SQL-MM 3: 9.4.4

## Examples

    SELECT ST_MLineFromText('MULTILINESTRING((1 2, 3 4), (4 5, 6 7))');

## See Also

ST_GeomFromText

## Name

ST_MPointFromText — Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1.

## Synopsis

`geometry ST_MPointFromText(`text WKT, integer srid`)`;

`geometry ST_MPointFromText(`text WKT`)`;

## Description

Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a MULTIPOINT

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. 3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 9.2.4

## Examples

    SELECT ST_MPointFromText('MULTIPOINT(1 2, 3 4)');
    SELECT ST_MPointFromText('MULTIPOINT(-70.9590 42.1180, -70.9611 42.1223)', 4326);

## See Also

ST_GeomFromText

## Name

ST_MPolyFromText — Makes a MultiPolygon Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1.

## Synopsis

`geometry ST_MPolyFromText(`text WKT, integer srid`)`;

`geometry ST_MPolyFromText(`text WKT`)`;

## Description

Makes a MultiPolygon from WKT with the given SRID. If SRID is not give, it defaults to -1.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Throws an error if the WKT is not a MULTIPOLYGON

If you are absolutely sure all your WKT geometries are multipolygons, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 9.6.4

## Examples

    SELECT ST_MPolyFromText('MULTIPOLYGON(((0 0 1,20 0 1,20 20 1,0 20 1,0 0 1),(5 5 3,5 7 3,7 7 3,7 5 3,5 5 3)))');
    SELECt ST_MPolyFromText('MULTIPOLYGON(((-70.916 42.1002,-70.9468 42.0946,-70.9765 42.0872,-70.9754 42.0875,-70.9749 42.0879,-70.9752 42.0881,-70.9754 42.0891,-70.9758 42.0894,-70.9759 42.0897,-70.9759 42.0899,-70.9754 42.0902,-70.9756 42.0906,-70.9753 42.0907,-70.9753 42.0917,-70.9757 42.0924,-70.9755 42.0928,-70.9755 42.0942,-70.9751 42.0948,-70.9755 42.0953,-70.9751 42.0958,-70.9751 42.0962,-70.9759 42.0983,-70.9767 42.0987,-70.9768 42.0991,-70.9771 42.0997,-70.9771 42.1003,-70.9768 42.1005,-70.977 42.1011,-70.9766 42.1019,-70.9768 42.1026,-70.9769 42.1033,-70.9775 42.1042,-70.9773 42.1043,-70.9776 42.1043,-70.9778 42.1048,-70.9773 42.1058,-70.9774 42.1061,-70.9779 42.1065,-70.9782 42.1078,-70.9788 42.1085,-70.9798 42.1087,-70.9806 42.109,-70.9807 42.1093,-70.9806 42.1099,-70.9809 42.1109,-70.9808 42.1112,-70.9798 42.1116,-70.9792 42.1127,-70.979 42.1129,-70.9787 42.1134,-70.979 42.1139,-70.9791 42.1141,-70.9987 42.1116,-71.0022 42.1273,
    	-70.9408 42.1513,-70.9315 42.1165,-70.916 42.1002)))',4326);

## See Also

ST_GeomFromText, ST_SRID

## Name

ST_Point — Returns an ST_Point with the given coordinate values. OGC alias for ST_MakePoint.

## Synopsis

`geometry ST_Point(`float x_lon, float y_lat`)`;

## Description

Returns an ST_Point with the given coordinate values. MM compliant alias for ST_MakePoint that takes just an x and y.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.2

## Examples: Geometry

    SELECT ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326)

## Examples: Geography

    SELECT CAST(ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326) As geography);

    -- the :: is PostgreSQL short-hand for casting.
    SELECT ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326)::geography;

    --If your point coordinates are in a different spatial reference from WGS-84 long lat, then you need to transform before casting
    -- This example we convert a point in Pennsylvania State Plane feet to WGS 84 and then geography
    SELECT ST_Transform(ST_SetSRID(ST_Point(3637510, 3014852),2273),4326)::geography;

## See Also

Section 4.2.1, “Geography Basics”, ST_MakePoint, ST_SetSRID, ST_Transform

## Name

ST_PointFromText — Makes a point Geometry from WKT with the given SRID. If SRID is not given, it defaults to unknown.

## Synopsis

`geometry ST_PointFromText(`text WKT`)`;

`geometry ST_PointFromText(`text WKT, integer srid`)`;

## Description

Constructs a PostGIS ST_Geometry point object from the OGC Well-Known text representation. If SRID is not give, it defaults to unknown (currently -1). If geometry is not a WKT point representation, returns null. If completely invalid WKT, then throws an error.

There are 2 variants of ST_PointFromText function, the first takes no SRID and returns a geometry with no defined spatial reference system. The second takes a spatial reference id as the second argument and returns an ST_Geometry that includes this srid as part of its meta-data. The srid must be defined in the spatial_ref_sys table.

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step. If you are building points from long lat coordinates and care more about performance and accuracy than OGC compliance, use ST_MakePoint or OGC compliant alias ST_Point.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2 - option SRID is from the conformance suite.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.8

## Examples

    SELECT ST_PointFromText('POINT(-71.064544 42.28787)');
    SELECT ST_PointFromText('POINT(-71.064544 42.28787)', 4326);

## See Also

ST_GeomFromText, ST_MakePoint, ST_Point, ST_SRID

## Name

ST_PointFromWKB — Makes a geometry from WKB with the given SRID

## Synopsis

`geometry ST_GeomFromWKB(`bytea geom`)`;

`geometry ST_GeomFromWKB(`bytea geom, integer srid`)`;

## Description

The `ST_PointFromWKB` function, takes a well-known binary representation of geometry and a Spatial Reference System ID (`SRID`) and creates an instance of the appropriate geometry type - in this case, a `POINT` geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to -1. `NULL` is returned if the input `bytea` does not represent a `POINT` geometry.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.7.2

This method implements the SQL/MM specification. SQL-MM 3: 6.1.9

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT
      ST_AsText(
    	ST_PointFromWKB(
    	  ST_AsEWKB('POINT(2 5)'::geometry)
    	)
      );
     st_astext
    ------------
     POINT(2 5)
    (1 row)

    SELECT
      ST_AsText(
    	ST_PointFromWKB(
    	  ST_AsEWKB('LINESTRING(2 5, 2 6)'::geometry)
    	)
      );
     st_astext
    -----------

    (1 row)

## See Also

ST_GeomFromWKB, ST_LineFromWKB

## Name

ST_Polygon — Returns a polygon built from the specified linestring and SRID.

## Synopsis

`geometry ST_Polygon(`geometry aLineString, integer srid`)`;

## Description

Returns a polygon built from the specified linestring and SRID.

ST_Polygon is similar to first version oST_MakePolygon except it also sets the spatial ref sys (SRID) of the polygon. Will not work with MULTILINESTRINGS so use LineMerge to merge multilines. Also does not create polygons with holes. Use ST_MakePolygon for that.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.3.2

This function supports 3d and will not drop the z-index.

## Examples

    --a 2d polygon
    SELECT ST_Polygon(ST_GeomFromText('LINESTRING(75.15 29.53,77 29,77.6 29.5, 75.15 29.53)'), 4326);

    --result--
    POLYGON((75.15 29.53,77 29,77.6 29.5,75.15 29.53))
    --a 3d polygon
    SELECT ST_AsEWKT(ST_Polygon(ST_GeomFromEWKT('LINESTRING(75.15 29.53 1,77 29 1,77.6 29.5 1, 75.15 29.53 1)'), 4326));

    result
    ------
    SRID=4326;POLYGON((75.15 29.53 1,77 29 1,77.6 29.5 1,75.15 29.53 1))

## See Also

ST_AsEWKT, ST_AsText, ST_GeomFromEWKT, ST_GeomFromText, ST_LineMerge, ST_MakePolygon

## Name

ST_PolygonFromText — Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1.

## Synopsis

`geometry ST_PolygonFromText(`text WKT`)`;

`geometry ST_PolygonFromText(`text WKT, integer srid`)`;

## Description

Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1. Returns null if WKT is not a polygon.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

If you are absolutely sure all your WKT geometries are polygons, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 8.3.6

## Examples

    SELECT ST_PolygonFromText('POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
    -71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');
    st_polygonfromtext
    ------------------
    010300000001000000050000006...

    SELECT ST_PolygonFromText('POINT(1 2)') IS NULL as point_is_notpoly;

    point_is_not_poly
    ----------
    t

## See Also

ST_GeomFromText

## Name

ST_WKBToSQL — Return a specified ST_Geometry value from Well-Known Binary representation (WKB). This is an alias name for ST_GeomFromWKB that takes no srid

## Synopsis

`geometry ST_WKBToSQL(`bytea WKB`)`;

## Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.36

## See Also

ST_GeomFromWKB

## Name

ST_WKTToSQL — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText

## Synopsis

`geometry ST_WKTToSQL(`text WKT`)`;

## Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.34

## See Also

ST_GeomFromText

## 8.4. Geometry Accessors

## Name

GeometryType — Returns the type of the geometry as a string. Eg: 'LINESTRING', 'POLYGON', 'MULTIPOINT', etc.

## Synopsis

`text GeometryType(`geometry geomA`)`;

## Description

Returns the type of the geometry as a string. Eg: 'LINESTRING', 'POLYGON', 'MULTIPOINT', etc.

OGC SPEC s2.1.1.1 - Returns the name of the instantiable subtype of Geometry of which this Geometry instance is a member. The name of the instantiable subtype of Geometry is returned as a string.

This function also indicates if the geometry is measured, by returning a string of the form 'POINTM'.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT GeometryType(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
     geometrytype
    --------------
     LINESTRING

    SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
    			--result
    			POLYHEDRALSURFACE

    SELECT GeometryType(geom) as result
      FROM
        (SELECT
           ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )')  AS geom
        ) AS g;
     result
    --------
     TIN

## See Also

ST_GeometryType

## Name

ST_Boundary — Returns the closure of the combinatorial boundary of this Geometry.

## Synopsis

`geometry ST_Boundary(`geometry geomA`)`;

## Description

Returns the closure of the combinatorial boundary of this Geometry. The combinatorial boundary is defined as described in section 3.12.3.2 of the OGC SPEC. Because the result of this function is a closure, and hence topologically closed, the resulting boundary can be represented using representational geometry primitives as discussed in the OGC SPEC, section 3.12.2.

Performed by the GEOS module

Prior to 2.0.0, this function throws an exception if used with `GEOMETRYCOLLECTION`. From 2.0.0 up it will return NULL instead (unsupported input).

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. OGC SPEC s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.14

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(1 1,0 0, -1 1)')));
    st_astext
    -----------
    MULTIPOINT(1 1,-1 1)

    SELECT ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((1 1,0 0, -1 1, 1 1))')));
    st_astext
    ----------
    LINESTRING(1 1,0 0,-1 1,1 1)

    --Using a 3d polygon
    SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('POLYGON((1 1 1,0 0 1, -1 1 1, 1 1 1))')));

    st_asewkt
    -----------------------------------
    LINESTRING(1 1 1,0 0 1,-1 1 1,1 1 1)

    --Using a 3d multilinestring
    SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('MULTILINESTRING((1 1 1,0 0 0.5, -1 1 1),(1 1 0.5,0 0 0.5, -1 1 0.5, 1 1 0.5) )')));

    st_asewkt
    ----------
    MULTIPOINT(-1 1 1,1 1 0.75)

## See Also

ST_ExteriorRing, ST_MakePolygon

## Name

ST_CoordDim — Return the coordinate dimension of the ST_Geometry value.

## Synopsis

`integer ST_CoordDim(`geometry geomA`)`;

## Description

Return the coordinate dimension of the ST_Geometry value.

This is the MM compliant alias name for ST_NDims

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.3

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_CoordDim('CIRCULARSTRING(1 2 3, 1 3 4, 5 6 7, 8 9 10, 11 12 13)');
    			---result--
    				3

    				SELECT ST_CoordDim(ST_Point(1,2));
    			--result--
    				2

## See Also

ST_NDims

## Name

ST_Dimension — The inherent dimension of this Geometry object, which must be less than or equal to the coordinate dimension.

## Synopsis

`integer ST_Dimension(`geometry g`)`;

## Description

The inherent dimension of this Geometry object, which must be less than or equal to the coordinate dimension. OGC SPEC s2.1.1.1 - returns 0 for `POINT`, 1 for `LINESTRING`, 2 for `POLYGON`, and the largest dimension of the components of a `GEOMETRYCOLLECTION`. If unknown (empty geometry) null is returned.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.2

Enhanced: 2.0.0 support for Polyhedral surfaces and TINs was introduced. No longer throws an exception if given empty geometry.

Prior to 2.0.0, this function throws an exception if used with empty geometry.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_Dimension('GEOMETRYCOLLECTION(LINESTRING(1 1,0 0),POINT(0 0))');
    ST_Dimension
    -----------
    1

## See Also

ST_NDims

## Name

ST_EndPoint — Returns the last point of a `LINESTRING` geometry as a `POINT`.

## Synopsis

`boolean ST_EndPoint(`geometry g`)`;

## Description

Returns the last point of a `LINESTRING` geometry as a `POINT` or `NULL` if the input parameter is not a `LINESTRING`.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.4

This function supports 3d and will not drop the z-index.

Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring. The older behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0 now.

## Examples

    postgis=# SELECT ST_AsText(ST_EndPoint('LINESTRING(1 1, 2 2, 3 3)'::geometry));
     st_astext
    ------------
     POINT(3 3)
    (1 row)

    postgis=# SELECT ST_EndPoint('POINT(1 1)'::geometry) IS NULL AS is_null;
      is_null
    ----------
     t
    (1 row)

    --3d endpoint
    SELECT ST_AsEWKT(ST_EndPoint('LINESTRING(1 1 2, 1 2 3, 0 0 5)'));
      st_asewkt
    --------------
     POINT(0 0 5)
    (1 row)

## See Also

ST_PointN, ST_StartPoint

## Name

ST_Envelope — Returns a geometry representing the double precision (float8) bounding box of the supplied geometry.

## Synopsis

`geometry ST_Envelope(`geometry g1`)`;

## Description

Returns the float8 minimum bounding box for the supplied geometry, as a geometry. The polygon is defined by the corner points of the bounding box ((`MINX`, `MINY`), (`MINX`, `MAXY`), (`MAXX`, `MAXY`), (`MAXX`, `MINY`), (`MINX`, `MINY`)). (PostGIS will add a `ZMIN`/`ZMAX` coordinate as well).

Degenerate cases (vertical lines, points) will return a geometry of lower dimension than `POLYGON`, ie. `POINT` or `LINESTRING`.

Availability: 1.5.0 behavior changed to output double precision instead of float4

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.15

## Examples

    SELECT ST_AsText(ST_Envelope('POINT(1 3)'::geometry));
     st_astext
    ------------
     POINT(1 3)
    (1 row)

    SELECT ST_AsText(ST_Envelope('LINESTRING(0 0, 1 3)'::geometry));
    		   st_astext
    --------------------------------
     POLYGON((0 0,0 3,1 3,1 0,0 0))
    (1 row)

    SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000001 1, 1.0000001 0, 0 0))'::geometry));
    						  st_astext
    --------------------------------------------------------------
     POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))
    (1 row)
    SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000000001 1, 1.0000000001 0, 0 0))'::geometry));
    						  st_astext
    --------------------------------------------------------------
     POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))
    (1 row)

    SELECT Box3D(geom), Box2D(geom), ST_AsText(ST_Envelope(geom)) As envelopewkt
    	FROM (SELECT 'POLYGON((0 0, 0 1000012333334.34545678, 1.0000001 1, 1.0000001 0, 0 0))'::geometry As geom) As foo;

## See Also

Box2D, Box3D

## Name

ST_ExteriorRing — Returns a line string representing the exterior ring of the `POLYGON` geometry. Return NULL if the geometry is not a polygon. Will not work with MULTIPOLYGON

## Synopsis

`geometry ST_ExteriorRing(`geometry a_polygon`)`;

## Description

Returns a line string representing the exterior ring of the `POLYGON` geometry. Return NULL if the geometry is not a polygon.

Only works with POLYGON geometry types

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. 2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 8.2.3, 8.3.3

This function supports 3d and will not drop the z-index.

## Examples

    --If you have a table of polygons
    SELECT gid, ST_ExteriorRing(the_geom) AS ering
    FROM sometable;

    --If you have a table of MULTIPOLYGONs
    --and want to return a MULTILINESTRING composed of the exterior rings of each polygon
    SELECT gid, ST_Collect(ST_ExteriorRing(the_geom)) AS erings
    	FROM (SELECT gid, (ST_Dump(the_geom)).geom As the_geom
    			FROM sometable) As foo
    GROUP BY gid;

    --3d Example
    SELECT ST_AsEWKT(
    	ST_ExteriorRing(
    	ST_GeomFromEWKT('POLYGON((0 0 1, 1 1 1, 1 2 1, 1 1 1, 0 0 1))')
    	)
    );

    st_asewkt
    ---------
    LINESTRING(0 0 1,1 1 1,1 2 1,1 1 1,0 0 1)

## See Also

ST_InteriorRingN, ST_Boundary, ST_NumInteriorRings

## Name

ST_GeometryN — Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL.

## Synopsis

`geometry ST_GeometryN(`geometry geomA, integer n`)`;

## Description

Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL

Index is 1-based as for OGC specs since version 0.8.0. Previous versions implemented this as 0-based instead.

If you want to extract all geometries, of a geometry, ST_Dump is more efficient and will also work for singular geoms.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Changed: 2.0.0 Prior versions would return NULL for singular geometries. This was changed to return the geometry for ST_GeometryN(..,1) case.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 9.1.5

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Standard Examples

    --Extracting a subset of points from a 3d multipoint
    SELECT n, ST_AsEWKT(ST_GeometryN(the_geom, n)) As geomewkt
    FROM (
    VALUES (ST_GeomFromEWKT('MULTIPOINT(1 2 7, 3 4 7, 5 6 7, 8 9 10)') ),
    ( ST_GeomFromEWKT('MULTICURVE(CIRCULARSTRING(2.5 2.5,4.5 2.5, 3.5 3.5), (10 11, 12 11))') )
    	)As foo(the_geom)
    	CROSS JOIN generate_series(1,100) n
    WHERE n <= ST_NumGeometries(the_geom);

     n |               geomewkt
    ---+-----------------------------------------
     1 | POINT(1 2 7)
     2 | POINT(3 4 7)
     3 | POINT(5 6 7)
     4 | POINT(8 9 10)
     1 | CIRCULARSTRING(2.5 2.5,4.5 2.5,3.5 3.5)
     2 | LINESTRING(10 11,12 11)

    --Extracting all geometries (useful when you want to assign an id)
    SELECT gid, n, ST_GeometryN(the_geom, n)
    FROM sometable CROSS JOIN generate_series(1,100) n
    WHERE n <= ST_NumGeometries(the_geom);

## Polyhedral Surfaces, TIN and Triangle Examples

    -- Polyhedral surface example
    -- Break a Polyhedral surface into its faces
    SELECT ST_AsEWKT(ST_GeometryN(p_geom,3)) As geom_ewkt
      FROM (SELECT ST_GeomFromEWKT('POLYHEDRALSURFACE(
    ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
    ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
    ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
    )')  AS p_geom )  AS a;

                    geom_ewkt
    ------------------------------------------
     POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0))

    -- TIN --
    SELECT ST_AsEWKT(ST_GeometryN(geom,2)) as wkt
      FROM
        (SELECT
           ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )')  AS geom
        ) AS g;
    -- result --
                     wkt
    -------------------------------------
     TRIANGLE((0 0 0,0 1 0,1 1 0,0 0 0))

## See Also

ST_Dump, ST_NumGeometries

## Name

ST_GeometryType — Return the geometry type of the ST_Geometry value.

## Synopsis

`text ST_GeometryType(`geometry g1`)`;

## Description

Returns the type of the geometry as a string. EG: 'ST_Linestring', 'ST_Polygon','ST_MultiPolygon' etc. This function differs from GeometryType(geometry) in the case of the string and ST in front that is returned, as well as the fact that it will not indicate whether the geometry is measured.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.4

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_GeometryType(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
    			--result
    			ST_LineString

    SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
    			--result
    			ST_PolyhedralSurface

    SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
    			--result
    			ST_PolyhedralSurface

    SELECT ST_GeometryType(geom) as result
      FROM
        (SELECT
           ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )')  AS geom
        ) AS g;
     result
    --------
     ST_Tin

## See Also

GeometryType

## Name

ST_InteriorRingN — Return the Nth interior linestring ring of the polygon geometry. Return NULL if the geometry is not a polygon or the given N is out of range.

## Synopsis

`geometry ST_InteriorRingN(`geometry a_polygon, integer n`)`;

## Description

Return the Nth interior linestring ring of the polygon geometry. Return NULL if the geometry is not a polygon or the given N is out of range. index starts at 1.

This will not work for MULTIPOLYGONs. Use in conjunction with ST_Dump for MULTIPOLYGONS

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.2.6, 8.3.5

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsText(ST_InteriorRingN(the_geom, 1)) As the_geom
    FROM (SELECT ST_BuildArea(
    		ST_Collect(ST_Buffer(ST_Point(1,2), 20,3),
    			ST_Buffer(ST_Point(1, 2), 10,3))) As the_geom
    		)  as foo

## See Also

ST_ExteriorRing ST_BuildArea, ST_Collect, ST_Dump, ST_NumInteriorRing, ST_NumInteriorRings

## Name

ST_IsClosed — Returns `TRUE` if the `LINESTRING`'s start and end points are coincident. For Polyhedral surface is closed (volumetric).

## Synopsis

`boolean ST_IsClosed(`geometry g`)`;

## Description

Returns `TRUE` if the `LINESTRING`'s start and end points are coincident. For Polyhedral Surfaces, it tells you if the surface is areal (open) or volumetric (closed).

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.5, 9.3.3

SQL-MM defines the result of `ST_IsClosed(`NULL`)` to be 0, while PostGIS returns `NULL`.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This function supports Polyhedral surfaces.

## Line String and Point Examples

    postgis=# SELECT ST_IsClosed('LINESTRING(0 0, 1 1)'::geometry);
     st_isclosed
    -------------
     f
    (1 row)

    postgis=# SELECT ST_IsClosed('LINESTRING(0 0, 0 1, 1 1, 0 0)'::geometry);
     st_isclosed
    -------------
     t
    (1 row)

    postgis=# SELECT ST_IsClosed('MULTILINESTRING((0 0, 0 1, 1 1, 0 0),(0 0, 1 1))'::geometry);
     st_isclosed
    -------------
     f
    (1 row)

    postgis=# SELECT ST_IsClosed('POINT(0 0)'::geometry);
     st_isclosed
    -------------
     t
    (1 row)

    postgis=# SELECT ST_IsClosed('MULTIPOINT((0 0), (1 1))'::geometry);
     st_isclosed
    -------------
     t
    (1 row)

## Polyhedral Surface Examples

    		-- A cube --
    		SELECT ST_IsClosed(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));

     st_isclosed
    -------------
     t

     -- Same as cube but missing a side --
     SELECT ST_IsClosed(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)) )'));

     st_isclosed
    -------------
     f

## See Also

ST_IsRing

## Name

ST_IsCollection — Returns `TRUE` if the argument is a collection (`MULTI*`, `GEOMETRYCOLLECTION`, ...)

## Synopsis

`boolean ST_IsCollection(`geometry g`)`;

## Description

Returns `TRUE` if the geometry type of the argument is either:

- GEOMETRYCOLLECTION

- MULTI{POINT,POLYGON,LINESTRING,CURVE,SURFACE}

- COMPOUNDCURVE

This function analyzes the type of the geometry. This means that it will return `TRUE` on collections that are empty or that contain a single element.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    postgis=# SELECT ST_IsCollection('LINESTRING(0 0, 1 1)'::geometry);
     st_iscollection
    -------------
     f
    (1 row)

    postgis=# SELECT ST_IsCollection('MULTIPOINT EMPTY'::geometry);
     st_iscollection
    -------------
     t
    (1 row)

    postgis=# SELECT ST_IsCollection('MULTIPOINT((0 0))'::geometry);
     st_iscollection
    -------------
     t
    (1 row)

    postgis=# SELECT ST_IsCollection('MULTIPOINT((0 0), (42 42))'::geometry);
     st_iscollection
    -------------
     t
    (1 row)

    postgis=# SELECT ST_IsCollection('GEOMETRYCOLLECTION(POINT(0 0))'::geometry);
     st_iscollection
    -------------
     t
    (1 row)

## See Also

ST_NumGeometries

## Name

ST_IsEmpty — Returns true if this Geometry is an empty geometrycollection, polygon, point etc.

## Synopsis

`boolean ST_IsEmpty(`geometry geomA`)`;

## Description

Returns true if this Geometry is an empty geometry. If true, then this Geometry represents an empty geometry collection, polygon, point etc.

SQL-MM defines the result of ST_IsEmpty(NULL) to be 0, while PostGIS returns NULL.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.7

This method supports Circular Strings and Curves

Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards

## Examples

    SELECT ST_IsEmpty(ST_GeomFromText('GEOMETRYCOLLECTION EMPTY'));
     st_isempty
    ------------
     t
    (1 row)

     SELECT ST_IsEmpty(ST_GeomFromText('POLYGON EMPTY'));
     st_isempty
    ------------
     t
    (1 row)

    SELECT ST_IsEmpty(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))'));

     st_isempty
    ------------
     f
    (1 row)

     SELECT ST_IsEmpty(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))')) = false;
     ?column?
    ----------
     t
    (1 row)

     SELECT ST_IsEmpty(ST_GeomFromText('CIRCULARSTRING EMPTY'));
      st_isempty
    ------------
     t
    (1 row)

## Name

ST_IsRing — Returns `TRUE` if this `LINESTRING` is both closed and simple.

## Synopsis

`boolean ST_IsRing(`geometry g`)`;

## Description

Returns `TRUE` if this `LINESTRING` is both ST_IsClosed (`ST_StartPoint(`g`)` `~=` `ST_Endpoint(`g`)`) and ST_IsSimple (does not self intersect).

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. 2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 7.1.6

SQL-MM defines the result of `ST_IsRing(`NULL`)` to be 0, while PostGIS returns `NULL`.

## Examples

    SELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom)
    FROM (SELECT 'LINESTRING(0 0, 0 1, 1 1, 1 0, 0 0)'::geometry AS the_geom) AS foo;
     st_isring | st_isclosed | st_issimple
    -----------+-------------+-------------
     t         | t           | t
    (1 row)

    SELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom)
    FROM (SELECT 'LINESTRING(0 0, 0 1, 1 0, 1 1, 0 0)'::geometry AS the_geom) AS foo;
     st_isring | st_isclosed | st_issimple
    -----------+-------------+-------------
     f         | t           | f
    (1 row)

## See Also

ST_IsClosed, ST_IsSimple, ST_StartPoint, ST_EndPoint

## Name

ST_IsSimple — Returns (TRUE) if this Geometry has no anomalous geometric points, such as self intersection or self tangency.

## Synopsis

`boolean ST_IsSimple(`geometry geomA`)`;

## Description

Returns true if this Geometry has no anomalous geometric points, such as self intersection or self tangency. For more information on the OGC's definition of geometry simplicity and validity, refer to "Ensuring OpenGIS compliancy of geometries"

SQL-MM defines the result of ST_IsSimple(NULL) to be 0, while PostGIS returns NULL.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.8

This function supports 3d and will not drop the z-index.

## Examples

     SELECT ST_IsSimple(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))'));
     st_issimple
    -------------
     t
    (1 row)

     SELECT ST_IsSimple(ST_GeomFromText('LINESTRING(1 1,2 2,2 3.5,1 3,1 2,2 1)'));
     st_issimple
    -------------
     f
    (1 row)

## See Also

ST_IsValid

## Name

ST_IsValid — Returns `true` if the `ST_Geometry` is well formed.

## Synopsis

`boolean ST_IsValid(`geometry g`)`;

`boolean ST_IsValid(`geometry g, integer flags`)`;

## Description

Test if an ST_Geometry value is well formed. For geometries that are invalid, the PostgreSQL NOTICE will provide details of why it is not valid. For more information on the OGC's definition of geometry simplicity and validity, refer to "Ensuring OpenGIS compliancy of geometries"

SQL-MM defines the result of ST_IsValid(NULL) to be 0, while PostGIS returns NULL.

The version accepting flags is available starting with 2.0.0 and requires GEOS >= 3.3.0. Such version does not print a NOTICE explaining the invalidity. Allowed `flags` are documented in ST_IsValidDetail.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.9

## Examples

    SELECT ST_IsValid(ST_GeomFromText('LINESTRING(0 0, 1 1)')) As good_line,
    	ST_IsValid(ST_GeomFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) As bad_poly
    --results
    NOTICE:  Self-intersection at or near point 0 0
     good_line | bad_poly
    -----------+----------
     t         | f

## See Also

ST_IsSimple, ST_IsValidReason, ST_IsValidDetail, ST_Summary

## Name

ST_IsValidReason — Returns text stating if a geometry is valid or not and if not valid, a reason why.

## Synopsis

`text ST_IsValidReason(`geometry geomA`)`;

`text ST_IsValidReason(`geometry geomA, integer flags`)`;

## Description

Returns text stating if a geometry is valid or not an if not valid, a reason why.

Useful in combination with ST_IsValid to generate a detailed report of invalid geometries and reasons.

Allowed `flags` are documented in ST_IsValidDetail.

Availability: 1.4 - requires GEOS >= 3.1.0.

Availability: 2.0 - requires GEOS >= 3.3.0 for the version taking flags.

## Examples

    --First 3 Rejects from a successful quintuplet experiment
    SELECT gid, ST_IsValidReason(the_geom) as validity_info
    FROM
    (SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), ST_Accum(f.line)) As the_geom, gid
    FROM (SELECT ST_Buffer(ST_MakePoint(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid
    	FROM generate_series(-4,6) x1
    	CROSS JOIN generate_series(2,5) y1
    	CROSS JOIN generate_series(1,8) z1
    	WHERE x1 > y1*0.5 AND z1 < x1*y1) As e
    	INNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_MakePoint(x1*10,y1), z1)),y1*1, z1*2) As line
    	FROM generate_series(-3,6) x1
    	CROSS JOIN generate_series(2,5) y1
    	CROSS JOIN generate_series(1,10) z1
    	WHERE x1 > y1*0.75 AND z1 < x1*y1) As f
    ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line))
    GROUP BY gid, e.buff) As quintuplet_experiment
    WHERE ST_IsValid(the_geom) = false
    ORDER BY gid
    LIMIT 3;

     gid  |      validity_info
    ------+--------------------------
     5330 | Self-intersection [32 5]
     5340 | Self-intersection [42 5]
     5350 | Self-intersection [52 5]

     --simple example
    SELECT ST_IsValidReason('LINESTRING(220227 150406,2220227 150407,222020 150410)');

     st_isvalidreason
    ------------------
     Valid Geometry

## See Also

ST_IsValid, ST_Summary

## Name

ST_IsValidDetail — Returns a valid_detail (valid,reason,location) row stating if a geometry is valid or not and if not valid, a reason why and a location where.

## Synopsis

`valid_detail ST_IsValidDetail(`geometry geom`)`;

`valid_detail ST_IsValidDetail(`geometry geom, integer flags`)`;

## Description

Returns a valid_detail row, formed by a boolean (valid) stating if a geometry is valid, a varchar (reason) stating a reason why it is invalid and a geometry (location) pointing out where it is invalid.

Useful to substitute and improve the combination of ST_IsValid and ST_IsValidReason to generate a detailed report of invalid geometries.

The 'flags' argument is a bitfield. It can have the following values:

- 1: Consider self-intersecting rings forming holes as valid. This is also know as "the ESRI flag". Note that this is against the OGC model.

Availability: 2.0.0 - requires GEOS >= 3.3.0.

## Examples

    --First 3 Rejects from a successful quintuplet experiment
    SELECT gid, reason(ST_IsValidDetail(the_geom)), ST_AsText(location(ST_IsValidDetail(the_geom))) as location
    FROM
    (SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), ST_Accum(f.line)) As the_geom, gid
    FROM (SELECT ST_Buffer(ST_MakePoint(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid
    	FROM generate_series(-4,6) x1
    	CROSS JOIN generate_series(2,5) y1
    	CROSS JOIN generate_series(1,8) z1
    	WHERE x1 > y1*0.5 AND z1 < x1*y1) As e
    	INNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_MakePoint(x1*10,y1), z1)),y1*1, z1*2) As line
    	FROM generate_series(-3,6) x1
    	CROSS JOIN generate_series(2,5) y1
    	CROSS JOIN generate_series(1,10) z1
    	WHERE x1 > y1*0.75 AND z1 < x1*y1) As f
    ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line))
    GROUP BY gid, e.buff) As quintuplet_experiment
    WHERE ST_IsValid(the_geom) = false
    ORDER BY gid
    LIMIT 3;

     gid  |      reason       |  location
    ------+-------------------+-------------
     5330 | Self-intersection | POINT(32 5)
     5340 | Self-intersection | POINT(42 5)
     5350 | Self-intersection | POINT(52 5)

     --simple example
    SELECT * FROM ST_IsValidDetail('LINESTRING(220227 150406,2220227 150407,222020 150410)');

     valid | reason | location
    -------+--------+----------
     t     |        |

## See Also

ST_IsValid, ST_IsValidReason

## Name

ST_M — Return the M coordinate of the point, or NULL if not available. Input must be a point.

## Synopsis

`float ST_M(`geometry a_point`)`;

## Description

Return the M coordinate of the point, or NULL if not available. Input must be a point.

This is not (yet) part of the OGC spec, but is listed here to complete the point coordinate extractor function list.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification.

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_M(ST_GeomFromEWKT('POINT(1 2 3 4)'));
     st_m
    ------
    	4
    (1 row)

## See Also

ST_GeomFromEWKT, ST_X, ST_Y, ST_Z

## Name

ST_NDims — Returns coordinate dimension of the geometry as a small int. Values are: 2,3 or 4.

## Synopsis

`integer ST_NDims(`geometry g1`)`;

## Description

Returns the coordinate dimension of the geometry. PostGIS supports 2 - (x,y) , 3 - (x,y,z) or 2D with measure - x,y,m, and 4 - 3D with measure space x,y,z,m

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_NDims(ST_GeomFromText('POINT(1 1)')) As d2point,
    	ST_NDims(ST_GeomFromEWKT('POINT(1 1 2)')) As d3point,
    	ST_NDims(ST_GeomFromEWKT('POINTM(1 1 0.5)')) As d2pointm;

    	 d2point | d3point | d2pointm
    ---------+---------+----------
    	   2 |       3 |        3

## See Also

ST_CoordDim, ST_Dimension, ST_GeomFromEWKT

## Name

ST_NPoints — Return the number of points (vertexes) in a geometry.

## Synopsis

`integer ST_NPoints(`geometry g1`)`;

## Description

Return the number of points in a geometry. Works for all geometries.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_NPoints(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
    --result
    4

    --Polygon in 3D space
    SELECT ST_NPoints(ST_GeomFromEWKT('LINESTRING(77.29 29.07 1,77.42 29.26 0,77.27 29.31 -1,77.29 29.07 3)'))
    --result
    4

## See Also

ST_NumPoints

## Name

ST_NRings — If the geometry is a polygon or multi-polygon returns the number of rings.

## Synopsis

`integer ST_NRings(`geometry geomA`)`;

## Description

If the geometry is a polygon or multi-polygon returns the number of rings. Unlike NumInteriorRings, it counts the outer rings as well.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_NRings(the_geom) As Nrings, ST_NumInteriorRings(the_geom) As ninterrings
    					FROM (SELECT ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))') As the_geom) As foo;
    	 nrings | ninterrings
    --------+-------------
    	  1 |           0
    (1 row)

## See Also

ST_NumInteriorRings

## Name

ST_NumGeometries — If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for single geometries will return 1, otherwise return NULL.

## Synopsis

`integer ST_NumGeometries(`geometry geom`)`;

## Description

Returns the number of Geometries. If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for single geometries will return 1, otherwise return NULL.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Changed: 2.0.0 In prior versions this would return NULL if the geometry was not a collection/MULTI type. 2.0.0+ now returns 1 for single geometries e.g POLYGON, LINESTRING, POINT.

This method implements the SQL/MM specification. SQL-MM 3: 9.1.4

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Prior versions would have returned NULL for this -- in 2.0.0 this returns 1
    SELECT ST_NumGeometries(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
    --result
    1

    --Geometry Collection Example - multis count as one geom in a collection
    SELECT ST_NumGeometries(ST_GeomFromEWKT('GEOMETRYCOLLECTION(MULTIPOINT(-2 3 , -2 2),
    LINESTRING(5 5 ,10 10),
    POLYGON((-7 4.2,-7.1 5,-7.1 4.3,-7 4.2)))'));
    --result
    3

## See Also

ST_GeometryN, ST_Multi

## Name

ST_NumInteriorRings — Return the number of interior rings of the first polygon in the geometry. This will work with both POLYGON and MULTIPOLYGON types but only looks at the first polygon. Return NULL if there is no polygon in the geometry.

## Synopsis

`integer ST_NumInteriorRings(`geometry a_polygon`)`;

## Description

Return the number of interior rings of the first polygon in the geometry. This will work with both POLYGON and MULTIPOLYGON types but only looks at the first polygon. Return NULL if there is no polygon in the geometry.

This method implements the SQL/MM specification. SQL-MM 3: 8.2.5

## Examples

    --If you have a regular polygon
    SELECT gid, field1, field2, ST_NumInteriorRings(the_geom) AS numholes
    FROM sometable;

    --If you have multipolygons
    --And you want to know the total number of interior rings in the MULTIPOLYGON
    SELECT gid, field1, field2, SUM(ST_NumInteriorRings(the_geom)) AS numholes
    FROM (SELECT gid, field1, field2, (ST_Dump(the_geom)).geom As the_geom
    	FROM sometable) As foo
    GROUP BY gid, field1,field2;

## See Also

ST_NumInteriorRing

## Name

ST_NumInteriorRing — Return the number of interior rings of the first polygon in the geometry. Synonym to ST_NumInteriorRings.

## Synopsis

`integer ST_NumInteriorRing(`geometry a_polygon`)`;

## Description

Return the number of interior rings of the first polygon in the geometry. Synonym to ST_NumInteriorRings. The OpenGIS specs are ambiguous about the exact function naming, so we provide both spellings.

This method implements the SQL/MM specification. SQL-MM 3: 8.2.5

## See Also

ST_NumInteriorRings

## Name

ST_NumPatches — Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.

## Synopsis

`integer ST_NumPatches(`geometry g1`)`;

## Description

Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries. This is an alias for ST_NumGeometries to support MM naming. Faster to use ST_NumGeometries if you don't care about MM convention.

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: ?

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_NumPatches(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
    		--result
    		6

## See Also

ST_GeomFromEWKT, ST_NumGeometries

## Name

ST_NumPoints — Return the number of points in an ST_LineString or ST_CircularString value.

## Synopsis

`integer ST_NumPoints(`geometry g1`)`;

## Description

Return the number of points in an ST_LineString or ST_CircularString value. Prior to 1.4 only works with Linestrings as the specs state. From 1.4 forward this is an alias for ST_NPoints which returns number of vertexes for not just line strings. Consider using ST_NPoints instead which is multi-purpose and works with many geometry types.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.2.4

## Examples

    SELECT ST_NumPoints(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
    		--result
    		4

## See Also

ST_NPoints

## Name

ST_PatchN — Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Otherwise, return NULL.

## Synopsis

`geometry ST_PatchN(`geometry geomA, integer n`)`;

## Description

>Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Otherwise, return NULL. This returns the same answer as ST_GeometryN for Polyhedral Surfaces. Using ST_GemoetryN is faster.

Index is 1-based.

If you want to extract all geometries, of a geometry, ST_Dump is more efficient.

Availability: 2.0.0

This method implements the SQL/MM specification. SQL-MM 3: ?

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

    --Extract the 2nd face of the polyhedral surface
    SELECT ST_AsEWKT(ST_PatchN(geom, 2)) As geomewkt
    FROM (
    VALUES (ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    	((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    	((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    	((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')) ) As foo(geom);

                  geomewkt
    ---+-----------------------------------------
     POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0))

## See Also

ST_AsEWKT, ST_GeomFromEWKT, ST_Dump, ST_GeometryN, ST_NumGeometries

## Name

ST_PointN — Return the Nth point in the first linestring or circular linestring in the geometry. Return NULL if there is no linestring in the geometry.

## Synopsis

`geometry ST_PointN(`geometry a_linestring, integer n`)`;

## Description

Return the Nth point in the first linestring or circular linestring in the geometry. Return NULL if there is no linestring in the geometry.

Index is 1-based as for OGC specs since version 0.8.0. Previous versions implemented this as 0-based instead.

If you want to get the nth point of each line string in a multilinestring, use in conjunction with ST_Dump

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.2.5, 7.3.5

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    -- Extract all POINTs from a LINESTRING
    SELECT ST_AsText(
       ST_PointN(
    	  column1,
    	  generate_series(1, ST_NPoints(column1))
       ))
    FROM ( VALUES ('LINESTRING(0 0, 1 1, 2 2)'::geometry) ) AS foo;

     st_astext
    ------------
     POINT(0 0)
     POINT(1 1)
     POINT(2 2)
    (3 rows)

    --Example circular string
    SELECT ST_AsText(ST_PointN(ST_GeomFromText('CIRCULARSTRING(1 2, 3 2, 1 2)'),2));

    st_astext
    ----------
    POINT(3 2)

## See Also

ST_NPoints

## Name

ST_SRID — Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table.

## Synopsis

`integer ST_SRID(`geometry g1`)`;

## Description

Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table. Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems”

spatial_ref_sys table is a table that catalogs all spatial reference systems known to PostGIS and is used for transformations from one spatial reference system to another. So verifying you have the right spatial reference system identifier is important if you plan to ever transform your geometries.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.5

This method supports Circular Strings and Curves

## Examples

    SELECT ST_SRID(ST_GeomFromText('POINT(-71.1043 42.315)',4326));
    		--result
    		4326

## See Also

Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems”, ST_GeomFromText, ST_SetSRID, ST_Transform

## Name

ST_StartPoint — Returns the first point of a `LINESTRING` geometry as a `POINT`.

## Synopsis

`geometry ST_StartPoint(`geometry geomA`)`;

## Description

Returns the first point of a `LINESTRING` geometry as a `POINT` or `NULL` if the input parameter is not a `LINESTRING`.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.3

This function supports 3d and will not drop the z-index.

Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring. The older behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0 now.

## Examples

    SELECT ST_AsText(ST_StartPoint('LINESTRING(0 1, 0 2)'::geometry));
     st_astext
    ------------
     POINT(0 1)
    (1 row)

    SELECT ST_StartPoint('POINT(0 1)'::geometry) IS NULL AS is_null;
      is_null
    ----------
     t
    (1 row)

    --3d line
    SELECT ST_AsEWKT(ST_StartPoint('LINESTRING(0 1 1, 0 2 2)'::geometry));
     st_asewkt
    ------------
     POINT(0 1 1)
    (1 row)

## See Also

ST_EndPoint, ST_PointN

## Name

ST_Summary — Returns a text summary of the contents of the geometry.

## Synopsis

`text ST_Summary(`geometry g`)`;

`text ST_Summary(`geography g`)`;

## Description

Returns a text summary of the contents of the geometry.

Flags shown square brackets after the geometry type have the following meaning:

- M: has M ordinate

- Z: has Z ordinate

- B: has a cached bounding box

- G: is geodetic (geography)

Availability: 1.2.2 - 2.0.0 added support for geography

## Examples

    =# SELECT ST_Summary(ST_GeomFromText('LINESTRING(0 0, 1 1)')) as geom,
            ST_Summary(ST_GeogFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) geog;
                geom             |          geog
    -----------------------------+--------------------------
     LineString[B] with 2 points | Polygon[BG] with 1 rings
                                 :    ring 0 has 5 points
                                 :
    (1 row)

    =# SELECT ST_Summary(ST_GeogFromText('LINESTRING(0 0 1, 1 1 1)')) As geog_line,
            ST_Summary(ST_GeomFromText('POLYGON((0 0 1, 1 1 2, 1 2 3, 1 1 1, 0 0 1))')) As geom_poly;
    ;
               geog_line           |        geom_poly
    -------------------------------+--------------------------
     LineString[ZBG] with 2 points | Polygon[ZB] with 1 rings
                                   :    ring 0 has 5 points
                                   :
    (1 row)

## See Also

PostGIS_DropBBox, PostGIS_AddBBox, ST_Force_3DM, ST_Force_3DZ, ST_Force_2D, geography

ST_IsValid, ST_IsValid, ST_IsValidReason, ST_IsValidDetail

## Name

ST_X — Return the X coordinate of the point, or NULL if not available. Input must be a point.

## Synopsis

`float ST_X(`geometry a_point`)`;

## Description

Return the X coordinate of the point, or NULL if not available. Input must be a point.

If you want to get the max min x values of any geometry look at ST_XMin, ST_XMax functions.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.3

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_X(ST_GeomFromEWKT('POINT(1 2 3 4)'));
     st_x
    ------
    	1
    (1 row)

    SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)')));
     st_y
    ------
      1.5
    (1 row)

## See Also

ST_Centroid, ST_GeomFromEWKT, ST_M, ST_XMax, ST_XMin, ST_Y, ST_Z

## Name

ST_XMax — Returns X maxima of a bounding box 2d or 3d or a geometry.

## Synopsis

`float ST_XMax(`box3d aGeomorBox2DorBox3D`)`;

## Description

Returns X maxima of a bounding box 2d or 3d or a geometry.

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_XMax('BOX3D(1 2 3, 4 5 6)');
    st_xmax
    -------
    4

    SELECT ST_XMax(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
    st_xmax
    -------
    5

    SELECT ST_XMax(CAST('BOX(-3 2, 3 4)' As box2d));
    st_xmax
    -------
    3
    --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
    SELECT ST_XMax('LINESTRING(1 3, 5 6)');

    --ERROR:  BOX3D parser - doesnt start with BOX3D(

    SELECT ST_XMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_xmax
    --------
    220288.248780547

## See Also

ST_XMin, ST_YMax, ST_YMin, ST_ZMax, ST_ZMin

## Name

ST_XMin — Returns X minima of a bounding box 2d or 3d or a geometry.

## Synopsis

`float ST_XMin(`box3d aGeomorBox2DorBox3D`)`;

## Description

Returns X minima of a bounding box 2d or 3d or a geometry.

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_XMin('BOX3D(1 2 3, 4 5 6)');
    st_xmin
    -------
    1

    SELECT ST_XMin(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
    st_xmin
    -------
    1

    SELECT ST_XMin(CAST('BOX(-3 2, 3 4)' As box2d));
    st_xmin
    -------
    -3
    --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
    SELECT ST_XMin('LINESTRING(1 3, 5 6)');

    --ERROR:  BOX3D parser - doesnt start with BOX3D(

    SELECT ST_XMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_xmin
    --------
    220186.995121892

## See Also

ST_XMax, ST_YMax, ST_YMin, ST_ZMax, ST_ZMin

## Name

ST_Y — Return the Y coordinate of the point, or NULL if not available. Input must be a point.

## Synopsis

`float ST_Y(`geometry a_point`)`;

## Description

Return the Y coordinate of the point, or NULL if not available. Input must be a point.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.4

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_Y(ST_GeomFromEWKT('POINT(1 2 3 4)'));
     st_y
    ------
    	2
    (1 row)

    SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)')));
     st_y
    ------
      1.5
    (1 row)

## See Also

ST_Centroid, ST_GeomFromEWKT, ST_M, ST_X, ST_YMax, ST_YMin, ST_Z

## Name

ST_YMax — Returns Y maxima of a bounding box 2d or 3d or a geometry.

## Synopsis

`float ST_YMax(`box3d aGeomorBox2DorBox3D`)`;

## Description

Returns Y maxima of a bounding box 2d or 3d or a geometry.

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_YMax('BOX3D(1 2 3, 4 5 6)');
    st_ymax
    -------
    5

    SELECT ST_YMax(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
    st_ymax
    -------
    6

    SELECT ST_YMax(CAST('BOX(-3 2, 3 4)' As box2d));
    st_ymax
    -------
    4
    --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
    SELECT ST_YMax('LINESTRING(1 3, 5 6)');

    --ERROR:  BOX3D parser - doesnt start with BOX3D(

    SELECT ST_YMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_ymax
    --------
    150506.126829327

## See Also

ST_XMin, ST_XMax, ST_YMin, ST_ZMax, ST_ZMin

## Name

ST_YMin — Returns Y minima of a bounding box 2d or 3d or a geometry.

## Synopsis

`float ST_YMin(`box3d aGeomorBox2DorBox3D`)`;

## Description

Returns Y minima of a bounding box 2d or 3d or a geometry.

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_YMin('BOX3D(1 2 3, 4 5 6)');
    st_ymin
    -------
    2

    SELECT ST_YMin(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
    st_ymin
    -------
    3

    SELECT ST_YMin(CAST('BOX(-3 2, 3 4)' As box2d));
    st_ymin
    -------
    2
    --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
    SELECT ST_YMin('LINESTRING(1 3, 5 6)');

    --ERROR:  BOX3D parser - doesnt start with BOX3D(

    SELECT ST_YMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_ymin
    --------
    150406

## See Also

ST_GeomFromEWKT, ST_XMin, ST_XMax, ST_YMax, ST_ZMax, ST_ZMin

## Name

ST_Z — Return the Z coordinate of the point, or NULL if not available. Input must be a point.

## Synopsis

`float ST_Z(`geometry a_point`)`;

## Description

Return the Z coordinate of the point, or NULL if not available. Input must be a point.

This method implements the SQL/MM specification.

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_Z(ST_GeomFromEWKT('POINT(1 2 3 4)'));
     st_z
    ------
    	3
    (1 row)

## See Also

ST_GeomFromEWKT, ST_M, ST_X, ST_Y, ST_ZMax, ST_ZMin

## Name

ST_ZMax — Returns Z minima of a bounding box 2d or 3d or a geometry.

## Synopsis

`float ST_ZMax(`box3d aGeomorBox2DorBox3D`)`;

## Description

Returns Z maxima of a bounding box 2d or 3d or a geometry.

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_ZMax('BOX3D(1 2 3, 4 5 6)');
    st_zmax
    -------
    6

    SELECT ST_ZMax(ST_GeomFromEWKT('LINESTRING(1 3 4, 5 6 7)'));
    st_zmax
    -------
    7

    SELECT ST_ZMax('BOX3D(-3 2 1, 3 4 1)' );
    st_zmax
    -------
    1
    --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
    SELECT ST_ZMax('LINESTRING(1 3 4, 5 6 7)');

    --ERROR:  BOX3D parser - doesnt start with BOX3D(

    SELECT ST_ZMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_zmax
    --------
    3

## See Also

ST_GeomFromEWKT, ST_XMin, ST_XMax, ST_YMax, ST_YMin, ST_ZMax

## Name

ST_Zmflag — Returns ZM (dimension semantic) flag of the geometries as a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d.

## Synopsis

`smallint ST_Zmflag(`geometry geomA`)`;

## Description

Returns ZM (dimension semantic) flag of the geometries as a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_Zmflag(ST_GeomFromEWKT('LINESTRING(1 2, 3 4)'));
     st_zmflag
    -----------
    		 0

    SELECT ST_Zmflag(ST_GeomFromEWKT('LINESTRINGM(1 2 3, 3 4 3)'));
     st_zmflag
    -----------
    		 1

    SELECT ST_Zmflag(ST_GeomFromEWKT('CIRCULARSTRING(1 2 3, 3 4 3, 5 6 3)'));
     st_zmflag
    -----------
    		 2
    SELECT ST_Zmflag(ST_GeomFromEWKT('POINT(1 2 3 4)'));
     st_zmflag
    -----------
    		 3

## See Also

ST_CoordDim, ST_NDims, ST_Dimension

## Name

ST_ZMin — Returns Z minima of a bounding box 2d or 3d or a geometry.

## Synopsis

`float ST_ZMin(`box3d aGeomorBox2DorBox3D`)`;

## Description

Returns Z minima of a bounding box 2d or 3d or a geometry.

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_ZMin('BOX3D(1 2 3, 4 5 6)');
    st_zmin
    -------
    3

    SELECT ST_ZMin(ST_GeomFromEWKT('LINESTRING(1 3 4, 5 6 7)'));
    st_zmin
    -------
    4

    SELECT ST_ZMin('BOX3D(-3 2 1, 3 4 1)' );
    st_zmin
    -------
    1
    --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
    SELECT ST_ZMin('LINESTRING(1 3 4, 5 6 7)');

    --ERROR:  BOX3D parser - doesnt start with BOX3D(

    SELECT ST_ZMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_zmin
    --------
    1

## See Also

ST_GeomFromEWKT, ST_GeomFromText, ST_XMin, ST_XMax, ST_YMax, ST_YMin, ST_ZMax

## 8.5. Geometry Editors

## Name

ST_AddPoint — Adds a point to a LineString before point <position> (0-based index).

## Synopsis

`geometry ST_AddPoint(`geometry linestring, geometry point`)`;

`geometry ST_AddPoint(`geometry linestring, geometry point, integer position`)`;

## Description

Adds a point to a LineString before point <position> (0-based index). Third parameter can be omitted or set to -1 for appending.

Availability: 1.1.0

This function supports 3d and will not drop the z-index.

## Examples

    		--guarantee all linestrings in a table are closed
    		--by adding the start point of each linestring to the end of the line string
    		--only for those that are not closed
    		UPDATE sometable
    		SET the_geom = ST_AddPoint(the_geom, ST_StartPoint(the_geom))
    		FROM sometable
    		WHERE ST_IsClosed(the_geom) = false;

    		--Adding point to a 3-d line
    		SELECT ST_AsEWKT(ST_AddPoint(ST_GeomFromEWKT('LINESTRING(0 0 1, 1 1 1)'), ST_MakePoint(1, 2, 3)));

    		--result
    		st_asewkt
    		----------
    		LINESTRING(0 0 1,1 1 1,1 2 3)

## See Also

ST_RemovePoint, ST_SetPoint

## Name

ST_Affine — Applies a 3d affine transformation to the geometry to do things like translate, rotate, scale in one step.

## Synopsis

`geometry ST_Affine(`geometry geomA, float a, float b, float c, float d, float e, float f, float g, float h, float i, float xoff, float yoff, float zoff`)`;

`geometry ST_Affine(`geometry geomA, float a, float b, float d, float e, float xoff, float yoff`)`;

## Description

Applies a 3d affine transformation to the geometry to do things like translate, rotate, scale in one step.

Version 1: The call

    ST_Affine(geom, a, b, c, d, e, f, g, h, i, xoff, yoff, zoff)

represents the transformation matrix

    / a  b  c  xoff \
    | d  e  f  yoff |
    | g  h  i  zoff |
    \ 0  0  0     1 /

and the vertices are transformed as follows:

    x' = a*x + b*y + c*z + xoff
    y' = d*x + e*y + f*z + yoff
    z' = g*x + h*y + i*z + zoff

All of the translate / scale functions below are expressed via such an affine transformation.

Version 2: Applies a 2d affine transformation to the geometry. The call

    ST_Affine(geom, a, b, d, e, xoff, yoff)

represents the transformation matrix

    /  a  b  0  xoff  \       /  a  b  xoff  \
    |  d  e  0  yoff  | rsp.  |  d  e  yoff  |
    |  0  0  1     0  |       \  0  0     1  /
    \  0  0  0     1  /

and the vertices are transformed as follows:

    x' = a*x + b*y + xoff
    y' = d*x + e*y + yoff
    z' = z

This method is a subcase of the 3D method above.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: 1.1.2. Name changed from Affine to ST_Affine in 1.2.2

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    --Rotate a 3d line 180 degrees about the z axis.  Note this is long-hand for doing ST_Rotate();
     SELECT ST_AsEWKT(ST_Affine(the_geom,  cos(pi()), -sin(pi()), 0,  sin(pi()), cos(pi()), 0,  0, 0, 1,  0, 0, 0)) As using_affine,
    	 ST_AsEWKT(ST_Rotate(the_geom, pi())) As using_rotate
    	FROM (SELECT ST_GeomFromEWKT('LINESTRING(1 2 3, 1 4 3)') As the_geom) As foo;
            using_affine         |        using_rotate
    -----------------------------+-----------------------------
     LINESTRING(-1 -2 3,-1 -4 3) | LINESTRING(-1 -2 3,-1 -4 3)
    (1 row)

    --Rotate a 3d line 180 degrees in both the x and z axis
    SELECT ST_AsEWKT(ST_Affine(the_geom, cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), 0, 0, 0))
    	FROM (SELECT ST_GeomFromEWKT('LINESTRING(1 2 3, 1 4 3)') As the_geom) As foo;
               st_asewkt
    -------------------------------
     LINESTRING(-1 -2 -3,-1 -4 -3)
    (1 row)

## See Also

ST_Rotate, ST_Scale, ST_Translate, ST_TransScale

## Name

ST_Force_2D — Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X and Y coordinates.

## Synopsis

`geometry ST_Force_2D(`geometry geomA`)`;

## Description

Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X and Y coordinates. This is useful for force OGC-compliant output (since OGC only specifies 2-D geometries).

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsEWKT(ST_Force_2D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    		st_asewkt
    -------------------------------------
    CIRCULARSTRING(1 1,2 3,4 5,6 7,5 6)

    SELECT  ST_AsEWKT(ST_Force_2D('POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))'));

    				  st_asewkt
    ----------------------------------------------
     POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))

## See Also

ST_Force_3D

## Name

ST_Force_3D — Forces the geometries into XYZ mode. This is an alias for ST_Force_3DZ.

## Synopsis

`geometry ST_Force_3D(`geometry geomA`)`;

## Description

Forces the geometries into XYZ mode. This is an alias for ST_Force_3DZ. If a geometry has no Z component, then a 0 Z coordinate is tacked on.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This function supports Polyhedral surfaces.

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

## Examples

    		--Nothing happens to an already 3D geometry
    		SELECT ST_AsEWKT(ST_Force_3D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    				   st_asewkt
    -----------------------------------------------
     CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)

    SELECT  ST_AsEWKT(ST_Force_3D('POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))'));

    						 st_asewkt
    --------------------------------------------------------------
     POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

## See Also

ST_AsEWKT, ST_Force_2D, ST_Force_3DM, ST_Force_3DZ

## Name

ST_Force_3DZ — Forces the geometries into XYZ mode. This is a synonym for ST_Force_3D.

## Synopsis

`geometry ST_Force_3DZ(`geometry geomA`)`;

## Description

Forces the geometries into XYZ mode. This is a synonym for ST_Force_3DZ. If a geometry has no Z component, then a 0 Z coordinate is tacked on.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    --Nothing happens to an already 3D geometry
    SELECT ST_AsEWKT(ST_Force_3DZ(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    				   st_asewkt
    -----------------------------------------------
     CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)

    SELECT  ST_AsEWKT(ST_Force_3DZ('POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))'));

    						 st_asewkt
    --------------------------------------------------------------
     POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

## See Also

ST_AsEWKT, ST_Force_2D, ST_Force_3DM, ST_Force_3D

## Name

ST_Force_3DM — Forces the geometries into XYM mode.

## Synopsis

`geometry ST_Force_3DM(`geometry geomA`)`;

## Description

Forces the geometries into XYM mode. If a geometry has no M component, then a 0 M coordinate is tacked on. If it has a Z component, then Z is removed

This method supports Circular Strings and Curves

## Examples

    --Nothing happens to an already 3D geometry
    SELECT ST_AsEWKT(ST_Force_3DM(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    				   st_asewkt
    ------------------------------------------------
     CIRCULARSTRINGM(1 1 0,2 3 0,4 5 0,6 7 0,5 6 0)

    SELECT  ST_AsEWKT(ST_Force_3DM('POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1))'));

    						  st_asewkt
    ---------------------------------------------------------------
     POLYGONM((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

## See Also

ST_AsEWKT, ST_Force_2D, ST_Force_3DM, ST_Force_3D, ST_GeomFromEWKT

## Name

ST_Force_4D — Forces the geometries into XYZM mode.

## Synopsis

`geometry ST_Force_4D(`geometry geomA`)`;

## Description

Forces the geometries into XYZM mode. 0 is tacked on for missing Z and M dimensions.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    --Nothing happens to an already 3D geometry
    SELECT ST_AsEWKT(ST_Force_4D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    						st_asewkt
    ---------------------------------------------------------
     CIRCULARSTRING(1 1 2 0,2 3 2 0,4 5 2 0,6 7 2 0,5 6 2 0)

    SELECT  ST_AsEWKT(ST_Force_4D('MULTILINESTRINGM((0 0 1,0 5 2,5 0 3,0 0 4),(1 1 1,3 1 1,1 3 1,1 1 1))'));

    									  st_asewkt
    --------------------------------------------------------------------------------------
     MULTILINESTRING((0 0 0 1,0 5 0 2,5 0 0 3,0 0 0 4),(1 1 0 1,3 1 0 1,1 3 0 1,1 1 0 1))

## See Also

ST_AsEWKT, ST_Force_2D, ST_Force_3DM, ST_Force_3D

## Name

ST_Force_Collection — Converts the geometry into a GEOMETRYCOLLECTION.

## Synopsis

`geometry ST_Force_Collection(`geometry geomA`)`;

## Description

Converts the geometry into a GEOMETRYCOLLECTION. This is useful for simplifying the WKB representation.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Availability: 1.2.2, prior to 1.3.4 this function will crash with Curves. This is fixed in 1.3.4+

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT  ST_AsEWKT(ST_Force_Collection('POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1))'));

    								   st_asewkt
    ----------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1)))

      SELECT ST_AsText(ST_Force_Collection('CIRCULARSTRING(220227 150406,2220227 150407,220227 150406)'));
    								   st_astext
    --------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))
    (1 row)

    -- POLYHEDRAL example --
    SELECT ST_AsEWKT(ST_Force_Collection('POLYHEDRALSURFACE(((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
     ((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
     ((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
     ((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
     ((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
     ((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1)))'))

    								   st_asewkt
    ----------------------------------------------------------------------------------
    GEOMETRYCOLLECTION(
      POLYGON((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
      POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
      POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
      POLYGON((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
      POLYGON((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
      POLYGON((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1))
    )

## See Also

ST_AsEWKT, ST_Force_2D, ST_Force_3DM, ST_Force_3D, ST_GeomFromEWKT

## Name

ST_ForceRHR — Forces the orientation of the vertices in a polygon to follow the Right-Hand-Rule.

## Synopsis

`boolean ST_ForceRHR(`geometry g`)`;

## Description

Forces the orientation of the vertices in a polygon to follow the Right-Hand-Rule. In GIS terminology, this means that the area that is bounded by the polygon is to the right of the boundary. In particular, the exterior ring is orientated in a clockwise direction and the interior rings in a counter-clockwise direction.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_AsEWKT(
      ST_ForceRHR(
    	'POLYGON((0 0 2, 5 0 2, 0 5 2, 0 0 2),(1 1 2, 1 3 2, 3 1 2, 1 1 2))'
      )
    );
    						  st_asewkt
    --------------------------------------------------------------
     POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))
    (1 row)

## See Also

ST_BuildArea, ST_Polygonize, ST_Reverse

## Name

ST_LineMerge — Returns a (set of) LineString(s) formed by sewing together a MULTILINESTRING.

## Synopsis

`geometry ST_LineMerge(`geometry amultilinestring`)`;

## Description

Returns a (set of) LineString(s) formed by sewing together the constituent line work of a MULTILINESTRING.

Only use with MULTILINESTRING/LINESTRINGs. If you feed a polygon or geometry collection into this function, it will return an empty GEOMETRYCOLLECTION

Availability: 1.1.0

requires GEOS >= 2.1.0

## Examples

    SELECT ST_AsText(ST_LineMerge(
    ST_GeomFromText('MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45 -33,-46 -32))')
    		)
    );
    st_astext
    --------------------------------------------------------------------------------------------------
    LINESTRING(-29 -27,-30 -29.7,-36 -31,-45 -33,-46 -32)
    (1 row)

    --If can't be merged - original MULTILINESTRING is returned
    SELECT ST_AsText(ST_LineMerge(
    ST_GeomFromText('MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45.2 -33.2,-46 -32))')
    )
    );
    st_astext
    ----------------
    MULTILINESTRING((-45.2 -33.2,-46 -32),(-29 -27,-30 -29.7,-36 -31,-45 -33))

## See Also

ST_Segmentize, ST_Line_Substring

## Name

ST_CollectionExtract — Given a (multi)geometry, returns a (multi)geometry consisting only of elements of the specified type.

## Synopsis

`geometry ST_CollectionExtract(`geometry collection, integer type`)`;

## Description

Given a (multi)geometry, returns a (multi)geometry consisting only of elements of the specified type. Sub-geometries that are not the specified type are ignored. If there are no sub-geometries of the right type, an EMPTY geometry will be returned. Only points, lines and polygons are supported. Type numbers are 1 == POINT, 2 == LINESTRING, 3 == POLYGON.

Availability: 1.5.0

Prior to 1.5.3 this function returned non-collection inputs untouched, no matter type. In 1.5.3 non-matching single geometries result in a NULL return. In of 2.0.0 every case of missing match results in a typed EMPTY return.

## Examples

    -- Constants: 1 == POINT, 2 == LINESTRING, 3 == POLYGON
    SELECT ST_AsText(ST_CollectionExtract(ST_GeomFromText('GEOMETRYCOLLECTION(GEOMETRYCOLLECTION(POINT(0 0)))'),1));
    st_astext
    ---------------
    MULTIPOINT(0 0)
    (1 row)

    SELECT ST_AsText(ST_CollectionExtract(ST_GeomFromText('GEOMETRYCOLLECTION(GEOMETRYCOLLECTION(LINESTRING(0 0, 1 1)),LINESTRING(2 2, 3 3))'),2));
    st_astext
    ---------------
    MULTILINESTRING((0 0, 1 1), (2 2, 3 3))
    (1 row)

## See Also

ST_Multi, ST_Dump, ST_CollectionHomogenize

## Name

ST_CollectionHomogenize — Given a geometry collection, returns the "simplest" representation of the contents.

## Synopsis

`geometry ST_CollectionHomogenize(`geometry collection`)`;

## Description

Given a geometry collection, returns the "simplest" representation of the contents. Singletons will be returned as singletons. Collections that are homogeneous will be returned as the appropriate multi-type.

Availability: 2.0.0

## Examples

      SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0))'));

    	st_astext
    	------------
    	 POINT(0 0)
    	(1 row)

      SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0),POINT(1 1))'));

    	st_astext
    	---------------------
    	 MULTIPOINT(0 0,1 1)
    	(1 row)

## See Also

ST_Multi, ST_CollectionExtract

## Name

ST_Multi — Returns the geometry as a MULTI* geometry. If the geometry is already a MULTI*, it is returned unchanged.

## Synopsis

`geometry ST_Multi(`geometry g1`)`;

## Description

Returns the geometry as a MULTI* geometry. If the geometry is already a MULTI*, it is returned unchanged.

## Examples

    SELECT ST_AsText(ST_Multi(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
    			743265 2967450,743265.625 2967416,743238 2967416))')));
    			st_astext
    			--------------------------------------------------------------------------------------------------
    			MULTIPOLYGON(((743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,
    			743238 2967416)))
    			(1 row)

## See Also

ST_AsText

## Name

ST_RemovePoint — Removes point from a linestring. Offset is 0-based.

## Synopsis

`geometry ST_RemovePoint(`geometry linestring, integer offset`)`;

## Description

Removes point from a linestring. Useful for turning a closed ring into an open line string

Availability: 1.1.0

This function supports 3d and will not drop the z-index.

## Examples

    --guarantee no LINESTRINGS are closed
    --by removing the end point.  The below assumes the_geom is of type LINESTRING
    UPDATE sometable
    	SET the_geom = ST_RemovePoint(the_geom, ST_NPoints(the_geom) - 1)
    	FROM sometable
    	WHERE ST_IsClosed(the_geom) = true;

## See Also

ST_AddPoint, ST_NPoints, ST_NumPoints

## Name

ST_Reverse — Returns the geometry with vertex order reversed.

## Synopsis

`geometry ST_Reverse(`geometry g1`)`;

## Description

Can be used on any geometry and reverses the order of the vertexes.

## Examples

    SELECT ST_AsText(the_geom) as line, ST_AsText(ST_Reverse(the_geom)) As reverseline
    FROM
    (SELECT ST_MakeLine(ST_MakePoint(1,2),
    		ST_MakePoint(1,10)) As the_geom) as foo;
    --result
    		line         |     reverseline
    ---------------------+----------------------
    LINESTRING(1 2,1 10) | LINESTRING(1 10,1 2)

## Name

ST_Rotate — Rotate a geometry rotRadians counter-clockwise about an origin.

## Synopsis

`geometry ST_Rotate(`geometry geomA, float rotRadians`)`;

`geometry ST_Rotate(`geometry geomA, float rotRadians, float x0, float y0`)`;

`geometry ST_Rotate(`geometry geomA, float rotRadians, geometry pointOrigin`)`;

## Description

Rotates geometry rotRadians counter-clockwise about the origin. The rotation origin can be specified either as a POINT geometry, or as x and y coordinates. If the origin is not specified, the geometry is rotated about POINT(0 0).

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Enhanced: 2.0.0 additional parameters for specifying the origin of rotation were added.

Availability: 1.1.2. Name changed from Rotate to ST_Rotate in 1.2.2

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Rotate 180 degrees
    SELECT ST_AsEWKT(ST_Rotate('LINESTRING (50 160, 50 50, 100 50)', pi()));
                   st_asewkt
    ---------------------------------------
     LINESTRING(-50 -160,-50 -50,-100 -50)
    (1 row)

    --Rotate 30 degrees counter-clockwise at x=50, y=160
    SELECT ST_AsEWKT(ST_Rotate('LINESTRING (50 160, 50 50, 100 50)', pi()/6, 50, 160));
                                     st_asewkt
    ---------------------------------------------------------------------------
     LINESTRING(50 160,105 64.7372055837117,148.301270189222 89.7372055837117)
    (1 row)

    --Rotate 60 degrees clockwise from centroid
    SELECT ST_AsEWKT(ST_Rotate(geom, -pi()/3, ST_Centroid(geom)))
    FROM (SELECT 'LINESTRING (50 160, 50 50, 100 50)'::geometry AS geom) AS foo;
                               st_asewkt
    --------------------------------------------------------------
     LINESTRING(116.4225 130.6721,21.1597 75.6721,46.1597 32.3708)
    (1 row)

## See Also

ST_Affine, ST_RotateX, ST_RotateY, ST_RotateZ

## Name

ST_RotateX — Rotate a geometry rotRadians about the X axis.

## Synopsis

`geometry ST_RotateX(`geometry geomA, float rotRadians`)`;

## Description

Rotate a geometry geomA - rotRadians about the X axis.

`ST_RotateX(geomA, rotRadians)` is short-hand for `ST_Affine(geomA, 1, 0, 0, 0, cos(rotRadians), -sin(rotRadians), 0, sin(rotRadians), cos(rotRadians), 0, 0, 0)`.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: 1.1.2. Name changed from RotateX to ST_RotateX in 1.2.2

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Rotate a line 90 degrees along x-axis
    SELECT ST_AsEWKT(ST_RotateX(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), pi()/2));
    		 st_asewkt
    ---------------------------
     LINESTRING(1 -3 2,1 -1 1)

## See Also

ST_Affine, ST_RotateY, ST_RotateZ

## Name

ST_RotateY — Rotate a geometry rotRadians about the Y axis.

## Synopsis

`geometry ST_RotateY(`geometry geomA, float rotRadians`)`;

## Description

Rotate a geometry geomA - rotRadians about the y axis.

`ST_RotateY(geomA, rotRadians)` is short-hand for `ST_Affine(geomA, cos(rotRadians), 0, sin(rotRadians), 0, 1, 0, -sin(rotRadians), 0, cos(rotRadians), 0, 0, 0)`.

Availability: 1.1.2. Name changed from RotateY to ST_RotateY in 1.2.2

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Rotate a line 90 degrees along y-axis
     SELECT ST_AsEWKT(ST_RotateY(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), pi()/2));
    		 st_asewkt
    ---------------------------
     LINESTRING(3 2 -1,1 1 -1)

## See Also

ST_Affine, ST_RotateX, ST_RotateZ

## Name

ST_RotateZ — Rotate a geometry rotRadians about the Z axis.

## Synopsis

`geometry ST_RotateZ(`geometry geomA, float rotRadians`)`;

## Description

Rotate a geometry geomA - rotRadians about the Z axis.

This is a synonym for ST_Rotate

`ST_RotateZ(geomA, rotRadians)` is short-hand for `SELECT ST_Affine(geomA, cos(rotRadians), -sin(rotRadians), 0, sin(rotRadians), cos(rotRadians), 0, 0, 0, 1, 0, 0, 0)`.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: 1.1.2. Name changed from RotateZ to ST_RotateZ in 1.2.2

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Rotate a line 90 degrees along z-axis
    SELECT ST_AsEWKT(ST_RotateZ(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), pi()/2));
    		 st_asewkt
    ---------------------------
     LINESTRING(-2 1 3,-1 1 1)

     --Rotate a curved circle around z-axis
    SELECT ST_AsEWKT(ST_RotateZ(the_geom, pi()/2))
    FROM (SELECT ST_LineToCurve(ST_Buffer(ST_GeomFromText('POINT(234 567)'), 3)) As the_geom) As foo;

    													   st_asewkt
    ----------------------------------------------------------------------------------------------------------------------------
     CURVEPOLYGON(CIRCULARSTRING(-567 237,-564.87867965644 236.12132034356,-564 234,-569.12132034356 231.87867965644,-567 237))

## See Also

ST_Affine, ST_RotateX, ST_RotateY

## Name

ST_Scale — Scales the geometry to a new size by multiplying the ordinates with the parameters. Ie: ST_Scale(geom, Xfactor, Yfactor, Zfactor).

## Synopsis

`geometry ST_Scale(`geometry geomA, float XFactor, float YFactor, float ZFactor`)`;

`geometry ST_Scale(`geometry geomA, float XFactor, float YFactor`)`;

## Description

Scales the geometry to a new size by multiplying the ordinates with the parameters. Ie: ST_Scale(geom, Xfactor, Yfactor, Zfactor).

`ST_Scale(geomA, XFactor, YFactor, ZFactor)` is short-hand for `ST_Affine(geomA, XFactor, 0, 0, 0, YFactor, 0, 0, 0, ZFactor, 0, 0, 0)`.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Availability: 1.1.0.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Version 1: scale X, Y, Z
    SELECT ST_AsEWKT(ST_Scale(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), 0.5, 0.75, 0.8));
    			  st_asewkt
    --------------------------------------
     LINESTRING(0.5 1.5 2.4,0.5 0.75 0.8)

    --Version 2: Scale X Y
     SELECT ST_AsEWKT(ST_Scale(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), 0.5, 0.75));
    			st_asewkt
    ----------------------------------
     LINESTRING(0.5 1.5 3,0.5 0.75 1)

## See Also

ST_Affine, ST_TransScale

## Name

ST_Segmentize — Return a modified geometry having no segment longer than the given distance. Distance computation is performed in 2d only.

## Synopsis

`geometry ST_Segmentize(`geometry geomA, float max_length`)`;

## Description

Returns a modified geometry having no segment longer than the given distance. Distance computation is performed in 2d only.

Availability: 1.2.2

This will only increase segments. It will not lengthen segments shorter than max length

## Examples

    SELECT ST_AsText(ST_Segmentize(
    ST_GeomFromText('MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45 -33,-46 -32))')
    		,5)
    );
    st_astext
    --------------------------------------------------------------------------------------------------
    MULTILINESTRING((-29 -27,-30 -29.7,-34.886615700134 -30.758766735029,-36 -31,
    -40.8809353009198 -32.0846522890933,-45 -33),
    (-45 -33,-46 -32))
    (1 row)

    SELECT ST_AsText(ST_Segmentize(ST_GeomFromText('POLYGON((-29 28, -30 40, -29 28))'),10));
    st_astext
    -----------------------
    POLYGON((-29 28,-29.8304547985374 37.9654575824488,-30 40,-29.1695452014626 30.0345424175512,-29 28))
    (1 row)

## See Also

ST_Line_Substring

## Name

ST_SetPoint — Replace point N of linestring with given point. Index is 0-based.

## Synopsis

`geometry ST_SetPoint(`geometry linestring, integer zerobasedposition, geometry point`)`;

## Description

Replace point N of linestring with given point. Index is 0-based. This is especially useful in triggers when trying to maintain relationship of joints when one vertex moves.

Availability: 1.1.0

This function supports 3d and will not drop the z-index.

## Examples

    --Change first point in line string from -1 3 to -1 1
    SELECT ST_AsText(ST_SetPoint('LINESTRING(-1 2,-1 3)', 0, 'POINT(-1 1)'));
    	   st_astext
    -----------------------
     LINESTRING(-1 1,-1 3)

    ---Change last point in a line string (lets play with 3d linestring this time)
    SELECT ST_AsEWKT(ST_SetPoint(foo.the_geom, ST_NumPoints(foo.the_geom) - 1, ST_GeomFromEWKT('POINT(-1 1 3)')))
    FROM (SELECT ST_GeomFromEWKT('LINESTRING(-1 2 3,-1 3 4, 5 6 7)') As the_geom) As foo;
    	   st_asewkt
    -----------------------
    LINESTRING(-1 2 3,-1 3 4,-1 1 3)

## See Also

ST_AddPoint, ST_NPoints, ST_NumPoints, ST_PointN, ST_RemovePoint

## Name

ST_SetSRID — Sets the SRID on a geometry to a particular integer value.

## Synopsis

`geometry ST_SetSRID(`geometry geom, integer srid`)`;

## Description

Sets the SRID on a geometry to a particular integer value. Useful in constructing bounding boxes for queries.

This function does not transform the geometry coordinates in any way - it simply sets the meta data defining the spatial reference system the geometry is assumed to be in. Use ST_Transform if you want to transform the geometry into a new projection.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method supports Circular Strings and Curves

## Examples

-- Mark a point as WGS 84 long lat --

    SELECT ST_SetSRID(ST_Point(-123.365556, 48.428611),4326) As wgs84long_lat;
    -- the ewkt representation (wrap with ST_AsEWKT) -
    SRID=4326;POINT(-123.365556 48.428611)

-- Mark a point as WGS 84 long lat and then transform to web mercator (Spherical Mercator) --

    SELECT ST_Transform(ST_SetSRID(ST_Point(-123.365556, 48.428611),4326),3785) As spere_merc;
    -- the ewkt representation (wrap with ST_AsEWKT) -
    SRID=3785;POINT(-13732990.8753491 6178458.96425423)

## See Also

Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems”, ST_AsEWKT, ST_Point, ST_SRID, ST_Transform, UpdateGeometrySRID

## Name

ST_SnapToGrid — Snap all points of the input geometry to a regular grid.

## Synopsis

`geometry ST_SnapToGrid(`geometry geomA, float originX, float originY, float sizeX, float sizeY`)`;

`geometry ST_SnapToGrid(`geometry geomA, float sizeX, float sizeY`)`;

`geometry ST_SnapToGrid(`geometry geomA, float size`)`;

`geometry ST_SnapToGrid(`geometry geomA, geometry pointOrigin, float sizeX, float sizeY, float sizeZ, float sizeM`)`;

## Description

Variant 1,2,3: Snap all points of the input geometry to the grid defined by its origin and cell size. Remove consecutive points falling on the same cell, eventually returning NULL if output points are not enough to define a geometry of the given type. Collapsed geometries in a collection are stripped from it. Useful for reducing precision.

Variant 4: Introduced 1.1.0 - Snap all points of the input geometry to the grid defined by its origin (the second argument, must be a point) and cell sizes. Specify 0 as size for any dimension you don't want to snap to a grid.

The returned geometry might loose its simplicity (see ST_IsSimple).

Before release 1.1.0 this function always returned a 2d geometry. Starting at 1.1.0 the returned geometry will have same dimensionality as the input one with higher dimension values untouched. Use the version taking a second geometry argument to define all grid dimensions.

Availability: 1.0.0RC1

Availability: 1.1.0 - Z and M support

This function supports 3d and will not drop the z-index.

## Examples

    --Snap your geometries to a precision grid of 10^-3
    UPDATE mytable
       SET the_geom = ST_SnapToGrid(the_geom, 0.001);

    SELECT ST_AsText(ST_SnapToGrid(
    			ST_GeomFromText('LINESTRING(1.1115678 2.123, 4.111111 3.2374897, 4.11112 3.23748667)'),
    			0.001)
    		);
    			  st_astext
    -------------------------------------
     LINESTRING(1.112 2.123,4.111 3.237)
     --Snap a 4d geometry
    SELECT ST_AsEWKT(ST_SnapToGrid(
    	ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 2.3456 1.11111,
    		4.111111 3.2374897 3.1234 1.1111, -1.11111112 2.123 2.3456 1.1111112)'),
     ST_GeomFromEWKT('POINT(1.12 2.22 3.2 4.4444)'),
     0.1, 0.1, 0.1, 0.01) );
    								  st_asewkt
    ------------------------------------------------------------------------------
     LINESTRING(-1.08 2.12 2.3 1.1144,4.12 3.22 3.1 1.1144,-1.08 2.12 2.3 1.1144)

    --With a 4d geometry - the ST_SnapToGrid(geom,size) only touches x and y coords but keeps m and z the same
    SELECT ST_AsEWKT(ST_SnapToGrid(ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 3 2.3456,
    		4.111111 3.2374897 3.1234 1.1111)'),
    	   0.01)      );
    						st_asewkt
    ---------------------------------------------------------
     LINESTRING(-1.11 2.12 3 2.3456,4.11 3.24 3.1234 1.1111)

## See Also

ST_Snap, ST_AsEWKT, ST_AsText, ST_GeomFromText, ST_GeomFromEWKT, ST_Simplify

## Name

ST_Snap — Snap segments and vertices of input geometry to vertices of a reference geometry.

## Synopsis

`geometry ST_Snap(`geometry input, geometry reference, float tolerance`)`;

## Description

Snaps the vertices and segments of a geometry another Geometry's vertices. A snap distance tolerance is used to control where snapping is performed.

Snapping one geometry to another can improve robustness for overlay operations by eliminating nearly-coincident edges (which cause problems during noding and intersection calculation).

Too much snapping can result in invalid topology being created, so the number and location of snapped vertices is decided using heuristics to determine when it is safe to snap. This can result in some potential snaps being omitted, however.

The returned geometry might loose its simplicity (see ST_IsSimple) and validity (see ST_IsValid).

Availability: 2.0.0 requires GEOS >= 3.3.0.

## Examples

A multipolygon shown with a linestring (before any snapping)
A multipolygon snapped to linestring to tolerance: 1.01 of distance. The new multipolygon is shown with reference linestring
    SELECT ST_AsText(ST_Snap(poly,line, ST_Distance(poly,line)*1.01)) AS polysnapped
    FROM (SELECT
       ST_GeomFromText('MULTIPOLYGON(
         ((26 125, 26 200, 126 200, 126 125, 26 125 ),
          ( 51 150, 101 150, 76 175, 51 150 )),
          (( 151 100, 151 200, 176 175, 151 100 )))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line

    	) As foo;

                                 polysnapped
    ---------------------------------------------------------------------
     MULTIPOLYGON(((26 125,26 200,126 200,126 125,101 100,26 125),
     (51 150,101 150,76 175,51 150)),((151 100,151 200,176 175,151 100)))
| A multipolygon snapped to linestring to tolerance: 1.25 of distance. The new multipolygon is shown with reference linestring
    SELECT ST_AsText(
        ST_Snap(poly,line, ST_Distance(poly,line)*1.25)
      ) AS polysnapped
    FROM (SELECT
      ST_GeomFromText('MULTIPOLYGON(
        (( 26 125, 26 200, 126 200, 126 125, 26 125 ),
          ( 51 150, 101 150, 76 175, 51 150 )),
          (( 151 100, 151 200, 176 175, 151 100 )))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line

    	) As foo;

                                 polysnapped
    ---------------------------------------------------------------------
    MULTIPOLYGON(((5 107,26 200,126 200,126 125,101 100,54 84,5 107),
    (51 150,101 150,76 175,51 150)),((151 100,151 200,176 175,151 100)))
The linestring snapped to the original multipolygon at tolerance 1.01 of distance. The new linestring is shown with reference multipolygon
    SELECT ST_AsText(
       ST_Snap(line, poly, ST_Distance(poly,line)*1.01)
      ) AS linesnapped
    FROM (SELECT
      ST_GeomFromText('MULTIPOLYGON(
         ((26 125, 26 200, 126 200, 126 125, 26 125),
          (51 150, 101 150, 76 175, 51 150 )),
          ((151 100, 151 200, 176 175, 151 100)))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
    	) As foo;

                  linesnapped
    ----------------------------------------
     LINESTRING(5 107,26 125,54 84,101 100)
| The linestring snapped to the original multipolygon at tolerance 1.25 of distance. The new linestring is shown with reference multipolygon
    SELECT ST_AsText(
     ST_Snap(line, poly, ST_Distance(poly,line)*1.25)
      ) AS linesnapped
    FROM (SELECT
      ST_GeomFromText('MULTIPOLYGON(
         (( 26 125, 26 200, 126 200, 126 125, 26 125 ),
          (51 150, 101 150, 76 175, 51 150 )),
          ((151 100, 151 200, 176 175, 151 100 )))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
    	) As foo;
                  linesnapped
    ---------------------------------------
    LINESTRING(26 125,54 84,101 100)

## See Also

ST_SnapToGrid

## Name

ST_Transform — Returns a new geometry with its coordinates transformed to the SRID referenced by the integer parameter.

## Synopsis

`geometry ST_Transform(`geometry g1, integer srid`)`;

## Description

Returns a new geometry with its coordinates transformed to spatial reference system referenced by the SRID integer parameter. The destination SRID must exist in the `SPATIAL_REF_SYS` table.

ST_Transform is often confused with ST_SetSRID(). ST_Transform actually changes the coordinates of a geometry from one spatial reference system to another, while ST_SetSRID() simply changes the SRID identifier of the geometry

Requires PostGIS be compiled with Proj support. Use PostGIS_Full_Version to confirm you have proj support compiled in.

If using more than one transformation, it is useful to have a functional index on the commonly used transformations to take advantage of index usage.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.6

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

## Examples

Change Mass state plane US feet geometry to WGS 84 long lat

    SELECT ST_AsText(ST_Transform(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
    	743265 2967450,743265.625 2967416,743238 2967416))',2249),4326)) As wgs_geom;

     wgs_geom
    ---------------------------
     POLYGON((-71.1776848522251 42.3902896512902,-71.1776843766326 42.3903829478009,
    -71.1775844305465 42.3903826677917,-71.1775825927231 42.3902893647987,-71.177684
    8522251 42.3902896512902));
    (1 row)

    --3D Circular String example
    SELECT ST_AsEWKT(ST_Transform(ST_GeomFromEWKT('SRID=2249;CIRCULARSTRING(743238 2967416 1,743238 2967450 2,743265 2967450 3,743265.625 2967416 3,743238 2967416 4)'),4326));

    				 st_asewkt
    --------------------------------------------------------------------------------------
     SRID=4326;CIRCULARSTRING(-71.1776848522251 42.3902896512902 1,-71.1776843766326 42.3903829478009 2,
     -71.1775844305465 42.3903826677917 3,
     -71.1775825927231 42.3902893647987 3,-71.1776848522251 42.3902896512902 4)

Example of creating a partial functional index. For tables where you are not sure all the geometries will be filled in, its best to use a partial index that leaves out null geometries which will both conserve space and make your index smaller and more efficient.

    CREATE INDEX idx_the_geom_26986_parcels
      ON parcels
      USING gist
      (ST_Transform(the_geom, 26986))
      WHERE the_geom IS NOT NULL;

## Configuring transformation behaviour

Sometimes coordinate transformation involving a grid-shift can fail, for example if PROJ.4 has not been built with grid-shift files or the coordinate does not lie within the range for which the grid shift is defined. By default, PostGIS will throw an error if a grid shift file is not present, but this behaviour can be configured on a per-SRID basis by altering the proj4text value within the spatial_ref_sys table.

For example, the proj4text parameter +datum=NAD87 is a shorthand form for the following +nadgrids parameter:

    +nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat

The @ prefix means no error is reported if the files are not present, but if the end of the list is reached with no file having been appropriate (ie. found and overlapping) then an error is issued.

If, conversely, you wanted to ensure that at least the standard files were present, but that if all files were scanned without a hit a null transformation is applied you could use:

    +nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat,null

The null grid shift file is a valid grid shift file covering the whole world and applying no shift. So for a complete example, if you wanted to alter PostGIS so that transformations to SRID 4267 that didn't lie within the correct range did not throw an ERROR, you would use the following:

    UPDATE spatial_ref_sys SET proj4text = '+proj=longlat +ellps=clrk66 +nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat,null +no_defs' WHERE srid = 4267;

## See Also

PostGIS_Full_Version, ST_AsText, ST_SetSRID, UpdateGeometrySRID

## Name

ST_Translate — Translates the geometry to a new location using the numeric parameters as offsets. Ie: ST_Translate(geom, X, Y) or ST_Translate(geom, X, Y,Z).

## Synopsis

`geometry ST_Translate(`geometry g1, float deltax, float deltay`)`;

`geometry ST_Translate(`geometry g1, float deltax, float deltay, float deltaz`)`;

## Description

Returns a new geometry whose coordinates are translated delta x,delta y,delta z units. Units are based on the units defined in spatial reference (SRID) for this geometry.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Availability: 1.2.2

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

Move a point 1 degree longitude

    	SELECT ST_AsText(ST_Translate(ST_GeomFromText('POINT(-71.01 42.37)',4326),1,0)) As wgs_transgeomtxt;

    	wgs_transgeomtxt
    	---------------------
    	POINT(-70.01 42.37)

Move a linestring 1 degree longitude and 1/2 degree latitude

    SELECT ST_AsText(ST_Translate(ST_GeomFromText('LINESTRING(-71.01 42.37,-71.11 42.38)',4326),1,0.5)) As wgs_transgeomtxt;
    		   wgs_transgeomtxt
    	---------------------------------------
    	LINESTRING(-70.01 42.87,-70.11 42.88)

Move a 3d point

    SELECT ST_AsEWKT(ST_Translate(CAST('POINT(0 0 0)' As geometry), 5, 12,3));
    	st_asewkt
    	---------
    	POINT(5 12 3)

Move a curve and a point

    SELECT ST_AsText(ST_Translate(ST_Collect('CURVEPOLYGON(CIRCULARSTRING(4 3,3.12 0.878,1 0,-1.121 5.1213,6 7, 8 9,4 3))','POINT(1 3)'),1,2));
    														 st_astext
    ------------------------------------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(CURVEPOLYGON(CIRCULARSTRING(5 5,4.12 2.878,2 2,-0.121 7.1213,7 9,9 11,5 5)),POINT(2 5))

## See Also

ST_Affine, ST_AsText, ST_GeomFromText

## Name

ST_TransScale — Translates the geometry using the deltaX and deltaY args, then scales it using the XFactor, YFactor args, working in 2D only.

## Synopsis

`geometry ST_TransScale(`geometry geomA, float deltaX, float deltaY, float XFactor, float YFactor`)`;

## Description

Translates the geometry using the deltaX and deltaY args, then scales it using the XFactor, YFactor args, working in 2D only.

`ST_TransScale(geomA, deltaX, deltaY, XFactor, YFactor)` is short-hand for `ST_Affine(geomA, XFactor, 0, 0, 0, YFactor, 0, 0, 0, 1, deltaX*XFactor, deltaY*YFactor, 0)`.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Availability: 1.1.0.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_AsEWKT(ST_TransScale(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), 0.5, 1, 1, 2));
    		  st_asewkt
    -----------------------------
     LINESTRING(1.5 6 3,1.5 4 1)

    --Buffer a point to get an approximation of a circle, convert to curve and then translate 1,2 and scale it 3,4
      SELECT ST_AsText(ST_Transscale(ST_LineToCurve(ST_Buffer('POINT(234 567)', 3)),1,2,3,4));
    														  st_astext
    ------------------------------------------------------------------------------------------------------------------------------
     CURVEPOLYGON(CIRCULARSTRING(714 2276,711.363961030679 2267.51471862576,705 2264,698.636038969321 2284.48528137424,714 2276))

## See Also

ST_Affine, ST_Translate

## 8.6. Geometry Outputs

## Name

ST_AsBinary — Return the Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.

## Synopsis

`bytea ST_AsBinary(`geometry g1`)`;

`bytea ST_AsBinary(`geometry g1, text NDR_or_XDR`)`;

`bytea ST_AsBinary(`geography g1`)`;

`bytea ST_AsBinary(`geography g1, text NDR_or_XDR`)`;

## Description

Returns the Well-Known Binary representation of the geometry. There are 2 variants of the function. The first variant takes no endian encoding parameter and defaults to server machine endian. The second variant takes a second argument denoting the encoding - using little-endian ('NDR') or big-endian ('XDR') encoding.

This is useful in binary cursors to pull data out of the database without converting it to a string representation.

The WKB spec does not include the SRID. To get the WKB with SRID format use ST_AsEWKB

ST_AsBinary is the reverse of ST_GeomFromWKB for geometry. Use ST_GeomFromWKB to convert to a postgis geometry from ST_AsBinary representation.

The default behavior in PostgreSQL 9.0 has been changed to output bytea in hex encoding. ST_AsBinary is the reverse of ST_GeomFromWKB for geometry. If your GUI tools require the old behavior, then SET bytea_output='escape' in your database.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Enhanced: 2.0.0 support for higher coordinate dimensions was introduced.

Enhanced: 2.0.0 support for specifying endian with geography was introduced.

Availability: 1.5.0 geography support was introduced.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.37

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsBinary(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));

    		   st_asbinary
    --------------------------------
    \001\003\000\000\000\001\000\000\000\005
    \000\000\000\000\000\000\000\000\000\000
    \000\000\000\000\000\000\000\000\000\000
    \000\000\000\000\000\000\000\000\000\000
    \000\000\000\360?\000\000\000\000\000\000
    \360?\000\000\000\000\000\000\360?\000\000
    \000\000\000\000\360?\000\000\000\000\000
    \000\000\000\000\000\000\000\000\000\000\000
    \000\000\000\000\000\000\000\000
    (1 row)

    SELECT ST_AsBinary(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326), 'XDR');
    		   st_asbinary
    --------------------------------
    \000\000\000\000\003\000\000\000\001\000\000\000\005\000\000\000\000\000
    \000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000
    \000?\360\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000
    \000\000\000\000?\360\000\000\000\000\000\000\000\000\000\000\000\000\000\000
    \000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000
    (1 row)

## See Also

ST_GeomFromWKB ST_AsEWKB, ST_AsText,

## Name

ST_AsEWKB — Return the Well-Known Binary (WKB) representation of the geometry with SRID meta data.

## Synopsis

`bytea ST_AsEWKB(`geometry g1`)`;

`bytea ST_AsEWKB(`geometry g1, text NDR_or_XDR`)`;

## Description

Returns the Well-Known Binary representation of the geometry with SRID metadata. There are 2 variants of the function. The first variant takes no endian encoding parameter and defaults to little endian. The second variant takes a second argument denoting the encoding - using little-endian ('NDR') or big-endian ('XDR') encoding.

This is useful in binary cursors to pull data out of the database without converting it to a string representation.

The WKB spec does not include the SRID. To get the OGC WKB format use ST_AsBinary

ST_AsEWKB is the reverse of ST_GeomFromEWKB. Use ST_GeomFromEWKB to convert to a postgis geometry from ST_AsEWKB representation.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_AsEWKB(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));

    		   st_asewkb
    --------------------------------
    \001\003\000\000 \346\020\000\000\001\000
    \000\000\005\000\000\000\000
    \000\000\000\000\000\000\000\000
    \000\000\000\000\000\000\000\000\000
    \000\000\000\000\000\000\000\000\000\000
    \000\000\360?\000\000\000\000\000\000\360?
    \000\000\000\000\000\000\360?\000\000\000\000\000
    \000\360?\000\000\000\000\000\000\000\000\000\000\000
    \000\000\000\000\000\000\000\000\000\000\000\000\000
    (1 row)

    			SELECT ST_AsEWKB(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326), 'XDR');
    		   st_asewkb
    --------------------------------
    \000 \000\000\003\000\000\020\346\000\000\000\001\000\000\000\005\000\000\000\000\
    000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000?
    \360\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000\000\000
    \000\000?\360\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000
    \000\000\000\000\000\000\000\000\000\000\000\000\000

## See Also

ST_AsBinary, ST_AsEWKT, ST_AsText, ST_GeomFromEWKT, ST_SRID

## Name

ST_AsEWKT — Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.

## Synopsis

`text ST_AsEWKT(`geometry g1`)`;

`text ST_AsEWKT(`geography g1`)`;

## Description

Returns the Well-Known Text representation of the geometry prefixed with the SRID.

The WKT spec does not include the SRID. To get the OGC WKT format use ST_AsText

WKT format does not maintain precision so to prevent floating truncation, use ST_AsBinary or ST_AsEWKB format for transport.

ST_AsEWKT is the reverse of ST_GeomFromEWKT. Use ST_GeomFromEWKT to convert to a postgis geometry from ST_AsEWKT representation.

Enhanced: 2.0.0 support for Geography, Polyhedral surfaces, Triangles and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_AsEWKT('0103000020E61000000100000005000000000000
    			000000000000000000000000000000000000000000000000000000
    			F03F000000000000F03F000000000000F03F000000000000F03
    			F000000000000000000000000000000000000000000000000'::geometry);

    		   st_asewkt
    --------------------------------
    SRID=4326;POLYGON((0 0,0 1,1 1,1 0,0 0))
    (1 row)

    SELECT ST_AsEWKT('0108000080030000000000000060E30A4100000000785C0241000000000000F03F0000000018
    E20A4100000000485F024100000000000000400000000018
    E20A4100000000305C02410000000000000840')

    --st_asewkt---
    CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)

## See Also

ST_AsBinary ST_AsEWKB ST_AsText, ST_GeomFromEWKT

## Name

ST_AsGeoJSON — Return the geometry as a GeoJSON element.

## Synopsis

`text ST_AsGeoJSON(`geometry geom, integer maxdecimaldigits=15, integer options=0`)`;

`text ST_AsGeoJSON(`geography geog, integer maxdecimaldigits=15, integer options=0`)`;

`text ST_AsGeoJSON(`integer gj_version, geometry geom, integer maxdecimaldigits=15, integer options=0`)`;

`text ST_AsGeoJSON(`integer gj_version, geography geog, integer maxdecimaldigits=15, integer options=0`)`;

## Description

Return the geometry as a Geometry Javascript Object Notation (GeoJSON) element. (Cf GeoJSON specifications 1.0). 2D and 3D Geometries are both supported. GeoJSON only support SFS 1.1 geometry type (no curve support for example).

The gj_version parameter is the major version of the GeoJSON spec. If specified, must be 1. This represents the spec version of GeoJSON.

The third argument may be used to reduce the maximum number of decimal places used in output (defaults to 15).

The last 'options' argument could be used to add Bbox or Crs in GeoJSON output:

- 0: means no option (default value)

- 1: GeoJSON Bbox

- 2: GeoJSON Short CRS (e.g EPSG:4326)

- 4: GeoJSON Long CRS (e.g urn:ogc:def:crs:EPSG::4326)

Version 1: ST_AsGeoJSON(geom) / precision=15 version=1 options=0

Version 2: ST_AsGeoJSON(geom, precision) / version=1 options=0

Version 3: ST_AsGeoJSON(geom, precision, options) / version=1

Version 4: ST_AsGeoJSON(gj_version, geom) / precision=15 options=0

Version 5: ST_AsGeoJSON(gj_version, geom, precision) /options=0

Version 6: ST_AsGeoJSON(gj_version, geom, precision,options)

Availability: 1.3.4

Availability: 1.5.0 geography support was introduced.

Changed: 2.0.0 support default args and named args.

This function supports 3d and will not drop the z-index.

## Examples

GeoJSON format is generally more efficient than other formats for use in ajax mapping. One popular javascript client that supports this is Open Layers. Example of its use is OpenLayers GeoJSON Example

    SELECT ST_AsGeoJSON(the_geom) from fe_edges limit 1;
    					   st_asgeojson
    -----------------------------------------------------------------------------------------------------------

    {"type":"MultiLineString","coordinates":[[[-89.734634999999997,31.492072000000000],
    [-89.734955999999997,31.492237999999997]]]}
    (1 row)
    --3d point
    SELECT ST_AsGeoJSON('LINESTRING(1 2 3, 4 5 6)');

    st_asgeojson
    -----------------------------------------------------------------------------------------
     {"type":"LineString","coordinates":[[1,2,3],[4,5,6]]}

## Name

ST_AsGML — Return the geometry as a GML version 2 or 3 element.

## Synopsis

`text ST_AsGML(`geometry geom, integer maxdecimaldigits=15, integer options=0`)`;

`text ST_AsGML(`geography geog, integer maxdecimaldigits=15, integer options=0`)`;

`text ST_AsGML(`integer version, geometry geom, integer maxdecimaldigits=15, integer options=0, text nprefix=null`)`;

`text ST_AsGML(`integer version, geography geog, integer maxdecimaldigits=15, integer options=0, text nprefix=null`)`;

## Description

Return the geometry as a Geography Markup Language (GML) element. The version parameter, if specified, may be either 2 or 3. If no version parameter is specified then the default is assumed to be 2. The precision argument may be used to reduce the maximum number of decimal places (`maxdecimaldigits`) used in output (defaults to 15).

GML 2 refer to 2.1.2 version, GML 3 to 3.1.1 version

The 'options' argument is a bitfield. It could be used to define CRS output type in GML output, and to declare data as lat/lon:

- 0: GML Short CRS (e.g EPSG:4326), default value

- 1: GML Long CRS (e.g urn:ogc:def:crs:EPSG::4326)

- 2: For GML 3 only, remove srsDimension attribute from output.

- 4: For GML 3 only, use <LineString> rather than <Curve> tag for lines.

- 16: Declare that datas are lat/lon (e.g srid=4326). Default is to assume that data are planars. This option is useful for GML 3.1.1 output only, related to axis order. So if you set it, it will swap the coordinates so order is lat lon instead of database lon lat.

- 32: Output the box of the geometry (envelope).

The 'namespace prefix' argument may be used to specify a custom namespace prefix or no prefix (if empty). If null or omitted 'gml' prefix is used

Availability: 1.3.2

Availability: 1.5.0 geography support was introduced.

Enhanced: 2.0.0 prefix support was introduced. Option 4 for GML3 was introduced to allow using LineString instead of Curve tag for lines. GML3 Support for Polyhedral surfaces and TINS was introduced. Option 32 was introduced to output the box.

Changed: 2.0.0 use default named args

Only version 3+ of ST_AsGML supports Polyhedral Surfaces and TINS.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples: Version 2

    SELECT ST_AsGML(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));
    		st_asgml
    		--------
    		<gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>0,0 0,1 1,1 1,0 0,0</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon>

## Examples: Version 3

    -- Flip coordinates and output extended EPSG (16 | 1)--
    SELECT ST_AsGML(3, ST_GeomFromText('POINT(5.234234233242 6.34534534534)',4326), 5, 17);
    			st_asgml
    			--------
    		<gml:Point srsName="urn:ogc:def:crs:EPSG::4326"><gml:pos>6.34535 5.23423</gml:pos></gml:Point>

    -- Output the envelope (32) --
    SELECT ST_AsGML(3, ST_GeomFromText('LINESTRING(1 2, 3 4, 10 20)',4326), 5, 32);
    		st_asgml
    		--------
    	<gml:Envelope srsName="EPSG:4326">
    		<gml:lowerCorner>1 2</gml:lowerCorner>
    		<gml:upperCorner>10 20</gml:upperCorner>
    	</gml:Envelope>

    -- Output the envelope (32) , reverse (lat lon instead of lon lat) (16), long srs (1)= 32 | 16 | 1 = 49 --
    SELECT ST_AsGML(3, ST_GeomFromText('LINESTRING(1 2, 3 4, 10 20)',4326), 5, 49);
    	st_asgml
    	--------
    <gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">
    	<gml:lowerCorner>2 1</gml:lowerCorner>
    	<gml:upperCorner>20 10</gml:upperCorner>
    </gml:Envelope>

    -- Polyhedral Example --
    SELECT ST_AsGML(3, ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
    	st_asgml
    	--------
     <gml:PolyhedralSurface>
    <gml:polygonPatches>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">0 0 0 0 0 1 0 1 1 0 1 0 0 0 0</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">0 0 0 0 1 0 1 1 0 1 0 0 0 0 0</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">0 0 0 1 0 0 1 0 1 0 0 1 0 0 0</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">1 1 0 1 1 1 1 0 1 1 0 0 1 1 0</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">0 1 0 0 1 1 1 1 1 1 1 0 0 1 0</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">0 0 1 1 0 1 1 1 1 0 1 1 0 0 1</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
    </gml:polygonPatches>
    </gml:PolyhedralSurface>

## See Also

ST_GeomFromGML

## Name

ST_AsHEXEWKB — Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding.

## Synopsis

`text ST_AsHEXEWKB(`geometry g1, text NDRorXDR`)`;

`text ST_AsHEXEWKB(`geometry g1`)`;

## Description

Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding. If no encoding is specified, then NDR is used.

Availability: 1.2.2

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_AsHEXEWKB(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));
    		which gives same answer as

    		SELECT ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326)::text;

    		st_ashexewkb
    		--------
    		0103000020E6100000010000000500
    		00000000000000000000000000000000
    		00000000000000000000000000000000F03F
    		000000000000F03F000000000000F03F000000000000F03
    		F000000000000000000000000000000000000000000000000

## Name

ST_AsKML — Return the geometry as a KML element. Several variants. Default version=2, default precision=15

## Synopsis

`text ST_AsKML(`geometry geom, integer maxdecimaldigits=15`)`;

`text ST_AsKML(`geography geog, integer maxdecimaldigits=15`)`;

`text ST_AsKML(`integer version, geometry geom, integer maxdecimaldigits=15, text nprefix=NULL`)`;

`text ST_AsKML(`integer version, geography geog, integer maxdecimaldigits=15, text nprefix=NULL`)`;

## Description

Return the geometry as a Keyhole Markup Language (KML) element. There are several variants of this function. maximum number of decimal places used in output (defaults to 15), version default to 2 and default namespace is no prefix.

Version 1: ST_AsKML(geom_or_geog, maxdecimaldigits) / version=2 / maxdecimaldigits=15

Version 2: ST_AsKML(version, geom_or_geog, maxdecimaldigits, nprefix) maxdecimaldigits=15 / nprefix=NULL

Requires PostGIS be compiled with Proj support. Use PostGIS_Full_Version to confirm you have proj support compiled in.

Availability: 1.2.2 - later variants that include version param came in 1.3.2

Enhanced: 2.0.0 - Add prefix namespace. Default is no prefix

Changed: 2.0.0 - uses default args and supports named args

AsKML output will not work with geometries that do not have an SRID

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsKML(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));

    		st_askml
    		--------
    		<Polygon><outerBoundaryIs><LinearRing><coordinates>0,0 0,1 1,1 1,0 0,0</coordinates></LinearRing></outerBoundaryIs></Polygon>

    		--3d linestring
    		SELECT ST_AsKML('SRID=4326;LINESTRING(1 2 3, 4 5 6)');
    		<LineString><coordinates>1,2,3 4,5,6</coordinates></LineString>

## See Also

ST_AsSVG, ST_AsGML

## Name

ST_AsSVG — Returns a Geometry in SVG path data given a geometry or geography object.

## Synopsis

`text ST_AsSVG(`geometry geom, integer rel=0, integer maxdecimaldigits=15`)`;

`text ST_AsSVG(`geography geog, integer rel=0, integer maxdecimaldigits=15`)`;

## Description

Return the geometry as Scalar Vector Graphics (SVG) path data. Use 1 as second argument to have the path data implemented in terms of relative moves, the default (or 0) uses absolute moves. Third argument may be used to reduce the maximum number of decimal digits used in output (defaults to 15). Point geometries will be rendered as cx/cy when 'rel' arg is 0, x/y when 'rel' is 1. Multipoint geometries are delimited by commas (","), GeometryCollection geometries are delimited by semicolons (";").

Availability: 1.2.2. Availability: 1.4.0 Changed in PostGIS 1.4.0 to include L command in absolute path to conform to http://www.w3.org/TR/SVG/paths.html#PathDataBNF

Changed: 2.0.0 to use default args and support named args

## Examples

    SELECT ST_AsSVG(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));

    		st_assvg
    		--------
    		M 0 0 L 0 -1 1 -1 1 0 Z

## Name

ST_AsX3D — Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML

## Synopsis

`text ST_AsX3D(`geometry g1, integer maxdecimaldigits=15, integer options=0`)`;

## Description

Returns a geometry as an X3D xml formatted node element http://web3d.org/x3d/specifications/ISO-IEC-19776-1.2-X3DEncodings-XML/Part01/EncodingOfNodes.html. If `maxdecimaldigits` (precision) is not specified then defaults to 15.

There are various options for translating PostGIS geometries to X3D since X3D geometry types don't map directly to PostGIS geometry types and some newer X3D types that might be better mappings we ahve avoided since most rendering tools don't currently support them. These are the mappings we have settled on. Feel free to post a bug ticket if you have thoughts on the idea or ways we can allow people to denote their preferred mappings. Below is how we currently map PostGIS 2D/3D types to X3D types

PostGIS Type | 2D X3D Type | 3D X3D Type
--- | --- | ---
LINESTRING | not yet implemented - will be PolyLine2D | LineSet
MULTILINESTRING | not yet implemented - will be PolyLine2D | IndexedLineSet
MULTIPOINT | Polypoint2D | PointSet
POINT | outputs the space delimited coordinates | outputs the space delimited coordinates
(MULTI) POLYGON, POLYHEDRALSURFACE | Invalid X3D markup | IndexedFaceSet (inner rings currently output as another faceset)
TIN | TriangleSet2D (Not Yet Implemented) | IndexedTriangleSet

2D geometry support not yet complete. Inner rings currently just drawn as separate polygons. We are working on these.

Lots of advancements happening in 3D space particularly with X3D Integration with HTML5

There is also a nice open source X3D viewer you can use to view rendered geometries. Free Wrl http://freewrl.sourceforge.net/ binaries available for Mac, Linux, and Windows. Use the FreeWRL_Launcher packaged to view the geometries.

Availability: 2.0.0: ISO-IEC-19776-1.2-X3DEncodings-XML

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Example: Create a fully functional X3D document - This will generate a cube that is viewable in FreeWrl and other X3D viewers.

    SELECT '<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.0//EN" "http://www.web3d.org/specifications/x3d-3.0.dtd">
    <X3D>
      <Scene>
        <Transform>
          <Shape>
           <Appearance>
                <Material emissiveColor=''0 0 1''/>
           </Appearance> ' ||
           ST_AsX3D( ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')) ||
          '</Shape>
        </Transform>
      </Scene>
    </X3D>' As x3ddoc;

    		x3ddoc
    		--------
    <?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.0//EN" "http://www.web3d.org/specifications/x3d-3.0.dtd">
    <X3D>
      <Scene>
        <Transform>
          <Shape>
           <Appearance>
                <Material emissiveColor='0 0 1'/>
           </Appearance>
           <IndexedFaceSet  coordIndex='0 1 2 3 -1 4 5 6 7 -1 8 9 10 11 -1 12 13 14 15 -1 16 17 18 19 -1 20 21 22 23'>
                <Coordinate point='0 0 0 0 0 1 0 1 1 0 1 0 0 0 0 0 1 0 1 1 0 1 0 0 0 0 0 1 0 0 1 0 1 0 0 1 1 1 0 1 1 1 1 0 1 1 0 0 0 1 0 0 1 1 1 1 1 1 1 0 0 0 1 1 0 1 1 1 1 0 1 1' />
          </IndexedFaceSet>
          </Shape>
        </Transform>
      </Scene>
    </X3D>

## Example: An Octagon elevated 3 Units and decimal precision of 6

    SELECT ST_AsX3D(
    ST_Translate(
        ST_Force_3d(
            ST_Buffer(ST_Point(10,10),5, 'quad_segs=2')), 0,0,
        3)
      ,6) As x3dfrag;

    x3dfrag
    --------
    <IndexedFaceSet coordIndex="0 1 2 3 4 5 6 7">
        <Coordinate point="15 10 3 13.535534 6.464466 3 10 5 3 6.464466 6.464466 3 5 10 3 6.464466 13.535534 3 10 15 3 13.535534 13.535534 3 " />
    </IndexedFaceSet>

## Example: TIN

    SELECT ST_AsX3D(ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )')) As x3dfrag;

    		x3dfrag
    		--------
    <IndexedTriangleSet  index='0 1 2 3 4 5'><Coordinate point='0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 1 1 0'/></IndexedTriangleSet>

## Example: Closed multilinestring (the boundary of a polygon with holes)

    SELECT ST_AsX3D(
    		    ST_GeomFromEWKT('MULTILINESTRING((20 0 10,16 -12 10,0 -16 10,-12 -12 10,-20 0 10,-12 16 10,0 24 10,16 16 10,20 0 10),
      (12 0 10,8 8 10,0 12 10,-8 8 10,-8 0 10,-8 -4 10,0 -8 10,8 -4 10,12 0 10))')
    ) As x3dfrag;

    		x3dfrag
    		--------
    <IndexedLineSet  coordIndex='0 1 2 3 4 5 6 7 0 -1 8 9 10 11 12 13 14 15 8'>
        <Coordinate point='20 0 10 16 -12 10 0 -16 10 -12 -12 10 -20 0 10 -12 16 10 0 24 10 16 16 10 12 0 10 8 8 10 0 12 10 -8 8 10 -8 0 10 -8 -4 10 0 -8 10 8 -4 10 ' />
     </IndexedLineSet>

## Name

ST_GeoHash — Return a GeoHash representation (geohash.org) of the geometry.

## Synopsis

`text ST_GeoHash(`geometry geom, integer maxchars=full_precision_of_point`)`;

## Description

Return a GeoHash representation (geohash.org) of the geometry. A GeoHash encodes a point into a text form that is sortable and searchable based on prefixing. A shorter GeoHash is a less precise representation of a point. It can also be thought of as a box, that contains the actual point.

If no `maxchars` is specficified ST_GeoHash returns a GeoHash based on full precision of the input geometry type. Points return a GeoHash with 20 characters of precision (about enough to hold the full double precision of the input). Other types return a GeoHash with a variable amount of precision, based on the size of the feature. Larger features are represented with less precision, smaller features with more precision. The idea is that the box implied by the GeoHash will always contain the input feature.

If `maxchars` is specified ST_GeoHash returns a GeoHash with at most that many characters so a possibly lower precision representation of the input geometry. For non-points, the starting point of the calculation is the center of the bounding box of the geometry.

Availability: 1.4.0

ST_GeoHash will not work with geometries that are not in geographic (lon/lat) coordinates.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_GeoHash(ST_SetSRID(ST_MakePoint(-126,48),4326));

    	 st_geohash
    ----------------------
     c0w3hf1s70w3hf1s70w3

    SELECT ST_GeoHash(ST_SetSRID(ST_MakePoint(-126,48),4326),5);

     st_geohash
    ------------
     c0w3h

## See Also

## Name

ST_AsText — Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.

## Synopsis

`text ST_AsText(`geometry g1`)`;

`text ST_AsText(`geography g1`)`;

## Description

Returns the Well-Known Text representation of the geometry/geography.

The WKT spec does not include the SRID. To get the SRID as part of the data, use the non-standard PostGIS ST_AsEWKT

WKT format does not maintain precision so to prevent floating truncation, use ST_AsBinary or ST_AsEWKB format for transport.

ST_AsText is the reverse of ST_GeomFromText. Use ST_GeomFromText to convert to a postgis geometry from ST_AsText representation.

Availability: 1.5 - support for geography was introduced.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.25

This method supports Circular Strings and Curves

## Examples

    SELECT ST_AsText('01030000000100000005000000000000000000
    000000000000000000000000000000000000000000000000
    F03F000000000000F03F000000000000F03F000000000000F03
    F000000000000000000000000000000000000000000000000');

    		   st_astext
    --------------------------------
     POLYGON((0 0,0 1,1 1,1 0,0 0))
    (1 row)

## See Also

ST_AsBinary, ST_AsEWKB, ST_AsEWKT, ST_GeomFromText

## Name

ST_AsLatLonText — Return the Degrees, Minutes, Seconds representation of the given point.

## Synopsis

`text ST_AsLatLonText(`geometry pt`)`;

`text ST_AsLatLonText(`geometry pt, text format`)`;

## Description

Returns the Degrees, Minutes, Seconds representation of the point.

It is assumed the point is in a lat/lon projection. The X (lon) and Y (lat) coordinates are normalized in the output to the "normal" range (-180 to +180 for lon, -90 to +90 for lat).

The text parameter is a format string containing the format for the resulting text, similar to a date format string. Valid tokens are "D" for degrees, "M" for minutes, "S" for seconds, and "C" for cardinal direction (NSEW). DMS tokens may be repeated to indicate desired width and precision ("SSS.SSSS" means " 1.0023").

"M", "S", and "C" are optional. If "C" is omitted, degrees are shown with a "-" sign if south or west. If "S" is omitted, minutes will be shown as decimal with as many digits of precision as you specify. If "M" is also omitted, degrees are shown as decimal with as many digits precision as you specify.

If the format string is omitted (or zero-length) a default format will be used.

Availability: 2.0

## Examples

Default format.

    SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)'));
          st_aslatlontext
    ----------------------------
     2°19'29.928"S 3°14'3.243"W

Providing a format (same as the default).

    SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D°M''S.SSS"C'));
          st_aslatlontext
    ----------------------------
     2°19'29.928"S 3°14'3.243"W

Characters other than D, M, S, C and . are just passed through.

    SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D degrees, M minutes, S seconds to the C'));
                                       st_aslatlontext
    --------------------------------------------------------------------------------------
     2 degrees, 19 minutes, 30 seconds to the S 3 degrees, 14 minutes, 3 seconds to the W

Signed degrees instead of cardinal directions.

    SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D°M''S.SSS"'));
          st_aslatlontext
    ----------------------------
     -2°19'29.928" -3°14'3.243"

Decimal degrees.

    SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D.DDDD degrees C'));
              st_aslatlontext
    -----------------------------------
     2.3250 degrees S 3.2342 degrees W

Excessively large values are normalized.

    SELECT (ST_AsLatLonText('POINT (-302.2342342 -792.32498)'));
            st_aslatlontext
    -------------------------------
     72°19'29.928"S 57°45'56.757"E

## 8.7. Operators

## Name

&& — Returns `TRUE` if A's 2D bounding box intersects B's 2D bounding box.

## Synopsis

`boolean &&(` geometry A , geometry B `)`;

`boolean &&(` geography A , geography B `)`;

## Description

The `&&` operator returns `TRUE` if the 2D bounding box of geometry A intersects the 2D bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Availability: 1.5.0 support for geography was introduced.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 && tbl2.column2 AS overlaps
    FROM ( VALUES
    	(1, 'LINESTRING(0 0, 3 3)'::geometry),
    	(2, 'LINESTRING(0 1, 0 5)'::geometry)) AS tbl1,
    ( VALUES
    	(3, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl2;

     column1 | column1 | overlaps
    ---------+---------+----------
    	   1 |       3 | t
    	   2 |       3 | f
    (2 rows)

## See Also

|&>, &>, &<|, &<, ~, @

## Name

&&& — Returns `TRUE` if A's 3D bounding box intersects B's 3D bounding box.

## Synopsis

`boolean &&&(` geometry A , geometry B `)`;

## Description

The `&&&` operator returns `TRUE` if the n-D bounding box of geometry A intersects the n-D bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

Availability: 2.0.0

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Examples: 3D LineStrings

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 &&& tbl2.column2 AS overlaps_3d,
    			            tbl1.column2 && tbl2.column2 AS overlaps_2d
    FROM ( VALUES
    	(1, 'LINESTRING Z(0 0 1, 3 3 2)'::geometry),
    	(2, 'LINESTRING Z(1 2 0, 0 5 -1)'::geometry)) AS tbl1,
    ( VALUES
    	(3, 'LINESTRING Z(1 2 1, 4 6 1)'::geometry)) AS tbl2;

     column1 | column1 | overlaps_3d | overlaps_2d
    ---------+---------+-------------+-------------
           1 |       3 | t           | t
           2 |       3 | f           | t

## Examples: 3M LineStrings

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 &&& tbl2.column2 AS overlaps_3zm,
    			            tbl1.column2 && tbl2.column2 AS overlaps_2d
    FROM ( VALUES
    	(1, 'LINESTRING M(0 0 1, 3 3 2)'::geometry),
    	(2, 'LINESTRING M(1 2 0, 0 5 -1)'::geometry)) AS tbl1,
    ( VALUES
    	(3, 'LINESTRING M(1 2 1, 4 6 1)'::geometry)) AS tbl2;

     column1 | column1 | overlaps_3zm | overlaps_2d
    ---------+---------+-------------+-------------
           1 |       3 | t           | t
           2 |       3 | f           | t

## See Also

&&

## Name

&< — Returns `TRUE` if A's bounding box overlaps or is to the left of B's.

## Synopsis

`boolean &<(` geometry A , geometry B `)`;

## Description

The `&<` operator returns `TRUE` if the bounding box of geometry A overlaps or is to the left of the bounding box of geometry B, or more accurately, overlaps or is NOT to the right of the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 &< tbl2.column2 AS overleft
    FROM
      ( VALUES
    	(1, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING(0 0, 3 3)'::geometry),
    	(3, 'LINESTRING(0 1, 0 5)'::geometry),
    	(4, 'LINESTRING(6 0, 6 1)'::geometry)) AS tbl2;

     column1 | column1 | overleft
    ---------+---------+----------
    	   1 |       2 | f
    	   1 |       3 | f
    	   1 |       4 | t
    (3 rows)

## See Also

&&, |&>, &>, &<|

## Name

&<| — Returns `TRUE` if A's bounding box overlaps or is below B's.

## Synopsis

`boolean &<|(` geometry A , geometry B `)`;

## Description

The `&<|` operator returns `TRUE` if the bounding box of geometry A overlaps or is below of the bounding box of geometry B, or more accurately, overlaps or is NOT above the bounding box of geometry B.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 &<| tbl2.column2 AS overbelow
    FROM
      ( VALUES
    	(1, 'LINESTRING(6 0, 6 4)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING(0 0, 3 3)'::geometry),
    	(3, 'LINESTRING(0 1, 0 5)'::geometry),
    	(4, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl2;

     column1 | column1 | overbelow
    ---------+---------+-----------
    	   1 |       2 | f
    	   1 |       3 | t
    	   1 |       4 | t
    (3 rows)

## See Also

&&, |&>, &>, &<

## Name

&> — Returns `TRUE` if A' bounding box overlaps or is to the right of B's.

## Synopsis

`boolean &>(` geometry A , geometry B `)`;

## Description

The `&>` operator returns `TRUE` if the bounding box of geometry A overlaps or is to the right of the bounding box of geometry B, or more accurately, overlaps or is NOT to the left of the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 &> tbl2.column2 AS overright
    FROM
      ( VALUES
    	(1, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING(0 0, 3 3)'::geometry),
    	(3, 'LINESTRING(0 1, 0 5)'::geometry),
    	(4, 'LINESTRING(6 0, 6 1)'::geometry)) AS tbl2;

     column1 | column1 | overright
    ---------+---------+-----------
    	   1 |       2 | t
    	   1 |       3 | t
    	   1 |       4 | f
    (3 rows)

## See Also

&&, |&>, &<|, &<

## Name

<< — Returns `TRUE` if A's bounding box is strictly to the left of B's.

## Synopsis

`boolean <<(` geometry A , geometry B `)`;

## Description

The `<<` operator returns `TRUE` if the bounding box of geometry A is strictly to the left of the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 << tbl2.column2 AS left
    FROM
      ( VALUES
    	(1, 'LINESTRING (1 2, 1 5)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (0 0, 4 3)'::geometry),
    	(3, 'LINESTRING (6 0, 6 5)'::geometry),
    	(4, 'LINESTRING (2 2, 5 6)'::geometry)) AS tbl2;

     column1 | column1 | left
    ---------+---------+------
    	   1 |       2 | f
    	   1 |       3 | t
    	   1 |       4 | t
    (3 rows)

## See Also

>>, |>>, <<|

## Name

<<| — Returns `TRUE` if A's bounding box is strictly below B's.

## Synopsis

`boolean <<|(` geometry A , geometry B `)`;

## Description

The `<<|` operator returns `TRUE` if the bounding box of geometry A is strictly below the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 <<| tbl2.column2 AS below
    FROM
      ( VALUES
    	(1, 'LINESTRING (0 0, 4 3)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (1 4, 1 7)'::geometry),
    	(3, 'LINESTRING (6 1, 6 5)'::geometry),
    	(4, 'LINESTRING (2 3, 5 6)'::geometry)) AS tbl2;

     column1 | column1 | below
    ---------+---------+-------
    	   1 |       2 | t
    	   1 |       3 | f
    	   1 |       4 | f
    (3 rows)

## See Also

<<, >>, |>>

## Name

= — Returns `TRUE` if A's bounding box is the same as B's. Uses double precision bounding box.

## Synopsis

`boolean =(` geometry A , geometry B `)`;

`boolean =(` geography A , geography B `)`;

## Description

The `=` operator returns `TRUE` if the bounding box of geometry/geography A is the same as the bounding box of geometry/geography B. PostgreSQL uses the =, <, and > operators defined for geometries to perform internal orderings and comparison of geometries (ie. in a GROUP BY or ORDER BY clause).

This is cause for a lot of confusion. When you compare geometryA = geometryB it will return true even when the geometries are clearly different IF their bounding boxes are the same. To check for true equality use ST_OrderingEquals or ST_Equals

This operand will NOT make use of any indexes that may be available on the geometries.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Changed: 2.0.0 , the bounding box of geometries was changed to use double precision instead of float4 precision of prior. The side effect of this is that in particular points in prior versions that were a little different may have returned true in prior versions and false in 2.0+ since their float4 boxes would be the same but there float8 (double precision), would be different.

## Examples

    SELECT 'LINESTRING(0 0, 0 1, 1 0)'::geometry = 'LINESTRING(1 1, 0 0)'::geometry;
     ?column?
    ----------
     t
    (1 row)

    SELECT ST_AsText(column1)
    FROM ( VALUES
    	('LINESTRING(0 0, 1 1)'::geometry),
    	('LINESTRING(1 1, 0 0)'::geometry)) AS foo;
    	  st_astext
    ---------------------
     LINESTRING(0 0,1 1)
     LINESTRING(1 1,0 0)
    (2 rows)

    -- Note: the GROUP BY uses the "=" to compare for geometry equivalency.
    SELECT ST_AsText(column1)
    FROM ( VALUES
    	('LINESTRING(0 0, 1 1)'::geometry),
    	('LINESTRING(1 1, 0 0)'::geometry)) AS foo
    GROUP BY column1;
    	  st_astext
    ---------------------
     LINESTRING(0 0,1 1)
    (1 row)

    -- In versions prior to 2.0, this used to return true --
     SELECT ST_GeomFromText('POINT(1707296.37 4820536.77)') =
    	ST_GeomFromText('POINT(1707296.27 4820536.87)') As pt_intersect;

    --pt_intersect --
    f

## See Also

ST_Equals, ST_OrderingEquals

## Name

>> — Returns `TRUE` if A's bounding box is strictly to the right of B's.

## Synopsis

`boolean >>(` geometry A , geometry B `)`;

## Description

The `>>` operator returns `TRUE` if the bounding box of geometry A is strictly to the right of the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 >> tbl2.column2 AS right
    FROM
      ( VALUES
    	(1, 'LINESTRING (2 3, 5 6)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (1 4, 1 7)'::geometry),
    	(3, 'LINESTRING (6 1, 6 5)'::geometry),
    	(4, 'LINESTRING (0 0, 4 3)'::geometry)) AS tbl2;

     column1 | column1 | right
    ---------+---------+-------
    	   1 |       2 | t
    	   1 |       3 | f
    	   1 |       4 | f
    (3 rows)

## See Also

<<, |>>, <<|

## Name

@ — Returns `TRUE` if A's bounding box is contained by B's.

## Synopsis

`boolean @(` geometry A , geometry B `)`;

## Description

The `@` operator returns `TRUE` if the bounding box of geometry A is completely contained by the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 @ tbl2.column2 AS contained
    FROM
      ( VALUES
    	(1, 'LINESTRING (1 1, 3 3)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (0 0, 4 4)'::geometry),
    	(3, 'LINESTRING (2 2, 4 4)'::geometry),
    	(4, 'LINESTRING (1 1, 3 3)'::geometry)) AS tbl2;

     column1 | column1 | contained
    ---------+---------+-----------
    	   1 |       2 | t
    	   1 |       3 | f
    	   1 |       4 | t
    (3 rows)

## See Also

~, &&

## Name

|&> — Returns `TRUE` if A's bounding box overlaps or is above B's.

## Synopsis

`boolean |&>(` geometry A , geometry B `)`;

## Description

The `|&>` operator returns `TRUE` if the bounding box of geometry A overlaps or is above the bounding box of geometry B, or more accurately, overlaps or is NOT below the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 |&> tbl2.column2 AS overabove
    FROM
      ( VALUES
    	(1, 'LINESTRING(6 0, 6 4)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING(0 0, 3 3)'::geometry),
    	(3, 'LINESTRING(0 1, 0 5)'::geometry),
    	(4, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl2;

     column1 | column1 | overabove
    ---------+---------+-----------
    	   1 |       2 | t
    	   1 |       3 | f
    	   1 |       4 | f
    (3 rows)

## See Also

&&, &>, &<|, &<

## Name

|>> — Returns `TRUE` if A's bounding box is strictly above B's.

## Synopsis

`boolean |>>(` geometry A , geometry B `)`;

## Description

The `|>>` operator returns `TRUE` if the bounding box of geometry A is strictly to the right of the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 |>> tbl2.column2 AS above
    FROM
      ( VALUES
    	(1, 'LINESTRING (1 4, 1 7)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (0 0, 4 2)'::geometry),
    	(3, 'LINESTRING (6 1, 6 5)'::geometry),
    	(4, 'LINESTRING (2 3, 5 6)'::geometry)) AS tbl2;

     column1 | column1 | above
    ---------+---------+-------
    	   1 |       2 | t
    	   1 |       3 | f
    	   1 |       4 | f
    (3 rows)

## See Also

<<, >>, <<|

## Name

~ — Returns `TRUE` if A's bounding box contains B's.

## Synopsis

`boolean ~(` geometry A , geometry B `)`;

## Description

The `~` operator returns `TRUE` if the bounding box of geometry A completely contains the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 ~ tbl2.column2 AS contains
    FROM
      ( VALUES
    	(1, 'LINESTRING (0 0, 3 3)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (0 0, 4 4)'::geometry),
    	(3, 'LINESTRING (1 1, 2 2)'::geometry),
    	(4, 'LINESTRING (0 0, 3 3)'::geometry)) AS tbl2;

     column1 | column1 | contains
    ---------+---------+----------
    	   1 |       2 | f
    	   1 |       3 | t
    	   1 |       4 | t
    (3 rows)

## See Also

@, &&

## Name

~= — Returns `TRUE` if A's bounding box is the same as B's.

## Synopsis

`boolean ~=(` geometry A , geometry B `)`;

## Description

The `~=` operator returns `TRUE` if the bounding box of geometry/geography A is the same as the bounding box of geometry/geography B.

This operand will make use of any indexes that may be available on the geometries.

Availability: 1.5.0 changed behavior

This function supports Polyhedral surfaces.

This operator has changed behavior in PostGIS 1.5 from testing for actual geometric equality to only checking for bounding box equality. To complicate things it also depends on if you have done a hard or soft upgrade which behavior your database has. To find out which behavior your database has you can run the query below. To check for true equality use ST_OrderingEquals or ST_Equals and to check for bounding box equality =; operator is a safer option.

## Examples

    select 'LINESTRING(0 0, 1 1)'::geometry ~= 'LINESTRING(0 1, 1 0)'::geometry as equality;
     equality   |
    -----------------+
              t    |

The above can be used to test if you have the new or old behavior of ~= operator.

## See Also

ST_Equals, ST_OrderingEquals, =

## Name

<-> — Returns the distance between two points. For point / point checks it uses floating point accuracy (as opposed to the double precision accuracy of the underlying point geometry). For other geometry types the distance between the floating point bounding box centroids is returned. Useful for doing distance ordering and nearest neighbor limits using KNN gist functionality.

## Synopsis

`double precision <->(` geometry A , geometry B `)`;

## Description

The `<->` operator returns distance between two points read from the spatial index for points (float precision). For other geometries it returns the distance from centroid of bounding box of geometries. Useful for doing nearest neighbor approximate distance ordering.

This operand will make use of any indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

Index only kicks in if one of the geometries is a constant (not in a subquery/cte). e.g. 'SRID=3005;POINT(1011102 450541)'::geometry instead of a.geom

Availability: 2.0.0 only available for PostgreSQL 9.1+

## Examples

    SELECT ST_Distance(geom, 'SRID=3005;POINT(1011102 450541)'::geometry) as d,edabbr, vaabbr
    FROM va2005
    ORDER BY d limit 10;

            d         | edabbr | vaabbr
    ------------------+--------+--------
                    0 | ALQ    | 128
     5541.57712511724 | ALQ    | 129A
     5579.67450712005 | ALQ    | 001
      6083.4207708641 | ALQ    | 131
      7691.2205404848 | ALQ    | 003
     7900.75451037313 | ALQ    | 122
     8694.20710669982 | ALQ    | 129B
     9564.24289057111 | ALQ    | 130
      12089.665931705 | ALQ    | 127
     18472.5531479404 | ALQ    | 002
    (10 rows)

Then the KNN raw answer:

    SELECT st_distance(geom, 'SRID=3005;POINT(1011102 450541)'::geometry) as d,edabbr, vaabbr
    FROM va2005
    ORDER BY geom <-> 'SRID=3005;POINT(1011102 450541)'::geometry limit 10;

            d         | edabbr | vaabbr
    ------------------+--------+--------
                    0 | ALQ    | 128
     5579.67450712005 | ALQ    | 001
     5541.57712511724 | ALQ    | 129A
     8694.20710669982 | ALQ    | 129B
     9564.24289057111 | ALQ    | 130
      6083.4207708641 | ALQ    | 131
      12089.665931705 | ALQ    | 127
      24795.264503022 | ALQ    | 124
     24587.6584922302 | ALQ    | 123
     26764.2555463114 | ALQ    | 125
    (10 rows)

Note the misordering in the actual distances and the different entries that actually show up in the top 10.

Finally the hybrid:

    WITH index_query AS (
      SELECT ST_Distance(geom, 'SRID=3005;POINT(1011102 450541)'::geometry) as d,edabbr, vaabbr
      	FROM va2005
      ORDER BY geom <-> 'SRID=3005;POINT(1011102 450541)'::geometry LIMIT 100)
      SELECT *
      	FROM index_query
      ORDER BY d limit 10;

            d         | edabbr | vaabbr
    ------------------+--------+--------
                    0 | ALQ    | 128
     5541.57712511724 | ALQ    | 129A
     5579.67450712005 | ALQ    | 001
      6083.4207708641 | ALQ    | 131
      7691.2205404848 | ALQ    | 003
     7900.75451037313 | ALQ    | 122
     8694.20710669982 | ALQ    | 129B
     9564.24289057111 | ALQ    | 130
      12089.665931705 | ALQ    | 127
     18472.5531479404 | ALQ    | 002
    (10 rows)

## See Also

ST_DWithin, ST_Distance, <#>

## Name

<#> — Returns the distance between bounding box of 2 geometries. For point / point checks it's almost the same as distance (though may be different since the bounding box is at floating point accuracy and geometries are double precision). Useful for doing distance ordering and nearest neighbor limits using KNN gist functionality.

## Synopsis

`double precision <#>(` geometry A , geometry B `)`;

## Description

The `<#>` KNN GIST operator returns distance between two floating point bounding boxes read from the spatial index if available. Useful for doing nearest neighbor approximate distance ordering.

This operand will make use of any indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

Index only kicks in if one of the geometries is a constant e.g. ORDER BY (ST_GeomFromText('POINT(1 2)') <#> geom) instead of g1.geom <#>.

Availability: 2.0.0 only available for PostgreSQL 9.1+

## Examples

    SELECT *
    FROM (
    SELECT b.tlid, b.mtfcc,
    	b.geom <#> ST_GeomFromText('LINESTRING(746149 2948672,745954 2948576,
    		745787 2948499,745740 2948468,745712 2948438,
    		745690 2948384,745677 2948319)',2249) As b_dist,
    		ST_Distance(b.geom, ST_GeomFromText('LINESTRING(746149 2948672,745954 2948576,
    		745787 2948499,745740 2948468,745712 2948438,
    		745690 2948384,745677 2948319)',2249)) As act_dist
        FROM bos_roads As b
        ORDER BY b_dist, b.tlid
        LIMIT 100) As foo
        ORDER BY act_dist, tlid LIMIT 10;

       tlid    | mtfcc |      b_dist      |     act_dist
    -----------+-------+------------------+------------------
      85732027 | S1400 |                0 |                0
      85732029 | S1400 |                0 |                0
      85732031 | S1400 |                0 |                0
      85734335 | S1400 |                0 |                0
      85736037 | S1400 |                0 |                0
     624683742 | S1400 |                0 | 128.528874268666
      85719343 | S1400 | 260.839270432962 | 260.839270432962
      85741826 | S1400 | 164.759294123275 | 260.839270432962
      85732032 | S1400 |           277.75 | 311.830282365264
      85735592 | S1400 |           222.25 | 311.830282365264
    (10 rows)

## See Also

ST_DWithin, ST_Distance, <->

## 8.8. Spatial Relationships and Measurements

## Name

ST_3DClosestPoint — Returns the 3-dimensional point on g1 that is closest to g2. This is the first point of the 3D shortest line.

## Synopsis

`geometry ST_3DClosestPoint(`geometry g1, geometry g2`)`;

## Description

Returns the 3-dimensional point on g1 that is closest to g2. This is the first point of the 3D shortest line. The 3D length of the 3D shortest line is the 3D distance.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Availability: 2.0.0

## Examples

linestring and point -- both 3d and 2d closest point
    SELECT ST_AsEWKT(ST_3DClosestPoint(line,pt)) AS cp3d_line_pt,
    		ST_AsEWKT(ST_ClosestPoint(line,pt)) As cp2d_line_pt
    	FROM (SELECT 'POINT(100 100 30)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)'::geometry As line
    		) As foo;

     cp3d_line_pt                        						|               cp2d_line_pt
    -----------------------------------------------------------+------------------------------------------
     POINT(54.6993798867619 128.935022917228 11.5475869506606) | POINT(73.0769230769231 115.384615384615)
linestring and multipoint -- both 3d and 2d closest point
    SELECT ST_AsEWKT(ST_3DClosestPoint(line,pt)) AS cp3d_line_pt,
    		ST_AsEWKT(ST_ClosestPoint(line,pt)) As cp2d_line_pt
    	FROM (SELECT 'MULTIPOINT(100 100 30, 50 74 1000)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)'::geometry As line
    		) As foo;

                           cp3d_line_pt                        | cp2d_line_pt
    -----------------------------------------------------------+--------------
     POINT(54.6993798867619 128.935022917228 11.5475869506606) | POINT(50 75)
Multilinestring and polygon both 3d and 2d closest point
    SELECT ST_AsEWKT(ST_3DClosestPoint(poly, mline)) As cp3d,
        ST_AsEWKT(ST_ClosestPoint(poly, mline)) As cp2d
            FROM (SELECT  ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
                    ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
                    (1 10 2, 5 20 1))') As mline ) As foo;
                       cp3d                    |     cp2d
    -------------------------------------------+--------------
     POINT(39.993580415989 54.1889925532825 5) | POINT(20 40)

## See Also

ST_AsEWKT, ST_ClosestPoint, ST_3DDistance, ST_3DShortestLine

## Name

ST_3DDistance — For geometry type Returns the 3-dimensional cartesian minimum distance (based on spatial ref) between two geometries in projected units.

## Synopsis

`float ST_3DDistance(`geometry g1, geometry g2`)`;

## Description

For geometry type returns the 3-dimensional minimum cartesian distance between two geometries in projected units (spatial ref units).

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This method implements the SQL/MM specification. SQL-MM ?

Availability: 2.0.0

## Examples

    -- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
    -- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
    SELECT ST_3DDistance(
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163)
    		) As dist_3d,
    		ST_Distance(
    			ST_Transform(ST_GeomFromText('POINT(-72.1235 42.3521)',4326),2163),
    			ST_Transform(ST_GeomFromText('LINESTRING(-72.1260 42.45, -72.123 42.1546)', 4326),2163)
    		) As dist_2d;

         dist_3d      |     dist_2d
    ------------------+-----------------
     127.295059324629 | 126.66425605671

    -- Multilinestring and polygon both 3d and 2d distance
    -- Same example as 3D closest point example
    SELECT ST_3DDistance(poly, mline) As dist3d,
        ST_Distance(poly, mline) As dist2d
            FROM (SELECT  ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
                    ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
                    (1 10 2, 5 20 1))') As mline ) As foo;
          dist3d       | dist2d
    -------------------+--------
     0.716635696066337 |      0

## See Also

ST_Distance, ST_3DClosestPoint, ST_3DDWithin, ST_3DMaxDistance, ST_3DShortestLine, ST_Transform

## Name

ST_3DDWithin — For 3d (z) geometry type Returns true if two geometries 3d distance is within number of units.

## Synopsis

`boolean ST_3DDWithin(`geometry g1, geometry g2, double precision distance_of_srid`)`;

## Description

For geometry type returns true if the 3d distance between two objects is within distance_of_srid specified projected units (spatial ref units).

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This method implements the SQL/MM specification. SQL-MM ?

Availability: 2.0.0

## Examples

    -- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
    -- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
    SELECT ST_3DDWithin(
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
    			126.8
    		) As within_dist_3d,
    ST_DWithin(
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
    			126.8
    		) As within_dist_2d;

     within_dist_3d | within_dist_2d
    ----------------+----------------
     f              | t

## See Also

ST_3DDistance, ST_Distance, ST_DWithin, ST_3DMaxDistance, ST_Transform

## Name

ST_3DDFullyWithin — Returns true if all of the 3D geometries are within the specified distance of one another.

## Synopsis

`boolean ST_3DDFullyWithin(`geometry g1, geometry g2, double precision distance`)`;

## Description

Returns true if the 3D geometries are fully within the specified distance of one another. The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

    		-- This compares the difference between fully within and distance within as well
    		-- as the distance fully within for the 2D footprint of the line/point vs. the 3d fully within
    		SELECT ST_3DDFullyWithin(geom_a, geom_b, 10) as D3DFullyWithin10, ST_3DDWithin(geom_a, geom_b, 10) as D3DWithin10,
    	ST_DFullyWithin(geom_a, geom_b, 20) as D2DFullyWithin20,
    	ST_3DDFullyWithin(geom_a, geom_b, 20) as D3DFullyWithin20 from
    		(select ST_GeomFromEWKT('POINT(1 1 2)') as geom_a,
    		ST_GeomFromEWKT('LINESTRING(1 5 2, 2 7 20, 1 9 100, 14 12 3)') as geom_b) t1;
     d3dfullywithin10 | d3dwithin10 | d2dfullywithin20 | d3dfullywithin20
    ------------------+-------------+------------------+------------------
     f                | t           | t                | f

## See Also

ST_3DMaxDistance, ST_3DDWithin, ST_DWithin, ST_DFullyWithin

## Name

ST_3DIntersects — Returns TRUE if the Geometries "spatially intersect" in 3d - only for points and linestrings

## Synopsis

`boolean ST_3DIntersects(` geometry geomA , geometry geomB `)`;

## Description

Overlaps, Touches, Within all imply spatial intersection. If any of the aforementioned returns true, then the geometries also spatially intersect. Disjoint implies false for spatial intersection.

Availability: 2.0.0

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This method implements the SQL/MM specification. SQL-MM 3: ?

## Geometry Examples

    SELECT ST_3DIntersects(pt, line), ST_Intersects(pt,line)
    	FROM (SELECT 'POINT(0 0 2)'::geometry As pt,
    		'LINESTRING (0 0 1, 0 2 3 )'::geometry As line) As foo;
     st_3dintersects | st_intersects
    -----------------+---------------
     f               | t
    (1 row)

## See Also

ST_Intersects

## Name

ST_3DLongestLine — Returns the 3-dimensional longest line between two geometries

## Synopsis

`geometry ST_3DLongestLine(`geometry g1, geometry g2`)`;

## Description

Returns the 3-dimensional longest line between two geometries. The function will only return the first longest line if more than one. The line returned will always start in g1 and end in g2. The 3D length of the line this function returns will always be the same as ST_3DMaxDistance returns for g1 and g2.

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

linestring and point -- both 3d and 2d longest line
    SELECT ST_AsEWKT(ST_3DLongestLine(line,pt)) AS lol3d_line_pt,
    		ST_AsEWKT(ST_LongestLine(line,pt)) As lol2d_line_pt
    	FROM (SELECT 'POINT(100 100 30)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)'::geometry As line
    		) As foo;

               lol3d_line_pt           |       lol2d_line_pt
    -----------------------------------+----------------------------
     LINESTRING(50 75 1000,100 100 30) | LINESTRING(98 190,100 100)
linestring and multipoint -- both 3d and 2d longest line
    SELECT ST_AsEWKT(ST_3DLongestLine(line,pt)) AS lol3d_line_pt,
    		ST_AsEWKT(ST_LongestLine(line,pt)) As lol2d_line_pt
    	FROM (SELECT 'MULTIPOINT(100 100 30, 50 74 1000)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)'::geometry As line
    		) As foo;

              lol3d_line_pt          |      lol2d_line_pt
    ---------------------------------+--------------------------
     LINESTRING(98 190 1,50 74 1000) | LINESTRING(98 190,50 74)
Multilinestring and polygon both 3d and 2d longest line
    SELECT ST_AsEWKT(ST_3DLongestLine(poly, mline)) As lol3d,
        ST_AsEWKT(ST_LongestLine(poly, mline)) As lol2d
            FROM (SELECT  ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
                    ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
                    (1 10 2, 5 20 1))') As mline ) As foo;
                lol3d             |          lol2d
    ------------------------------+--------------------------
     LINESTRING(175 150 5,1 10 2) | LINESTRING(175 150,1 10)

## See Also

ST_3DClosestPoint, ST_3DDistance, ST_LongestLine, ST_3DShortestLine, ST_3DMaxDistance

## Name

ST_3DMaxDistance — For geometry type Returns the 3-dimensional cartesian maximum distance (based on spatial ref) between two geometries in projected units.

## Synopsis

`float ST_3DMaxDistance(`geometry g1, geometry g2`)`;

## Description

For geometry type returns the 3-dimensional maximum cartesian distance between two geometries in projected units (spatial ref units).

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Availability: 2.0.0

## Examples

    -- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
    -- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
    SELECT ST_3DMaxDistance(
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 10000)'),2163),
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163)
    		) As dist_3d,
    		ST_MaxDistance(
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 10000)'),2163),
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163)
    		) As dist_2d;

         dist_3d      |     dist_2d
    ------------------+------------------
     24383.7467488441 | 22247.8472107251

## See Also

ST_Distance, ST_3DDWithin, ST_3DMaxDistance, ST_Transform

## Name

ST_3DShortestLine — Returns the 3-dimensional shortest line between two geometries

## Synopsis

`geometry ST_3DShortestLine(`geometry g1, geometry g2`)`;

## Description

Returns the 3-dimensional shortest line between two geometries. The function will only return the first shortest line if more than one, that the function finds. If g1 and g2 intersects in just one point the function will return a line with both start and end in that intersection-point. If g1 and g2 are intersecting with more than one point the function will return a line with start and end in the same point but it can be any of the intersecting points. The line returned will always start in g1 and end in g2. The 3D length of the line this function returns will always be the same as ST_3DDistance returns for g1 and g2.

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

linestring and point -- both 3d and 2d shortest line
    SELECT ST_AsEWKT(ST_3DShortestLine(line,pt)) AS shl3d_line_pt,
    		ST_AsEWKT(ST_ShortestLine(line,pt)) As shl2d_line_pt
    	FROM (SELECT 'POINT(100 100 30)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)'::geometry As line
    		) As foo;

     shl3d_line_pt                        						                 |               shl2d_line_pt
    ----------------------------------------------------------------------------+------------------------------------------------------
     LINESTRING(54.6993798867619 128.935022917228 11.5475869506606,100 100 30)  | LINESTRING(73.0769230769231 115.384615384615,100 100)
linestring and multipoint -- both 3d and 2d shortest line
    SELECT ST_AsEWKT(ST_3DShortestLine(line,pt)) AS shl3d_line_pt,
    		ST_AsEWKT(ST_ShortestLine(line,pt)) As shl2d_line_pt
    	FROM (SELECT 'MULTIPOINT(100 100 30, 50 74 1000)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)'::geometry As line
    		) As foo;

                           shl3d_line_pt                                       | shl2d_line_pt
    ---------------------------------------------------------------------------+------------------------
     LINESTRING(54.6993798867619 128.935022917228 11.5475869506606,100 100 30) | LINESTRING(50 75,50 74)
Multilinestring and polygon both 3d and 2d shortest line
    SELECT ST_AsEWKT(ST_3DShortestLine(poly, mline)) As shl3d,
        ST_AsEWKT(ST_ShortestLine(poly, mline)) As shl2d
            FROM (SELECT  ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
                    ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
                    (1 10 2, 5 20 1))') As mline ) As foo;
                       shl3d                                                                           |     shl2d
    ---------------------------------------------------------------------------------------------------+------------------------
     LINESTRING(39.993580415989 54.1889925532825 5,40.4078575708294 53.6052383805529 5.03423778139177) | LINESTRING(20 40,20 40)

## See Also

ST_3DClosestPoint, ST_3DDistance, ST_LongestLine, ST_ShortestLine, ST_3DMaxDistance

## Name

ST_Area — Returns the area of the surface if it is a polygon or multi-polygon. For "geometry" type area is in SRID units. For "geography" area is in square meters.

## Synopsis

`float ST_Area(`geometry g1`)`;

`float ST_Area(`geography geog, boolean use_spheroid=true`)`;

## Description

Returns the area of the geometry if it is a polygon or multi-polygon. Return the area measurement of an ST_Surface or ST_MultiSurface value. For geometry Area is in the units of the srid. For geography area is in square meters and defaults to measuring about the spheroid of the geography (currently only WGS84). To measure around the faster but less accurate sphere -- ST_Area(geog,false).

Enhanced: 2.0.0 - support for 2D polyhedral surfaces was introduced.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.1.2, 9.5.3

This function supports Polyhedral surfaces.

For polyhedral surfaces, only supports 2D polyhedral surfaces (not 2.5D). For 2.5D, may give a non-zero answer, but only for the faces that sit completely in XY plane.

## Examples

Return area in square feet for a plot of Massachusetts land and multiply by conversion to get square meters. Note this is in square feet because 2249 is Mass State Plane Feet

    SELECT ST_Area(the_geom) As sqft, ST_Area(the_geom)*POWER(0.3048,2) As sqm
    		FROM (SELECT
    		ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
    			743265 2967450,743265.625 2967416,743238 2967416))',2249) ) As foo(the_geom);
      sqft   |     sqm
    ---------+-------------
     928.625 | 86.27208552

Return area square feet and transform to Massachusetts state plane meters (26986) to get square meters. Note this is in square feet because 2249 is Mass State Plane Feet and transformed area is in square meters since 26986 is state plane mass meters

    SELECT ST_Area(the_geom) As sqft, ST_Area(ST_Transform(the_geom,26986)) As sqm
    		FROM (SELECT
    		ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
    			743265 2967450,743265.625 2967416,743238 2967416))',2249) ) As foo(the_geom);
      sqft   |       sqm
    ---------+------------------
     928.625 | 86.2724304199219

Return area square feet and square meters using Geography data type. Note that we transform to our geometry to geography (before you can do that make sure your geometry is in WGS 84 long lat 4326). Geography always measures in meters. This is just for demonstration to compare. Normally your table will be stored in geography data type already.

    SELECT ST_Area(the_geog)/POWER(0.3048,2) As sqft_spheroid,  ST_Area(the_geog,false)/POWER(0.3048,2) As sqft_sphere, ST_Area(the_geog) As sqm_spheroid
    		FROM (SELECT
    		geography(
    		ST_Transform(
    			ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,743238 2967416))',
    				2249
    				) ,4326
    			)
    		)
    	) As foo(the_geog);
     sqft_spheroid   |   sqft_sphere    |   sqm_spheroid
    -----------------+------------------+------------------
    928.684405217197 | 927.186481558724 | 86.2776044452694

     --if your data is in geography already
     SELECT ST_Area(the_geog)/POWER(0.3048,2) As  sqft, ST_Area(the_geog) As sqm
    	FROM somegeogtable;

## See Also

ST_GeomFromText, ST_GeographyFromText, ST_SetSRID, ST_Transform

## Name

ST_Azimuth — Returns the angle in radians from the horizontal of the vector defined by pointA and pointB. Angle is computed clockwise from down-to-up: on the clock: 12=0; 3=PI/2; 6=PI; 9=3PI/2.

## Synopsis

`float ST_Azimuth(`geometry pointA, geometry pointB`)`;

`float ST_Azimuth(`geography pointA, geography pointB`)`;

## Description

Returns the azimuth of the segment defined by the given Point geometries, or NULL if the two points are coincident. Return value is in radians. Angle is computed clockwise from down-to-up: on the clock: 12=0; 3=PI/2; 6=PI; 9=3PI/2

The Azimuth is mathematical concept defined as the angle, in this case measured in radian, between a reference plane and a point.

Availability: 1.1.0

Enhanced: 2.0.0 support for geography was introduced.

Azimuth is especially useful in conjunction with ST_Translate for shifting an object along its perpendicular axis. See upgis_lineshift Plpgsqlfunctions PostGIS wiki section for example of this.

## Examples

Geometry Azimuth in degrees

    SELECT ST_Azimuth(ST_Point(25,45), ST_Point(75,100))/(2*pi())*360 as degAz,
    	ST_Azimuth(ST_Point(75,100), ST_Point(25,45))/(2*pi())*360 As degAzrev;

    -- NOTE easier to remember syntax using PostgreSQL built-in degrees function --
    -- Both yield same answer --
    SELECT degrees( ST_Azimuth(ST_Point(25,45), ST_Point(75,100)) ) as degAz,
    	degrees( ST_Azimuth(ST_Point(75,100), ST_Point(25,45)) ) As degAzrev;

          degaz       |     degazrev
    ------------------+------------------
     42.2736890060937 | 222.273689006094

degAz is path to travel (azimuth), horizontal line (which starts at the start point and ends where we want the end point to fall) and points (start point: 25,45 is in green) | degAzrev is azimuth curve shown, horizontal line (which starts at the start point and ends where we want the end point to fall) and points (start point: 75,100 is in green)

## See Also

ST_Point, ST_Translate

## Name

ST_Centroid — Returns the geometric center of a geometry.

## Synopsis

`geometry ST_Centroid(`geometry g1`)`;

## Description

Computes the geometric center of a geometry, or equivalently, the center of mass of the geometry as a `POINT`. For [`MULTI`]`POINT`s, this is computed as the arithmetric mean of the input coordinates. For [`MULTI`]`LINESTRING`s, this is computed as the weighted length of each line segment. For [`MULTI`]`POLYGON`s, "weight" is thought in terms of area. If an empty geometry is supplied, an empty `GEOMETRYCOLLECTION` is returned. If `NULL` is supplied, `NULL` is returned.

The centroid is equal to the centroid of the set of component Geometries of highest dimension (since the lower-dimension geometries contribute zero "weight" to the centroid).

Computation will be more accurate if performed by the GEOS module (enabled at compile time).

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.1.4, 9.5.5

## Examples

In each of the following illustrations, the blue dot represents the centroid of the source geometry.

Centroid of a `MULTIPOINT` | Centroid of a `LINESTRING`
Centroid of a `POLYGON` | Centroid of a `GEOMETRYCOLLECTION`

    SELECT ST_AsText(ST_Centroid('MULTIPOINT ( -1 0, -1 2, -1 3, -1 4, -1 7, 0 1, 0 3, 1 1, 2 0, 6 0, 7 8, 9 8, 10 6 )'));
    				st_astext
    ------------------------------------------
     POINT(2.30769230769231 3.30769230769231)
    (1 row)

## See Also

ST_PointOnSurface

## Name

ST_ClosestPoint — Returns the 2-dimensional point on g1 that is closest to g2. This is the first point of the shortest line.

## Synopsis

`geometry ST_ClosestPoint(`geometry g1, geometry g2`)`;

## Description

Returns the 2-dimensional point on g1 that is closest to g2. This is the first point of the shortest line.

Availability: 1.5.0

## Examples

Closest between point and linestring is the point itself, but closest point between a linestring and point is the point on line string that is closest.
    SELECT ST_AsText(ST_ClosestPoint(pt,line)) AS cp_pt_line,
    	ST_AsText(ST_ClosestPoint(line,pt)) As cp_line_pt
    FROM (SELECT 'POINT(100 100)'::geometry As pt,
    		'LINESTRING (20 80, 98 190, 110 180, 50 75 )'::geometry As line
    	) As foo;

       cp_pt_line   |                cp_line_pt
    ----------------+------------------------------------------
     POINT(100 100) | POINT(73.0769230769231 115.384615384615)
| closest point on polygon A to polygon B
    SELECT ST_AsText(
    		ST_ClosestPoint(
    			ST_GeomFromText('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'),
    			ST_Buffer(ST_GeomFromText('POINT(110 170)'), 20)
    			)
    		) As ptwkt;

                      ptwkt
    ------------------------------------------
     POINT(140.752120669087 125.695053378061)

## See Also

ST_Distance, ST_LongestLine, ST_ShortestLine, ST_MaxDistance

## Name

ST_Contains — Returns true if and only if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A.

## Synopsis

`boolean ST_Contains(`geometry geomA, geometry geomB`)`;

## Description

Geometry A contains Geometry B if and only if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A. An important subtlety of this definition is that A does not contain its boundary, but A does contain itself. Contrast that to ST_ContainsProperly where geometry A does not Contain Properly itself.

Returns TRUE if geometry B is completely inside geometry A. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID. ST_Contains is the inverse of ST_Within. So ST_Contains(A,B) implies ST_Within(B,A) except in the case of invalid geometries where the result is always false regardless or not defined.

Performed by the GEOS module

Do not call with a `GEOMETRYCOLLECTION` as an argument

Do not use this function with invalid geometries. You will get unexpected results.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries. To avoid index use, use the function _ST_Contains.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3 - same as within(geometry B, geometry A)

This method implements the SQL/MM specification. SQL-MM 3: 5.1.31

There are certain subtleties to ST_Contains and ST_Within that are not intuitively obvious. For details check out Subtleties of OGC Covers, Contains, Within

## Examples

The `ST_Contains` predicate returns `TRUE` in all the following illustrations.

`LINESTRING` / `MULTIPOINT` | `POLYGON` / `POINT`
`POLYGON` / `LINESTRING` | `POLYGON` / `POLYGON`

The `ST_Contains` predicate returns `FALSE` in all the following illustrations.

`POLYGON` / `MULTIPOINT` | `POLYGON` / `LINESTRING`

    -- A circle within a circle
    SELECT ST_Contains(smallc, bigc) As smallcontainsbig,
    	   ST_Contains(bigc,smallc) As bigcontainssmall,
    	   ST_Contains(bigc, ST_Union(smallc, bigc)) as bigcontainsunion,
    	   ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
    	   ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
    	   ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
    FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
    			 ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;

    -- Result
      smallcontainsbig | bigcontainssmall | bigcontainsunion | bigisunion | bigcoversexterior | bigcontainsexterior
    ------------------+------------------+------------------+------------+-------------------+---------------------
     f                | t                | t                | t          | t        | f

    -- Example demonstrating difference between contains and contains properly
    SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
       ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
    FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
    			 ( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
    			 ( ST_Point(1,1) )
    	  ) As foo(geomA);

      geomtype    | acontainsa | acontainspropa | acontainsba | acontainspropba
    --------------+------------+----------------+-------------+-----------------
    ST_Polygon    | t          | f              | f           | f
    ST_LineString | t          | f              | f           | f
    ST_Point      | t          | t              | f           | f

## See Also

ST_Boundary, ST_ContainsProperly, ST_Covers, ST_CoveredBy, ST_Equals, ST_Within

## Name

ST_ContainsProperly — Returns true if B intersects the interior of A but not the boundary (or exterior). A does not contain properly itself, but does contain itself.

## Synopsis

`boolean ST_ContainsProperly(`geometry geomA, geometry geomB`)`;

## Description

Returns true if B intersects the interior of A but not the boundary (or exterior).

A does not contain properly itself, but does contain itself.

Every point of the other geometry is a point of this geometry's interior. The DE-9IM Intersection Matrix for the two geometries matches [T**FF*FF*] used in ST_Relate

From JTS docs slightly reworded: The advantage to using this predicate over ST_Contains and ST_Intersects is that it can be computed efficiently, with no need to compute topology at individual points. An example use case for this predicate is computing the intersections of a set of geometries with a large polygonal geometry. Since intersection is a fairly slow operation, it can be more efficient to use containsProperly to filter out test geometries which lie wholly inside the area. In these cases the intersection is known a priori to be exactly the original test geometry.

Availability: 1.4.0 - requires GEOS >= 3.1.0.

Do not call with a `GEOMETRYCOLLECTION` as an argument

Do not use this function with invalid geometries. You will get unexpected results.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries. To avoid index use, use the function _ST_ContainsProperly.

## Examples

    	--a circle within a circle
    	SELECT ST_ContainsProperly(smallc, bigc) As smallcontainspropbig,
    	ST_ContainsProperly(bigc,smallc) As bigcontainspropsmall,
    	ST_ContainsProperly(bigc, ST_Union(smallc, bigc)) as bigcontainspropunion,
    	ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
    	ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
    	ST_ContainsProperly(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
    	FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
    	ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
    	--Result
      smallcontainspropbig | bigcontainspropsmall | bigcontainspropunion | bigisunion | bigcoversexterior | bigcontainsexterior
    ------------------+------------------+------------------+------------+-------------------+---------------------
     f                     | t                    | f                    | t          | t                 | f

     --example demonstrating difference between contains and contains properly
     SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
     ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
     FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
    		  ( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
    		  ( ST_Point(1,1) )
    	) As foo(geomA);

      geomtype    | acontainsa | acontainspropa | acontainsba | acontainspropba
    --------------+------------+----------------+-------------+-----------------
    ST_Polygon    | t          | f              | f           | f
    ST_LineString | t          | f              | f           | f
    ST_Point      | t          | t              | f           | f

## See Also

ST_GeometryType, ST_Boundary, ST_Contains, ST_Covers, ST_CoveredBy, ST_Equals, ST_Relate, ST_Within

## Name

ST_Covers — Returns 1 (TRUE) if no point in Geometry B is outside Geometry A

## Synopsis

`boolean ST_Covers(`geometry geomA, geometry geomB`)`;

`boolean ST_Covers(`geography geogpolyA, geography geogpointB`)`;

## Description

Returns 1 (TRUE) if no point in Geometry/Geography B is outside Geometry/Geography A

Performed by the GEOS module

Do not call with a `GEOMETRYCOLLECTION` as an argument

For geography only Polygon covers point is supported.

Do not use this function with invalid geometries. You will get unexpected results.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries. To avoid index use, use the function _ST_Covers.

Availability: 1.2.2 - requires GEOS >= 3.0

Availability: 1.5 - support for geography was introduced.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

Not an OGC standard, but Oracle has it too.

There are certain subtleties to ST_Contains and ST_Within that are not intuitively obvious. For details check out Subtleties of OGC Covers, Contains, Within

## Examples

Geometry example

    	--a circle covering a circle
    SELECT ST_Covers(smallc,smallc) As smallinsmall,
    	ST_Covers(smallc, bigc) As smallcoversbig,
    	ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
    	ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
    FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
    	ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
    	--Result
     smallinsmall | smallcoversbig | bigcoversexterior | bigcontainsexterior
    --------------+----------------+-------------------+---------------------
     t            | f              | t                 | f
    (1 row)

Geeography Example

    -- a point with a 300 meter buffer compared to a point, a point and its 10 meter buffer
    SELECT ST_Covers(geog_poly, geog_pt) As poly_covers_pt,
    	ST_Covers(ST_Buffer(geog_pt,10), geog_pt) As buff_10m_covers_cent
    	FROM (SELECT ST_Buffer(ST_GeogFromText('SRID=4326;POINT(-99.327 31.4821)'), 300) As geog_poly,
    				ST_GeogFromText('SRID=4326;POINT(-99.33 31.483)') As geog_pt ) As foo;

     poly_covers_pt | buff_10m_covers_cent
    ----------------+------------------
     f              | t

## See Also

ST_Contains, ST_CoveredBy, ST_Within

## Name

ST_CoveredBy — Returns 1 (TRUE) if no point in Geometry/Geography A is outside Geometry/Geography B

## Synopsis

`boolean ST_CoveredBy(`geometry geomA, geometry geomB`)`;

`boolean ST_CoveredBy(`geography geogA, geography geogB`)`;

## Description

Returns 1 (TRUE) if no point in Geometry/Geography A is outside Geometry/Geography B

Performed by the GEOS module

Do not call with a `GEOMETRYCOLLECTION` as an argument

Do not use this function with invalid geometries. You will get unexpected results.

Availability: 1.2.2 - requires GEOS >= 3.0

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries. To avoid index use, use the function _ST_CoveredBy.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

Not an OGC standard, but Oracle has it too.

There are certain subtleties to ST_Contains and ST_Within that are not intuitively obvious. For details check out Subtleties of OGC Covers, Contains, Within

## Examples

    	--a circle coveredby a circle
    SELECT ST_CoveredBy(smallc,smallc) As smallinsmall,
    	ST_CoveredBy(smallc, bigc) As smallcoveredbybig,
    	ST_CoveredBy(ST_ExteriorRing(bigc), bigc) As exteriorcoveredbybig,
    	ST_Within(ST_ExteriorRing(bigc),bigc) As exeriorwithinbig
    FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
    	ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
    	--Result
     smallinsmall | smallcoveredbybig | exteriorcoveredbybig | exeriorwithinbig
    --------------+-------------------+----------------------+------------------
     t            | t                 | t                    | f
    (1 row)

## See Also

ST_Contains, ST_Covers, ST_ExteriorRing, ST_Within

## Name

ST_Crosses — Returns `TRUE` if the supplied geometries have some, but not all, interior points in common.

## Synopsis

`boolean ST_Crosses(`geometry g1, geometry g2`)`;

## Description

`ST_Crosses` takes two geometry objects and returns `TRUE` if their intersection "spatially cross", that is, the geometries have some, but not all interior points in common. The intersection of the interiors of the geometries must not be the empty set and must have a dimensionality less than the the maximum dimension of the two input geometries. Additionally, the intersection of the two geometries must not equal either of the source geometries. Otherwise, it returns `FALSE`.

In mathematical terms, this is expressed as:

TODO: Insert appropriate MathML markup here or use a gif. Simple HTML markup does not work well in both IE and Firefox.

The DE-9IM Intersection Matrix for the two geometries is:

- T*T****** (for Point/Line, Point/Area, and Line/Area situations)

- T*****T** (for Line/Point, Area/Point, and Area/Line situations)

- 0******** (for Line/Line situations)

For any other combination of dimensions this predicate returns false.

The OpenGIS Simple Features Specification defines this predicate only for Point/Line, Point/Area, Line/Line, and Line/Area situations. JTS / GEOS extends the definition to apply to Line/Point, Area/Point and Area/Line situations as well. This makes the relation symmetric.

Do not call with a `GEOMETRYCOLLECTION` as an argument

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.29

## Examples

The following illustrations all return `TRUE`.

`MULTIPOINT` / `LINESTRING` | `MULTIPOINT` / `POLYGON`
`LINESTRING` / `POLYGON` | `LINESTRING` / `LINESTRING`

Consider a situation where a user has two tables: a table of roads and a table of highways.

    CREATE TABLE roads (
      id serial NOT NULL,
      the_geom geometry,
      CONSTRAINT roads_pkey PRIMARY KEY (road_id)
    );
    CREATE TABLE highways (
      id serial NOT NULL,
      the_gem geometry,
      CONSTRAINT roads_pkey PRIMARY KEY (road_id)
    );

To determine a list of roads that cross a highway, use a query similiar to:

    SELECT roads.id
    FROM roads, highways
    WHERE ST_Crosses(roads.the_geom, highways.the_geom);

## Name

ST_LineCrossingDirection — Given 2 linestrings, returns a number between -3 and 3 denoting what kind of crossing behavior. 0 is no crossing.

## Synopsis

`integer ST_LineCrossingDirection(`geometry linestringA, geometry linestringB`)`;

## Description

Given 2 linestrings, returns a number between -3 and 3 denoting what kind of crossing behavior. 0 is no crossing. This is only supported for `LINESTRING`

Definition of integer constants is as follows:

- 0: LINE NO CROSS

- -1: LINE CROSS LEFT

- 1: LINE CROSS RIGHT

- -2: LINE MULTICROSS END LEFT

- 2: LINE MULTICROSS END RIGHT

- -3: LINE MULTICROSS END SAME FIRST LEFT

- 3: LINE MULTICROSS END SAME FIRST RIGHT

Availability: 1.4

## Examples

Line 1 (green), Line 2 ball is start point, triangle are end points. Query below.
    SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
    	  ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
    FROM (
    SELECT
     ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
     ST_GeomFromText('LINESTRING(171 154,20 140,71 74,161 53)') As line2
    	) As foo;

     l1_cross_l2 | l2_cross_l1
    -------------+-------------
               3 |          -3
| Line 1 (green), Line 2 (blue) ball is start point, triangle are end points. Query below.
    SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
    	  ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
    FROM (
     SELECT
      ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
      ST_GeomFromText('LINESTRING (171 154, 20 140, 71 74, 2.99 90.16)') As line2
    ) As foo;

     l1_cross_l2 | l2_cross_l1
    -------------+-------------
               2 |          -2
Line 1 (green), Line 2 (blue) ball is start point, triangle are end points. Query below.
    SELECT
    	ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
    	ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
    FROM (
     SELECT
      ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
      ST_GeomFromText('LINESTRING (20 140, 71 74, 161 53)') As line2
      ) As foo;

     l1_cross_l2 | l2_cross_l1
    -------------+-------------
              -1 |          1
| Line 1 (green), Line 2 (blue) ball is start point, triangle are end points. Query below.
    SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
    	  ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
    FROM (SELECT
    	ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
    	ST_GeomFromText('LINESTRING(2.99 90.16,71 74,20 140,171 154)') As line2
    	) As foo;

     l1_cross_l2 | l2_cross_l1
    -------------+-------------
              -2 |          2

    SELECT s1.gid, s2.gid, ST_LineCrossingDirection(s1.the_geom, s2.the_geom)
    	FROM streets s1 CROSS JOIN streets s2 ON (s1.gid != s2.gid AND s1.the_geom && s2.the_geom )
    WHERE ST_CrossingDirection(s1.the_geom, s2.the_geom) > 0;

## See Also

ST_Crosses

## Name

ST_Disjoint — Returns TRUE if the Geometries do not "spatially intersect" - if they do not share any space together.

## Synopsis

`boolean ST_Disjoint(` geometry A , geometry B `)`;

## Description

Overlaps, Touches, Within all imply geometries are not spatially disjoint. If any of the aforementioned returns true, then the geometries are not spatially disjoint. Disjoint implies false for spatial intersection.

Do not call with a `GEOMETRYCOLLECTION` as an argument

Performed by the GEOS module

This function call does not use indexes

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 //s2.1.13.3 - a.Relate(b, 'FF*FF****')

This method implements the SQL/MM specification. SQL-MM 3: 5.1.26

## Examples

    SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
     st_disjoint
    ---------------
     t
    (1 row)
    SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
     st_disjoint
    ---------------
     f
    (1 row)

## See Also

ST_IntersectsST_Intersects

## Name

ST_Distance — For geometry type Returns the 2-dimensional cartesian minimum distance (based on spatial ref) between two geometries in projected units. For geography type defaults to return spheroidal minimum distance between two geographies in meters.

## Synopsis

`float ST_Distance(`geometry g1, geometry g2`)`;

`float ST_Distance(`geography gg1, geography gg2`)`;

`float ST_Distance(`geography gg1, geography gg2, boolean use_spheroid`)`;

## Description

For geometry type returns the 2-dimensional minimum cartesian distance between two geometries in projected units (spatial ref units). For geography type defaults to return the minimum distance around WGS 84 spheroid between two geographies in meters. Pass in false to return answer in sphere instead of spheroid.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.23

Availability: 1.5.0 geography support was introduced in 1.5. Speed improvements for planar to better handle large or many vertex geometries

## Examples

    --Geometry example - units in planar degrees 4326 is WGS 84 long lat unit=degrees
    SELECT ST_Distance(
    		ST_GeomFromText('POINT(-72.1235 42.3521)',4326),
    		ST_GeomFromText('LINESTRING(-72.1260 42.45, -72.123 42.1546)', 4326)
    	);
    st_distance
    -----------------
    0.00150567726382282

    -- Geometry example - units in meters (SRID: 26986 Massachusetts state plane meters) (most accurate for Massachusetts)
    SELECT ST_Distance(
    			ST_Transform(ST_GeomFromText('POINT(-72.1235 42.3521)',4326),26986),
    			ST_Transform(ST_GeomFromText('LINESTRING(-72.1260 42.45, -72.123 42.1546)', 4326),26986)
    		);
    st_distance
    -----------------
    123.797937878454

    -- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (least accurate)
    SELECT ST_Distance(
    			ST_Transform(ST_GeomFromText('POINT(-72.1235 42.3521)',4326),2163),
    			ST_Transform(ST_GeomFromText('LINESTRING(-72.1260 42.45, -72.123 42.1546)', 4326),2163)
    		);

    st_distance
    ------------------
    126.664256056812

    -- Geography example -- same but note units in meters - use sphere for slightly faster less accurate
    SELECT ST_Distance(gg1, gg2) As spheroid_dist, ST_Distance(gg1, gg2, false) As sphere_dist
    FROM (SELECT
    	ST_GeographyFromText('SRID=4326;POINT(-72.1235 42.3521)') As gg1,
    	ST_GeographyFromText('SRID=4326;LINESTRING(-72.1260 42.45, -72.123 42.1546)') As gg2
    	) As foo  ;

      spheroid_dist   |   sphere_dist
    ------------------+------------------
     123.802076746848 | 123.475736916397

## See Also

ST_3DDistance, ST_DWithin, ST_Distance_Sphere, ST_Distance_Spheroid, ST_MaxDistance, ST_Transform

## Name

ST_HausdorffDistance — Returns the Hausdorff distance between two geometries. Basically a measure of how similar or dissimilar 2 geometries are. Units are in the units of the spatial reference system of the geometries.

## Synopsis

`float ST_HausdorffDistance(`geometry g1, geometry g2`)`;

`float ST_HausdorffDistance(`geometry g1, geometry g2, float densifyFrac`)`;

## Description

Implements algorithm for computing a distance metric which can be thought of as the "Discrete Hausdorff Distance". This is the Hausdorff distance restricted to discrete points for one of the geometries. Wikipedia article on Hausdorff distance Martin Davis note on how Hausdorff Distance calculation was used to prove correctness of the CascadePolygonUnion approach.

When densifyFrac is specified, this function performs a segment densification before computing the discrete hausdorff distance. The densifyFrac parameter sets the fraction by which to densify each segment. Each segment will be split into a number of equal-length subsegments, whose fraction of the total length is closest to the given fraction.

The current implementation supports only vertices as the discrete locations. This could be extended to allow an arbitrary density of points to be used.

This algorithm is NOT equivalent to the standard Hausdorff distance. However, it computes an approximation that is correct for a large subset of useful cases. One important part of this subset is Linestrings that are roughly parallel to each other, and roughly equal in length. This is a useful metric for line matching.

Availability: 1.5.0 - requires GEOS >= 3.2.0

## Examples

    postgis=# SELECT st_HausdorffDistance(
    				'LINESTRING (0 0, 2 0)'::geometry,
    				'MULTIPOINT (0 1, 1 0, 2 1)'::geometry);
     st_hausdorffdistance
     ----------------------
    					 1
    (1 row)

    postgis=# SELECT st_hausdorffdistance('LINESTRING (130 0, 0 0, 0 150)'::geometry, 'LINESTRING (10 10, 10 150, 130 10)'::geometry, 0.5);
     st_hausdorffdistance
     ----------------------
    					70
    (1 row)

## Name

ST_MaxDistance — Returns the 2-dimensional largest distance between two geometries in projected units.

## Synopsis

`float ST_MaxDistance(`geometry g1, geometry g2`)`;

## Description

Some useful description here.

Returns the 2-dimensional maximum distance between two linestrings in projected units. If g1 and g2 is the same geometry the function will return the distance between the two vertices most far from each other in that geometry.

Availability: 1.5.0

## Examples

    postgis=# SELECT ST_MaxDistance('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
       st_maxdistance
    -----------------
     2
    (1 row)

    postgis=# SELECT ST_MaxDistance('POINT(0 0)'::geometry, 'LINESTRING ( 2 2, 2 2 )'::geometry);
      st_maxdistance
    ------------------
     2.82842712474619
    (1 row)

## See Also

ST_Distance, ST_LongestLine

## Name

ST_Distance_Sphere — Returns minimum distance in meters between two lon/lat geometries. Uses a spherical earth and radius of 6370986 meters. Faster than ST_Distance_Spheroid ST_Distance_Spheroid, but less accurate. PostGIS versions prior to 1.5 only implemented for points.

## Synopsis

`float ST_Distance_Sphere(`geometry geomlonlatA, geometry geomlonlatB`)`;

## Description

Returns minimum distance in meters between two lon/lat points. Uses a spherical earth and radius of 6370986 meters. Faster than ST_Distance_Spheroid, but less accurate. PostGIS Versions prior to 1.5 only implemented for points.

This function currently does not look at the SRID of a geometry and will always assume its in WGS 84 long lat. Prior versions of this function only support points.

Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points.

## Examples

    SELECT round(CAST(ST_Distance_Sphere(ST_Centroid(the_geom), ST_GeomFromText('POINT(-118 38)',4326)) As numeric),2) As dist_meters,
    round(CAST(ST_Distance(ST_Transform(ST_Centroid(the_geom),32611),
    		ST_Transform(ST_GeomFromText('POINT(-118 38)', 4326),32611)) As numeric),2) As dist_utm11_meters,
    round(CAST(ST_Distance(ST_Centroid(the_geom), ST_GeomFromText('POINT(-118 38)', 4326)) As numeric),5) As dist_degrees,
    round(CAST(ST_Distance(ST_Transform(the_geom,32611),
    		ST_Transform(ST_GeomFromText('POINT(-118 38)', 4326),32611)) As numeric),2) As min_dist_line_point_meters
    FROM
    	(SELECT ST_GeomFromText('LINESTRING(-118.584 38.374,-118.583 38.5)', 4326) As the_geom) as foo;
    	 dist_meters | dist_utm11_meters | dist_degrees | min_dist_line_point_meters
    	-------------+-------------------+--------------+----------------------------
    		70424.47 |          70438.00 |      0.72900 |                   65871.18

## See Also

ST_Distance, ST_Distance_Spheroid

## Name

ST_Distance_Spheroid — Returns the minimum distance between two lon/lat geometries given a particular spheroid. PostGIS versions prior to 1.5 only support points.

## Synopsis

`float ST_Distance_Spheroid(`geometry geomlonlatA, geometry geomlonlatB, spheroid measurement_spheroid`)`;

## Description

Returns minimum distance in meters between two lon/lat geometries given a particular spheroid. See the explanation of spheroids given for ST_Length_Spheroid. PostGIS version prior to 1.5 only support points.

This function currently does not look at the SRID of a geometry and will always assume its represented in the coordinates of the passed in spheroid. Prior versions of this function only support points.

Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points.

## Examples

    SELECT round(CAST(
    		ST_Distance_Spheroid(ST_Centroid(the_geom), ST_GeomFromText('POINT(-118 38)',4326), 'SPHEROID["WGS 84",6378137,298.257223563]')
    			As numeric),2) As dist_meters_spheroid,
    		round(CAST(ST_Distance_Sphere(ST_Centroid(the_geom), ST_GeomFromText('POINT(-118 38)',4326)) As numeric),2) As dist_meters_sphere,
    round(CAST(ST_Distance(ST_Transform(ST_Centroid(the_geom),32611),
    		ST_Transform(ST_GeomFromText('POINT(-118 38)', 4326),32611)) As numeric),2) As dist_utm11_meters
    FROM
    	(SELECT ST_GeomFromText('LINESTRING(-118.584 38.374,-118.583 38.5)', 4326) As the_geom) as foo;
     dist_meters_spheroid | dist_meters_sphere | dist_utm11_meters
    ----------------------+--------------------+-------------------
    			 70454.92 |           70424.47 |          70438.00

## See Also

ST_Distance, ST_Distance_Sphere

## Name

ST_DFullyWithin — Returns true if all of the geometries are within the specified distance of one another

## Synopsis

`boolean ST_DFullyWithin(`geometry g1, geometry g2, double precision distance`)`;

## Description

Returns true if the geometries is fully within the specified distance of one another. The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

Availability: 1.5.0

## Examples

    postgis=# SELECT ST_DFullyWithin(geom_a, geom_b, 10) as DFullyWithin10, ST_DWithin(geom_a, geom_b, 10) as DWithin10, ST_DFullyWithin(geom_a, geom_b, 20) as DFullyWithin20 from
    		(select ST_GeomFromText('POINT(1 1)') as geom_a,ST_GeomFromText('LINESTRING(1 5, 2 7, 1 9, 14 12)') as geom_b) t1;

    -----------------
     DFullyWithin10 | DWithin10 | DFullyWithin20 |
    ---------------+----------+---------------+
     f             | t        | t             |

## See Also

ST_MaxDistance, ST_DWithin

## Name

ST_DWithin — Returns true if the geometries are within the specified distance of one another. For geometry units are in those of spatial reference and For geography units are in meters and measurement is defaulted to use_spheroid=true (measure around spheroid), for faster check, use_spheroid=false to measure along sphere.

## Synopsis

`boolean ST_DWithin(`geometry g1, geometry g2, double precision distance_of_srid`)`;

`boolean ST_DWithin(`geography gg1, geography gg2, double precision distance_meters`)`;

`boolean ST_DWithin(`geography gg1, geography gg2, double precision distance_meters, boolean use_spheroid`)`;

## Description

Returns true if the geometries are within the specified distance of one another.

For Geometries: The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID.

For geography units are in meters and measurement is defaulted to use_spheroid=true (measure around WGS 84 spheroid), for faster check, use_spheroid=false to measure along sphere.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

Prior to 1.3, ST_Expand was commonly used in conjunction with && and ST_Distance to achieve the same effect and in pre-1.3.4 this function was basically short-hand for that construct. From 1.3.4, ST_DWithin uses a more short-circuit distance function which should make it more efficient than prior versions for larger buffer regions.

Use ST_3DDWithin if you have 3D geometries.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

Availability: 1.5.0 support for geography was introduced

## Examples

    --Find the nearest hospital to each school
    --that is within 3000 units of the school.
    -- We do an ST_DWithin search to utilize indexes to limit our search list
    -- that the non-indexable ST_Distance needs to process
    --If the units of the spatial reference is meters then units would be meters
    SELECT DISTINCT ON (s.gid) s.gid, s.school_name, s.the_geom, h.hospital_name
    	FROM schools s
    		LEFT JOIN hospitals h ON ST_DWithin(s.the_geom, h.the_geom, 3000)
    	ORDER BY s.gid, ST_Distance(s.the_geom, h.the_geom);

    --The schools with no close hospitals
    --Find all schools with no hospital within 3000 units
    --away from the school.  Units is in units of spatial ref (e.g. meters, feet, degrees)
    SELECT s.gid, s.school_name
    	FROM schools s
    		LEFT JOIN hospitals h ON ST_DWithin(s.the_geom, h.the_geom, 3000)
    	WHERE h.gid IS NULL;

## See Also

ST_Distance, ST_Expand

## Name

ST_Equals — Returns true if the given geometries represent the same geometry. Directionality is ignored.

## Synopsis

`boolean ST_Equals(`geometry A, geometry B`)`;

## Description

Returns TRUE if the given Geometries are "spatially equal". Use this for a 'better' answer than '='. Note by spatially equal we mean ST_Within(A,B) = true and ST_Within(B,A) = true and also mean ordering of points can be different but represent the same geometry structure. To verify the order of points is consistent, use ST_OrderingEquals (it must be noted ST_OrderingEquals is a little more stringent than simply verifying order of points are the same).

This function will return false if either geometry is invalid even if they are binary equal.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2

This method implements the SQL/MM specification. SQL-MM 3: 5.1.24

## Examples

    SELECT ST_Equals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
    		ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
     st_equals
    -----------
     t
    (1 row)

    SELECT ST_Equals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
    		ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
     st_equals
    -----------
     t
    (1 row)

## See Also

ST_IsValid, ST_OrderingEquals, ST_Reverse, ST_Within

## Name

ST_HasArc — Returns true if a geometry or geometry collection contains a circular string

## Synopsis

`boolean ST_HasArc(`geometry geomA`)`;

## Description

Returns true if a geometry or geometry collection contains a circular string

Availability: 1.2.3?

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_HasArc(ST_Collect('LINESTRING(1 2, 3 4, 5 6)', 'CIRCULARSTRING(1 1, 2 3, 4 5, 6 7, 5 6)'));
    		st_hasarc
    		--------
    		t

## See Also

ST_CurveToLine, ST_LineToCurve

## Name

ST_Intersects — Returns TRUE if the Geometries/Geography "spatially intersect in 2D" - (share any portion of space) and FALSE if they don't (they are Disjoint). For geography -- tolerance is 0.00001 meters (so any points that close are considered to intersect)

## Synopsis

`boolean ST_Intersects(` geometry geomA , geometry geomB `)`;

`boolean ST_Intersects(` geography geogA , geography geogB `)`;

## Description

Overlaps, Touches, Within all imply spatial intersection. If any of the aforementioned returns true, then the geometries also spatially intersect. Disjoint implies false for spatial intersection.

Do not call with a `GEOMETRYCOLLECTION` as an argument for geometry version. The geography version supports GEOMETRYCOLLECTION since its a thin wrapper around distance implementation.

Performed by the GEOS module (for geometry), geography is native

Availability: 1.5 support for geography was introduced.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

For geography, this function has a distance tolerance of about 0.00001 meters and uses the sphere rather than spheroid calculation.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 //s2.1.13.3 - ST_Intersects(g1, g2 ) --> Not (ST_Disjoint(g1, g2 ))

This method implements the SQL/MM specification. SQL-MM 3: 5.1.27

## Geometry Examples

    SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
     st_intersects
    ---------------
     f
    (1 row)
    SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
     st_intersects
    ---------------
     t
    (1 row)

## Geography Examples

    SELECT ST_Intersects(
    		ST_GeographyFromText('SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456 72.4568)'),
    		ST_GeographyFromText('SRID=4326;POINT(-43.23456 72.4567772)')
    		);

     st_intersects
    ---------------
    t

## See Also

ST_3DIntersects, ST_Disjoint

## Name

ST_Length — Returns the 2d length of the geometry if it is a linestring or multilinestring. geometry are in units of spatial reference and geography are in meters (default spheroid)

## Synopsis

`float ST_Length(`geometry a_2dlinestring`)`;

`float ST_Length(`geography geog, boolean use_spheroid=true`)`;

## Description

For geometry: Returns the cartesian 2D length of the geometry if it is a linestring, multilinestring, ST_Curve, ST_MultiCurve. 0 is returned for areal geometries. For areal geometries use ST_Perimeter. Geometry: Measurements are in the units of the spatial reference system of the geometry. Geography: Units are in meters and also acts as a Perimeter function for areal geogs.

Currently for geometry this is an alias for ST_Length2D, but this may change to support higher dimensions.

Changed: 2.0.0 Breaking change -- in prior versions applying this to a MULTI/POLYGON of type geography would give you the perimeter of the POLYGON/MULTIPOLYGON. In 2.0.0 this was changed to return 0 to be in line with geometry behavior. Please use ST_Perimeter if you want the perimeter of a polygon

For geography measurement defaults spheroid measurement. To use the faster less accurate sphere use ST_Length(gg,false);

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 7.1.2, 9.3.4

Availability: 1.5.0 geography support was introduced in 1.5.

## Geometry Examples

Return length in feet for line string. Note this is in feet because 2249 is Mass State Plane Feet

    SELECT ST_Length(ST_GeomFromText('LINESTRING(743238 2967416,743238 2967450,743265 2967450,
    743265.625 2967416,743238 2967416)',2249));
    st_length
    ---------
     122.630744000095

    --Transforming WGS 84 linestring to Massachusetts state plane meters
    SELECT ST_Length(
    	ST_Transform(
    		ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45, -72.1240 42.45666, -72.123 42.1546)'),
    		26986
    	)
    );
    st_length
    ---------
    34309.4563576191

## Geography Examples

Return length of WGS 84 geography line

    			-- default calculation is using a sphere rather than spheroid
    SELECT ST_Length(the_geog) As length_spheroid,  ST_Length(the_geog,false) As length_sphere
    FROM (SELECT ST_GeographyFromText(
    'SRID=4326;LINESTRING(-72.1260 42.45, -72.1240 42.45666, -72.123 42.1546)') As the_geog)
     As foo;
     length_spheroid  |  length_sphere
    ------------------+------------------
     34310.5703627305 | 34346.2060960742
    (1 row)

## See Also

ST_GeographyFromText, ST_GeomFromEWKT, ST_Length_Spheroid, ST_Perimeter, ST_Transform

## Name

ST_Length2D — Returns the 2-dimensional length of the geometry if it is a linestring or multi-linestring. This is an alias for `ST_Length`

## Synopsis

`float ST_Length2D(`geometry a_2dlinestring`)`;

## Description

Returns the 2-dimensional length of the geometry if it is a linestring or multi-linestring. This is an alias for `ST_Length`

## See Also

ST_Length, ST_3DLength

## Name

ST_3DLength — Returns the 3-dimensional or 2-dimensional length of the geometry if it is a linestring or multi-linestring.

## Synopsis

`float ST_3DLength(`geometry a_3dlinestring`)`;

## Description

Returns the 3-dimensional or 2-dimensional length of the geometry if it is a linestring or multi-linestring. For 2-d lines it will just return the 2-d length (same as ST_Length and ST_Length2D)

This function supports 3d and will not drop the z-index.

Changed: 2.0.0 In prior versions this used to be called ST_Length3D

## Examples

Return length in feet for a 3D cable. Note this is in feet because 2249 is Mass State Plane Feet

    SELECT ST_3DLength(ST_GeomFromText('LINESTRING(743238 2967416 1,743238 2967450 1,743265 2967450 3,
    743265.625 2967416 3,743238 2967416 3)',2249));
    ST_3DLength
    -----------
    122.704716741457

## See Also

ST_Length, ST_Length2D

## Name

ST_Length_Spheroid — Calculates the 2D or 3D length of a linestring/multilinestring on an ellipsoid. This is useful if the coordinates of the geometry are in longitude/latitude and a length is desired without reprojection.

## Synopsis

`float ST_Length_Spheroid(`geometry a_linestring, spheroid a_spheroid`)`;

## Description

Calculates the length of a geometry on an ellipsoid. This is useful if the coordinates of the geometry are in longitude/latitude and a length is desired without reprojection. The ellipsoid is a separate database type and can be constructed as follows:

SPHEROID[<NAME>,<SEMI-MAJOR
AXIS>,<INVERSE FLATTENING>]

SPHEROID["GRS_1980",6378137,298.257222101]

Will return 0 for anything that is not a MULTILINESTRING or LINESTRING

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_Length_Spheroid( geometry_column,
    			  'SPHEROID["GRS_1980",6378137,298.257222101]' )
    			  FROM geometry_table;

    SELECT ST_Length_Spheroid( the_geom, sph_m ) As tot_len,
    ST_Length_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,
    ST_Length_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2
    			  FROM (SELECT ST_GeomFromText('MULTILINESTRING((-118.584 38.374,-118.583 38.5),
    	(-71.05957 42.3589 , -71.061 43))') As the_geom,
    CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m)  as foo;
    	tot_len      |    len_line1     |    len_line2
    ------------------+------------------+------------------
     85204.5207562955 | 13986.8725229309 | 71217.6482333646

     --3D
    SELECT ST_Length_Spheroid( the_geom, sph_m ) As tot_len,
    ST_Length_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,
    ST_Length_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2
    			  FROM (SELECT ST_GeomFromEWKT('MULTILINESTRING((-118.584 38.374 20,-118.583 38.5 30),
    	(-71.05957 42.3589 75, -71.061 43 90))') As the_geom,
    CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m)  as foo;

    	 tot_len      |    len_line1    |    len_line2
    ------------------+-----------------+------------------
     85204.5259107402 | 13986.876097711 | 71217.6498130292

## See Also

ST_GeometryN, ST_Length, ST_3DLength_Spheroid

## Name

ST_Length2D_Spheroid — Calculates the 2D length of a linestring/multilinestring on an ellipsoid. This is useful if the coordinates of the geometry are in longitude/latitude and a length is desired without reprojection.

## Synopsis

`float ST_Length2D_Spheroid(`geometry a_linestring, spheroid a_spheroid`)`;

## Description

Calculates the 2D length of a geometry on an ellipsoid. This is useful if the coordinates of the geometry are in longitude/latitude and a length is desired without reprojection. The ellipsoid is a separate database type and can be constructed as follows:

SPHEROID[<NAME>,<SEMI-MAJOR
AXIS>,<INVERSE FLATTENING>]

SPHEROID["GRS_1980",6378137,298.257222101]

Will return 0 for anything that is not a MULTILINESTRING or LINESTRING

This is much like ST_Length_Spheroid and ST_3DLength_Spheroid except it will throw away the Z coordinate in calculations.

## Examples

    SELECT ST_Length2D_Spheroid( geometry_column,
    			  'SPHEROID["GRS_1980",6378137,298.257222101]' )
    			  FROM geometry_table;

    SELECT ST_Length2D_Spheroid( the_geom, sph_m ) As tot_len,
    ST_Length2D_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,
    ST_Length2D_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2
    			  FROM (SELECT ST_GeomFromText('MULTILINESTRING((-118.584 38.374,-118.583 38.5),
    	(-71.05957 42.3589 , -71.061 43))') As the_geom,
    CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m)  as foo;
    	tot_len      |    len_line1     |    len_line2
    ------------------+------------------+------------------
     85204.5207562955 | 13986.8725229309 | 71217.6482333646

     --3D Observe same answer
    SELECT ST_Length2D_Spheroid( the_geom, sph_m ) As tot_len,
    ST_Length2D_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,
    ST_Length2D_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2
    			  FROM (SELECT ST_GeomFromEWKT('MULTILINESTRING((-118.584 38.374 20,-118.583 38.5 30),
    	(-71.05957 42.3589 75, -71.061 43 90))') As the_geom,
    CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m)  as foo;

    	tot_len      |    len_line1     |    len_line2
    ------------------+------------------+------------------
     85204.5207562955 | 13986.8725229309 | 71217.6482333646

## See Also

ST_GeometryN, ST_Length_Spheroid, ST_3DLength_Spheroid

## Name

ST_3DLength_Spheroid — Calculates the length of a geometry on an ellipsoid, taking the elevation into account. This is just an alias for ST_Length_Spheroid.

## Synopsis

`float ST_3DLength_Spheroid(`geometry a_linestring, spheroid a_spheroid`)`;

## Description

Calculates the length of a geometry on an ellipsoid, taking the elevation into account. This is just an alias for ST_Length_Spheroid.

Changed: 2.0.0 In prior versions this used to return 0 for anything that is not a MULTILINESTRING or LINESTRING and in 2.0.0 on returns the perimeter of if given a polgon.

This function is just an alias for ST_Length_Spheroid.

This function supports 3d and will not drop the z-index.

Changed: 2.0.0 In prior versions this used to be called ST_Length3d_Spheroid

## Examples

    See ST_Length_Spheroid

## See Also

ST_GeometryN, ST_Length, ST_Length_Spheroid

## Name

ST_LongestLine — Returns the 2-dimensional longest line points of two geometries. The function will only return the first longest line if more than one, that the function finds. The line returned will always start in g1 and end in g2. The length of the line this function returns will always be the same as st_maxdistance returns for g1 and g2.

## Synopsis

`geometry ST_LongestLine(`geometry g1, geometry g2`)`;

## Description

Returns the 2-dimensional longest line between the points of two geometries.

Availability: 1.5.0

## Examples

Longest line between point and line
    SELECT ST_AsText(
    	ST_LongestLine('POINT(100 100)'::geometry,
    		'LINESTRING (20 80, 98 190, 110 180, 50 75 )'::geometry)
    	) As lline;

       lline
    -----------------
    LINESTRING(100 100,98 190)
| longest line between polygon and polygon
    SELECT ST_AsText(
    	ST_LongestLine(
    		ST_GeomFromText('POLYGON((175 150, 20 40,
    			50 60, 125 100, 175 150))'),
    		ST_Buffer(ST_GeomFromText('POINT(110 170)'), 20)
    		)
    	) As llinewkt;

       lline
    -----------------
    LINESTRING(20 40,121.111404660392 186.629392246051)

longest straight distance to travel from one part of an elegant city to the other Note the max distance = to the length of the line.
    SELECT ST_AsText(ST_LongestLine(c.the_geom, c.the_geom)) As llinewkt,
    	ST_MaxDistance(c.the_geom,c.the_geom) As max_dist,
    	ST_Length(ST_LongestLine(c.the_geom, c.the_geom)) As lenll
    FROM (SELECT ST_BuildArea(ST_Collect(the_geom)) As the_geom
    	FROM (SELECT ST_Translate(ST_SnapToGrid(ST_Buffer(ST_Point(50 ,generate_series(50,190, 50)
    			),40, 'quad_segs=2'),1), x, 0)  As the_geom
    			FROM generate_series(1,100,50) As x)  AS foo
    ) As c;

              llinewkt          |     max_dist     |      lenll
    ---------------------------+------------------+------------------
     LINESTRING(23 22,129 178) | 188.605408193933 | 188.605408193933

## See Also

ST_MaxDistance, ST_ShortestLine, ST_LongestLine

## Name

ST_OrderingEquals — Returns true if the given geometries represent the same geometry and points are in the same directional order.

## Synopsis

`boolean ST_OrderingEquals(`geometry A, geometry B`)`;

## Description

ST_OrderingEquals compares two geometries and returns t (TRUE) if the geometries are equal and the coordinates are in the same order; otherwise it returns f (FALSE).

This function is implemented as per the ArcSDE SQL specification rather than SQL-MM. http://edndoc.esri.com/arcsde/9.1/sql_api/sqlapi3.htm#ST_OrderingEquals

This method implements the SQL/MM specification. SQL-MM 3: 5.1.43

## Examples

    SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
    		ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
     st_orderingequals
    -----------
     f
    (1 row)

    SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
    		ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
     st_orderingequals
    -----------
     t
    (1 row)

    SELECT ST_OrderingEquals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
    		ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
     st_orderingequals
    -----------
     f
    (1 row)

## See Also

ST_Equals, ST_Reverse

## Name

ST_Overlaps — Returns TRUE if the Geometries share space, are of the same dimension, but are not completely contained by each other.

## Synopsis

`boolean ST_Overlaps(`geometry A, geometry B`)`;

## Description

Returns TRUE if the Geometries "spatially overlap". By that we mean they intersect, but one does not completely contain another.

Performed by the GEOS module

Do not call with a GeometryCollection as an argument

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries. To avoid index use, use the function _ST_Overlaps.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.32

## Examples

The following illustrations all return `TRUE`.

`MULTIPOINT` / `MULTIPOINT` | `LINESTRING` / `LINESTRING` | `POLYGON` / `POLYGON`

    --a point on a line is contained by the line and is of a lower dimension, and therefore does not overlap the line
    			nor crosses

    SELECT ST_Overlaps(a,b) As a_overlap_b,
    	ST_Crosses(a,b) As a_crosses_b,
    		ST_Intersects(a, b) As a_intersects_b, ST_Contains(b,a) As b_contains_a
    FROM (SELECT ST_GeomFromText('POINT(1 0.5)') As a, ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)')  As b)
    	As foo

    a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a
    ------------+-------------+----------------+--------------
    f           | f           | t              | t

    --a line that is partly contained by circle, but not fully is defined as intersecting and crossing,
    -- but since of different dimension it does not overlap
    SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b,
    	ST_Intersects(a, b) As a_intersects_b,
    	ST_Contains(a,b) As a_contains_b
    FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 0.5)'), 3)  As a, ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)')  As b)
    	As foo;

     a_overlap_b | a_crosses_b | a_intersects_b | a_contains_b
    -------------+-------------+----------------+--------------
     f           | t           | t              | f

     -- a 2-dimensional bent hot dog (aka buffered line string) that intersects a circle,
     --	but is not fully contained by the circle is defined as overlapping since they are of the same dimension,
    --	but it does not cross, because the intersection of the 2 is of the same dimension
    --	as the maximum dimension of the 2

    SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b, ST_Intersects(a, b) As a_intersects_b,
    ST_Contains(b,a) As b_contains_a,
    ST_Dimension(a) As dim_a, ST_Dimension(b) as dim_b, ST_Dimension(ST_Intersection(a,b)) As dima_intersection_b
    FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 0.5)'), 3)  As a,
    	ST_Buffer(ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)'),0.5)  As b)
    	As foo;

     a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a | dim_a | dim_b | dima_intersection_b
    -------------+-------------+----------------+--------------+-------+-------+---------------------
     t           | f           | t              | f            |     2 |     2 |              2

## See Also

ST_Contains, ST_Crosses, ST_Dimension, ST_Intersects

## Name

ST_Perimeter — Return the length measurement of the boundary of an ST_Surface or ST_MultiSurface geometry or geography. (Polygon, Multipolygon). geometry measurement is in units of spatial reference and geography is in meters.

## Synopsis

`float ST_Perimeter(`geometry g1`)`;

`float ST_Perimeter(`geography geog, boolean use_spheroid=true`)`;

## Description

Returns the 2D perimeter of the geometry/geography if it is a ST_Surface, ST_MultiSurface (Polygon, Multipolygon). 0 is returned for non-areal geometries. For linestrings use ST_Length. Measurements for geometry are in the units of the spatial reference system of the geometry. Measurements for geography are in meters. If `use_spheroid` is set to false, then will model earth as a sphere instead of a spheroid.

Currently this is an alias for ST_Perimeter2D, but this may change to support higher dimensions.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 8.1.3, 9.5.4

Availability 2.0.0: Support for geography was introduced

## Examples: Geometry

Return perimeter in feet for polygon and multipolygon. Note this is in feet because 2249 is Mass State Plane Feet

    SELECT ST_Perimeter(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,743265 2967450,
    743265.625 2967416,743238 2967416))', 2249));
    st_perimeter
    ---------
     122.630744000095
    (1 row)

    SELECT ST_Perimeter(ST_GeomFromText('MULTIPOLYGON(((763104.471273676 2949418.44119003,
    763104.477769673 2949418.42538203,
    763104.189609677 2949418.22343004,763104.471273676 2949418.44119003)),
    ((763104.471273676 2949418.44119003,763095.804579742 2949436.33850239,
    763086.132105649 2949451.46730207,763078.452329651 2949462.11549407,
    763075.354136904 2949466.17407812,763064.362142565 2949477.64291974,
    763059.953961626 2949481.28983009,762994.637609571 2949532.04103014,
    762990.568508415 2949535.06640477,762986.710889563 2949539.61421415,
    763117.237897679 2949709.50493431,763235.236617789 2949617.95619822,
    763287.718121842 2949562.20592617,763111.553321674 2949423.91664605,
    763104.471273676 2949418.44119003)))', 2249));
    st_perimeter
    ---------
     845.227713366825
    (1 row)

## Examples: Geography

Return perimeter in meters and feet for polygon and multipolygon. Note this is geography (WGS 84 long lat)

    SELECT  ST_Perimeter(geog) As per_meters, ST_Perimeter(geog)/0.3048 As per_ft
    FROM ST_GeogFromText('POLYGON((-71.1776848522251 42.3902896512902,-71.1776843766326 42.3903829478009,
    -71.1775844305465 42.3903826677917,-71.1775825927231 42.3902893647987,-71.1776848522251 42.3902896512902))') As geog;

       per_meters    |      per_ft
    -----------------+------------------
    37.3790462565251 | 122.634666195949

    -- Multipolygon example --
    SELECT  ST_Perimeter(geog) As per_meters, ST_Perimeter(geog,false) As per_sphere_meters,  ST_Perimeter(geog)/0.3048 As per_ft
    FROM ST_GeogFromText('MULTIPOLYGON(((-71.1044543107478 42.340674480411,-71.1044542869917 42.3406744369506,
    -71.1044553562977 42.340673886454,-71.1044543107478 42.340674480411)),
    ((-71.1044543107478 42.340674480411,-71.1044860600303 42.3407237015564,-71.1045215770124 42.3407653385914,
    -71.1045498002983 42.3407946553165,-71.1045611902745 42.3408058316308,-71.1046016507427 42.340837442371,
    -71.104617893173 42.3408475056957,-71.1048586153981 42.3409875993595,-71.1048736143677 42.3409959528211,
    -71.1048878050242 42.3410084812078,-71.1044020965803 42.3414730072048,
    -71.1039672113619 42.3412202916693,-71.1037740497748 42.3410666421308,
    -71.1044280218456 42.3406894151355,-71.1044543107478 42.340674480411)))') As geog;

        per_meters    | per_sphere_meters |      per_ft
    ------------------+-------------------+------------------
     257.634283683311 |  257.412311446337 | 845.256836231335

## See Also

ST_GeogFromText, ST_GeomFromText, ST_Length

## Name

ST_Perimeter2D — Returns the 2-dimensional perimeter of the geometry, if it is a polygon or multi-polygon. This is currently an alias for ST_Perimeter.

## Synopsis

`float ST_Perimeter2D(`geometry geomA`)`;

## Description

Returns the 2-dimensional perimeter of the geometry, if it is a polygon or multi-polygon.

This is currently an alias for ST_Perimeter. In future versions ST_Perimeter may return the highest dimension perimeter for a geometry. This is still under consideration

## See Also

ST_Perimeter

## Name

ST_3DPerimeter — Returns the 3-dimensional perimeter of the geometry, if it is a polygon or multi-polygon.

## Synopsis

`float ST_3DPerimeter(`geometry geomA`)`;

## Description

Returns the 3-dimensional perimeter of the geometry, if it is a polygon or multi-polygon. If the geometry is 2-dimensional, then the 2-dimensional perimeter is returned.

This function supports 3d and will not drop the z-index.

Changed: 2.0.0 In prior versions this used to be called ST_Perimeter3D

## Examples

Perimeter of a slightly elevated polygon in the air in Massachusetts state plane feet

    SELECT ST_3DPerimeter(the_geom), ST_Perimeter2d(the_geom), ST_Perimeter(the_geom) FROM
    			(SELECT ST_GeomFromEWKT('SRID=2249;POLYGON((743238 2967416 2,743238 2967450 1,
    743265.625 2967416 1,743238 2967416 2))') As the_geom) As foo;

      ST_3DPerimeter  |  st_perimeter2d  |   st_perimeter
    ------------------+------------------+------------------
     105.465793597674 | 105.432997272188 | 105.432997272188

## See Also

ST_GeomFromEWKT, ST_Perimeter, ST_Perimeter2D

## Name

ST_PointOnSurface — Returns a `POINT` guaranteed to lie on the surface.

## Synopsis

`geometry ST_PointOnSurface(`geometry g1`)`;

## Description

Returns a `POINT` guaranteed to intersect a surface.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.14.2 // s3.2.18.2

This method implements the SQL/MM specification. SQL-MM 3: 8.1.5, 9.5.6. According to the specs, ST_PointOnSurface works for surface geometries (POLYGONs, MULTIPOLYGONS, CURVED POLYGONS). So PostGIS seems to be extending what the spec allows here. Most databases Oracle,DB II, ESRI SDE seem to only support this function for surfaces. SQL Server 2008 like PostGIS supports for all common geometries.

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsText(ST_PointOnSurface('POINT(0 5)'::geometry));
     st_astext
    ------------
     POINT(0 5)
    (1 row)

    SELECT ST_AsText(ST_PointOnSurface('LINESTRING(0 5, 0 10)'::geometry));
     st_astext
    ------------
     POINT(0 5)
    (1 row)

    SELECT ST_AsText(ST_PointOnSurface('POLYGON((0 0, 0 5, 5 5, 5 0, 0 0))'::geometry));
       st_astext
    ----------------
     POINT(2.5 2.5)
    (1 row)

    SELECT ST_AsEWKT(ST_PointOnSurface(ST_GeomFromEWKT('LINESTRING(0 5 1, 0 0 1, 0 10 2)')));
       st_asewkt
    ----------------
     POINT(0 0 1)
    (1 row)

## See Also

ST_Centroid, ST_Point_Inside_Circle

## Name

ST_Project — Returns a `POINT` projected from a start point using a bearing and distance.

## Synopsis

`geography ST_Project(`geography g1, float distance, float azimuth`)`;

## Description

Returns a `POINT` projected from a start point using an azimuth (bearing) and distance.

Distance, azimuth and projection are all aspects of the same operation, describing (or in the case of projection, constructing) the relationship between two points on the world.

The azimuth is sometimes called the heading or the bearing in navigation. It is measured relative to true north (azimuth zero). East is azimuth 90, south is azimuth 180, west is azimuth 270.

The distance is given in meters.

## Examples

    SELECT ST_AsText(ST_Project('POINT(0 0)'::geography, 100000, 45));
                      st_astext
    	------------------------------------------
    	 POINT(0.63523102912532 0.63947233472882)
    	(1 row)

## See Also

ST_Azimuth, ST_Distance

## Name

ST_Relate — Returns true if this Geometry is spatially related to anotherGeometry, by testing for intersections between the Interior, Boundary and Exterior of the two geometries as specified by the values in the intersectionMatrixPattern. If no intersectionMatrixPattern is passed in, then returns the maximum intersectionMatrixPattern that relates the 2 geometries.

## Synopsis

`boolean ST_Relate(`geometry geomA, geometry geomB, text intersectionMatrixPattern`)`;

`text ST_Relate(`geometry geomA, geometry geomB`)`;

`text ST_Relate(`geometry geomA, geometry geomB, int BoundaryNodeRule`)`;

## Description

Version 1: Takes geomA, geomB, intersectionMatrix and Returns 1 (TRUE) if this Geometry is spatially related to anotherGeometry, by testing for intersections between the Interior, Boundary and Exterior of the two geometries as specified by the values in the DE-9IM matrix pattern.

This is especially useful for testing compound checks of intersection, crosses, etc in one step.

Do not call with a GeometryCollection as an argument

This is the "allowable" version that returns a boolean, not an integer. This is defined in OGC spec

This DOES NOT automagically include an index call. The reason for that is some relationships are anti e.g. Disjoint. If you are using a relationship pattern that requires intersection, then include the && index call.

Version 2: Takes geomA and geomB and returns the Section 4.3.6, “Dimensionally Extended 9 Intersection Model (DE-9IM)”

Version 3: same as version 2 bu allows to specify a boundary node rule (1:OGC/MOD2, 2:Endpoint, 3:MultivalentEndpoint, 4:MonovalentEndpoint)

Do not call with a GeometryCollection as an argument

not in OGC spec, but implied. see s2.1.13.2

Performed by the GEOS module

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.25

Enhanced: 2.0.0 - added support for specifying boundary node rule (requires GEOS >= 3.0).

## Examples

    --Find all compounds that intersect and not touch a poly (interior intersects)
    SELECT l.* , b.name As poly_name
    	FROM polys As b
    INNER JOIN compounds As l
    ON (p.the_geom && b.the_geom
    AND ST_Relate(l.the_geom, b.the_geom,'T********'));

    SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2));
    st_relate
    -----------
    0FFFFF212

    SELECT ST_Relate(ST_GeometryFromText('LINESTRING(1 2, 3 4)'), ST_GeometryFromText('LINESTRING(5 6, 7 8)'));
    st_relate
    -----------
    FF1FF0102

    SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2), '0FFFFF212');
    st_relate
    -----------
    t

    SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2), '*FF*FF212');
    st_relate
    -----------
    t

## See Also

ST_Crosses, Section 4.3.6, “Dimensionally Extended 9 Intersection Model (DE-9IM)”, ST_Disjoint, ST_Intersects, ST_Touches

## Name

ST_RelateMatch — Returns true if intersectionMattrixPattern1 implies intersectionMatrixPattern2

## Synopsis

`boolean ST_RelateMatch(`text intersectionMatrix, text intersectionMatrixPattern`)`;

## Description

Takes intersectionMatrix and intersectionMatrixPattern and Returns true if the intersectionMatrix satisfies the intersectionMatrixPattern. For more information refer to Section 4.3.6, “Dimensionally Extended 9 Intersection Model (DE-9IM)”.

Availability: 2.0.0 - requires GEOS >= 3.3.0.

## Examples

    SELECT ST_RelateMatch('101202FFF', 'TTTTTTFFF') ;
    -- result --
    t
    --example of common intersection matrix patterns and example matrices
    -- comparing relationships of involving one invalid geometry and ( a line and polygon that intersect at interior and boundary)
    SELECT mat.name, pat.name, ST_RelateMatch(mat.val, pat.val) As satisfied
        FROM
            ( VALUES ('Equality', 'T1FF1FFF1'),
                    ('Overlaps', 'T*T***T**'),
                    ('Within', 'T*F**F***'),
                    ('Disjoint', 'FF*FF****') As pat(name,val)
            CROSS JOIN
                (	VALUES ('Self intersections (invalid)', '111111111'),
                        ('IE2_BI1_BB0_BE1_EI1_EE2', 'FF2101102'),
                        ('IB1_IE1_BB0_BE0_EI2_EI1_EE2', 'F11F00212')
                ) As mat(name,val);

## See Also

Section 4.3.6, “Dimensionally Extended 9 Intersection Model (DE-9IM)”, ST_Relate

## Name

ST_ShortestLine — Returns the 2-dimensional shortest line between two geometries

## Synopsis

`geometry ST_ShortestLine(`geometry g1, geometry g2`)`;

## Description

Returns the 2-dimensional shortest line between two geometries. The function will only return the first shortest line if more than one, that the function finds. If g1 and g2 intersects in just one point the function will return a line with both start and end in that intersection-point. If g1 and g2 are intersecting with more than one point the function will return a line with start and end in the same point but it can be any of the intersecting points. The line returned will always start in g1 and end in g2. The length of the line this function returns will always be the same as st_distance returns for g1 and g2.

Availability: 1.5.0

## Examples

Shortest line between point and linestring
    SELECT ST_AsText(
    	ST_ShortestLine('POINT(100 100)'::geometry,
    		'LINESTRING (20 80, 98 190, 110 180, 50 75 )'::geometry)
    	) As sline;

       sline
    -----------------
    LINESTRING(100 100,73.0769230769231 115.384615384615)
| shortest line between polygon and polygon
    SELECT ST_AsText(
    		ST_ShortestLine(
    			ST_GeomFromText('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'),
    			ST_Buffer(ST_GeomFromText('POINT(110 170)'), 20)
    			)
    		) As slinewkt;

     LINESTRING(140.752120669087 125.695053378061,121.111404660392 153.370607753949)

## See Also

ST_ClosestPoint, ST_Distance, ST_LongestLine, ST_MaxDistance

## Name

ST_Touches — Returns `TRUE` if the geometries have at least one point in common, but their interiors do not intersect.

## Synopsis

`boolean ST_Touches(`geometry g1, geometry g2`)`;

## Description

Returns `TRUE` if the only points in common between `g1` and `g2` lie in the union of the boundaries of `g1` and `g2`. The `ST_Touches` relation applies to all Area/Area, Line/Line, Line/Area, Point/Area and Point/Line pairs of relationships, but not to the Point/Point pair.

In mathematical terms, this predicate is expressed as:

The allowable DE-9IM Intersection Matrices for the two geometries are:

- FT*******

- F**T*****

- F***T****

Do not call with a `GEOMETRYCOLLECTION` as an argument

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries. To avoid using an index, use `_ST_Touches` instead.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.28

## Examples

The `ST_Touches` predicate returns `TRUE` in all the following illustrations.

`POLYGON` / `POLYGON` | `POLYGON` / `POLYGON` | `POLYGON` / `LINESTRING`
`LINESTRING` / `LINESTRING` | `LINESTRING` / `LINESTRING` | `POLYGON` / `POINT`

    SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(1 1)'::geometry);
     st_touches
    ------------
     f
    (1 row)

    SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(0 2)'::geometry);
     st_touches
    ------------
     t
    (1 row)

## Name

ST_Within — Returns true if the geometry A is completely inside geometry B

## Synopsis

`boolean ST_Within(`geometry A, geometry B`)`;

## Description

Returns TRUE if geometry A is completely inside geometry B. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID. It is a given that if ST_Within(A,B) is true and ST_Within(B,A) is true, then the two geometries are considered spatially equal.

Performed by the GEOS module

Do not call with a `GEOMETRYCOLLECTION` as an argument

Do not use this function with invalid geometries. You will get unexpected results.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries. To avoid index use, use the function _ST_Within.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3 - a.Relate(b, 'T*F**F***')

This method implements the SQL/MM specification. SQL-MM 3: 5.1.30

## Examples

    --a circle within a circle
    SELECT ST_Within(smallc,smallc) As smallinsmall,
    	ST_Within(smallc, bigc) As smallinbig,
    	ST_Within(bigc,smallc) As biginsmall,
    	ST_Within(ST_Union(smallc, bigc), bigc) as unioninbig,
    	ST_Within(bigc, ST_Union(smallc, bigc)) as biginunion,
    	ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion
    FROM
    (
    SELECT ST_Buffer(ST_GeomFromText('POINT(50 50)'), 20) As smallc,
    	ST_Buffer(ST_GeomFromText('POINT(50 50)'), 40) As bigc) As foo;
    --Result
     smallinsmall | smallinbig | biginsmall | unioninbig | biginunion | bigisunion
    --------------+------------+------------+------------+------------+------------
     t            | t          | f          | t          | t          | t
    (1 row)

## See Also

ST_Contains, ST_Equals, ST_IsValid

## 8.9. Geometry Processing

## Name

ST_Buffer — (T) For geometry: Returns a geometry that represents all points whose distance from this Geometry is less than or equal to distance. Calculations are in the Spatial Reference System of this Geometry. For geography: Uses a planar transform wrapper. Introduced in 1.5 support for different end cap and mitre settings to control shape. buffer_style options: quad_segs=#,endcap=round|flat|square,join=round|mitre|bevel,mitre_limit=#.#

## Synopsis

`geometry ST_Buffer(`geometry g1, float radius_of_buffer`)`;

`geometry ST_Buffer(`geometry g1, float radius_of_buffer, integer num_seg_quarter_circle`)`;

`geometry ST_Buffer(`geometry g1, float radius_of_buffer, text buffer_style_parameters`)`;

`geography ST_Buffer(`geography g1, float radius_of_buffer_in_meters`)`;

## Description

Returns a geometry/geography that represents all points whose distance from this Geometry/geography is less than or equal to distance.

Geometry: Calculations are in the Spatial Reference System of the geometry. Introduced in 1.5 support for different end cap and mitre settings to control shape.

Negative radii: For polygons, a negative radius can be used, which will shrink the polygon rather than expanding it.

Geography: For geography this is really a thin wrapper around the geometry implementation. It first determines the best SRID that fits the bounding box of the geography object (favoring UTM, Lambert Azimuthal Equal Area (LAEA) north/south pole, and falling back on mercator in worst case scenario) and then buffers in that planar spatial ref and retransforms back to WGS84 geography.

For geography this may not behave as expected if object is sufficiently large that it falls between two UTM zones or crosses the dateline

Availability: 1.5 - ST_Buffer was enhanced to support different endcaps and join types. These are useful for example to convert road linestrings into polygon roads with flat or square edges instead of rounded edges. Thin wrapper for geography was added. - requires GEOS >= 3.2 to take advantage of advanced geometry functionality.

The optional third parameter (currently only applies to geometry) can either specify number of segments used to approximate a quarter circle (integer case, defaults to 8) or a list of blank-separated key=value pairs (string case) to tweak operations as follows:

- 'quad_segs=#' : number of segments used to approximate a quarter circle (defaults to 8).

- 'endcap=round|flat|square' : endcap style (defaults to "round", needs GEOS-3.2 or higher for a different value). 'butt' is also accepted as a synonym for 'flat'.

- 'join=round|mitre|bevel' : join style (defaults to "round", needs GEOS-3.2 or higher for a different value). 'miter' is also accepted as a synonym for 'mitre'.

- 'mitre_limit=#.#' : mitre ratio limit (only affects mitered join style). 'miter_limit' is also accepted as a synonym for 'mitre_limit'.

Units of radius are measured in units of the spatial reference system.

The inputs can be POINTS, MULTIPOINTS, LINESTRINGS, MULTILINESTRINGS, POLYGONS, MULTIPOLYGONS, and GeometryCollections.

This function ignores the third dimension (z) and will always give a 2-d buffer even when presented with a 3d-geometry.

Performed by the GEOS module.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.17

People often make the mistake of using this function to try to do radius searches. Creating a buffer to to a radius search is slow and pointless. Use ST_DWithin instead.

## Examples

quad_segs=8 (default)
    SELECT ST_Buffer(
     ST_GeomFromText('POINT(100 90)'),
     50, 'quad_segs=8');
| quad_segs=2 (lame)
    SELECT ST_Buffer(
     ST_GeomFromText('POINT(100 90)'),
     50, 'quad_segs=2');
endcap=round join=round (default)
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'endcap=round join=round');
| endcap=square
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'endcap=square join=round');
| endcap=flat
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'endcap=flat join=round');
join=bevel
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'join=bevel');
| join=mitre mitre_limit=5.0 (default mitre limit)
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'join=mitre mitre_limit=5.0');
| join=mitre mitre_limit=1
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'join=mitre mitre_limit=1.0');

    --A buffered point approximates a circle
    -- A buffered point forcing approximation of (see diagram)
    -- 2 points per circle is poly with 8 sides (see diagram)
    SELECT ST_NPoints(ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50)) As promisingcircle_pcount,
    ST_NPoints(ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50, 2)) As lamecircle_pcount;

    promisingcircle_pcount | lamecircle_pcount
    ------------------------+-------------------
    			 33 |                9

    --A lighter but lamer circle
    -- only 2 points per quarter circle is an octagon
    --Below is a 100 meter octagon
    -- Note coordinates are in NAD 83 long lat which we transform
    to Mass state plane meter and then buffer to get measurements in meters;
    SELECT ST_AsText(ST_Buffer(
    ST_Transform(
    ST_SetSRID(ST_MakePoint(-71.063526, 42.35785),4269), 26986)
    ,100,2)) As octagon;
    ----------------------
    POLYGON((236057.59057465 900908.759918696,236028.301252769 900838.049240578,235
    957.59057465 900808.759918696,235886.879896532 900838.049240578,235857.59057465
    900908.759918696,235886.879896532 900979.470596815,235957.59057465 901008.759918
    696,236028.301252769 900979.470596815,236057.59057465 900908.759918696))

## See Also

ST_Collect, ST_DWithin, ST_SetSRID, ST_Transform, ST_Union

## Name

ST_BuildArea — Creates an areal geometry formed by the constituent linework of given geometry

## Synopsis

`geometry ST_BuildArea(`geometry A`)`;

## Description

Creates an areal geometry formed by the constituent linework of given geometry. The return type can be a Polygon or MultiPolygon, depending on input. If the input lineworks do not form polygons NULL is returned. The inputs can be LINESTRINGS, MULTILINESTRINGS, POLYGONS, MULTIPOLYGONS, and GeometryCollections.

This function will assume all inner geometries represent holes

Input linework must be correctly noded for this function to work properly

Availability: 1.1.0 - requires GEOS >= 2.1.0.

## Examples

This will create a donut
    SELECT ST_BuildArea(ST_Collect(smallc,bigc))
    FROM (SELECT
    	ST_Buffer(
    	  ST_GeomFromText('POINT(100 90)'), 25) As smallc,
    	ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50) As bigc) As foo;
This will create a gaping hole inside the circle with prongs sticking out
    SELECT ST_BuildArea(ST_Collect(line,circle))
    FROM (SELECT
    	ST_Buffer(
    		ST_MakeLine(ST_MakePoint(10, 10),ST_MakePoint(190, 190)),
    				5)  As line,
    	ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50) As circle) As foo;

    --this creates the same gaping hole
    --but using linestrings instead of polygons
    SELECT ST_BuildArea(
    	ST_Collect(ST_ExteriorRing(line),ST_ExteriorRing(circle))
    	)
    FROM (SELECT ST_Buffer(
    	ST_MakeLine(ST_MakePoint(10, 10),ST_MakePoint(190, 190))
    		,5)  As line,
    	ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50) As circle) As foo;

## See Also

ST_Node, ST_MakePolygon, ST_BdPolyFromText, ST_BdMPolyFromTextwrappers to this function with standard OGC interface

## Name

ST_Collect — Return a specified ST_Geometry value from a collection of other geometries.

## Synopsis

`geometry ST_Collect(`geometry set g1field`)`;

`geometry ST_Collect(`geometry g1, geometry g2`)`;

`geometry ST_Collect(`geometry[] g1_array`)`;

## Description

Output type can be a MULTI* or a GEOMETRYCOLLECTION. Comes in 2 variants. Variant 1 collects 2 geometries. Variant 2 is an aggregate function that takes a set of geometries and collects them into a single ST_Geometry.

Aggregate version: This function returns a GEOMETRYCOLLECTION or a MULTI object from a set of geometries. The ST_Collect() function is an "aggregate" function in the terminology of PostgreSQL. That means that it operates on rows of data, in the same way the SUM() and AVG() functions do. For example, "SELECT ST_Collect(GEOM) FROM GEOMTABLE GROUP BY ATTRCOLUMN" will return a separate GEOMETRYCOLLECTION for each distinct value of ATTRCOLUMN.

Non-Aggregate version: This function returns a geometry being a collection of two input geometries. Output type can be a MULTI* or a GEOMETRYCOLLECTION.

ST_Collect and ST_Union are often interchangeable. ST_Collect is in general orders of magnitude faster than ST_Union because it does not try to dissolve boundaries or validate that a constructed MultiPolgon doesn't have overlapping regions. It merely rolls up single geometries into MULTI and MULTI or mixed geometry types into Geometry Collections. Unfortunately geometry collections are not well-supported by GIS tools. To prevent ST_Collect from returning a Geometry Collection when collecting MULTI geometries, one can use the below trick that utilizes ST_Dump to expand the MULTIs out to singles and then regroup them.

Availability: 1.4.0 - ST_Collect(geomarray) was introduced. ST_Collect was enhanced to handle more geometries faster.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves This method supports Circular Strings and Curves, but will never return a MULTICURVE or MULTI as one would expect and PostGIS does not currently support those.

## Examples

Aggregate example (http://postgis.refractions.net/pipermail/postgis-users/2008-June/020331.html)

    SELECT stusps,
    	   ST_Multi(ST_Collect(f.the_geom)) as singlegeom
    	 FROM (SELECT stusps, (ST_Dump(the_geom)).geom As the_geom
    				FROM
    				somestatetable ) As f
    GROUP BY stusps

Non-Aggregate example

    SELECT ST_AsText(ST_Collect(ST_GeomFromText('POINT(1 2)'),
    	ST_GeomFromText('POINT(-2 3)') ));

    st_astext
    ----------
    MULTIPOINT(1 2,-2 3)

    --Collect 2 d points
    SELECT ST_AsText(ST_Collect(ST_GeomFromText('POINT(1 2)'),
    		ST_GeomFromText('POINT(1 2)') ) );

    st_astext
    ----------
    MULTIPOINT(1 2,1 2)

    --Collect 3d points
    SELECT ST_AsEWKT(ST_Collect(ST_GeomFromEWKT('POINT(1 2 3)'),
    		ST_GeomFromEWKT('POINT(1 2 4)') ) );

    		st_asewkt
    -------------------------
     MULTIPOINT(1 2 3,1 2 4)

     --Example with curves
    SELECT ST_AsText(ST_Collect(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)'),
    ST_GeomFromText('CIRCULARSTRING(220227 150406,2220227 150407,220227 150406)')));
    																st_astext
    ------------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(CIRCULARSTRING(220268 150415,220227 150505,220227 150406),
     CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))

    --New ST_Collect array construct
    SELECT ST_Collect(ARRAY(SELECT the_geom FROM sometable));

    SELECT ST_AsText(ST_Collect(ARRAY[ST_GeomFromText('LINESTRING(1 2, 3 4)'),
    			ST_GeomFromText('LINESTRING(3 4, 4 5)')])) As wktcollect;

    --wkt collect --
    MULTILINESTRING((1 2,3 4),(3 4,4 5))

## See Also

ST_Dump, ST_Union

## Name

ST_ConcaveHull — The concave hull of a geometry represents a possibly concave geometry that encloses all geometries within the set. You can think of it as shrink wrapping.

## Synopsis

`geometry ST_ConcaveHull(`geometry geomA, float target_percent, boolean allow_holes=false`)`;

## Description

The concave hull of a geometry represents a possibly concave geometry that encloses all geometries within the set. Defaults to false for allowing polygons with holes. The result is never higher than a single polygon.

The target_percent is the target percent of area of convex hull the PostGIS solution will try to approach before giving up or exiting. One can think of the concave hull as the geometry you get by vacuum sealing a set of geometries. The target_percent of 1 will give you the same answer as the convex hull. A target_percent between 0 and 0.99 will give you something that should have a smaller area than the convex hull. This is different from a convex hull which is more like wrapping a rubber band around the set of geometries.

It is usually used with MULTI and Geometry Collections. Although it is not an aggregate - you can use it in conjunction with ST_Collect or ST_Union to get the concave hull of a set of points/linestring/polygons ST_ConcaveHull(ST_Collect(somepointfield), 0.80).

It is much slower to compute than convex hull but encloses the geometry better and is also useful for image recognition.

Performed by the GEOS module

Note - If you are using with points, linestrings, or geometry collections use ST_Collect. If you are using with polygons, use ST_Union since it may fail with invalid geometries.

Note - The smaller you make the target percent, the longer it takes to process the concave hull and more likely to run into topological exceptions. Also the more floating points and number of points you accrue. First try a 0.99 which does a first hop, is usually very fast, sometimes as fast as computing the convex hull, and usually gives much better than 99% of shrink since it almost always overshoots. Second hope of 0.98 it slower, others get slower usually quadratically. To reduce precision and float points, use ST_SimplifyPreserveTopology or ST_SnapToGrid after ST_ConcaveHull. ST_SnapToGrid is a bit faster, but could result in invalid geometries where as ST_SimplifyPreserveTopology almost always preserves the validity of the geometry.

More real world examples and brief explanation of the technique are shown http://www.bostongis.com/postgis_concavehull.snippet

Also check out Simon Greener's article on demonstrating ConcaveHull introduced in Oracle 11G R2. http://www.spatialdbadvisor.com/oracle_spatial_tips_tricks/172/concave-hull-geometries-in-oracle-11gr2. The solution we get at 0.75 target percent of convex hull is similar to the shape Simon gets with Oracle SDO_CONCAVEHULL_BOUNDARY.

Availability: 2.0.0

## Examples

    --Get estimate of infected area based on point observations
    SELECT d.disease_type,
    	ST_ConcaveHull(ST_Collect(d.pnt_geom), 0.99) As geom
    	FROM disease_obs As d
    	GROUP BY d.disease_type;

ST_ConcaveHull of 2 polygons encased in target 100% shrink concave hull
    -- geometries overlaid with concavehull
    -- at target 100% shrink (this is the same as convex hull - since no shrink)
    SELECT
    	ST_ConcaveHull(
    		ST_Union(ST_GeomFromText('POLYGON((175 150, 20 40,
    			50 60, 125 100, 175 150))'),
    		ST_Buffer(ST_GeomFromText('POINT(110 170)'), 20)
    		), 1)
    	 As convexhull;
| -- geometries overlaid with concavehull at target 90% of convex hull area
    -- geometries overlaid with concavehull at target 90% shrink
    SELECT
    	ST_ConcaveHull(
    		ST_Union(ST_GeomFromText('POLYGON((175 150, 20 40,
    			50 60, 125 100, 175 150))'),
    		ST_Buffer(ST_GeomFromText('POINT(110 170)'), 20)
    		), 0.9)
    	 As target_90;
L Shape points overlaid with convex hull
    -- this produces a table of 42 points that form an L shape
    SELECT (ST_DumpPoints(ST_GeomFromText(
    'MULTIPOINT(14 14,34 14,54 14,74 14,94 14,114 14,134 14,
    150 14,154 14,154 6,134 6,114 6,94 6,74 6,54 6,34 6,
    14 6,10 6,8 6,7 7,6 8,6 10,6 30,6 50,6 70,6 90,6 110,6 130,
    6 150,6 170,6 190,6 194,14 194,14 174,14 154,14 134,14 114,
    14 94,14 74,14 54,14 34,14 14)'))).geom
    	INTO TABLE l_shape;

    SELECT ST_ConvexHull(ST_Collect(geom))
    FROM l_shape;
| ST_ConcaveHull of L points at target 99% of convex hull
    SELECT ST_ConcaveHull(ST_Collect(geom), 0.99)
    	FROM l_shape;
Concave Hull of L points at target 80% convex hull area
    	-- Concave Hull L shape points
    	-- at target 80% of convexhull
    	SELECT ST_ConcaveHull(ST_Collect(geom), 0.80)
    	FROM l_shape;
| multilinestring overlaid with Convex hull multilinestring with overlaid with Concave hull of linestrings at 99% target -- first hop
    SELECT ST_ConcaveHull(ST_GeomFromText('MULTILINESTRING((106 164,30 112,74 70,82 112,130 94,
    	130 62,122 40,156 32,162 76,172 88),
    (132 178,134 148,128 136,96 128,132 108,150 130,
    170 142,174 110,156 96,158 90,158 88),
    (22 64,66 28,94 38,94 68,114 76,112 30,
    132 10,168 18,178 34,186 52,184 74,190 100,
    190 122,182 148,178 170,176 184,156 164,146 178,
    132 186,92 182,56 158,36 150,62 150,76 128,88 118))'),0.99)

## See Also

ST_Collect, ST_ConvexHull, ST_SimplifyPreserveTopology, ST_SnapToGrid

## Name

ST_ConvexHull — The convex hull of a geometry represents the minimum convex geometry that encloses all geometries within the set.

## Synopsis

`geometry ST_ConvexHull(`geometry geomA`)`;

## Description

The convex hull of a geometry represents the minimum convex geometry that encloses all geometries within the set.

One can think of the convex hull as the geometry you get by wrapping an elastic band around a set of geometries. This is different from a concave hull which is analogous to shrink-wrapping your geometries.

It is usually used with MULTI and Geometry Collections. Although it is not an aggregate - you can use it in conjunction with ST_Collect to get the convex hull of a set of points. ST_ConvexHull(ST_Collect(somepointfield)).

It is often used to determine an affected area based on a set of point observations.

Performed by the GEOS module

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.16

This function supports 3d and will not drop the z-index.

## Examples

    --Get estimate of infected area based on point observations
    SELECT d.disease_type,
    	ST_ConvexHull(ST_Collect(d.the_geom)) As the_geom
    	FROM disease_obs As d
    	GROUP BY d.disease_type;

Convex Hull of a MultiLinestring and a MultiPoint seen together with the MultiLinestring and MultiPoint

    SELECT ST_AsText(ST_ConvexHull(
    	ST_Collect(
    		ST_GeomFromText('MULTILINESTRING((100 190,10 8),(150 10, 20 30))'),
    			ST_GeomFromText('MULTIPOINT(50 5, 150 30, 50 10, 10 10)')
    			)) );
    ---st_astext--
    POLYGON((50 5,10 8,10 10,100 190,150 30,150 10,50 5))

## See Also

ST_Collect, ST_ConcaveHull, ST_MinimumBoundingCircle

## Name

ST_CurveToLine — Converts a CIRCULARSTRING/CURVEDPOLYGON to a LINESTRING/POLYGON

## Synopsis

`geometry ST_CurveToLine(`geometry curveGeom`)`;

`geometry ST_CurveToLine(`geometry curveGeom, integer segments_per_qtr_circle`)`;

## Description

Converst a CIRCULAR STRING to regular LINESTRING or CURVEPOLYGON to POLYGON. Useful for outputting to devices that can't support CIRCULARSTRING geometry types

Converts a given geometry to a linear geometry. Each curved geometry or segment is converted into a linear approximation using the default value of 32 segments per quarter circle

Availability: 1.2.2?

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.7

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_AsText(ST_CurveToLine(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)')));

    --Result --
     LINESTRING(220268 150415,220269.95064912 150416.539364228,220271.823415575 150418.17258804,220273.613787707 150419.895736857,
     220275.317452352 150421.704659462,220276.930305234 150423.594998003,220278.448460847 150425.562198489,
     220279.868261823 150427.60152176,220281.186287736 150429.708054909,220282.399363347 150431.876723113,
     220283.50456625 150434.10230186,220284.499233914 150436.379429536,220285.380970099 150438.702620341,220286.147650624 150441.066277505,
     220286.797428488 150443.464706771,220287.328738321 150445.892130112,220287.740300149 150448.342699654,
     220288.031122486 150450.810511759,220288.200504713 150453.289621251,220288.248038775 150455.77405574,
     220288.173610157 150458.257830005,220287.977398166 150460.734960415,220287.659875492 150463.199479347,
     220287.221807076 150465.64544956,220286.664248262 150468.066978495,220285.988542259 150470.458232479,220285.196316903 150472.81345077,
     220284.289480732 150475.126959442,220283.270218395 150477.39318505,220282.140985384 150479.606668057,
     220280.90450212 150481.762075989,220279.5637474 150483.85421628,220278.12195122 150485.87804878,
     220276.582586992 150487.828697901,220274.949363179 150489.701464356,220273.226214362 150491.491836488,
     220271.417291757 150493.195501133,220269.526953216 150494.808354014,220267.559752731 150496.326509628,
     220265.520429459 150497.746310603,220263.41389631 150499.064336517,220261.245228106 150500.277412127,
     220259.019649359 150501.38261503,220256.742521683 150502.377282695,220254.419330878 150503.259018879,
     220252.055673714 150504.025699404,220249.657244448 150504.675477269,220247.229821107 150505.206787101,
     220244.779251566 150505.61834893,220242.311439461 150505.909171266,220239.832329968 150506.078553494,
     220237.347895479 150506.126087555,220234.864121215 150506.051658938,220232.386990804 150505.855446946,
     220229.922471872 150505.537924272,220227.47650166 150505.099855856,220225.054972724 150504.542297043,
     220222.663718741 150503.86659104,220220.308500449 150503.074365683,
     220217.994991777 150502.167529512,220215.72876617 150501.148267175,
     220213.515283163 150500.019034164,220211.35987523 150498.7825509,
     220209.267734939 150497.441796181,220207.243902439 150496,
     220205.293253319 150494.460635772,220203.420486864 150492.82741196,220201.630114732 150491.104263143,
     220199.926450087 150489.295340538,220198.313597205 150487.405001997,220196.795441592 150485.437801511,
     220195.375640616 150483.39847824,220194.057614703 150481.291945091,220192.844539092 150479.123276887,220191.739336189 150476.89769814,
     220190.744668525 150474.620570464,220189.86293234 150472.297379659,220189.096251815 150469.933722495,
     220188.446473951 150467.535293229,220187.915164118 150465.107869888,220187.50360229 150462.657300346,
     220187.212779953 150460.189488241,220187.043397726 150457.710378749,220186.995863664 150455.22594426,
     220187.070292282 150452.742169995,220187.266504273 150450.265039585,220187.584026947 150447.800520653,
     220188.022095363 150445.35455044,220188.579654177 150442.933021505,220189.25536018 150440.541767521,
     220190.047585536 150438.18654923,220190.954421707 150435.873040558,220191.973684044 150433.60681495,
     220193.102917055 150431.393331943,220194.339400319 150429.237924011,220195.680155039 150427.14578372,220197.12195122 150425.12195122,
     220198.661315447 150423.171302099,220200.29453926 150421.298535644,220202.017688077 150419.508163512,220203.826610682 150417.804498867,
     220205.716949223 150416.191645986,220207.684149708 150414.673490372,220209.72347298 150413.253689397,220211.830006129 150411.935663483,
     220213.998674333 150410.722587873,220216.22425308 150409.61738497,220218.501380756 150408.622717305,220220.824571561 150407.740981121,
     220223.188228725 150406.974300596,220225.586657991 150406.324522731,220227 150406)

    --3d example
    SELECT ST_AsEWKT(ST_CurveToLine(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)')));
    Output
    ------
     LINESTRING(220268 150415 1,220269.95064912 150416.539364228 1.0181172856673,
     220271.823415575 150418.17258804 1.03623457133459,220273.613787707 150419.895736857 1.05435185700189,....AD INFINITUM ....
    	220225.586657991 150406.324522731 1.32611114201132,220227 150406 3)

    --use only 2 segments to approximate quarter circle
    SELECT ST_AsText(ST_CurveToLine(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)'),2));
    st_astext
    ------------------------------
     LINESTRING(220268 150415,220287.740300149 150448.342699654,220278.12195122 150485.87804878,
     220244.779251566 150505.61834893,220207.243902439 150496,220187.50360229 150462.657300346,
     220197.12195122 150425.12195122,220227 150406)

## See Also

ST_LineToCurve

## Name

ST_Difference — Returns a geometry that represents that part of geometry A that does not intersect with geometry B.

## Synopsis

`geometry ST_Difference(`geometry geomA, geometry geomB`)`;

## Description

Returns a geometry that represents that part of geometry A that does not intersect with geometry B. One can think of this as GeometryA - ST_Intersection(A,B). If A is completely contained in B then an empty geometry collection is returned.

Note - order matters. B - A will always return a portion of B

Performed by the GEOS module

Do not call with a GeometryCollection as an argument

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.20

This function supports 3d and will not drop the z-index. However it seems to only consider x y when doing the difference and tacks back on the Z-Index

## Examples

The original linestrings shown together. | The difference of the two linestrings

    --Safe for 2d. This is same geometries as what is shown for st_symdifference
    SELECT ST_AsText(
    	ST_Difference(
    			ST_GeomFromText('LINESTRING(50 100, 50 200)'),
    			ST_GeomFromText('LINESTRING(50 50, 50 150)')
    		)
    	);

    st_astext
    ---------
    LINESTRING(50 150,50 200)

    --When used in 3d doesn't quite do the right thing
    SELECT ST_AsEWKT(ST_Difference(ST_GeomFromEWKT('MULTIPOINT(-118.58 38.38 5,-118.60 38.329 6,-118.614 38.281 7)'), ST_GeomFromEWKT('POINT(-118.614 38.281 5)')));
    st_asewkt
    ---------
    MULTIPOINT(-118.6 38.329 6,-118.58 38.38 5)

## See Also

ST_SymDifference

## Name

ST_Dump — Returns a set of geometry_dump (geom,path) rows, that make up a geometry g1.

## Synopsis

`geometry_dump[] ST_Dump(`geometry g1`)`;

## Description

This is a set-returning function (SRF). It returns a set of geometry_dump rows, formed by a geometry (geom) and an array of integers (path). When the input geometry is a simple type (POINT,LINESTRING,POLYGON) a single record will be returned with an empty path array and the input geometry as geom. When the input geometry is a collection or multi it will return a record for each of the collection components, and the path will express the position of the component inside the collection.

ST_Dump is useful for expanding geometries. It is the reverse of a GROUP BY in that it creates new rows. For example it can be use to expand MULTIPOLYGONS into POLYGONS.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: PostGIS 1.0.0RC1. Requires PostgreSQL 7.3 or higher.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Standard Examples

    SELECT sometable.field1, sometable.field1,
          (ST_Dump(sometable.the_geom)).geom AS the_geom
    FROM sometable;

    -- Break a compound curve into its constituent linestrings and circularstrings
    SELECT ST_AsEWKT(a.geom), ST_HasArc(a.geom)
      FROM ( SELECT (ST_Dump(p_geom)).geom AS geom
             FROM (SELECT ST_GeomFromEWKT('COMPOUNDCURVE(CIRCULARSTRING(0 0, 1 1, 1 0),(1 0, 0 1))') AS p_geom) AS b
            ) AS a;
              st_asewkt          | st_hasarc
    -----------------------------+----------
     CIRCULARSTRING(0 0,1 1,1 0) | t
     LINESTRING(1 0,0 1)         | f
    (2 rows)

## Polyhedral Surfaces, TIN and Triangle Examples

    -- Polyhedral surface example
    -- Break a Polyhedral surface into its faces
    SELECT (a.p_geom).path[1] As path, ST_AsEWKT((a.p_geom).geom) As geom_ewkt
      FROM (SELECT ST_Dump(ST_GeomFromEWKT('POLYHEDRALSURFACE(
    ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),  ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),  ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
    )') ) AS p_geom )  AS a;

     path |                geom_ewkt
    ------+------------------------------------------
        1 | POLYGON((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0))
        2 | POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0))
        3 | POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0))
        4 | POLYGON((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0))
        5 | POLYGON((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0))
        6 | POLYGON((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1))

    -- TIN --
    SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt
      FROM
        (SELECT
           ST_Dump( ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )') ) AS gdump
        ) AS g;
    -- result --
     path |                 wkt
    ------+-------------------------------------
     {1}  | TRIANGLE((0 0 0,0 0 1,0 1 0,0 0 0))
     {2}  | TRIANGLE((0 0 0,0 1 0,1 1 0,0 0 0))

## See Also

geometry_dump, Section 13.5, “PostGIS Geometry / Geography / Raster Dump Functions”, ST_Collect, ST_Collect, ST_GeometryN

## Name

ST_DumpPoints — Returns a set of geometry_dump (geom,path) rows of all points that make up a geometry.

## Synopsis

`geometry_dump[]ST_DumpPoints(`geometry geom`)`;

## Description

This set-returning function (SRF) returns a set of `geometry_dump` rows formed by a geometry (`geom`) and an array of integers (`path`).

The `geom` component of `geometry_dump` are all the `POINT`s that make up the supplied geometry

The `path` component of `geometry_dump` (an `integer[]`) is an index reference enumerating the `POINT`s of the supplied geometry. For example, if a `LINESTRING` is supplied, a path of `{i}` is returned where `i` is the `nth` coordinate in the `LINESTRING`. If a `POLYGON` is supplied, a path of `{i,j}` is returned where `i` is the ring number (1 is outer; inner rings follow) and `j` enumerates the `POINT`s (again 1-based index).

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: 1.5.0

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Standard Geometry Examples

    SELECT path, ST_AsText(geom)
    FROM (
      SELECT (ST_DumpPoints(g.geom)).*
      FROM
        (SELECT
           'GEOMETRYCOLLECTION(
              POINT ( 0 1 ),
              LINESTRING ( 0 3, 3 4 ),
              POLYGON (( 2 0, 2 3, 0 2, 2 0 )),
              POLYGON (( 3 0, 3 3, 6 3, 6 0, 3 0 ),
                       ( 5 1, 4 2, 5 2, 5 1 )),
              MULTIPOLYGON (
                      (( 0 5, 0 8, 4 8, 4 5, 0 5 ),
                       ( 1 6, 3 6, 2 7, 1 6 )),
                      (( 5 4, 5 8, 6 7, 5 4 ))
              )
            )'::geometry AS geom
        ) AS g
      ) j;

       path    | st_astext
    -----------+------------
     {1,1}     | POINT(0 1)
     {2,1}     | POINT(0 3)
     {2,2}     | POINT(3 4)
     {3,1,1}   | POINT(2 0)
     {3,1,2}   | POINT(2 3)
     {3,1,3}   | POINT(0 2)
     {3,1,4}   | POINT(2 0)
     {4,1,1}   | POINT(3 0)
     {4,1,2}   | POINT(3 3)
     {4,1,3}   | POINT(6 3)
     {4,1,4}   | POINT(6 0)
     {4,1,5}   | POINT(3 0)
     {4,2,1}   | POINT(5 1)
     {4,2,2}   | POINT(4 2)
     {4,2,3}   | POINT(5 2)
     {4,2,4}   | POINT(5 1)
     {5,1,1,1} | POINT(0 5)
     {5,1,1,2} | POINT(0 8)
     {5,1,1,3} | POINT(4 8)
     {5,1,1,4} | POINT(4 5)
     {5,1,1,5} | POINT(0 5)
     {5,1,2,1} | POINT(1 6)
     {5,1,2,2} | POINT(3 6)
     {5,1,2,3} | POINT(2 7)
     {5,1,2,4} | POINT(1 6)
     {5,2,1,1} | POINT(5 4)
     {5,2,1,2} | POINT(5 8)
     {5,2,1,3} | POINT(6 7)
     {5,2,1,4} | POINT(5 4)
    (29 rows)

## Polyhedral Surfaces, TIN and Triangle Examples

    -- Polyhedral surface cube --
    SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt
      FROM
        (SELECT
           ST_DumpPoints(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )') ) AS gdump
        ) AS g;
    -- result --
      path   |     wkt
    ---------+--------------
     {1,1,1} | POINT(0 0 0)
     {1,1,2} | POINT(0 0 1)
     {1,1,3} | POINT(0 1 1)
     {1,1,4} | POINT(0 1 0)
     {1,1,5} | POINT(0 0 0)
     {2,1,1} | POINT(0 0 0)
     {2,1,2} | POINT(0 1 0)
     {2,1,3} | POINT(1 1 0)
     {2,1,4} | POINT(1 0 0)
     {2,1,5} | POINT(0 0 0)
     {3,1,1} | POINT(0 0 0)
     {3,1,2} | POINT(1 0 0)
     {3,1,3} | POINT(1 0 1)
     {3,1,4} | POINT(0 0 1)
     {3,1,5} | POINT(0 0 0)
     {4,1,1} | POINT(1 1 0)
     {4,1,2} | POINT(1 1 1)
     {4,1,3} | POINT(1 0 1)
     {4,1,4} | POINT(1 0 0)
     {4,1,5} | POINT(1 1 0)
     {5,1,1} | POINT(0 1 0)
     {5,1,2} | POINT(0 1 1)
     {5,1,3} | POINT(1 1 1)
     {5,1,4} | POINT(1 1 0)
     {5,1,5} | POINT(0 1 0)
     {6,1,1} | POINT(0 0 1)
     {6,1,2} | POINT(1 0 1)
     {6,1,3} | POINT(1 1 1)
     {6,1,4} | POINT(0 1 1)
     {6,1,5} | POINT(0 0 1)
    (30 rows)

    -- Triangle --
    SELECT (g.gdump).path, ST_AsText((g.gdump).geom) as wkt
      FROM
        (SELECT
           ST_DumpPoints( ST_GeomFromEWKT('TRIANGLE ((
                    0 0,
                    0 9,
                    9 0,
                    0 0
                ))') ) AS gdump
        ) AS g;
    -- result --
     path |    wkt
    ------+------------
     {1}  | POINT(0 0)
     {2}  | POINT(0 9)
     {3}  | POINT(9 0)
     {4}  | POINT(0 0)

    -- TIN --
    SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt
      FROM
        (SELECT
           ST_DumpPoints( ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )') ) AS gdump
        ) AS g;
    -- result --
      path   |     wkt
    ---------+--------------
     {1,1,1} | POINT(0 0 0)
     {1,1,2} | POINT(0 0 1)
     {1,1,3} | POINT(0 1 0)
     {1,1,4} | POINT(0 0 0)
     {2,1,1} | POINT(0 0 0)
     {2,1,2} | POINT(0 1 0)
     {2,1,3} | POINT(1 1 0)
     {2,1,4} | POINT(0 0 0)
    (8 rows)

## See Also

geometry_dump, Section 13.5, “PostGIS Geometry / Geography / Raster Dump Functions”, ST_Dump, ST_DumpRings

## Name

ST_DumpRings — Returns a set of `geometry_dump` rows, representing the exterior and interior rings of a polygon.

## Synopsis

`geometry_dump[] ST_DumpRings(`geometry a_polygon`)`;

## Description

This is a set-returning function (SRF). It returns a set of `geometry_dump` rows, defined as an `integer[]` and a `geometry`, aliased "path" and "geom" respectively. The "path" field holds the polygon ring index containing a single integer: 0 for the shell, >0 for holes. The "geom" field contains the corresponding ring as a polygon.

Availability: PostGIS 1.1.3. Requires PostgreSQL 7.3 or higher.

This only works for POLYGON geometries. It will not work for MULTIPOLYGONS

This function supports 3d and will not drop the z-index.

## Examples

    SELECT sometable.field1, sometable.field1,
    	  (ST_DumpRings(sometable.the_geom)).geom As the_geom
    FROM sometableOfpolys;

    SELECT ST_AsEWKT(geom) As the_geom, path
    	FROM ST_DumpRings(
    		ST_GeomFromEWKT('POLYGON((-8149064 5133092 1,-8149064 5132986 1,-8148996 5132839 1,-8148972 5132767 1,-8148958 5132508 1,-8148941 5132466 1,-8148924 5132394 1,
    		-8148903 5132210 1,-8148930 5131967 1,-8148992 5131978 1,-8149237 5132093 1,-8149404 5132211 1,-8149647 5132310 1,-8149757 5132394 1,
    		-8150305 5132788 1,-8149064 5133092 1),
    		(-8149362 5132394 1,-8149446 5132501 1,-8149548 5132597 1,-8149695 5132675 1,-8149362 5132394 1))')
    		)  as foo;
     path |                                            the_geom
    ----------------------------------------------------------------------------------------------------------------
      {0} | POLYGON((-8149064 5133092 1,-8149064 5132986 1,-8148996 5132839 1,-8148972 5132767 1,-8148958 5132508 1,
    	  |          -8148941 5132466 1,-8148924 5132394 1,
    	  |          -8148903 5132210 1,-8148930 5131967 1,
    	  |          -8148992 5131978 1,-8149237 5132093 1,
    	  |          -8149404 5132211 1,-8149647 5132310 1,-8149757 5132394 1,-8150305 5132788 1,-8149064 5133092 1))
      {1} | POLYGON((-8149362 5132394 1,-8149446 5132501 1,
    	  |          -8149548 5132597 1,-8149695 5132675 1,-8149362 5132394 1))

## See Also

geometry_dump, Section 13.5, “PostGIS Geometry / Geography / Raster Dump Functions”, ST_Dump, ST_ExteriorRing, ST_InteriorRingN

## Name

ST_FlipCoordinates — Returns a version of the given geometry with X and Y axis flipped. Useful for people who have built latitude/longitude features and need to fix them.

## Synopsis

`geometry ST_FlipCoordinates(`geometry geom`)`;

## Description

Returns a version of the given geometry with X and Y axis flipped.

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

Availability: 2.0.0

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Example

    SELECT ST_AsEWKT(ST_FlipCoordinates(GeomFromEWKT('POINT(1 2)')));
     st_asewkt
    ------------
    POINT(2 1)

## Name

ST_Intersection — (T) Returns a geometry that represents the shared portion of geomA and geomB. The geography implementation does a transform to geometry to do the intersection and then transform back to WGS84.

## Synopsis

`geometry ST_Intersection(` geometry geomA , geometry geomB `)`;

`geography ST_Intersection(` geography geogA , geography geogB `)`;

## Description

Returns a geometry that represents the point set intersection of the Geometries.

In other words - that portion of geometry A and geometry B that is shared between the two geometries.

If the geometries do not share any space (are disjoint), then an empty geometry collection is returned.

ST_Intersection in conjunction with ST_Intersects is very useful for clipping geometries such as in bounding box, buffer, region queries where you only want to return that portion of a geometry that sits in a country or region of interest.

Geography: For geography this is really a thin wrapper around the geometry implementation. It first determines the best SRID that fits the bounding box of the 2 geography objects (if geography objects are within one half zone UTM but not same UTM will pick one of those) (favoring UTM or Lambert Azimuthal Equal Area (LAEA) north/south pole, and falling back on mercator in worst case scenario) and then intersection in that best fit planar spatial ref and retransforms back to WGS84 geography.

Do not call with a `GEOMETRYCOLLECTION` as an argument

Performed by the GEOS module

Availability: 1.5 support for geography data type was introduced.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.18

## Examples

    SELECT ST_AsText(ST_Intersection('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry));
     st_astext
    ---------------
    GEOMETRYCOLLECTION EMPTY
    (1 row)
    SELECT ST_AsText(ST_Intersection('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry));
     st_astext
    ---------------
    POINT(0 0)
    (1 row)

    ---Clip all lines (trails) by country (here we assume country geom are POLYGON or MULTIPOLYGONS)
    -- NOTE: we are only keeping intersections that result in a LINESTRING or MULTILINESTRING because we don't
    -- care about trails that just share a point
    -- the dump is needed to expand a geometry collection into individual single MULT* parts
    -- the below is fairly generic and will work for polys, etc. by just changing the where clause
    SELECT clipped.gid, clipped.f_name, clipped_geom
    FROM (SELECT trails.gid, trails.f_name, (ST_Dump(ST_Intersection(country.the_geom, trails.the_geom))).geom As clipped_geom
    FROM country
    	INNER JOIN trails
    	ON ST_Intersects(country.the_geom, trails.the_geom))  As clipped
    	WHERE ST_Dimension(clipped.clipped_geom) = 1 ;

    --For polys e.g. polygon landmarks, you can also use the sometimes faster hack that buffering anything by 0.0
    -- except a polygon results in an empty geometry collection
    --(so a geometry collection containing polys, lines and points)
    -- buffered by 0.0 would only leave the polygons and dissolve the collection shell
    SELECT poly.gid,  ST_Multi(ST_Buffer(
    				ST_Intersection(country.the_geom, poly.the_geom),
    				0.0)
    				) As clipped_geom
    FROM country
    	INNER JOIN poly
    	ON ST_Intersects(country.the_geom, poly.the_geom)
    	WHERE Not ST_IsEmpty(ST_Buffer(ST_Intersection(country.the_geom, poly.the_geom),0.0));

## See Also

ST_Difference, ST_Dimension, ST_Dump, ST_SymDifference, ST_Intersects, ST_Multi

## Name

ST_LineToCurve — Converts a LINESTRING/POLYGON to a CIRCULARSTRING, CURVED POLYGON

## Synopsis

`geometry ST_LineToCurve(`geometry geomANoncircular`)`;

## Description

Converts plain LINESTRING/POLYGONS to CIRCULAR STRINGs and Curved Polygons. Note much fewer points are needed to describe the curved equivalent.

Availability: 1.2.2?

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

## Examples

    SELECT ST_AsText(ST_LineToCurve(foo.the_geom)) As curvedastext,ST_AsText(foo.the_geom) As non_curvedastext
    	FROM (SELECT ST_Buffer('POINT(1 3)'::geometry, 3) As the_geom) As foo;

    curvedatext                                                            non_curvedastext
    --------------------------------------------------------------------|-----------------------------------------------------------------
    CURVEPOLYGON(CIRCULARSTRING(4 3,3.12132034355964 0.878679656440359, | POLYGON((4 3,3.94235584120969 2.41472903395162,3.77163859753386 1.85194970290473,
    1 0,-1.12132034355965 5.12132034355963,4 3))                        |  3.49440883690764 1.33328930094119,3.12132034355964 0.878679656440359,
                                                                        |  2.66671069905881 0.505591163092366,2.14805029709527 0.228361402466141,
                                                                        |  1.58527096604839 0.0576441587903094,1 0,
                                                                        |  0.414729033951621 0.0576441587903077,-0.148050297095264 0.228361402466137,
                                                                        |  -0.666710699058802 0.505591163092361,-1.12132034355964 0.878679656440353,
                                                                        |  -1.49440883690763 1.33328930094119,-1.77163859753386 1.85194970290472
                                                                        |  --ETC-- ,3.94235584120969 3.58527096604839,4 3))
    --3D example
    SELECT ST_AsEWKT(ST_LineToCurve(ST_GeomFromEWKT('LINESTRING(1 2 3, 3 4 8, 5 6 4, 7 8 4, 9 10 4)')));

    			 st_asewkt
    ------------------------------------
     CIRCULARSTRING(1 2 3,5 6 4,9 10 4)

## See Also

ST_CurveToLine

## Name

ST_MakeValid — Attempts to make an invalid geometry valid w/out loosing vertices.

## Synopsis

`geometry ST_MakeValid(`geometry input`)`;

## Description

The function attempts to create a valid representation of a given invalid geometry without loosing any of the input vertices. Already-valid geometries are returned w/out further intervention.

Supported inputs are: LINESTRINGS, MULTILINESTRINGS, POLYGONS, MULTIPOLYGONS.

In case of full or partial dimensional collapses, the output geometry may be a collection of lower-to-equal dimension geometries or a geometry of lower dimension.

Single polygons may become multi-geometries in case of self-intersections.

Availability: 2.0.0, requires GEOS-3.3.0 or higher.

This function supports 3d and will not drop the z-index.

## See Also

ST_IsValid ST_CollectionExtract

## Name

ST_MemUnion — Same as ST_Union, only memory-friendly (uses less memory and more processor time).

## Synopsis

`geometry ST_MemUnion(`geometry set geomfield`)`;

## Description

Some useful description here.

Same as ST_Union, only memory-friendly (uses less memory and more processor time). This aggregate function works by unioning the geometries one at a time to previous result as opposed to ST_Union aggregate which first creates an array and then unions

This function supports 3d and will not drop the z-index.

## Examples

    See ST_Union

## See Also

ST_Union

## Name

ST_MinimumBoundingCircle — Returns the smallest circle polygon that can fully contain a geometry. Default uses 48 segments per quarter circle.

## Synopsis

`geometry ST_MinimumBoundingCircle(`geometry geomA, integer num_segs_per_qt_circ=48`)`;

## Description

Returns the smallest circle polygon that can fully contain a geometry.

The circle is approximated by a polygon with a default of 48 segments per quarter circle. This number can be increased with little performance penalty to obtain a more accurate result.

It is often used with MULTI and Geometry Collections. Although it is not an aggregate - you can use it in conjunction with ST_Collect to get the minimum bounding circle of a set of geometries. ST_MinimumBoundingCircle(ST_Collect(somepointfield)).

The ratio of the area of a polygon divided by the area of its Minimum Bounding Circle is often referred to as the Roeck test.

Availability: 1.4.0 - requires GEOS

## Examples

    SELECT d.disease_type,
    	ST_MinimumBoundingCircle(ST_Collect(d.the_geom)) As the_geom
    	FROM disease_obs As d
    	GROUP BY d.disease_type;

Minimum bounding circle of a point and linestring. Using 8 segs to approximate a quarter circle

    SELECT ST_AsText(ST_MinimumBoundingCircle(
    		ST_Collect(
    			ST_GeomFromEWKT('LINESTRING(55 75,125 150)'),
    				ST_Point(20, 80)), 8
    				)) As wktmbc;
    wktmbc
    -----------
    POLYGON((135.59714732062 115,134.384753327498 102.690357210921,130.79416296937 90.8537670908995,124.963360620072 79.9451031602111,117.116420743937 70.3835792560632,107.554896839789 62.5366393799277,96.6462329091006 56.70583703063,84.8096427890789 53.115246672502,72.5000000000001 51.9028526793802,60.1903572109213 53.1152466725019,48.3537670908996 56.7058370306299,37.4451031602112 62.5366393799276,27.8835792560632 70.383579256063,20.0366393799278 79.9451031602109,14.20583703063 90.8537670908993,10.615246672502 102.690357210921,9.40285267938019 115,10.6152466725019 127.309642789079,14.2058370306299 139.1462329091,20.0366393799275 150.054896839789,27.883579256063 159.616420743937,
    37.4451031602108 167.463360620072,48.3537670908992 173.29416296937,60.190357210921 176.884753327498,
    72.4999999999998 178.09714732062,84.8096427890786 176.884753327498,96.6462329091003 173.29416296937,107.554896839789 167.463360620072,
    117.116420743937 159.616420743937,124.963360620072 150.054896839789,130.79416296937 139.146232909101,134.384753327498 127.309642789079,135.59714732062 115))

## See Also

ST_Collect, ST_ConvexHull

## Name

ST_Polygonize — Aggregate. Creates a GeometryCollection containing possible polygons formed from the constituent linework of a set of geometries.

## Synopsis

`geometry ST_Polygonize(`geometry set geomfield`)`;

`geometry ST_Polygonize(`geometry[] geom_array`)`;

## Description

Creates a GeometryCollection containing possible polygons formed from the constituent linework of a set of geometries.

Geometry Collections are often difficult to deal with with third party tools, so use ST_Polygonize in conjunction with ST_Dump to dump the polygons out into individual polygons.

Input linework must be correctly noded for this function to work properly

Availability: 1.0.0RC1 - requires GEOS >= 2.1.0.

## Examples: Polygonizing single linestrings

    SELECT ST_AsEWKT(ST_Polygonize(the_geom_4269)) As geomtextrep
    FROM (SELECT the_geom_4269 FROM ma.suffolk_edges ORDER BY tlid LIMIT 45) As foo;

    geomtextrep
    -------------------------------------
     SRID=4269;GEOMETRYCOLLECTION(POLYGON((-71.040878 42.285678,-71.040943 42.2856,-71.04096 42.285752,-71.040878 42.285678)),
     POLYGON((-71.17166 42.353675,-71.172026 42.354044,-71.17239 42.354358,-71.171794 42.354971,-71.170511 42.354855,
     -71.17112 42.354238,-71.17166 42.353675)))
    (1 row)

    --Use ST_Dump to dump out the polygonize geoms into individual polygons
    SELECT ST_AsEWKT((ST_Dump(foofoo.polycoll)).geom) As geomtextrep
    FROM (SELECT ST_Polygonize(the_geom_4269) As polycoll
    	FROM (SELECT the_geom_4269 FROM ma.suffolk_edges
    		ORDER BY tlid LIMIT 45) As foo) As foofoo;

    geomtextrep
    ------------------------
     SRID=4269;POLYGON((-71.040878 42.285678,-71.040943 42.2856,-71.04096 42.285752,
    -71.040878 42.285678))
     SRID=4269;POLYGON((-71.17166 42.353675,-71.172026 42.354044,-71.17239 42.354358
    ,-71.171794 42.354971,-71.170511 42.354855,-71.17112 42.354238,-71.17166 42.353675))
    (2 rows)

## See Also

ST_Node, ST_Dump

## Name

ST_Node — Node a set of linestrings.

## Synopsis

`geometry ST_Node(`geometry geom`)`;

## Description

Fully node a set of linestrings using the least possible number of nodes while preserving all of the input ones.

This function supports 3d and will not drop the z-index.

Availability: 2.0.0 - requires GEOS >= 3.3.0.

Due to a bug in GEOS up to 3.3.1 this function fails to node self-intersecting lines. This is fixed with GEOS 3.3.2 or higher.

## Examples

    SELECT ST_AsEWKT(
    		ST_Node('LINESTRINGZ(0 0 0, 10 10 10, 0 10 5, 10 0 3)'::geometry)
    	) As  output;
    output
    -----------
    MULTILINESTRING((0 0 0,5 5 4.5),(5 5 4.5,10 10 10,0 10 5,5 5 4.5),(5 5 4.5,10 0 3))

## See Also

ST_UnaryUnion

## Name

ST_OffsetCurve — Return an offset line at a given distance and side from an input line. Useful for computing parallel lines about a center line

## Synopsis

`geometry ST_OffsetCurve(`geometry line, float signed_distance, text style_parameters=''`)`;

## Description

Return an offset line at a given distance and side from an input line. All points of the returned geometries are not further than the given distance from the input geometry.

For positive distance the offset will be at the left side of the input line and retain the same direction. For a negative distance it'll be at the right side and in the opposite direction.

Availability: 2.0 - requires GEOS >= 3.2, improved with GEOS >= 3.3

The optional third parameter allows specifying a list of blank-separated key=value pairs to tweak operations as follows:

- 'quad_segs=#' : number of segments used to approximate a quarter circle (defaults to 8).

- 'join=round|mitre|bevel' : join style (defaults to "round"). 'miter' is also accepted as a synonym for 'mitre'.

- 'mitre_limit=#.#' : mitre ratio limit (only affects mitred join style). 'miter_limit' is also accepted as a synonym for 'mitre_limit'.

Units of distance are measured in units of the spatial reference system.

The inputs can only be LINESTRINGS.

Performed by the GEOS module.

This function ignores the third dimension (z) and will always give a 2-d result even when presented with a 3d-geometry.

## Examples

Compute an open buffer around roads

    SELECT ST_Union(
     ST_OffsetCurve(f.the_geom,  f.width/2, 'quad_segs=4 join=round'),
     ST_OffsetCurve(f.the_geom, -f.width/2, 'quad_segs=4 join=round')
    ) as track
    FROM someroadstable;

15, 'quad_segs=4 join=round' original line and its offset 15 units.
    SELECT ST_AsText(ST_OffsetCurve(ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
    	44 16,24 16,20 16,18 16,17 17,
    	16 18,16 20,16 40,16 60,16 80,16 100,
    	16 120,16 140,16 160,16 180,16 195)'),
    	15, 'quad_segs=4 join=round'));
    --output --
    LINESTRING(164 1,18 1,12.2597485145237 2.1418070123307,
    	7.39339828220179 5.39339828220179,
    	5.39339828220179 7.39339828220179,
    	2.14180701233067 12.2597485145237,1 18,1 195)
| -15, 'quad_segs=4 join=round' original line and its offset -15 units
    SELECT ST_AsText(ST_OffsetCurve(geom,
    	-15, 'quad_segs=4 join=round')) As notsocurvy
    	FROM ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
    	44 16,24 16,20 16,18 16,17 17,
    	16 18,16 20,16 40,16 60,16 80,16 100,
    	16 120,16 140,16 160,16 180,16 195)') As geom;
    -- notsocurvy --
    LINESTRING(31 195,31 31,164 31)
double-offset to get more curvy, note the first reverses direction, so -30 + 15 = -15
    SELECT ST_AsText(ST_OffsetCurve(ST_OffsetCurve(geom,
    	-30, 'quad_segs=4 join=round'), -15, 'quad_segs=4 join=round')) As morecurvy
    	FROM ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
    	44 16,24 16,20 16,18 16,17 17,
    	16 18,16 20,16 40,16 60,16 80,16 100,
    	16 120,16 140,16 160,16 180,16 195)') As geom;
    -- morecurvy --
    LINESTRING(164 31,46 31,40.2597485145236 32.1418070123307,
    35.3933982822018 35.3933982822018,
    32.1418070123307 40.2597485145237,31 46,31 195)
| double-offset to get more curvy,combined with regular offset 15 to get parallel lines. Overlaid with original.
    SELECT ST_AsText(ST_Collect(
    	ST_OffsetCurve(geom, 15, 'quad_segs=4 join=round'),
    	ST_OffsetCurve(ST_OffsetCurve(geom,
    	-30, 'quad_segs=4 join=round'), -15, 'quad_segs=4 join=round')
    	)
    ) As parallel_curves
    	FROM ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
    	44 16,24 16,20 16,18 16,17 17,
    	16 18,16 20,16 40,16 60,16 80,16 100,
    	16 120,16 140,16 160,16 180,16 195)') As geom;
    -- parallel curves  --
    MULTILINESTRING((164 1,18 1,12.2597485145237 2.1418070123307,
    7.39339828220179 5.39339828220179,5.39339828220179 7.39339828220179,
    2.14180701233067 12.2597485145237,1 18,1 195),
    (164 31,46 31,40.2597485145236 32.1418070123307,35.3933982822018 35.3933982822018,
    32.1418070123307 40.2597485145237,31 46,31 195))
15, 'quad_segs=4 join=bevel' shown with original line
    SELECT ST_AsText(ST_OffsetCurve(ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
    	44 16,24 16,20 16,18 16,17 17,
    	16 18,16 20,16 40,16 60,16 80,16 100,
    	16 120,16 140,16 160,16 180,16 195)'),
    		15, 'quad_segs=4 join=bevel'));
    -- output --
    LINESTRING(164 1,18 1,7.39339828220179 5.39339828220179,
    	5.39339828220179 7.39339828220179,1 18,1 195)
| 15,-15 collected, join=mitre mitre_limit=2.1
    SELECT ST_AsText(ST_Collect(
    	ST_OffsetCurve(geom, 15, 'quad_segs=4 join=mitre mitre_limit=2.2'),
    	ST_OffsetCurve(geom, -15, 'quad_segs=4 join=mitre mitre_limit=2.2')
    	) )
    	FROM ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
    	44 16,24 16,20 16,18 16,17 17,
    	16 18,16 20,16 40,16 60,16 80,16 100,
    	16 120,16 140,16 160,16 180,16 195)') As geom;
    -- output --
    MULTILINESTRING((164 1,11.7867965644036 1,1 11.7867965644036,1 195),
    	(31 195,31 31,164 31))

## See Also

ST_Buffer

## Name

ST_RemoveRepeatedPoints — Returns a version of the given geometry with duplicated points removed.

## Synopsis

`geometry ST_RemoveRepeatedPoints(`geometry geom`)`;

## Description

Returns a version of the given geometry with duplicated points removed. Will actually do something only with (multi)lines, (multi)polygons and multipoints but you can safely call it with any kind of geometry. Since simplification occurs on a object-by-object basis you can also feed a GeometryCollection to this function.

Availability: 2.0.0

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

## See Also

ST_Simplify

## Name

ST_SharedPaths — Returns a collection containing paths shared by the two input linestrings/multilinestrings.

## Synopsis

`geometry ST_SharedPaths(`geometry lineal1, geometry lineal2`)`;

## Description

Returns a collection containing paths shared by the two input geometries. Those going in the same direction are in the first element of the collection, those going in the opposite direction are in the second element. The paths themselves are given in the direction of the first geometry.

Availability: 2.0.0 requires GEOS >= 3.3.0.

## Examples: Finding shared paths

A multilinestring and a linestring
The shared path of multilinestring and linestring overlaid with original geometries.
     SELECT ST_AsText(
      ST_SharedPaths(
        ST_GeomFromText('MULTILINESTRING((26 125,26 200,126 200,126 125,26 125),
     	   (51 150,101 150,76 175,51 150))'),
     	ST_GeomFromText('LINESTRING(151 100,126 156.25,126 125,90 161, 76 175)')
     	)
      ) As wkt

                                    wkt
    -------------------------------------------------------------
    GEOMETRYCOLLECTION(MULTILINESTRING((126 156.25,126 125),
     (101 150,90 161),(90 161,76 175)),MULTILINESTRING EMPTY)
    -- same example but linestring orientation flipped
    SELECT ST_AsText(
      ST_SharedPaths(
       ST_GeomFromText('LINESTRING(76 175,90 161,126 125,126 156.25,151 100)'),
       ST_GeomFromText('MULTILINESTRING((26 125,26 200,126 200,126 125,26 125),
     	   (51 150,101 150,76 175,51 150))')
     	)
      ) As wkt

                                    wkt
    -------------------------------------------------------------
    GEOMETRYCOLLECTION(MULTILINESTRING EMPTY,
    MULTILINESTRING((76 175,90 161),(90 161,101 150),(126 125,126 156.25)))

## See Also

ST_Dump, ST_GeometryN, ST_NumGeometries

## Name

ST_Shift_Longitude — Reads every point/vertex in every component of every feature in a geometry, and if the longitude coordinate is <0, adds 360 to it. The result would be a 0-360 version of the data to be plotted in a 180 centric map

## Synopsis

`geometry ST_Shift_Longitude(`geometry geomA`)`;

## Description

Reads every point/vertex in every component of every feature in a geometry, and if the longitude coordinate is <0, adds 360 to it. The result would be a 0-360 version of the data to be plotted in a 180 centric map

This is only useful for data in long lat e.g. 4326 (WGS 84 long lat)

Pre-1.3.4 bug prevented this from working for MULTIPOINT. 1.3.4+ works with MULTIPOINT as well.

This function supports 3d and will not drop the z-index.

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --3d points
    SELECT ST_AsEWKT(ST_Shift_Longitude(ST_GeomFromEWKT('SRID=4326;POINT(-118.58 38.38 10)'))) As geomA,
    	ST_AsEWKT(ST_Shift_Longitude(ST_GeomFromEWKT('SRID=4326;POINT(241.42 38.38 10)'))) As geomb
    geomA							  geomB
    ----------						  -----------
    SRID=4326;POINT(241.42 38.38 10) SRID=4326;POINT(-118.58 38.38 10)

    --regular line string
    SELECT ST_AsText(ST_Shift_Longitude(ST_GeomFromText('LINESTRING(-118.58 38.38, -118.20 38.45)')))

    st_astext
    ----------
    LINESTRING(241.42 38.38,241.8 38.45)

## See Also

ST_GeomFromEWKT, ST_GeomFromText, ST_AsEWKT

## Name

ST_Simplify — Returns a "simplified" version of the given geometry using the Douglas-Peucker algorithm.

## Synopsis

`geometry ST_Simplify(`geometry geomA, float tolerance`)`;

## Description

Returns a "simplified" version of the given geometry using the Douglas-Peucker algorithm. Will actually do something only with (multi)lines and (multi)polygons but you can safely call it with any kind of geometry. Since simplification occurs on a object-by-object basis you can also feed a GeometryCollection to this function.

Note that returned geometry might loose its simplicity (see ST_IsSimple)

Note topology may not be preserved and may result in invalid geometries. Use (see ST_SimplifyPreserveTopology) to preserve topology.

Performed by the GEOS module.

Availability: 1.2.2

## Examples

A circle simplified too much becomes a triangle, medium an octagon,

    SELECT ST_Npoints(the_geom) As np_before, ST_NPoints(ST_Simplify(the_geom,0.1)) As np01_notbadcircle, ST_NPoints(ST_Simplify(the_geom,0.5)) As np05_notquitecircle,
    ST_NPoints(ST_Simplify(the_geom,1)) As np1_octagon, ST_NPoints(ST_Simplify(the_geom,10)) As np10_triangle,
    (ST_Simplify(the_geom,100) is null) As  np100_geometrygoesaway
    FROM (SELECT ST_Buffer('POINT(1 3)', 10,12) As the_geom) As foo;
    -result
     np_before | np01_notbadcircle | np05_notquitecircle | np1_octagon | np10_triangle | np100_geometrygoesaway
    -----------+-------------------+---------------------+-------------+---------------+------------------------
    		49 |                33 |                  17 |           9 |             4 | t

## See Also

ST_IsSimple, ST_SimplifyPreserveTopology

## Name

ST_SimplifyPreserveTopology — Returns a "simplified" version of the given geometry using the Douglas-Peucker algorithm. Will avoid creating derived geometries (polygons in particular) that are invalid.

## Synopsis

`geometry ST_SimplifyPreserveTopology(`geometry geomA, float tolerance`)`;

## Description

Returns a "simplified" version of the given geometry using the Douglas-Peucker algorithm. Will avoid creating derived geometries (polygons in particular) that are invalid. Will actually do something only with (multi)lines and (multi)polygons but you can safely call it with any kind of geometry. Since simplification occurs on a object-by-object basis you can also feed a GeometryCollection to this function.

Performed by the GEOS module.

Requires GEOS 3.0.0+

Availability: 1.3.3

## Examples

Same example as Simplify, but we see Preserve Topology prevents oversimplification. The circle can at most become a square.

    SELECT ST_Npoints(the_geom) As np_before, ST_NPoints(ST_SimplifyPreserveTopology(the_geom,0.1)) As np01_notbadcircle, ST_NPoints(ST_SimplifyPreserveTopology(the_geom,0.5)) As np05_notquitecircle,
    ST_NPoints(ST_SimplifyPreserveTopology(the_geom,1)) As np1_octagon, ST_NPoints(ST_SimplifyPreserveTopology(the_geom,10)) As np10_square,
    ST_NPoints(ST_SimplifyPreserveTopology(the_geom,100)) As  np100_stillsquare
    FROM (SELECT ST_Buffer('POINT(1 3)', 10,12) As the_geom) As foo;

    --result--
     np_before | np01_notbadcircle | np05_notquitecircle | np1_octagon | np10_square | np100_stillsquare
    -----------+-------------------+---------------------+-------------+---------------+-------------------
    		49 |                33 |                  17 |           9 |             5 |                 5

## See Also

ST_Simplify

## Name

ST_Split — Returns a collection of geometries resulting by splitting a geometry.

## Synopsis

`geometry ST_Split(`geometry input, geometry blade`)`;

## Description

The function supports splitting a line by point, a line by line, a polygon by line. The returned geometry is always a collection.

Think of this function as the opposite of ST_Union. Theoretically applying ST_Union to the elements of the returned collection should always yield the original geometry.

Availability: 2.0.0

## Examples

Polygon Cut by Line

Before Split | After split

    -- this creates a geometry collection consisting of the 2 halves of the polygon
    -- this is similar to the example we demonstrated in ST_BuildArea
    SELECT ST_Split(circle, line)
    FROM (SELECT
        ST_MakeLine(ST_MakePoint(10, 10),ST_MakePoint(190, 190)) As line,
        ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50) As circle) As foo;

    -- result --
     GEOMETRYCOLLECTION(POLYGON((150 90,149.039264020162 80.2454838991936,146.193976625564 70.8658283817455,..), POLYGON(..)))

    -- To convert to individual polygons, you can use ST_Dump or ST_GeometryN
    SELECT ST_AsText((ST_Dump(ST_Split(circle, line))).geom) As wkt
    FROM (SELECT
        ST_MakeLine(ST_MakePoint(10, 10),ST_MakePoint(190, 190)) As line,
        ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50) As circle) As foo;

    -- result --
    wkt
    ---------------
    POLYGON((150 90,149.039264020162 80.2454838991936,..))
    POLYGON((60.1371179574584 60.1371179574584,58.4265193848728 62.2214883490198,53.8060233744357 ..))

Multilinestring Cut by point

Before Split | After split

    SELECT ST_AsText(ST_Split(mline, pt)) As wktcut
            FROM (SELECT
        ST_GeomFromText('MULTILINESTRING((10 10, 190 190), (15 15, 30 30, 100 90))') As mline,
        ST_Point(30,30) As pt) As foo;

    wktcut
    ------
    GEOMETRYCOLLECTION(
        LINESTRING(10 10,30 30),
        LINESTRING(30 30,190 190),
        LINESTRING(15 15,30 30),
        LINESTRING(30 30,100 90)
    )

## See Also

ST_AsText, ST_BuildArea, ST_Dump, ST_GeometryN, ST_Union

## Name

ST_SymDifference — Returns a geometry that represents the portions of A and B that do not intersect. It is called a symmetric difference because ST_SymDifference(A,B) = ST_SymDifference(B,A).

## Synopsis

`geometry ST_SymDifference(`geometry geomA, geometry geomB`)`;

## Description

Returns a geometry that represents the portions of A and B that do not intersect. It is called a symmetric difference because ST_SymDifference(A,B) = ST_SymDifference(B,A). One can think of this as ST_Union(geomA,geomB) - ST_Intersection(A,B).

Performed by the GEOS module

Do not call with a GeometryCollection as an argument

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.21

This function supports 3d and will not drop the z-index. However it seems to only consider x y when doing the difference and tacks back on the Z-Index

## Examples

The original linestrings shown together | The symmetric difference of the two linestrings

    --Safe for 2d - symmetric difference of 2 linestrings
    SELECT ST_AsText(
    	ST_SymDifference(
    		ST_GeomFromText('LINESTRING(50 100, 50 200)'),
    		ST_GeomFromText('LINESTRING(50 50, 50 150)')
    	)
    );

    st_astext
    ---------
    MULTILINESTRING((50 150,50 200),(50 50,50 100))

    --When used in 3d doesn't quite do the right thing
    SELECT ST_AsEWKT(ST_SymDifference(ST_GeomFromEWKT('LINESTRING(1 2 1, 1 4 2)'),
    	ST_GeomFromEWKT('LINESTRING(1 1 3, 1 3 4)')))

    st_astext
    ------------
    MULTILINESTRING((1 3 2.75,1 4 2),(1 1 3,1 2 2.25))

## See Also

ST_Difference, ST_Intersection, ST_Union

## Name

ST_Union — Returns a geometry that represents the point set union of the Geometries.

## Synopsis

`geometry ST_Union(`geometry set g1field`)`;

`geometry ST_Union(`geometry g1, geometry g2`)`;

`geometry ST_Union(`geometry[] g1_array`)`;

## Description

Output type can be a MULTI*, single geometry, or Geometry Collection. Comes in 2 variants. Variant 1 unions 2 geometries resulting in a new geometry with no intersecting regions. Variant 2 is an aggregate function that takes a set of geometries and unions them into a single ST_Geometry resulting in no intersecting regions.

Aggregate version: This function returns a MULTI geometry or NON-MULTI geometry from a set of geometries. The ST_Union() function is an "aggregate" function in the terminology of PostgreSQL. That means that it operates on rows of data, in the same way the SUM() and AVG() functions do.

Non-Aggregate version: This function returns a geometry being a union of two input geometries. Output type can be a MULTI*, NON-MULTI or GEOMETRYCOLLECTION.

ST_Collect and ST_Union are often interchangeable. ST_Union is in general orders of magnitude slower than ST_Collect because it tries to dissolve boundaries and reorder geometries to ensure that a constructed Multi* doesn't have intersecting regions.

Performed by the GEOS module.

NOTE: this function was formerly called GeomUnion(), which was renamed from "Union" because UNION is an SQL reserved word.

Availability: 1.4.0 - ST_Union was enhanced. ST_Union(geomarray) was introduced and also faster aggregate collection in PostgreSQL. If you are using GEOS 3.1.0+ ST_Union will use the faster Cascaded Union algorithm described in http://blog.cleverelephant.ca/2009/01/must-faster-unions-in-postgis-14.html

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

Aggregate version is not explicitly defined in OGC SPEC.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.19 the z-index (elevation) when polygons are involved.

## Examples

Aggregate example

    SELECT stusps,
    	   ST_Multi(ST_Union(f.the_geom)) as singlegeom
    	 FROM sometable As f
    GROUP BY stusps

Non-Aggregate example

    SELECT ST_AsText(ST_Union(ST_GeomFromText('POINT(1 2)'),
    	ST_GeomFromText('POINT(-2 3)') ) )

    st_astext
    ----------
    MULTIPOINT(-2 3,1 2)

    SELECT ST_AsText(ST_Union(ST_GeomFromText('POINT(1 2)'),
    		ST_GeomFromText('POINT(1 2)') ) );
    st_astext
    ----------
    POINT(1 2)

    --3d example - sort of supports 3d (and with mixed dimensions!)
    SELECT ST_AsEWKT(st_union(the_geom))
    FROM
    (SELECT ST_GeomFromEWKT('POLYGON((-7 4.2,-7.1 4.2,-7.1 4.3,
    -7 4.2))') as the_geom
    UNION ALL
    SELECT ST_GeomFromEWKT('POINT(5 5 5)') as the_geom
    UNION ALL
    	SELECT ST_GeomFromEWKT('POINT(-2 3 1)') as the_geom
    UNION ALL
    SELECT ST_GeomFromEWKT('LINESTRING(5 5 5, 10 10 10)') as the_geom ) as foo;

    st_asewkt
    ---------
    GEOMETRYCOLLECTION(POINT(-2 3 1),LINESTRING(5 5 5,10 10 10),POLYGON((-7 4.2 5,-7.1 4.2 5,-7.1 4.3 5,-7 4.2 5)));

    --3d example not mixing dimensions
    SELECT ST_AsEWKT(st_union(the_geom))
    FROM
    (SELECT ST_GeomFromEWKT('POLYGON((-7 4.2 2,-7.1 4.2 3,-7.1 4.3 2,
    -7 4.2 2))') as the_geom
    UNION ALL
    SELECT ST_GeomFromEWKT('POINT(5 5 5)') as the_geom
    UNION ALL
    	SELECT ST_GeomFromEWKT('POINT(-2 3 1)') as the_geom
    UNION ALL
    SELECT ST_GeomFromEWKT('LINESTRING(5 5 5, 10 10 10)') as the_geom ) as foo;

    st_asewkt
    ---------
    GEOMETRYCOLLECTION(POINT(-2 3 1),LINESTRING(5 5 5,10 10 10),POLYGON((-7 4.2 2,-7.1 4.2 3,-7.1 4.3 2,-7 4.2 2)))

    --Examples using new Array construct
    SELECT ST_Union(ARRAY(SELECT the_geom FROM sometable));

    SELECT ST_AsText(ST_Union(ARRAY[ST_GeomFromText('LINESTRING(1 2, 3 4)'),
    			ST_GeomFromText('LINESTRING(3 4, 4 5)')])) As wktunion;

    --wktunion---
    MULTILINESTRING((3 4,4 5),(1 2,3 4))

## See Also

ST_Collect ST_UnaryUnion

## Name

ST_UnaryUnion — Like ST_Union, but working at the geometry component level.

## Synopsis

`geometry ST_UnaryUnion(`geometry geom`)`;

## Description

Unlike ST_Union, ST_UnaryUnion does dissolve boundaries between components of a multipolygon (invalid) and does perform union between the components of a geometrycollection. Each components of the input geometry is assumed to be valid, so you won't get a valid multipolygon out of a bow-tie polygon (invalid).

You may use this function to node a set of linestrings. You may mix ST_UnaryUnion with ST_Collect to fine-tune how many geometries at once you want to dissolve to be nice on both memory size and CPU time, finding the balance between ST_Union and ST_MemUnion.

This function supports 3d and will not drop the z-index.

Availability: 2.0.0 - requires GEOS >= 3.3.0.

## See Also

ST_Union ST_MemUnion ST_Collect

## 8.10. Linear Referencing

## Name

ST_Line_Interpolate_Point — Returns a point interpolated along a line. Second argument is a float8 between 0 and 1 representing fraction of total length of linestring the point has to be located.

## Synopsis

`geometry ST_Line_Interpolate_Point(`geometry a_linestring, float a_fraction`)`;

## Description

Returns a point interpolated along a line. First argument must be a LINESTRING. Second argument is a float8 between 0 and 1 representing fraction of total linestring length the point has to be located.

See ST_Line_Locate_Point for computing the line location nearest to a Point.

Since release 1.1.1 this function also interpolates M and Z values (when present), while prior releases set them to 0.0.

Availability: 0.8.2, Z and M supported added in 1.1.1

This function supports 3d and will not drop the z-index.

## Examples

A linestring with the interpolated point at 20% position (0.20)

    --Return point 20% along 2d line
    SELECT ST_AsEWKT(ST_Line_Interpolate_Point(the_line, 0.20))
    	FROM (SELECT ST_GeomFromEWKT('LINESTRING(25 50, 100 125, 150 190)') as the_line) As foo;
       st_asewkt
    ----------------
     POINT(51.5974135047432 76.5974135047432)

    --Return point mid-way of 3d line
    SELECT ST_AsEWKT(ST_Line_Interpolate_Point(the_line, 0.5))
    	FROM (SELECT ST_GeomFromEWKT('LINESTRING(1 2 3, 4 5 6, 6 7 8)') as the_line) As foo;

    	st_asewkt
    --------------------
     POINT(3.5 4.5 5.5)

    --find closest point on a line to a point or other geometry
     SELECT ST_AsText(ST_Line_Interpolate_Point(foo.the_line, ST_Line_Locate_Point(foo.the_line, ST_GeomFromText('POINT(4 3)'))))
    FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 4 5, 6 7)') As the_line) As foo;
       st_astext
    ----------------
     POINT(3 4)

## See Also

ST_AsText, ST_AsEWKT, ST_Length, ST_Line_Locate_Point

## Name

ST_Line_Locate_Point — Returns a float between 0 and 1 representing the location of the closest point on LineString to the given Point, as a fraction of total 2d line length.

## Synopsis

`float ST_Line_Locate_Point(`geometry a_linestring, geometry a_point`)`;

## Description

Returns a float between 0 and 1 representing the location of the closest point on LineString to the given Point, as a fraction of total 2d line length.

You can use the returned location to extract a Point (ST_Line_Interpolate_Point) or a substring (ST_Line_Substring).

This is useful for approximating numbers of addresses

Availability: 1.1.0

## Examples

    --Rough approximation of finding the street number of a point along the street
    --Note the whole foo thing is just to generate dummy data that looks
    --like house centroids and street
    --We use ST_DWithin to exclude
    --houses too far away from the street to be considered on the street
    SELECT ST_AsText(house_loc) As as_text_house_loc,
    	startstreet_num +
    		CAST( (endstreet_num - startstreet_num)
    			* ST_Line_Locate_Point(street_line, house_loc) As integer) As street_num
    FROM
    (SELECT ST_GeomFromText('LINESTRING(1 2, 3 4)') As street_line,
    	ST_MakePoint(x*1.01,y*1.03) As house_loc, 10 As startstreet_num,
    		20 As endstreet_num
    FROM generate_series(1,3) x CROSS JOIN generate_series(2,4) As y)
    As foo
    WHERE ST_DWithin(street_line, house_loc, 0.2);

     as_text_house_loc | street_num
    -------------------+------------
     POINT(1.01 2.06)  |         10
     POINT(2.02 3.09)  |         15
     POINT(3.03 4.12)  |         20

     --find closest point on a line to a point or other geometry
     SELECT ST_AsText(ST_Line_Interpolate_Point(foo.the_line, ST_Line_Locate_Point(foo.the_line, ST_GeomFromText('POINT(4 3)'))))
    FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 4 5, 6 7)') As the_line) As foo;
       st_astext
    ----------------
     POINT(3 4)

## See Also

ST_DWithin, ST_Length2D, ST_Line_Interpolate_Point, ST_Line_Substring

## Name

ST_Line_Substring — Return a linestring being a substring of the input one starting and ending at the given fractions of total 2d length. Second and third arguments are float8 values between 0 and 1.

## Synopsis

`geometry ST_Line_Substring(`geometry a_linestring, float startfraction, float endfraction`)`;

## Description

Return a linestring being a substring of the input one starting and ending at the given fractions of total 2d length. Second and third arguments are float8 values between 0 and 1. This only works with LINESTRINGs. To use with contiguous MULTILINESTRINGs use in conjunction with ST_LineMerge.

If 'start' and 'end' have the same value this is equivalent to ST_Line_Interpolate_Point.

See ST_Line_Locate_Point for computing the line location nearest to a Point.

Since release 1.1.1 this function also interpolates M and Z values (when present), while prior releases set them to unspecified values.

Availability: 1.1.0, Z and M supported added in 1.1.1

This function supports 3d and will not drop the z-index.

## Examples

A linestring seen with 1/3 midrange overlaid (0.333, 0.666)

    --Return the approximate 1/3 mid-range part of a linestring
    SELECT ST_AsText(ST_Line_SubString(ST_GeomFromText('LINESTRING(25 50, 100 125, 150 190)'), 0.333, 0.666));

    										   st_astext
    ------------------------------------------------------------------------------------------------
    LINESTRING(69.2846934853974 94.2846934853974,100 125,111.700356260683 140.210463138888)

    --The below example simulates a while loop in
    --SQL using PostgreSQL generate_series() to cut all
    --linestrings in a table to 100 unit segments
    -- of which no segment is longer than 100 units
    -- units are measured in the SRID units of measurement
    -- It also assumes all geometries are LINESTRING or contiguous MULTILINESTRING
    --and no geometry is longer than 100 units*10000
    --for better performance you can reduce the 10000
    --to match max number of segments you expect

    SELECT field1, field2, ST_Line_Substring(the_geom, 100.00*n/length,
      CASE
    	WHEN 100.00*(n+1) < length THEN 100.00*(n+1)/length
    	ELSE 1
      END) As the_geom
    FROM
      (SELECT sometable.field1, sometable.field2,
      ST_LineMerge(sometable.the_geom) AS the_geom,
      ST_Length(sometable.the_geom) As length
      FROM sometable
      ) AS t
    CROSS JOIN generate_series(0,10000) AS n
    WHERE n*100.00/length < 1;

## See Also

ST_Length, ST_Line_Interpolate_Point, ST_LineMerge

## Name

ST_LocateAlong — Return a derived geometry collection value with elements that match the specified measure. Polygonal elements are not supported.

## Synopsis

`geometry ST_LocateAlong(`geometry ageom_with_measure, float a_measure, float offset`)`;

## Description

Return a derived geometry collection value with elements that match the specified measure. Polygonal elements are not supported.

If an offset is provided, the resultant will be offset to the left or right of the input line by the specified number of units. A positive offset will be to the left, and a negative one to the right.

Semantic is specified by: ISO/IEC CD 13249-3:200x(E) - Text for Continuation CD Editing Meeting

Availability: 1.1.0 by old name ST_Locate_Along_Measure.

Changed: 2.0.0 in prior versions this used to be called ST_Locate_Along_Measure. The old name has been deprecated and will be removed in the future but is still available.

Use this function only for geometries with an M component

This function supports M coordinates.

## Examples

    SELECT ST_AsText(the_geom)
    		FROM
    		(SELECT ST_LocateAlong(
    			ST_GeomFromText('MULTILINESTRINGM((1 2 3, 3 4 2, 9 4 3),
    		(1 2 3, 5 4 5))'),3) As the_geom) As foo;

    						 st_asewkt
    -----------------------------------------------------------
     MULTIPOINT M (1 2 3)

    --Geometry collections are difficult animals so dump them
    --to make them more digestable
    SELECT ST_AsText((ST_Dump(the_geom)).geom)
    	FROM
    	(SELECT ST_LocateAlong(
    			ST_GeomFromText('MULTILINESTRINGM((1 2 3, 3 4 2, 9 4 3),
    	(1 2 3, 5 4 5))'),3) As the_geom) As foo;

       st_asewkt
    ---------------
     POINTM(1 2 3)
     POINTM(9 4 3)
     POINTM(1 2 3)

## See Also

ST_Dump, ST_LocateBetween

## Name

ST_LocateBetween — Return a derived geometry collection value with elements that match the specified range of measures inclusively. Polygonal elements are not supported.

## Synopsis

`geometry ST_LocateBetween(`geometry geomA, float measure_start, float measure_end, float offset`)`;

## Description

Return a derived geometry collection value with elements that match the specified range of measures inclusively. Polygonal elements are not supported.

Semantic is specified by: ISO/IEC CD 13249-3:200x(E) - Text for Continuation CD Editing Meeting

Availability: 1.1.0 by old name ST_Locate_Between_Measures.

Changed: 2.0.0 - in prior versions this used to be called ST_Locate_Between_Measures. The old name has been deprecated and will be removed in the future but is still available for backward compatibility.

This function supports M coordinates.

## Examples

    SELECT ST_AsText(the_geom)
    		FROM
    		(SELECT ST_LocateBetween(
    			ST_GeomFromText('MULTILINESTRING M ((1 2 3, 3 4 2, 9 4 3),
    		(1 2 3, 5 4 5))'),1.5, 3) As the_geom) As foo;

    							 st_asewkt
    ------------------------------------------------------------------------
     GEOMETRYCOLLECTION M (LINESTRING M (1 2 3,3 4 2,9 4 3),POINT M (1 2 3))

    --Geometry collections are difficult animals so dump them
    --to make them more digestable
    SELECT ST_AsText((ST_Dump(the_geom)).geom)
    		FROM
    		(SELECT ST_LocateBetween(
    			ST_GeomFromText('MULTILINESTRING M ((1 2 3, 3 4 2, 9 4 3),
    		(1 2 3, 5 4 5))'),1.5, 3) As the_geom) As foo;

    		   st_asewkt
    --------------------------------
     LINESTRING M (1 2 3,3 4 2,9 4 3)
     POINT M (1 2 3)

## See Also

ST_Dump, ST_LocateAlong

## Name

ST_LocateBetweenElevations — Return a derived geometry (collection) value with elements that intersect the specified range of elevations inclusively. Only 3D, 4D LINESTRINGS and MULTILINESTRINGS are supported.

## Synopsis

`geometry ST_LocateBetweenElevations(`geometry geom_mline, float elevation_start, float elevation_end`)`;

## Description

Return a derived geometry (collection) value with elements that intersect the specified range of elevations inclusively. Only 3D, 3DM LINESTRINGS and MULTILINESTRINGS are supported.

Availability: 1.4.0

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsEWKT(ST_LocateBetweenElevations(
    			ST_GeomFromEWKT('LINESTRING(1 2 3, 4 5 6)'),2,4)) As ewelev;
    								   ewelev
    ----------------------------------------------------------------
    	MULTILINESTRING((1 2 3,2 3 4))

    SELECT ST_AsEWKT(ST_LocateBetweenElevations(
    			ST_GeomFromEWKT('LINESTRING(1 2 6, 4 5 -1, 7 8 9)'),6,9)) As ewelev;

    				ewelev
    ----------------------------------------------------------------
    GEOMETRYCOLLECTION(POINT(1 2 6),LINESTRING(6.1 7.1 6,7 8 9))

    --Geometry collections are difficult animals so dump them
    --to make them more digestable
    SELECT ST_AsEWKT((ST_Dump(the_geom)).geom)
    		FROM
    		(SELECT ST_LocateBetweenElevations(
    			ST_GeomFromEWKT('LINESTRING(1 2 6, 4 5 -1, 7 8 9)'),6,9) As the_geom) As foo;

    		   st_asewkt
    --------------------------------
    POINT(1 2 6)
    LINESTRING(6.1 7.1 6,7 8 9)

## See Also

ST_Dump

## Name

ST_InterpolatePoint — Return the value of the measure dimension of a geometry at the point closed to the provided point.

## Synopsis

`float ST_InterpolatePoint(`geometry line, geometry point`)`;

## Description

Return the value of the measure dimension of a geometry at the point closed to the provided point.

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_InterpolatePoint('LINESTRING M (0 0 0, 10 0 20)', 'POINT(5 5)');
     st_interpolatepoint
     ---------------------
    			            10

## See Also

ST_AddMeasure, ST_LocateAlong, ST_LocateBetween

## Name

ST_AddMeasure — Return a derived geometry with measure elements linearly interpolated between the start and end points. If the geometry has no measure dimension, one is added. If the geometry has a measure dimension, it is over-written with new values. Only LINESTRINGS and MULTILINESTRINGS are supported.

## Synopsis

`geometry ST_AddMeasure(`geometry geom_mline, float measure_start, float measure_end`)`;

## Description

Return a derived geometry with measure elements linearly interpolated between the start and end points. If the geometry has no measure dimension, one is added. If the geometry has a measure dimension, it is over-written with new values. Only LINESTRINGS and MULTILINESTRINGS are supported.

Availability: 1.5.0

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsText(ST_AddMeasure(
    ST_GeomFromEWKT('LINESTRING(1 0, 2 0, 4 0)'),1,4)) As ewelev;
               ewelev
    --------------------------------
     LINESTRINGM(1 0 1,2 0 2,4 0 4)

    SELECT ST_AsText(ST_AddMeasure(
    ST_GeomFromEWKT('LINESTRING(1 0 4, 2 0 4, 4 0 4)'),10,40)) As ewelev;
                     ewelev
    ----------------------------------------
     LINESTRING(1 0 4 10,2 0 4 20,4 0 4 40)

    SELECT ST_AsText(ST_AddMeasure(
    ST_GeomFromEWKT('LINESTRINGM(1 0 4, 2 0 4, 4 0 4)'),10,40)) As ewelev;
                     ewelev
    ----------------------------------------
     LINESTRINGM(1 0 10,2 0 20,4 0 40)

    SELECT ST_AsText(ST_AddMeasure(
    ST_GeomFromEWKT('MULTILINESTRINGM((1 0 4, 2 0 4, 4 0 4),(1 0 4, 2 0 4, 4 0 4))'),10,70)) As ewelev;
                                 ewelev
    -----------------------------------------------------------------
     MULTILINESTRINGM((1 0 10,2 0 20,4 0 40),(1 0 40,2 0 50,4 0 70))

## 8.11. Long Transactions Support

This module and associated pl/pgsql functions have been implemented to provide long locking support required by Web Feature Service specification.

Users must use serializable transaction level otherwise locking mechanism would break.

## Name

AddAuth — Add an authorization token to be used in current transaction.

## Synopsis

`boolean AddAuth(`text auth_token`)`;

## Description

Add an authorization token to be used in current transaction.

Creates/adds to a temp table called temp_lock_have_table the current transaction identifier and authorization token key.

Availability: 1.1.3

## Examples

    		SELECT LockRow('towns', '353', 'priscilla');
    		BEGIN TRANSACTION;
    			SELECT AddAuth('joey');
    			UPDATE towns SET the_geom = ST_Translate(the_geom,2,2) WHERE gid = 353;
    		COMMIT;

    		---Error--
    		ERROR:  UPDATE where "gid" = '353' requires authorization 'priscilla'

## See Also

LockRow

## Name

CheckAuth — Creates trigger on a table to prevent/allow updates and deletes of rows based on authorization token.

## Synopsis

`integer CheckAuth(`text a_schema_name, text a_table_name, text a_key_column_name`)`;

`integer CheckAuth(`text a_table_name, text a_key_column_name`)`;

## Description

Creates trigger on a table to prevent/allow updates and deletes of rows based on authorization token. Identify rows using <rowid_col> column.

If a_schema_name is not passed in, then searches for table in current schema.

If an authorization trigger already exists on this table function errors. If Transaction support is not enabled, function throws an exception.

Availability: 1.1.3

## Examples

    			SELECT CheckAuth('public', 'towns', 'gid');
    			result
    			------
    			0

## See Also

EnableLongTransactions

## Name

DisableLongTransactions — Disable long transaction support. This function removes the long transaction support metadata tables, and drops all triggers attached to lock-checked tables.

## Synopsis

`text DisableLongTransactions(``)`;

## Description

Disable long transaction support. This function removes the long transaction support metadata tables, and drops all triggers attached to lock-checked tables.

Drops meta table called `authorization_table` and a view called `authorized_tables` and all triggers called `checkauthtrigger`

Availability: 1.1.3

## Examples

    SELECT DisableLongTransactions();
    --result--
    Long transactions support disabled

## See Also

EnableLongTransactions

## Name

EnableLongTransactions — Enable long transaction support. This function creates the required metadata tables, needs to be called once before using the other functions in this section. Calling it twice is harmless.

## Synopsis

`text EnableLongTransactions(``)`;

## Description

Enable long transaction support. This function creates the required metadata tables, needs to be called once before using the other functions in this section. Calling it twice is harmless.

Creates a meta table called `authorization_table` and a view called `authorized_tables`

Availability: 1.1.3

## Examples

    SELECT EnableLongTransactions();
    --result--
    Long transactions support enabled

## See Also

DisableLongTransactions

## Name

LockRow — Set lock/authorization for specific row in table

## Synopsis

`integer LockRow(`text a_schema_name, text a_table_name, text a_row_key, text an_auth_token, timestamp expire_dt`)`;

`integer LockRow(`text a_table_name, text a_row_key, text an_auth_token, timestamp expire_dt`)`;

`integer LockRow(`text a_table_name, text a_row_key, text an_auth_token`)`;

## Description

Set lock/authorization for specific row in table <authid> is a text value, <expires> is a timestamp defaulting to now()+1hour. Returns 1 if lock has been assigned, 0 otherwise (already locked by other auth)

Availability: 1.1.3

## Examples

    SELECT LockRow('public', 'towns', '2', 'joey');
    LockRow
    -------
    1

    --Joey has already locked the record and Priscilla is out of luck
    SELECT LockRow('public', 'towns', '2', 'priscilla');
    LockRow
    -------
    0

## See Also

UnlockRows

## Name

UnlockRows — Remove all locks held by specified authorization id. Returns the number of locks released.

## Synopsis

`integer UnlockRows(`text auth_token`)`;

## Description

Remove all locks held by specified authorization id. Returns the number of locks released.

Availability: 1.1.3

## Examples

    		SELECT LockRow('towns', '353', 'priscilla');
    		SELECT LockRow('towns', '2', 'priscilla');
    		SELECT UnLockRows('priscilla');
    		UnLockRows
    		------------
    		2

## See Also

LockRow

## 8.12. Miscellaneous Functions

## Name

ST_Accum — Aggregate. Constructs an array of geometries.

## Synopsis

`geometry[] ST_Accum(`geometry set geomfield`)`;

## Description

Aggregate. Constructs an array of geometries.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT (ST_Accum(the_geom)) As all_em, ST_AsText((ST_Accum(the_geom))[1]) As grabone,
    (ST_Accum(the_geom))[2:4] as grab_rest
    			FROM (SELECT ST_MakePoint(a*CAST(random()*10 As integer), a*CAST(random()*10 As integer), a*CAST(random()*10 As integer)) As the_geom
    				FROM generate_series(1,4) a) As foo;

    all_em|grabone   | grab_rest

    -------------------------------------------------------------------------------+

     {0101000080000000000000144000000000000024400000000000001040:
     0101000080000000000
    00018400000000000002C400000000000003040:
    0101000080000000000000354000000000000038400000000000001840:
    010100008000000000000040400000000000003C400000000000003040} |
     POINT(5 10) | {010100008000000000000018400000000000002C400000000000003040:
     0101000080000000000000354000000000000038400000000000001840:
     010100008000000000000040400000000000003C400000000000003040}
    (1 row)

## See Also

ST_Collect

## Name

Box2D — Returns a BOX2D representing the maximum extents of the geometry.

## Synopsis

`box2d Box2D(`geometry geomA`)`;

## Description

Returns a BOX2D representing the maximum extents of the geometry.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT Box2D(ST_GeomFromText('LINESTRING(1 2, 3 4, 5 6)'));
    	box2d
    	---------
    	BOX(1 2,5 6)

    	SELECT Box2D(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)'));
    	box2d
    	--------
    	BOX(220186.984375 150406,220288.25 150506.140625)

## See Also

Box3D, ST_GeomFromText

## Name

Box3D — Returns a BOX3D representing the maximum extents of the geometry.

## Synopsis

`box3d Box3D(`geometry geomA`)`;

## Description

Returns a BOX3D representing the maximum extents of the geometry.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Examples

    SELECT Box3D(ST_GeomFromEWKT('LINESTRING(1 2 3, 3 4 5, 5 6 5)'));
    	Box3d
    	---------
    	BOX3D(1 2 3,5 6 5)

    	SELECT Box3D(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 1,220227 150406 1)'));
    	Box3d
    	--------
    	BOX3D(220227 150406 1,220268 150415 1)

## See Also

Box2D, ST_GeomFromEWKT

## Name

ST_Estimated_Extent — Return the 'estimated' extent of the given spatial table. The estimated is taken from the geometry column's statistics. The current schema will be used if not specified.

## Synopsis

`box2d ST_Estimated_Extent(`text schema_name, text table_name, text geocolumn_name`)`;

`box2d ST_Estimated_Extent(`text table_name, text geocolumn_name`)`;

## Description

Return the 'estimated' extent of the given spatial table. The estimated is taken from the geometry column's statistics. The current schema will be used if not specified.

For PostgreSQL>=8.0.0 statistics are gathered by VACUUM ANALYZE and resulting extent will be about 95% of the real one.

In absence of statistics (empty table or no ANALYZE called) this function returns NULL. Prior to version 1.5.4 an exception was thrown instead.

For PostgreSQL<8.0.0 statistics are gathered by update_geometry_stats() and resulting extent will be exact.

Availability: 1.0.0

This method supports Circular Strings and Curves

## Examples

    SELECT ST_Estimated_extent('ny', 'edges', 'the_geom');
    --result--
    BOX(-8877653 4912316,-8010225.5 5589284)

    SELECT ST_Estimated_Extent('feature_poly', 'the_geom');
    --result--
    BOX(-124.659652709961 24.6830825805664,-67.7798080444336 49.0012092590332)

## See Also

ST_Extent

## Name

ST_Expand — Returns bounding box expanded in all directions from the bounding box of the input geometry. Uses double-precision

## Synopsis

`geometry ST_Expand(`geometry g1, float units_to_expand`)`;

`box2d ST_Expand(`box2d g1, float units_to_expand`)`;

`box3d ST_Expand(`box3d g1, float units_to_expand`)`;

## Description

This function returns a bounding box expanded in all directions from the bounding box of the input geometry, by an amount specified in the second argument. Uses double-precision. Very useful for distance() queries, or bounding box queries to add an index filter to the query.

There are 3 variants of this. The one that takes a geometry will return a POLYGON geometry representation of the bounding box and is the most commonly used variant.

ST_Expand is similar in concept to ST_Buffer except while buffer expands the geometry in all directions, ST_Expand expands the bounding box an x,y,z unit amount.

Units are in the units of the spatial reference system in use denoted by the SRID

Pre 1.3, ST_Expand was used in conjunction with distance to do indexable queries. Something of the form `the_geom && ST_Expand('POINT(10 20)', 10) AND ST_Distance(the_geom, 'POINT(10 20)') < 10` Post 1.2, this was replaced with the easier ST_DWithin construct.

Bounding boxes of all geometries are currently 2-d even if they are 3-dimensional geometries.

Availability: 1.5.0 behavior changed to output double precision instead of float4 coordinates.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

Examples below use US National Atlas Equal Area (SRID=2163) which is a meter projection

    --10 meter expanded box around bbox of a linestring
    SELECT CAST(ST_Expand(ST_GeomFromText('LINESTRING(2312980 110676,2312923 110701,2312892 110714)', 2163),10) As box2d);
    					 st_expand
    ------------------------------------
     BOX(2312882 110666,2312990 110724)

    --10 meter expanded 3d box of a 3d box
    SELECT ST_Expand(CAST('BOX3D(778783 2951741 1,794875 2970042.61545891 10)' As box3d),10)
    							  st_expand
    -----------------------------------------------------
     BOX3D(778773 2951731 -9,794885 2970052.61545891 20)

     --10 meter geometry astext rep of a expand box around a point geometry
     SELECT ST_AsEWKT(ST_Expand(ST_GeomFromEWKT('SRID=2163;POINT(2312980 110676)'),10));
    											st_asewkt
    -------------------------------------------------------------------------------------------------
     SRID=2163;POLYGON((2312970 110666,2312970 110686,2312990 110686,2312990 110666,2312970 110666))

## See Also

ST_AsEWKT, ST_Buffer, ST_DWithin, ST_GeomFromEWKT, ST_GeomFromText, ST_SRID

## Name

ST_Extent — an aggregate function that returns the bounding box that bounds rows of geometries.

## Synopsis

`box2d ST_Extent(`geometry set geomfield`)`;

## Description

ST_Extent returns a bounding box that encloses a set of geometries. The ST_Extent function is an "aggregate" function in the terminology of SQL. That means that it operates on lists of data, in the same way the SUM() and AVG() functions do.

Since it returns a bounding box, the spatial Units are in the units of the spatial reference system in use denoted by the SRID

ST_Extent is similar in concept to Oracle Spatial/Locator's SDO_AGGR_MBR

Since ST_Extent returns a bounding box, the SRID meta-data is lost. Use ST_SetSRID to force it back into a geometry with SRID meta data. The coordinates are in the units of the spatial ref of the orginal geometries.

ST_Extent will return boxes with only an x and y component even with (x,y,z) coordinate geometries. To maintain x,y,z use ST_3DExtent instead.

Availability: 1.4.0

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

Examples below use Massachusetts State Plane ft (SRID=2249)

    SELECT ST_Extent(the_geom) as bextent FROM sometable;
    					 st_bextent
    ------------------------------------
    BOX(739651.875 2908247.25,794875.8125 2970042.75)

    --Return extent of each category of geometries
    SELECT ST_Extent(the_geom) as bextent
    FROM sometable
    GROUP BY category ORDER BY category;

    					  bextent                       |         name
    ----------------------------------------------------+----------------
     BOX(778783.5625 2951741.25,794875.8125 2970042.75) | A
     BOX(751315.8125 2919164.75,765202.6875 2935417.25) | B
     BOX(739651.875 2917394.75,756688.375 2935866)      | C

     --Force back into a geometry
     -- and render the extended text representation of that geometry
    SELECT ST_SetSRID(ST_Extent(the_geom),2249) as bextent FROM sometable;

    				bextent
    --------------------------------------------------------------------------------
     SRID=2249;POLYGON((739651.875 2908247.25,739651.875 2970042.75,794875.8125 2970042.75,
     794875.8125 2908247.25,739651.875 2908247.25))

## See Also

ST_AsEWKT, ST_3DExtent, ST_SetSRID, ST_SRID

## Name

ST_3DExtent — an aggregate function that returns the box3D bounding box that bounds rows of geometries.

## Synopsis

`box3d ST_3DExtent(`geometry set geomfield`)`;

## Description

ST_3DExtent returns a box3d (includes Z coordinate) bounding box that encloses a set of geometries. The ST_3DExtent function is an "aggregate" function in the terminology of SQL. That means that it operates on lists of data, in the same way the SUM() and AVG() functions do.

Since it returns a bounding box, the spatial Units are in the units of the spatial reference system in use denoted by the SRID

Since ST_3DExtent returns a bounding box, the SRID meta-data is lost. Use ST_SetSRID to force it back into a geometry with SRID meta data. The coordinates are in the units of the spatial ref of the orginal geometries.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Changed: 2.0.0 In prior versions this used to be called ST_Extent3D

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_3DExtent(foo.the_geom) As b3extent
    FROM (SELECT ST_MakePoint(x,y,z) As the_geom
    	FROM generate_series(1,3) As x
    		CROSS JOIN generate_series(1,2) As y
    		CROSS JOIN generate_series(0,2) As Z) As foo;
    	  b3extent
    --------------------
     BOX3D(1 1 0,3 2 2)

    --Get the extent of various elevated circular strings
    SELECT ST_3DExtent(foo.the_geom) As b3extent
    FROM (SELECT ST_Translate(ST_Force_3DZ(ST_LineToCurve(ST_Buffer(ST_MakePoint(x,y),1))),0,0,z) As the_geom
    	FROM generate_series(1,3) As x
    		CROSS JOIN generate_series(1,2) As y
    		CROSS JOIN generate_series(0,2) As Z) As foo;

    	b3extent
    --------------------
     BOX3D(1 0 0,4 2 2)

## See Also

ST_Extent, ST_Force_3DZ

## Name

Find_SRID — The syntax is find_srid(<db/schema>, <table>, <column>) and the function returns the integer SRID of the specified column by searching through the GEOMETRY_COLUMNS table.

## Synopsis

`integer Find_SRID(`varchar a_schema_name, varchar a_table_name, varchar a_geomfield_name`)`;

## Description

The syntax is find_srid(<db/schema>, <table>, <column>) and the function returns the integer SRID of the specified column by searching through the GEOMETRY_COLUMNS table. If the geometry column has not been properly added with the AddGeometryColumns() function, this function will not work either.

## Examples

     SELECT Find_SRID('public', 'tiger_us_state_2007', 'the_geom_4269');
    find_srid
    ----------
    4269

## See Also

ST_SRID

## Name

ST_Mem_Size — Returns the amount of space (in bytes) the geometry takes.

## Synopsis

`integer ST_Mem_Size(`geometry geomA`)`;

## Description

Returns the amount of space (in bytes) the geometry takes.

This is a nice compliment to PostgreSQL built in functions pg_size_pretty, pg_relation_size, pg_total_relation_size.

pg_relation_size which gives the byte size of a table may return byte size lower than ST_Mem_Size. This is because pg_relation_size does not add toasted table contribution and large geometries are stored in TOAST tables. pg_total_relation_size - includes, the table, the toasted tables, and the indexes.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Return how much byte space Boston takes up  in our Mass data set
    SELECT pg_size_pretty(SUM(ST_Mem_Size(the_geom))) as totgeomsum,
    pg_size_pretty(SUM(CASE WHEN town = 'BOSTON' THEN st_mem_size(the_geom) ELSE 0 END)) As bossum,
    CAST(SUM(CASE WHEN town = 'BOSTON' THEN st_mem_size(the_geom) ELSE 0 END)*1.00 /
    		SUM(st_mem_size(the_geom))*100 As numeric(10,2)) As perbos
    FROM towns;

    totgeomsum	bossum	perbos
    ----------	------	------
    1522 kB		30 kB	1.99

    SELECT ST_Mem_Size(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)'));

    ---
    73

    --What percentage of our table is taken up by just the geometry
    SELECT pg_total_relation_size('public.neighborhoods') As fulltable_size, sum(ST_Mem_Size(the_geom)) As geomsize,
    sum(ST_Mem_Size(the_geom))*1.00/pg_total_relation_size('public.neighborhoods')*100 As pergeom
    FROM neighborhoods;
    fulltable_size geomsize  pergeom
    ------------------------------------------------
    262144         96238	 36.71188354492187500000

## See Also

## Name

ST_Point_Inside_Circle — Is the point geometry insert circle defined by center_x, center_y, radius

## Synopsis

`boolean ST_Point_Inside_Circle(`geometry a_point, float center_x, float center_y, float radius`)`;

## Description

The syntax for this functions is point_inside_circle(<geometry>,<circle_center_x>,<circle_center_y>,<radius>). Returns the true if the geometry is a point and is inside the circle. Returns false otherwise.

This only works for points as the name suggests

## Examples

    SELECT ST_Point_Inside_Circle(ST_Point(1,2), 0.5, 2, 3);
     st_point_inside_circle
    ------------------------
     t

## See Also

ST_DWithin

## 8.13. Exceptional Functions

These functions are rarely used functions that should only be used if your data is corrupted in someway. They are used for troubleshooting corruption and also fixing things that should under normal circumstances, never happen.

## Name

PostGIS_AddBBox — Add bounding box to the geometry.

## Synopsis

`geometry PostGIS_AddBBox(`geometry geomA`)`;

## Description

Add bounding box to the geometry. This would make bounding box based queries faster, but will increase the size of the geometry.

Bounding boxes are automatically added to geometries so in general this is not needed unless the generated bounding box somehow becomes corrupted or you have an old install that is lacking bounding boxes. Then you need to drop the old and readd.

This method supports Circular Strings and Curves

## Examples

    UPDATE sometable
     SET the_geom =  PostGIS_AddBBox(the_geom)
     WHERE PostGIS_HasBBox(the_geom) = false;

## See Also

PostGIS_DropBBox, PostGIS_HasBBox

## Name

PostGIS_DropBBox — Drop the bounding box cache from the geometry.

## Synopsis

`geometry PostGIS_DropBBox(`geometry geomA`)`;

## Description

Drop the bounding box cache from the geometry. This reduces geometry size, but makes bounding-box based queries slower. It is also used to drop a corrupt bounding box. A tale-tell sign of a corrupt cached bounding box is when your ST_Intersects and other relation queries leave out geometries that rightfully should return true.

Bounding boxes are automatically added to geometries and improve speed of queries so in general this is not needed unless the generated bounding box somehow becomes corrupted or you have an old install that is lacking bounding boxes. Then you need to drop the old and readd. This kind of corruption has been observed in 8.3-8.3.6 series whereby cached bboxes were not always recalculated when a geometry changed and upgrading to a newer version without a dump reload will not correct already corrupted boxes. So one can manually correct using below and readd the bbox or do a dump reload.

This method supports Circular Strings and Curves

## Examples

    --This example drops bounding boxes where the cached box is not correct
    			--The force to ST_AsBinary before applying Box2D forces a recalculation of the box, and Box2D applied to the table geometry always
    			-- returns the cached bounding box.
    			UPDATE sometable
     SET the_geom =  PostGIS_DropBBox(the_geom)
     WHERE Not (Box2D(ST_AsBinary(the_geom)) = Box2D(the_geom));

    	UPDATE sometable
     SET the_geom =  PostGIS_AddBBox(the_geom)
     WHERE Not PostGIS_HasBBOX(the_geom);

## See Also

PostGIS_AddBBox, PostGIS_HasBBox, Box2D

## Name

PostGIS_HasBBox — Returns TRUE if the bbox of this geometry is cached, FALSE otherwise.

## Synopsis

`boolean PostGIS_HasBBox(`geometry geomA`)`;

## Description

Returns TRUE if the bbox of this geometry is cached, FALSE otherwise. Use PostGIS_AddBBox and PostGIS_DropBBox to control caching.

This method supports Circular Strings and Curves

## Examples

    SELECT the_geom
    FROM sometable WHERE PostGIS_HasBBox(the_geom) = false;

## See Also

PostGIS_AddBBox, PostGIS_DropBBox

## Chapter 9. Raster Reference

The functions given below are the ones which a user of PostGIS Raster is likely to need and which are currently available in PostGIS Raster. There are other functions which are required support functions to the raster objects which are not of use to a general user.

`raster` is a new PostGIS type for storing and analyzing raster data.

For loading rasters from raster files please refer to Section 5.1, “Loading and Creating Rasters”

For the examples in this reference we will be using a raster table of dummy rasters - Formed with the following code

    CREATE TABLE dummy_rast(rid integer, rast raster);
    INSERT INTO dummy_rast(rid, rast)
    VALUES (1,
    ('01' -- little endian (uint8 ndr)
    ||
    '0000' -- version (uint16 0)
    ||
    '0000' -- nBands (uint16 0)
    ||
    '0000000000000040' -- scaleX (float64 2)
    ||
    '0000000000000840' -- scaleY (float64 3)
    ||
    '000000000000E03F' -- ipX (float64 0.5)
    ||
    '000000000000E03F' -- ipY (float64 0.5)
    ||
    '0000000000000000' -- skewX (float64 0)
    ||
    '0000000000000000' -- skewY (float64 0)
    ||
    '00000000' -- SRID (int32 0)
    ||
    '0A00' -- width (uint16 10)
    ||
    '1400' -- height (uint16 20)
    )::raster
    ),
    -- Raster: 5 x 5 pixels, 3 bands, PT_8BUI pixel type, NODATA = 0
    (2,  ('01000003009A9999999999A93F9A9999999999A9BF000000E02B274A' ||
    '41000000007719564100000000000000000000000000000000FFFFFFFF050005000400FDFEFDFEFEFDFEFEFDF9FAFEF' ||
    'EFCF9FBFDFEFEFDFCFAFEFEFE04004E627AADD16076B4F9FE6370A9F5FE59637AB0E54F58617087040046566487A1506CA2E3FA5A6CAFFBFE4D566DA4CB3E454C5665')::raster);

## 9.1. Raster Support Data types

Abstract

This section lists the PostgreSQL data types specifically created to support raster functionality.

## Name

geomval — A spatial datatype with two fields - geom (holding a geometry object) and val (holding a double precision pixel value from a raster band).

## Description

geomval is a compound data type consisting of a geometry object referenced by the .geom field and val, a double precision value that represents the pixel value at a particular geometric location in a raster band. It is used by the ST_DumpAsPolygon and Raster intersection family of functions as an output type to explode a raster band into geometry polygons.

## See Also

Section 13.5, “PostGIS Geometry / Geography / Raster Dump Functions”

## Name

histogram — A composite type used as record output of the ST_Histogram and ST_ApproxHistogram functions.

## Description

A composite type used as record outputs of the ST_Histogram `ST_ApproxHistogram` functions. Note that depending on `exclude_nodata_value` of function, may or may not contain nodata pixels.

Each histogram record in results corresponds to a bin for a selected raster band.

`min` double precision

  minimum pixel value in this bin

`max` double precision

  Maximum pixel value in this bin.

`count` integer

  count of pixels in this bin.

`percent` double precision

  Percent of pixels of the overall population in this bin.

## See Also

ST_Histogram

## Name

raster — raster spatial data type.

## Description

raster is a spatial data type used to represent raster data such as those imported from jpegs, tiffs, pngs, digital elevation models. Each raster has 1 or more bands each having a set of pixel values. Rasters can be georeferenced.

Requires PostGIS be compiled with GDAL support. Currently rasters can be implicitly converted to geometry type, but the conversion returns the ST_ConvexHull of the raster. This auto casting may be removed in the near future so don't rely on it.

## Casting Behavior

This section lists the automatic as well as explicit casts allowed for this data type

Cast To | Behavior
geometry | automatic

## See Also

Chapter 9, Raster Reference

## Name

reclassarg — A composite type used as input into the ST_Reclass function defining the behavior of reclassification.

## Description

A composite type used as input into the ST_Reclass function defining the behavior of reclassification.

`nband` integer

  The band number of band to reclassify.

`reclassexpr` text

  range expression consisting of comma delimited range:map_range mappings. : to define mapping that defines how to map old band values to new band values. ( means >, ) means less than, ] < or equal, [ means > or equal

      1. [a-b] = a <= x <= b

      2. (a-b] = a < x <= b

      3. [a-b) = a <= x < b

      4. (a-b) = a < x < b

  ( notation is optional so a-b means the same as (a-b)

`pixeltype` text

  One of defined pixel types as described in ST_BandPixelType

`nodataval` double precision

  Value to treat as no data. For image outputs that support transparency, these will be blank.

## Example: Reclassify band 2 as an 8BUI where 255 is nodata value

    SELECT ROW(2, '0-100:1-10, 101-500:11-150,501 - 10000: 151-254', '8BUI', 255)::reclassarg;

## Example: Reclassify band 1 as an 1BB and no nodata value defined

    SELECT ROW(1, '0-100]:0, (100-255:1', '1BB', NULL)::reclassarg;

## See Also

ST_Reclass

## Name

summarystats — A composite type used as output of the ST_SummaryStats function.

## Description

A composite type used as output the `ST_SummaryStats` function. Note that depending on `exclude_nodata_value` of function, may or may not contain nodata pixels.

`count` bigint

  count of pixels in raster band. Depending on arguments may or many not include nodata pixel values.

`sum` double precision

  sum of all pixel values in band

`mean` double precision

  Mean of pixel values

`stddev` double precision

  Standard deviation of pixel values.

`min` double precision

  Minimum pixel value

`max` double precision

  Maximum pixel value

## See Also

ST_SummaryStats

## 9.2. Raster Management

## Name

AddRasterConstraints — Adds raster constraints to a loaded raster table for a specific column that constrains spatial ref, scaling, blocksize, alignment, bands, band type and a flag to denote if raster column is regularly blocked. The table must be loaded with data for the constraints to be inferred. Returns true of the constraint setting was accomplished and if issues a notice.

## Synopsis

`boolean AddRasterConstraints(`name rasttable, name rastcolumn, boolean srid, boolean scale_x, boolean scale_y, boolean blocksize_x, boolean blocksize_y, boolean same_alignment, boolean regular_blocking, boolean num_bands=true , boolean pixel_types=true , boolean nodata_values=true , boolean out_db=true , boolean extent=true `)`;

`boolean AddRasterConstraints(`name rasttable, name rastcolumn, text[] VARIADIC constraints`)`;

`boolean AddRasterConstraints(`name rastschema, name rasttable, name rastcolumn, text[] VARIADIC constraints`)`;

`boolean AddRasterConstraints(`name rastschema, name rasttable, name rastcolumn, boolean srid=true, boolean scale_x=true, boolean scale_y=true, boolean blocksize_x=true, boolean blocksize_y=true, boolean same_alignment=true, boolean regular_blocking=true, boolean num_bands=true, boolean pixel_types=true, boolean nodata_values=true , boolean out_db=true , boolean extent=true `)`;

## Description

Generates constraints on a raster column that are used to display information in the `raster_columns` raster catalog. The `rastschema` is the name of the table schema the table resides in. The `srid` must be an integer value reference to an entry in the SPATIAL_REF_SYS table.

`raster2pgsql` loader uses this function to register raster tables

Valid constraint names to pass in: refer to Section 5.2.1, “Raster Columns Catalog” for more details.

- `blocksize` sets both X and Y blocksize

- `blocksize_x` sets X tile (width in pixels of each tile)

- `blocksize_y` sets Y tile (height in pixels of each tile)

- `extent` computes extent of whole table and applys constraint all rasters must be within that extent

- `num_bands` number of bands

- `pixel_types` reads array of pixel types for each band ensure all band n have same pixel type

- `regular_blocking` apply informational flag to denote all tiles are regularly blocked

- `same_alignment` ensures they all have same alignment meaning any two tiles you compare will return true for. Refer to ST_SameAlignment

- `srid` ensures all have same srid

- More -- any listed as inputs into the above functions

This function infers the constraints from the data already present in the table. As such for it to work, you must create the raster column first and then load it with data.

If you need to load more data in your tables after you have already applied constraints, you may want to run the DropRasterConstraints if the extent of your data has changed.

Availability: 2.0.0

## Examples: Apply all possible constraints on column based on data

    CREATE TABLE myrasters(rid SERIAL primary key, rast raster);
    INSERT INTO myrasters(rast)
    SELECT ST_AddBand(ST_MakeEmptyRaster(1000, 1000, 0.3, -0.3, 2, 2, 0, 0,4326), 1, '8BSI'::text, -129, NULL);

    SELECT AddRasterConstraints('myrasters'::name, 'rast'::name);

    -- verify if registered correctly in the raster_columns view --
    SELECT srid, scale_x, scale_y, blocksize_x, blocksize_y, num_bands, pixel_types, nodata_values
    	FROM raster_columns
    	WHERE r_table_name = 'myrasters';

     srid | scale_x | scale_y | blocksize_x | blocksize_y | num_bands | pixel_types| nodata_values
    ------+---------+---------+-------------+-------------+-----------+-------------+---------------
     4326 |       2 |       2 |        1000 |        1000 |         1 | {8BSI}      | {0}

## Examples: Apply single constraint

    CREATE TABLE public.myrasters2(rid SERIAL primary key, rast raster);
    INSERT INTO myrasters2(rast)
    SELECT ST_AddBand(ST_MakeEmptyRaster(1000, 1000, 0.3, -0.3, 2, 2, 0, 0,4326), 1, '8BSI'::text, -129, NULL);

    SELECT AddRasterConstraints('public'::name, 'myrasters2'::name, 'rast'::name,'regular_blocking', 'blocksize');
    -- get notice--
    NOTICE:  Adding regular blocking constraint
    INFO:  The regular_blocking constraint is just a flag indicating that the column "rast" is regularly blocked.  As no function exist yet to assert that a raster column is regularly blocked, it is up to the end-user to ensure that the column is truly regularly blocked.
    CONTEXT:  PL/pgSQL function "addrasterconstraints" line 85 at assignment
    NOTICE:  Adding blocksize-X constraint
    NOTICE:  Adding blocksize-Y constraint

## See Also

Section 5.2.1, “Raster Columns Catalog”, ST_AddBand, ST_MakeEmptyRaster, DropRasterConstraints, ST_BandPixelType, ST_SRID

## Name

DropRasterConstraints — Drops PostGIS raster constraints that refer to a raster table column. Useful if you need to reload data or update your raster column data.

## Synopsis

`boolean DropRasterConstraints(`name rasttable, name rastcolumn, boolean srid, boolean scale_x, boolean scale_y, boolean blocksize_x, boolean blocksize_y, boolean same_alignment, boolean regular_blocking, boolean num_bands=true, boolean pixel_types=true, boolean nodata_values=true, boolean out_db=true , boolean extent=true`)`;

`boolean DropRasterConstraints(`name rastschema, name rasttable, name rastcolumn, boolean srid=true, boolean scale_x=true, boolean scale_y=true, boolean blocksize_x=true, boolean blocksize_y=true, boolean same_alignment=true, boolean regular_blocking=true, boolean num_bands=true, boolean pixel_types=true, boolean nodata_values=true, boolean out_db=true , boolean extent=true`)`;

`boolean DropRasterConstraints(`name rastschema, name rasttable, name rastcolumn, text[] constraints`)`;

## Description

Drops PostGIS raster constraints that refer to a raster table column that were added by AddRasterConstraints. Useful if you need to load more data or update your raster column data. You do not need to do this if you want to get rid of a raster table or a raster column.

To drop a raster table use the standard

    DROP TABLE mytable

To drop just a raster column and leave the rest of the table, use standard SQL

    ALTER TABLE mytable DROP COLUMN rast

the table will disappear from the `raster_columns` catalog if the column or table is dropped. However if only the constraints are dropped, the raster column will still be listed in the `raster_columns` catalog, but there will be no other information about it aside from the column name and table.

Availability: 2.0.0

## Examples

    SELECT DropRasterConstraints ('myrasters','rast');
    ----RESULT output ---
    t

    -- verify change in raster_columns --
    SELECT srid, scale_x, scale_y, blocksize_x, blocksize_y, num_bands, pixel_types, nodata_values
    	FROM raster_columns
    	WHERE r_table_name = 'myrasters';

     srid | scale_x | scale_y | blocksize_x | blocksize_y | num_bands | pixel_types| nodata_values
    ------+---------+---------+-------------+-------------+-----------+-------------+---------------
        0 |         |         |             |             |           |             |

## See Also

AddRasterConstraints

## Name

PostGIS_Raster_Lib_Build_Date — Reports full raster library build date.

## Synopsis

`text PostGIS_Raster_Lib_Build_Date(``)`;

## Description

Reports raster build date

## Examples

    SELECT PostGIS_Raster_Lib_Build_Date();
    postgis_raster_lib_build_date
    -----------------------------
    2010-04-28 21:15:10

## See Also

PostGIS_Raster_Lib_Version

## Name

PostGIS_Raster_Lib_Version — Reports full raster version and build configuration infos.

## Synopsis

`text PostGIS_Raster_Lib_Version(``)`;

## Description

Reports full raster version and build configuration infos.

## Examples

    SELECT PostGIS_Raster_Lib_Version();
    postgis_raster_lib_version
    -----------------------------
     2.0.0

## See Also

PostGIS_Lib_Version

## Name

ST_GDALDrivers — Returns a list of raster formats supported by your lib gdal. These are the formats you can output your raster using ST_AsGDALRaster.

## Synopsis

`setof record ST_GDALDrivers(`integer OUT idx, text OUT short_name, text OUT long_name, text OUT create_options`)`;

## Description

Returns a list of raster formats short_name,long_name and creator options of each format supported by your lib gdal. Use the short_name as input in the `format` parameter of ST_AsGDALRaster. Options vary depending on what drivers your libgdal was compiled with. `create_options` returns an xml formatted set of CreationOptionList/Option consisting of name and optional `type`, `description` and set of `VALUE` for each creator option for the specific driver.

Availability: 2.0.0 - requires GDAL >= 1.6.0.

## Examples: List of Drivers

    SELECT short_name, long_name
    FROM st_gdaldrivers()
    ORDER BY short_name;
      short_name    |              long_name
    ----------------+--------------------------------------
    AAIGrid         | Arc/Info ASCII Grid
    DTED            | DTED Elevation Raster
    EHdr            | ESRI .hdr Labelled
    FIT             | FIT Image
    GIF             | Graphics Interchange Format (.gif)
    GSAG            | Golden Software ASCII Grid (.grd)
    GSBG            | Golden Software Binary Grid (.grd)
    GTiff           | GeoTIFF
    HF2             | HF2/HFZ heightfield raster
    HFA             | Erdas Imagine Images (.img)
    ILWIS           | ILWIS Raster Map
    INGR            | Intergraph Raster
    JPEG            | JPEG JFIF
    KMLSUPEROVERLAY | Kml Super Overlay
    NITF            | National Imagery Transmission Format
    PNG             | Portable Network Graphics
    R               | R Object Data Store
    SAGA            | SAGA GIS Binary Grid (.sdat)
    SRTMHGT         | SRTMHGT File Format
    USGSDEM         | USGS Optional ASCII DEM (and CDED)
    VRT             | Virtual Raster
    XPM             | X11 PixMap Format

## Example: List of options for each driver

    -- Output the create options XML column of JPEG as a table  --
    -- Note you can use these creator options in ST_AsGDALRaster options argument
    SELECT (xpath('@name', g.opt))[1]::text As oname,
           (xpath('@type', g.opt))[1]::text As otype,
           (xpath('@description', g.opt))[1]::text As descrip
    FROM (SELECT unnest(xpath('/CreationOptionList/Option', create_options::xml)) As opt
    FROM  st_gdaldrivers()
    WHERE short_name = 'JPEG') As g;

        oname    |  otype  |           descrip
    -------------+---------+-----------------------------
     PROGRESSIVE | boolean |
     QUALITY     | int     | good=100, bad=0, default=75
     WORLDFILE   | boolean |

    -- raw xml output for creator options for GeoTiff --
    SELECT create_options
    FROM st_gdaldrivers()
    WHERE short_name = 'GTiff';

    <CreationOptionList>
        <Option name="COMPRESS" type="string-select">
            <Value>NONE</Value>
            <Value>LZW</Value>
            <Value>PACKBITS</Value>
            <Value>JPEG</Value>
            <Value>CCITTRLE</Value>
            <Value>CCITTFAX3</Value>
            <Value>CCITTFAX4</Value>
            <Value>DEFLATE</Value>
        </Option>
        <Option name="PREDICTOR" type="int" description="Predictor Type"/>
        <Option name="JPEG_QUALITY" type="int" description="JPEG quality 1-100" default="75"/>
        <Option name="ZLEVEL" type="int" description="DEFLATE compression level 1-9" default="6"/>
        <Option name="NBITS" type="int" description="BITS for sub-byte files (1-7), sub-uint16 (9-15), sub-uint32 (17-31)"/>
        <Option name="INTERLEAVE" type="string-select" default="PIXEL">
            <Value>BAND</Value>
            <Value>PIXEL</Value>
        </Option>
        <Option name="TILED" type="boolean" description="Switch to tiled format"/>
        <Option name="TFW" type="boolean" description="Write out world file"/>
        <Option name="RPB" type="boolean" description="Write out .RPB (RPC) file"/>
        <Option name="BLOCKXSIZE" type="int" description="Tile Width"/>
        <Option name="BLOCKYSIZE" type="int" description="Tile/Strip Height"/>
        <Option name="PHOTOMETRIC" type="string-select">
            <Value>MINISBLACK</Value>
            <Value>MINISWHITE</Value>
            <Value>PALETTE</Value>
            <Value>RGB</Value>
            <Value>CMYK</Value>
            <Value>YCBCR</Value>
            <Value>CIELAB</Value>
            <Value>ICCLAB</Value>
            <Value>ITULAB</Value>
        </Option>
        <Option name="SPARSE_OK" type="boolean" description="Can newly created files have missing blocks?" default="FALSE"/>
        <Option name="ALPHA" type="boolean" description="Mark first extrasample as being alpha"/>
        <Option name="PROFILE" type="string-select" default="GDALGeoTIFF">
            <Value>GDALGeoTIFF</Value>
            <Value>GeoTIFF</Value>
            <Value>BASELINE</Value>
        </Option>
        <Option name="PIXELTYPE" type="string-select">
            <Value>DEFAULT</Value>
            <Value>SIGNEDBYTE</Value>
        </Option>
        <Option name="BIGTIFF" type="string-select" description="Force creation of BigTIFF file">
            <Value>YES</Value>
            <Value>NO</Value>
            <Value>IF_NEEDED</Value>
            <Value>IF_SAFER</Value>
        </Option>
        <Option name="ENDIANNESS" type="string-select" default="NATIVE" description="Force endianness of created file. For DEBUG purpose mostly">
            <Value>NATIVE</Value>
            <Value>INVERTED</Value>
            <Value>LITTLE</Value>
            <Value>BIG</Value>
        </Option>
        <Option name="COPY_SRC_OVERVIEWS" type="boolean" default="NO" description="Force copy of overviews of source dataset (CreateCopy())"/>
    </CreationOptionList>

    -- Output the create options XML column for GTiff as a table  --
    SELECT (xpath('@name', g.opt))[1]::text As oname,
           (xpath('@type', g.opt))[1]::text As otype,
           (xpath('@description', g.opt))[1]::text As descrip,
           array_to_string(xpath('Value/text()', g.opt),', ') As vals
    FROM (SELECT unnest(xpath('/CreationOptionList/Option', create_options::xml)) As opt
    FROM  st_gdaldrivers()
    WHERE short_name = 'GTiff') As g;

           oname        |     otype     |                               descrip                                |                                   vals
    --------------------+---------------+----------------------------------------------------------------------+---------------------------------------------------------------------------
     COMPRESS           | string-select |                                                                      | NONE, LZW, PACKBITS, JPEG, CCITTRLE, CCITTFAX3, CCITTFAX4, DEFLATE
     PREDICTOR          | int           | Predictor Type                                                       |
     JPEG_QUALITY       | int           | JPEG quality 1-100                                                   |
     ZLEVEL             | int           | DEFLATE compression level 1-9                                        |
     NBITS              | int           | BITS for sub-byte files (1-7), sub-uint16 (9-15), sub-uint32 (17-31) |
     INTERLEAVE         | string-select |                                                                      | BAND, PIXEL
     TILED              | boolean       | Switch to tiled format                                               |
     TFW                | boolean       | Write out world file                                                 |
     RPB                | boolean       | Write out .RPB (RPC) file                                            |
     BLOCKXSIZE         | int           | Tile Width                                                           |
     BLOCKYSIZE         | int           | Tile/Strip Height                                                    |
     PHOTOMETRIC        | string-select |                                                                      | MINISBLACK, MINISWHITE, PALETTE, RGB, CMYK, YCBCR, CIELAB, ICCLAB, ITULAB
     SPARSE_OK          | boolean       | Can newly created files have missing blocks?                         |
     ALPHA              | boolean       | Mark first extrasample as being alpha                                |
     PROFILE            | string-select |                                                                      | GDALGeoTIFF, GeoTIFF, BASELINE
     PIXELTYPE          | string-select |                                                                      | DEFAULT, SIGNEDBYTE
     BIGTIFF            | string-select | Force creation of BigTIFF file                                       | YES, NO, IF_NEEDED, IF_SAFER
     ENDIANNESS         | string-select | Force endianness of created file. For DEBUG purpose mostly           | NATIVE, INVERTED, LITTLE, BIG
     COPY_SRC_OVERVIEWS | boolean       | Force copy of overviews of source dataset (CreateCopy())             |
    (19 rows)

## See Also

ST_AsGDALRaster, ST_SRID

## 9.3. Raster Constructors

## Name

ST_AddBand — Returns a raster with the new band(s) of given type added with given initial value in the given index location. If no index is specified, the band is added to the end.

## Synopsis

`raster ST_AddBand(`raster rast, text pixeltype, double precision initialvalue=0, double precision nodataval=NULL`)`;

`raster ST_AddBand(`raster rast, integer index, text pixeltype, double precision initialvalue=0, double precision nodataval=NULL`)`;

`raster ST_AddBand(`raster torast, raster fromrast, integer fromband=1, integer torastindex=at_end`)`;

`raster ST_AddBand(`raster torast, raster[] fromrasts, integer fromband=1`)`;

## Description

Returns a raster with a new band added in given position (index), of given type, of given initial value, and of given nodata value. If no index is specified, the band is added to the end. If no `fromband` is specified, band 1 is assumed. Pixel type is a string representation of one of the pixel types specified in ST_BandPixelType. If an existing index is specified all subsequent bands >= that index are incremented by 1. If an initial value greater than the max of the pixel type is specified, then the initial value is set to the highest value allowed by the pixel type. The last version add the `fromband` from `fromrast` raster to `torast` in position `torastindex`.

For the version that takes an array of bands if `torast` is NULL, then the `fromband` band of each raster in the array is accumulated into a new raster

## Examples: Single Add Band versions

    -- Add another band of type 8 bit unsigned integer with pixels initialized to 200
    UPDATE dummy_rast
        SET rast = ST_AddBand(rast,'8BUI'::text,200)
    WHERE rid = 1;

    -- Create an empty raster 100x100 units, with upper left  right at 0, add 2 bands (band 1 is 0/1 boolean bit switch, band2 allows values 0-15)
    INSERT INTO dummy_rast(rid,rast)
        VALUES(10, ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(100, 100, 0, 0, 1, -1, 0, 0, 0), '1BB'::text), '4BUI'::text) );

    -- output meta data of raster bands to verify all is right --
    SELECT  (bmd).*
    FROM (SELECT ST_BandMetaData(rast,generate_series(1,2)) As bmd
        FROM dummy_rast WHERE rid = 10) AS foo;
     --result --
     pixeltype | nodatavalue | isoutdb | path
    -----------+----------------+-------------+---------+------
     1BB       |             | f       |
     4BUI      |             | f       |

    -- output meta data of raster -
    SELECT  (rmd).width, (rmd).height, (rmd).numbands
    FROM (SELECT ST_MetaData(rast) As rmd
        FROM dummy_rast WHERE rid = 10) AS foo;
    -- result --
     upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands
    ------------+------------+-------+--------+------------+------------+-------+-------+------+----------
              0 |          0 |   100 |    100 |      1 |     -1 |     0 |     0 |   0 |        2

## Examples: Multi-Band versions

    -- Aggregate the 1st band of a table of like rasters into a single raster
    -- with as many bands as there are test_types and as many rows (new rasters) as there are mice
    -- NOTE: The ORDER BY test_type is only supported in PostgreSQL 9.0+
    -- for 8.4 and below it usually works to order your data in a subselect (but not guaranteed)
    -- The resulting raster will have a band for each test_type alphabetical by test_type
    -- For mouse lovers: No mice were harmed in this exercise
    SELECT mouse, ST_AddBand(NULL, array_agg(rast ORDER BY test_type), 1 ) As rast
    	FROM mice_studies
    			GROUP BY mouse;

## See Also

ST_BandMetaData, ST_BandPixelType, ST_MakeEmptyRaster, ST_MetaData, ST_NumBands, ST_Reclass

## Name

ST_AsRaster — Converts a PostGIS geometry to a PostGIS raster.

## Synopsis

`raster ST_AsRaster(`geometry geom, raster ref, text pixeltype, double precision value=1, double precision nodataval=0, boolean touched=false`)`;

`raster ST_AsRaster(`geometry geom, raster ref, text[] pixeltype=ARRAY['8BUI'], double precision[] value=ARRAY[1], double precision[] nodataval=ARRAY[0], boolean touched=false`)`;

`raster ST_AsRaster(`geometry geom, double precision scalex, double precision scaley, double precision gridx, double precision gridy, text pixeltype, double precision value=1, double precision nodataval=0, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(`geometry geom, double precision scalex, double precision scaley, double precision gridx=NULL, double precision gridy=NULL, text[] pixeltype=ARRAY['8BUI'], double precision[] value=ARRAY[1], double precision[] nodataval=ARRAY[0], double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(`geometry geom, double precision scalex, double precision scaley, text pixeltype, double precision value=1, double precision nodataval=0, double precision upperleftx=NULL, double precision upperlefty=NULL, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(`geometry geom, double precision scalex, double precision scaley, text[] pixeltype, double precision[] value=ARRAY[1], double precision[] nodataval=ARRAY[0], double precision upperleftx=NULL, double precision upperlefty=NULL, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(`geometry geom, integer width, integer height, double precision gridx, double precision gridy, text pixeltype, double precision value=1, double precision nodataval=0, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(`geometry geom, integer width, integer height, double precision gridx=NULL, double precision gridy=NULL, text[] pixeltype=ARRAY['8BUI'], double precision[] value=ARRAY[1], double precision[] nodataval=ARRAY[0], double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(`geometry geom, integer width, integer height, text pixeltype, double precision value=1, double precision nodataval=0, double precision upperleftx=NULL, double precision upperlefty=NULL, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(`geometry geom, integer width, integer height, text[] pixeltype, double precision[] value=ARRAY[1], double precision[] nodataval=ARRAY[0], double precision upperleftx=NULL, double precision upperlefty=NULL, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

## Description

Converts a PostGIS geometry to a PostGIS raster. The many variants offers three groups of possibilities for setting the alignment and pixelsize of the resulting raster.

The first group, composed of the two first variants, produce a raster having the same alignment (`scalex`, `scaley`, `gridx` and `gridy`), pixel type and nodata value as the provided reference raster. You generally pass this reference raster by joining the table containing the geometry with the table containing the reference raster.

The second group, composed of four variants, let you set the dimensions of the raster by providing the parameters of a pixel size (`scalex` & `scaley` and `skewx` & `skewy`). The `width` & `height` of the resulting raster will be adjusted to fit the extent of the geometry. In most cases, you must cast integer `scalex` & `scaley` arguments to double precision so that PostgreSQL choose the right variant.

The third group, composed of four variants, let you fix the dimensions of the raster by providing the dimensions of the raster (`width` & `height`). The parameters of the pixel size (`scalex` & `scaley` and `skewx` & `skewy`) of the resulting raster will be adjusted to fit the extent of the geometry.

The two first variants of each of those two last groups let you specify the alignment with an arbitrary corner of the alignment grid (`gridx` & `gridy`) and the two last variants takes the upper left corner (`upperleftx` & `upperlefty`).

Each group of variant allows producing a one band raster or a multiple bands raster. To produce a multiple bands raster, you must provide an array of pixel types (`pixeltype[]`), an array of initial values (`value`) and an array of nodata values (`nodataval`). If not provided pixeltyped defaults to 8BUI, values to 1 and nodataval to 0.

The output raster will be in the same spatial reference as the source geometry. The only exception is for variants with a reference raster. In this case the resulting raster will get the same SRID as the reference raster.

The optional `touched` parameter defaults to false and maps to the GDAL ALL_TOUCHED rasterization option, which determines if pixels touched by lines or polygons will be burned. Not just those on the line render path, or whose center point is within the polygon.

This is particularly useful for rendering jpegs and pngs of geometries directly from the database when using in combination with ST_AsPNG and other ST_AsGDALRaster family of functions.

Availability: 2.0.0 - requires GDAL >= 1.6.0.

Not yet capable of rendering complex geometry types such as curves, TINS, and PolyhedralSurfaces, but should be able too once GDAL can.

## Examples: Output geometries as PNG files

black circle

    -- this will output a black circle taking up 150 x 150 pixels --
    SELECT ST_AsPNG(ST_AsRaster(ST_Buffer(ST_Point(1,5),10),150, 150, '2BUI'));

example from buffer rendered with just PostGIS

    -- the bands map to RGB bands - the value (118,154,118) - teal  --
    SELECT ST_AsPNG(
    	ST_AsRaster(
    		ST_Buffer(
    			ST_GeomFromText('LINESTRING(50 50,150 150,150 50)'), 10,'join=bevel'),
    			200,200,ARRAY['8BUI', '8BUI', '8BUI'], ARRAY[118,154,118], ARRAY[0,0,0]));

## See Also

ST_BandPixelType, ST_Buffer, ST_GDALDrivers, ST_AsGDALRaster, ST_AsPNG, ST_AsJPEG, ST_SRID

## Name

ST_Band — Returns one or more bands of an existing raster as a new raster. Useful for building new rasters from existing rasters.

## Synopsis

`raster ST_Band(`raster rast, integer[] nbands = ARRAY[1]`)`;

`raster ST_Band(`raster rast, text nbands, character delimiter=,`)`;

`raster ST_Band(`raster rast, integer nband`)`;

## Description

Returns a single band of an existing raster as a new raster. Useful for building new rasters from existing rasters or export of only selected bands of a raster. If no band is specified, band 1 is assumed. Used as a helper function in various functions such as for deleting a band.

Availability: 2.0.0

## Examples

    -- Make 2 new rasters: 1 containing band 1 of dummy, second containing band 2 of dummy and then reclassified as a 2BUI
    SELECT ST_NumBands(rast1) As numb1, ST_BandPixelType(rast1) As pix1,
     ST_NumBands(rast2) As numb2,  ST_BandPixelType(rast2) As pix2
    FROM (
        SELECT ST_Band(rast) As rast1, ST_Reclass(ST_Band(rast,3), '100-200):1, [200-254:2', '2BUI') As rast2
            FROM dummy_rast
            WHERE rid = 2) As foo;

     numb1 | pix1 | numb2 | pix2
    -------+------+-------+------
         1 | 8BUI |     1 | 2BUI

    -- Return bands 2 and 3. Use text to define bands
    SELECT ST_NumBands(ST_Band(rast, '2,3')) As num_bands
        FROM dummy_rast WHERE rid=2;

    num_bands
    ----------
    2

    -- Return bands 2 and 3. Use array to define bands
    SELECT ST_NumBands(ST_Band(rast, ARRAY[2,3])) As num_bands
        FROM dummy_rast
    WHERE rid=2;

original (column rast) | dupe_band | sing_band

    --Make a new raster with 2nd band of original and 1st band repeated twice,
    and another with just the third band
    SELECT rast, ST_Band(rast, ARRAY[2,1,1]) As dupe_band,
    	ST_Band(rast, 3) As sing_band
    FROM samples.than_chunked
    WHERE rid=35;

## See Also

ST_AddBand, ST_NumBands, , ST_Reclass

## Name

ST_MakeEmptyRaster — Returns an empty raster (having no bands) of given dimensions (width & height), upperleft X and Y, pixel size and rotation (scalex, scaley, skewx & skewy) and reference system (srid). If a raster is passed in, returns a new raster with the same size, alignment and SRID. If srid is left out, the spatial ref is set to unknown (0).

## Synopsis

`raster ST_MakeEmptyRaster(`raster rast`)`;

`raster ST_MakeEmptyRaster(`integer width, integer height, float8 upperleftx, float8 upperlefty, float8 scalex, float8 scaley, float8 skewx, float8 skewy, integer srid=unknown`)`;

`raster ST_MakeEmptyRaster(`integer width, integer height, float8 upperleftx, float8 upperlefty, float8 pixelsize`)`;

## Description

Returns an empty raster (having no band) of given dimensions (width & height) and georeferenced in spatial (or world) coordinates with upper left X (upperleftx), upper left Y (upperlefty), pixel size and rotation (scalex, scaley, skewx & skewy) and reference system (srid).

The last version use a single parameter to specify the pixel size (pixelsize). scalex is set to this argument and scaley is set to the negative value of this argument. skewx and skewy are set to 0.

If an existing raster is passed in, it returns a new raster with the same meta data settings (without the bands).

If no srid is specified it defaults to 0. After you create an empty raster you probably want to add bands to it and maybe edit it. Refer to ST_AddBand to define bands and ST_SetValue to set initial pixel values.

## Examples

    INSERT INTO dummy_rast(rid,rast)
    VALUES(3, ST_MakeEmptyRaster( 100, 100, 0.0005, 0.0005, 1, 1, 0, 0, 4326) );

    --use an existing raster as template for new raster
    INSERT INTO dummy_rast(rid,rast)
    SELECT 4, ST_MakeEmptyRaster(rast)
    FROM dummy_rast WHERE rid = 3;

    -- output meta data of rasters we just added
    SELECT rid, (md).*
    FROM (SELECT rid, ST_MetaData(rast) As md
    	FROM dummy_rast
    	WHERE rid IN(3,4)) As foo;

    -- output --
     rid | upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands
    -----+------------+------------+-------+--------+------------+------------+-------+-------+------+----------
       3 |     0.0005 |     0.0005 |   100 |    100 |          1 |          1 |    0  |     0 | 4326 |        0
       4 |     0.0005 |     0.0005 |   100 |    100 |          1 |          1 |    0  |     0 | 4326 |        0

## See Also

ST_AddBand, ST_MetaData, ST_ScaleX, ST_ScaleY, ST_SetValue, ST_SkewX, , ST_SkewY

## 9.4. Raster Accessors

## Name

ST_GeoReference — Returns the georeference meta data in GDAL or ESRI format as commonly seen in a world file. Default is GDAL.

## Synopsis

`text ST_GeoReference(`raster rast, text format=GDAL`)`;

## Description

Returns the georeference meta data including carriage return in GDAL or ESRI format as commonly seen in a world file. Default is GDAL if no type specified. type is string 'GDAL' or 'ESRI'.

Difference between format representations is as follows:

`GDAL`:

    scalex
    skewy
    skewx
    scaley
    upperleftx
    upperlefty

`ESRI`:

    scalex
    skewy
    skewx
    scaley
    upperleftx + scalex*0.5
    upperlefty + scaley*0.5

## Examples

    SELECT ST_GeoReference(rast, 'ESRI') As esri_ref, ST_GeoReference(rast, 'GDAL') As gdal_ref
     FROM dummy_rast WHERE rid=1;

       esri_ref   |   gdal_ref
    --------------+--------------
     2.0000000000 | 2.0000000000
     0.0000000000 : 0.0000000000
     0.0000000000 : 0.0000000000
     3.0000000000 : 3.0000000000
     1.5000000000 : 0.5000000000
     2.0000000000 : 0.5000000000

## See Also

ST_SetGeoReference, ST_ScaleX, ST_ScaleY

## Name

ST_Height — Returns the height of the raster in pixels.

## Synopsis

`integer ST_Height(`raster rast`)`;

## Description

Returns the height of the raster.

## Examples

    SELECT rid, ST_Height(rast) As rastheight
    FROM dummy_rast;

     rid | rastheight
    -----+------------
       1 |         20
       2 |          5

## See Also

ST_Width

## Name

ST_MetaData — Returns basic meta data about a raster object such as pixel size, rotation (skew), upper, lower left, etc.

## Synopsis

`record ST_MetaData(`raster rast`)`;

## Description

Returns basic meta data about a raster object such as pixel size, rotation (skew), upper, lower left, etc. Columns returned: upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands

## Examples

    SELECT rid, (foo.md).*
     FROM (SELECT rid, ST_MetaData(rast) As md
    FROM dummy_rast) As foo;

     rid | upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands
     ----+------------+------------+-------+--------+--------+-----------+-------+-------+------+-------
       1 |        0.5 |        0.5 |    10 |     20 |      2 |      3 |		0 |     0 |    0 |        0
       2 | 3427927.75 |    5793244 |     5 |      5 |   0.05 |  -0.05 |		0 |     0 |    0 |        3

## See Also

ST_BandMetaData, ST_NumBands

## Name

ST_NumBands — Returns the number of bands in the raster object.

## Synopsis

`integer ST_NumBands(`raster rast`)`;

## Description

Returns the number of bands in the raster object.

## Examples

    SELECT rid, ST_NumBands(rast) As numbands
    FROM dummy_rast;

    rid | numbands
    ----+----------
      1 |        0
      2 |        3

## See Also

ST_Value

## Name

ST_PixelHeight — Returns the pixel height in geometric units of the spatial reference system.

## Synopsis

`double precision ST_PixelHeight(`raster rast`)`;

## Description

Returns the height of a pixel in geometric units of the spatial reference system. In the common case where there is no skew, the pixel height is just the scale ratio between geometric coordinates and raster pixels.

Refer to ST_PixelWidth for a diagrammatic visualization of the relationship.

## Examples: Rasters with no skew

    SELECT ST_Height(rast) As rastheight, ST_PixelHeight(rast) As pixheight,
     ST_ScaleX(rast) As scalex, ST_ScaleY(rast) As scaley, ST_SkewX(rast) As skewx,
            ST_SkewY(rast) As skewy
    FROM dummy_rast;

     rastheight | pixheight | scalex | scaley | skewx | skewy
    ------------+-----------+--------+--------+-------+----------
             20 |         3 |      2 |      3 |     0 |        0
              5 |      0.05 |   0.05 |  -0.05 |     0 |        0

## Examples: Rasters with skew different than 0

    SELECT ST_Height(rast) As rastheight, ST_PixelHeight(rast) As pixheight,
     ST_ScaleX(rast) As scalex, ST_ScaleY(rast) As scaley, ST_SkewX(rast) As skewx,
            ST_SkewY(rast) As skewy
    FROM (SELECT ST_SetSKew(rast,0.5,0.5) As rast
            FROM dummy_rast) As skewed;

    rastheight |     pixheight     | scalex | scaley | skewx | skewy
    -----------+-------------------+--------+--------+-------+----------
            20 |  3.04138126514911 |      2 |      3 |   0.5 |      0.5
             5 | 0.502493781056044 |   0.05 |  -0.05 |   0.5 |      0.5

## See Also

ST_PixelWidth, ST_ScaleX, ST_ScaleY, ST_SkewX, ST_SkewY

## Name

ST_PixelWidth — Returns the pixel width in geometric units of the spatial reference system.

## Synopsis

`double precision ST_PixelWidth(`raster rast`)`;

## Description

Returns the width of a pixel in geometric units of the spatial reference system. In the common case where there is no skew, the pixel width is just the scale ratio between geometric coordinates and raster pixels.

The following diagram demonstrates the relationship:

Pixel Width: Pixel size in the i direction

Pixel Height: Pixel size in the j direction

## Examples: Rasters with no skew

    SELECT ST_Width(rast) As rastwidth, ST_PixelWidth(rast) As pixwidth,
    	ST_ScaleX(rast) As scalex, ST_ScaleY(rast) As scaley, ST_SkewX(rast) As skewx,
    	ST_SkewY(rast) As skewy
    	FROM dummy_rast;

    	rastwidth | pixwidth | scalex | scaley | skewx | skewy
    	-----------+----------+--------+--------+-------+----------
    	10 |        2 |      2 |      3 |     0 |        0
    	 5 |     0.05 |   0.05 |  -0.05 |     0 |        0

## Examples: Rasters with skew different than 0

    SELECT ST_Width(rast) As rastwidth, ST_PixelWidth(rast) As pixwidth,
    	ST_ScaleX(rast) As scalex, ST_ScaleY(rast) As scaley, ST_SkewX(rast) As skewx,
    	ST_SkewY(rast) As skewy
    	FROM (SELECT ST_SetSkew(rast,0.5,0.5) As rast
    	FROM dummy_rast) As skewed;

    	rastwidth |     pixwidth      | scalex | scaley | skewx | skewy
    	-----------+-------------------+--------+--------+-------+----------
    	10 |  2.06155281280883 |      2 |      3 |   0.5 |      0.5
    	 5 | 0.502493781056044 |   0.05 |  -0.05 |   0.5 |      0.5

## See Also

ST_PixelHeight, ST_ScaleX, ST_ScaleY, ST_SkewX, ST_SkewY

## Name

ST_ScaleX — Returns the X component of the pixel width in units of coordinate reference system.

## Synopsis

`float8 ST_ScaleX(`raster rast`)`;

## Description

Returns the X component of the pixel width in units of coordinate reference system. Refer to World File for more details.

Changed: 2.0.0. In WKTRaster versions this was called ST_PixelSizeX.

## Examples

    SELECT rid, ST_ScaleX(rast) As rastpixwidth
    FROM dummy_rast;

     rid | rastpixwidth
    -----+--------------
       1 |            2
       2 |         0.05

## See Also

ST_Width

## Name

ST_ScaleY — Returns the Y component of the pixel height in units of coordinate reference system.

## Synopsis

`float8 ST_ScaleY(`raster rast`)`;

## Description

Returns the Y component of the pixel height in units of coordinate reference system. May be negative. Refer to World File for more details.

Changed: 2.0.0. In WKTRaster versions this was called ST_PixelSizeY.

## Examples

    SELECT rid, ST_ScaleY(rast) As rastpixheight
    FROM dummy_rast;

     rid | rastpixheight
    -----+---------------
       1 |             3
       2 |         -0.05

## See Also

ST_Height

## Name

ST_Raster2WorldCoordX — Returns the geometric X coordinate upper left of a raster, column and row. Numbering of columns and rows starts at 1.

## Synopsis

`float8 ST_Raster2WorldCoordX(`raster rast, integer xcolumn`)`;

`float8 ST_Raster2WorldCoordX(`raster rast, integer xcolumn, integer yrow`)`;

## Description

Returns the upper left X coordinate of a raster column row in geometric units of the georeferenced raster. Numbering of columns and rows starts at 1 but if you pass in a negative number or number higher than number of columns in raster, it will give you coordinates outside of the raster file to left or right with the assumption that the skew and pixel sizes are same as selected raster.

For non-skewed rasters, providing the X column is sufficient. For skewed rasters, the georeferenced coordinate is a function of the ST_ScaleX and ST_SkewX and row and column. An error will be raised if you give just the X column for a skewed raster.

## Examples

    -- non-skewed raster providing column is sufficient
    SELECT rid, ST_Raster2WorldCoordX(rast,1) As x1coord,
    	ST_Raster2WorldCoordX(rast,2) As x2coord,
    	ST_ScaleX(rast) As pixelx
    FROM dummy_rast;

     rid |  x1coord   |  x2coord  | pixelx
    -----+------------+-----------+--------
       1 |        0.5 |       2.5 |      2
       2 | 3427927.75 | 3427927.8 |   0.05

    -- for fun lets skew it
    SELECT rid, ST_Raster2WorldCoordX(rast, 1, 1) As x1coord,
    	ST_Raster2WorldCoordX(rast, 2, 3) As x2coord,
    	ST_ScaleX(rast) As pixelx
    FROM (SELECT rid, ST_SetSkew(rast, 100.5, 0) As rast FROM dummy_rast) As foo;

     rid |  x1coord   |  x2coord  | pixelx
    -----+------------+-----------+--------
       1 |        0.5 |     203.5 |      2
       2 | 3427927.75 | 3428128.8 |   0.05

## See Also

ST_ScaleX, ST_Raster2WorldCoordY, ST_SetSkew, ST_SkewX

## Name

ST_Raster2WorldCoordY — Returns the geometric Y coordinate upper left corner of a raster, column and row. Numbering of columns and rows starts at 1.

## Synopsis

`float8 ST_Raster2WorldCoordY(`raster rast, integer yrow`)`;

`float8 ST_Raster2WorldCoordY(`raster rast, integer xcolumn, integer yrow`)`;

## Description

Returns the upper left Y coordinate of a raster column row in geometric units of the georeferenced raster. Numbering of columns and rows starts at 1 but if you pass in a negative number or number higher than number of columns/rows in raster, it will give you coordinates outside of the raster file to left or right with the assumption that the skew and pixel sizes are same as selected raster tile.

For non-skewed rasters, providing the Y column is sufficient. For skewed rasters, the georeferenced coordinate is a function of the ST_ScaleY and ST_SkewY and row and column. An error will be raised if you give just the Y row for a skewed raster.

## Examples

    -- non-skewed raster providing row is sufficient
    SELECT rid, ST_Raster2WorldCoordY(rast,1) As y1coord,
    	ST_Raster2WorldCoordY(rast,3) As y2coord,
    	ST_ScaleY(rast) As pixely
    FROM dummy_rast;

     rid | y1coord |  y2coord  | pixely
    -----+---------+-----------+--------
       1 |     0.5 |       6.5 |      3
       2 | 5793244 | 5793243.9 |  -0.05

    -- for fun lets skew it
    SELECT rid, ST_Raster2WorldCoordY(rast,1,1) As y1coord,
    	ST_Raster2WorldCoordY(rast,2,3) As y2coord,
    	ST_ScaleY(rast) As pixely
    FROM (SELECT rid, ST_SetSkew(rast,0,100.5) As rast FROM dummy_rast) As foo;

     rid | y1coord |  y2coord  | pixely
    -----+---------+-----------+--------
       1 |     0.5 |       107 |      3
       2 | 5793244 | 5793344.4 |  -0.05

## See Also

ST_ScaleY, ST_Raster2WorldCoordX, ST_SetSkew, ST_SkewY

## Name

ST_Rotation — Returns the rotation of the raster in radian.

## Synopsis

`float8 ST_Rotation(`raster rast`)`;

## Description

Returns the uniform rotation of the raster in radian. If a raster does not have uniform rotation, NaN is returned. Refer to World File for more details.

## Examples

    SELECT rid, ST_Rotation(ST_SetScale(ST_SetSkew(rast, sqrt(2)), sqrt(2))) as rot FROM dummy_rast;

     rid |        rot
    -----+-------------------
       1 | 0.785398163397448
       2 | 0.785398163397448

## See Also

ST_SetRotation, ST_SetScale, ST_SetSkew

## Name

ST_SkewX — Returns the georeference X skew (or rotation parameter).

## Synopsis

`float8 ST_SkewX(`raster rast`)`;

## Description

Returns the georeference X skew (or rotation parameter). Refer to World File for more details.

## Examples

    SELECT rid, ST_SkewX(rast) As skewx, ST_SkewY(rast) As skewy,
        ST_GeoReference(rast) as georef
    FROM dummy_rast;

     rid | skewx | skewy |       georef
    -----+-------+-------+--------------------
       1 |     0 |     0 | 2.0000000000
                         : 0.0000000000
                         : 0.0000000000
                         : 3.0000000000
                         : 0.5000000000
                         : 0.5000000000
                         :
       2 |     0 |     0 | 0.0500000000
                         : 0.0000000000
                         : 0.0000000000
                         : -0.0500000000
                         : 3427927.7500000000
                         : 5793244.0000000000

## See Also

ST_GeoReference, ST_SkewY, ST_SetSkew

## Name

ST_SkewY — Returns the georeference Y skew (or rotation parameter).

## Synopsis

`float8 ST_SkewY(`raster rast`)`;

## Description

Returns the georeference Y skew (or rotation parameter). Refer to World File for more details.

## Examples

    SELECT rid, ST_SkewX(rast) As skewx, ST_SkewY(rast) As skewy,
        ST_GeoReference(rast) as georef
    FROM dummy_rast;

     rid | skewx | skewy |       georef
    -----+-------+-------+--------------------
       1 |     0 |     0 | 2.0000000000
                         : 0.0000000000
                         : 0.0000000000
                         : 3.0000000000
                         : 0.5000000000
                         : 0.5000000000
                         :
       2 |     0 |     0 | 0.0500000000
                         : 0.0000000000
                         : 0.0000000000
                         : -0.0500000000
                         : 3427927.7500000000
                         : 5793244.0000000000

## See Also

ST_GeoReference, ST_SkewX, ST_SetSkew

## Name

ST_SRID — Returns the spatial reference identifier of the raster as defined in spatial_ref_sys table.

## Synopsis

`integer ST_SRID(`raster rast`)`;

## Description

Returns the spatial reference identifier of the raster object as defined in the spatial_ref_sys table.

From PostGIS 2.0+ the srid of a non-georeferenced raster/geometry is 0 instead of the prior -1.

## Examples

    SELECT ST_SRID(rast) As srid
    FROM dummy_rast WHERE rid=1;

    srid
    ----------------
    0

## See Also

Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems”, ST_SRID

## Name

ST_UpperLeftX — Returns the upper left X coordinate of raster in projected spatial ref.

## Synopsis

`float8 ST_UpperLeftX(`raster rast`)`;

## Description

Returns the upper left X coordinate of raster in projected spatial ref.

## Examples

    SELECt rid, ST_UpperLeftX(rast) As ulx
    FROM dummy_rast;

     rid |    ulx
    -----+------------
       1 |        0.5
       2 | 3427927.75

## See Also

ST_UpperLeftY, ST_GeoReference, Box3D

## Name

ST_UpperLeftY — Returns the upper left Y coordinate of raster in projected spatial ref.

## Synopsis

`float8 ST_UpperLeftY(`raster rast`)`;

## Description

Returns the upper left Y coordinate of raster in projected spatial ref.

## Examples

    SELECT rid, ST_UpperLeftY(rast) As uly
    FROM dummy_rast;

     rid |   uly
    -----+---------
       1 |     0.5
       2 | 5793244

## See Also

ST_UpperLeftX, ST_GeoReference, Box3D

## Name

ST_Width — Returns the width of the raster in pixels.

## Synopsis

`integer ST_Width(`raster rast`)`;

## Description

Returns the width of the raster in pixels.

## Examples

    SELECT ST_Width(rast) As rastwidth
    FROM dummy_rast WHERE rid=1;

    rastwidth
    ----------------
    10

## See Also

ST_Height

## Name

ST_World2RasterCoordX — Returns the column in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw) represented in world spatial reference system of raster.

## Synopsis

`integer ST_World2RasterCoordX(`raster rast, geometry pt`)`;

`integer ST_World2RasterCoordX(`raster rast, double precision xw`)`;

`integer ST_World2RasterCoordX(`raster rast, double precision xw, double precision yw`)`;

## Description

Returns the column in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw). A point, or (both xw and yw world coordinates are required if a raster is skewed). If a raster is not skewed then xw is sufficient. World coordinates are in the spatial reference coordinate system of the raster.

## Examples

    SELECT rid, ST_World2RasterCoordX(rast,3427927.8) As xcoord,
    		ST_World2RasterCoordX(rast,3427927.8,20.5) As xcoord_xwyw,
    		ST_World2RasterCoordX(rast,ST_GeomFromText('POINT(3427927.8 20.5)',ST_SRID(rast))) As ptxcoord
    FROM dummy_rast;

     rid | xcoord  |  xcoord_xwyw   | ptxcoord
    -----+---------+---------+----------
       1 | 1713964 | 1713964 |  1713964
       2 |       1 |       1 |        1

## See Also

ST_Raster2WorldCoordX, ST_Raster2WorldCoordY, ST_SRID

## Name

ST_World2RasterCoordY — Returns the row in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw) represented in world spatial reference system of raster.

## Synopsis

`integer ST_World2RasterCoordY(`raster rast, geometry pt`)`;

`integer ST_World2RasterCoordY(`raster rast, double precision xw`)`;

`integer ST_World2RasterCoordY(`raster rast, double precision xw, double precision yw`)`;

## Description

Returns the row in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw). A point, or (both xw and yw world coordinates are required if a raster is skewed). If a raster is not skewed then xw is sufficient. World coordinates are in the spatial reference coordinate system of the raster.

## Examples

    SELECT rid, ST_World2RasterCoordY(rast,20.5) As ycoord,
    		ST_World2RasterCoordY(rast,3427927.8,20.5) As ycoord_xwyw,
    		ST_World2RasterCoordY(rast,ST_GeomFromText('POINT(3427927.8 20.5)',ST_SRID(rast))) As ptycoord
    FROM dummy_rast;

     rid |  ycoord   | ycoord_xwyw | ptycoord
    -----+-----------+-------------+-----------
       1 |         7 |           7 |         7
       2 | 115864471 |   115864471 | 115864471

## See Also

ST_Raster2WorldCoordX, ST_Raster2WorldCoordY, ST_SRID

## Name

ST_IsEmpty — Returns true if the raster is empty (width = 0 and height = 0). Otherwise, returns false.

## Synopsis

`boolean ST_IsEmpty(`raster rast`)`;

## Description

Returns true if the raster is empty (width = 0 and height = 0). Otherwise, returns false.

## Examples

    SELECT ST_IsEmpty(ST_MakeEmptyRaster(100, 100, 0, 0, 0, 0, 0, 0))
    st_isempty |
    -----------+
    f          |

    SELECT ST_IsEmpty(ST_MakeEmptyRaster(0, 0, 0, 0, 0, 0, 0, 0))
    st_isempty |
    -----------+
    t          |

## See Also

ST_HasNoBand

## 9.5. Raster Band Accessors

## Name

ST_BandMetaData — Returns basic meta data for a specific raster band. band num 1 is assumed if none-specified.

## Synopsis

`record ST_BandMetaData(`raster rast, integer bandnum=1`)`;

## Description

Returns basic meta data about a raster band. Columns returned pixeltype | nodatavalue | isoutdb | path.

If raster contains no bands then an error is thrown.

If band has no NODATA value, nodatavalue will be NULL.

## Examples

    SELECT rid, (foo.md).*
     FROM (SELECT rid, ST_BandMetaData(rast,1) As md
    FROM dummy_rast WHERE rid=2) As foo;

     rid | pixeltype | nodatavalue | isoutdb | path
    -----+-----------+----------------+-------------+---------+------
       2 | 8BUI      |           0 | f       |

## See Also

ST_MetaData, ST_BandPixelType

## Name

ST_BandNoDataValue — Returns the value in a given band that represents no data. If no band num 1 is assumed.

## Synopsis

`double precision ST_BandNoDataValue(`raster rast, integer bandnum=1`)`;

## Description

Returns the value that represents no data for the band

## Examples

    SELECT ST_BandNoDataValue(rast,1) As bnval1,
        ST_BandNoDataValue(rast,2) As bnval2, ST_BandNoDataValue(rast,3) As bnval3
    FROM dummy_rast
    WHERE rid = 2;

     bnval1 | bnval2 | bnval3
    --------+--------+--------
          0 |      0 |      0

## See Also

ST_NumBands

## Name

ST_BandIsNoData — Returns true if the band is filled with only nodata values.

## Synopsis

`boolean ST_BandIsNoData(`raster rast, integer band, boolean forceChecking=true`)`;

`boolean ST_BandIsNoData(`raster rast, boolean forceChecking=true`)`;

## Description

Returns true if the band is filled with only nodata values. Band 1 is assumed if not specified. If the last argument is TRUE, the entire band is checked pixel by pixel. Otherwise, the function simply returns the value of the isnodata flag for the band. The default value for this parameter is FALSE, if not specified.

Availability: 2.0.0

If the flag is dirty (this is, the result is different using TRUE as last parameter and not using it) you should update the raster to set this flag to true, by using ST_SetBandIsNodata function, or ST_SetBandNodataValue function with TRUE as last argument. The loader (raster2pgsql.py) currently can not properly set the flag while loading raster data. See ST_SetBandIsNoData.

## Examples

    -- Create dummy table with one raster column
    create table dummy_rast (rid integer, rast raster);

    -- Add raster with two bands, one pixel/band. In the first band, nodatavalue = pixel value = 3.
    -- In the second band, nodatavalue = 13, pixel value = 4
    insert into dummy_rast values(1,
    (
    '01' -- little endian (uint8 ndr)
    ||
    '0000' -- version (uint16 0)
    ||
    '0200' -- nBands (uint16 0)
    ||
    '17263529ED684A3F' -- scaleX (float64 0.000805965234044584)
    ||
    'F9253529ED684ABF' -- scaleY (float64 -0.00080596523404458)
    ||
    '1C9F33CE69E352C0' -- ipX (float64 -75.5533328537098)
    ||
    '718F0E9A27A44840' -- ipY (float64 49.2824585505576)
    ||
    'ED50EB853EC32B3F' -- skewX (float64 0.000211812383858707)
    ||
    '7550EB853EC32B3F' -- skewY (float64 0.000211812383858704)
    ||
    'E6100000' -- SRID (int32 4326)
    ||
    '0100' -- width (uint16 1)
    ||
    '0100' -- height (uint16 1)
    ||
    '6' -- hasnodatavalue and isnodata value set to true.
    ||
    '2' -- first band type (4BUI)
    ||
    '03' -- novalue==3
    ||
    '03' -- pixel(0,0)==3 (same that nodata)
    ||
    '0' -- hasnodatavalue set to false
    ||
    '5' -- second band type (16BSI)
    ||
    '0D00' -- novalue==13
    ||
    '0400' -- pixel(0,0)==4
    )::raster
    );

    select st_bandisnodata(rast, 1) from dummy_rast where rid = 1; -- Expected true
    select st_bandisnodata(rast, 2) from dummy_rast where rid = 1; -- Expected false

## See Also

ST_BandNoDataValue, ST_NumBands, ST_SetBandNoDataValue, ST_SetBandIsNoData

## Name

ST_BandPath — Returns system file path to a band stored in file system. If no bandnum specified, 1 is assumed.

## Synopsis

`text ST_BandPath(`raster rast, integer bandnum=1`)`;

## Description

Returns system file path to a band. Throws an error if called with an in db band.

## Examples

## See Also

## Name

ST_BandPixelType — Returns the type of pixel for given band. If no bandnum specified, 1 is assumed.

## Synopsis

`text ST_BandPixelType(`raster rast, integer bandnum=1`)`;

## Description

Returns the value that represents no data for the band

There are 11 pixel types. Pixel Types supported are as follows:

- 1BB - 1-bit boolean

- 2BUI - 2-bit unsigned integer

- 4BUI - 4-bit unsigned integer

- 8BSI - 8-bit signed integer

- 8BUI - 8-bit unsigned integer

- 16BSI - 16-bit signed integer

- 16BUI - 16-bit unsigned integer

- 32BSI - 32-bit signed integer

- 32BUI - 32-bit unsigned integer

- 32BF - 32-bit float

- 64BF - 64-bit float

## Examples

    SELECT ST_BandPixelType(rast,1) As btype1,
        ST_BandPixelType(rast,2) As btype2, ST_BandPixelType(rast,3) As btype3
    FROM dummy_rast
    WHERE rid = 2;

     btype1 | btype2 | btype3
    --------+--------+--------
     8BUI   | 8BUI   | 8BUI

## See Also

ST_NumBands

## Name

ST_HasNoBand — Returns true if there is no band with given band number. If no band number is specified, then band number 1 is assumed.

## Synopsis

`boolean ST_HasNoBand(`raster rast, integer bandnum=1`)`;

## Description

Returns true if there is no band with given band number. If no band number is specified, then band number 1 is assumed.

Availability: 2.0.0

## Examples

    SELECT rid, ST_HasNoBand(rast) As hb1, ST_HasNoBand(rast,2) as hb2,
    ST_HasNoBand(rast,4) as hb4, ST_NumBands(rast) As numbands
    FROM dummy_rast;

    rid | hb1 | hb2 | hb4 | numbands
    -----+-----+-----+-----+----------
    1 | t   | t   | t   |        0
    2 | f   | f   | t   |        3

## See Also

ST_NumBands

## 9.6. Raster Pixel Accessors and Setters

## Name

ST_PixelAsPolygon — Returns the geometry that bounds the pixel for a particular row and column.

## Synopsis

`geometry ST_PixelAsPolygon(`raster rast, integer columnx, integer rowy`)`;

## Description

Returns the geometry that bounds the pixel for a particular row and column.

## Examples

    -- get raster pixel polygon
    SELECT i,j, ST_AsText(ST_PixelAsPolygon(foo.rast, i,j)) As b1pgeom
    FROM dummy_rast As foo
    	CROSS JOIN generate_series(1,2) As i
    	CROSS JOIN generate_series(1,1) As j
    WHERE rid=2;

     i | j |                                                    b1pgeom
    ---+---+-----------------------------------------------------------------------------
     1 | 1 | POLYGON((3427927.75 5793244,3427927.8 5793244,3427927.8 5793243.95,...
     2 | 1 | POLYGON((3427927.8 5793244,3427927.85 5793244,3427927.85 5793243.95, ..

## See Also

ST_DumpAsPolygons, ST_Intersection, ST_AsText

## Name

ST_PixelAsPolygons — Returns the geometry that bounds every pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel.

## Synopsis

`setof record ST_PixelAsPolygons(`raster rast, integer band=1`)`;

## Description

Returns the geometry that bounds every pixel of a raster band along with the value (double precision), the X and the Y raster coordinates (integers) of each pixel.

## Examples

    -- get raster pixel polygon
    SELECT (gv).x, (gv).y, (gv).val, ST_AsText((gv).geom) geom
    FROM (SELECT ST_PixelAsPolygons(
                     ST_SetValue(ST_SetValue(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 0.001, -0.001, 0.001, 0.001, 4269),
                                                        '8BUI'::text, 1, 0),
                                             2, 2, 10),
                                 1, 1, NULL)
    ) gv
    ) foo;

     x | y | val |                geom
    ---+---+-----------------------------------------------------------------------------
     1 | 1 |     | POLYGON((0 0,0.001 0.001,0.002 0,0.001 -0.001,0 0))
     1 | 2 |   1 | POLYGON((0.001 -0.001,0.002 0,0.003 -0.001,0.002 -0.002,0.001 -0.001))
     2 | 1 |   1 | POLYGON((0.001 0.001,0.002 0.002,0.003 0.001,0.002 0,0.001 0.001))
     2 | 2 |  10 | POLYGON((0.002 0,0.003 0.001,0.004 0,0.003 -0.001,0.002 0))

## See Also

ST_DumpAsPolygons, ST_PixelAsPolygon, ST_AsText

## Name

ST_Value — Returns the value of a given band in a given columnx, rowy pixel or at a particular geometric point. Band numbers start at 1 and assumed to be 1 if not specified. If `exclude_nodata_value` is set to false, then all pixels include `nodata` pixels are considered to intersect and return value. If `exclude_nodata_value` is not passed in then reads it from metadata of raster.

## Synopsis

`double precision ST_Value(`raster rast, geometry pt, boolean exclude_nodata_value=true`)`;

`double precision ST_Value(`raster rast, integer bandnum, geometry pt, boolean exclude_nodata_value=true`)`;

`double precision ST_Value(`raster rast, integer columnx, integer rowy, boolean exclude_nodata_value=true`)`;

`double precision ST_Value(`raster rast, integer bandnum, integer columnx, integer rowy, boolean exclude_nodata_value=true`)`;

## Description

Returns the value of a given band in a given columnx, rowy pixel or at a given geometry point. Band numbers start at 1 and band is assumed to be 1 if not specified. If `exclude_nodata_value` is set to true, then only non `nodata` pixels are considered. If `exclude_nodata_value` is set to false, then all pixels are considered.

Enhanced: 2.0.0 exclude_nodata_value optional argument was added.

## Examples

    -- get raster values at particular postgis geometry points
    -- the srid of your geometry should be same as for your raster
    SELECT rid, ST_Value(rast, foo.pt_geom) As b1pval, ST_Value(rast, 2, foo.pt_geom) As b2pval
    FROM dummy_rast CROSS JOIN (SELECT ST_SetSRID(ST_Point(3427927.77, 5793243.76), 0) As pt_geom) As foo
    WHERE rid=2;

     rid | b1pval | b2pval
    -----+--------+--------
       2 |    252 |     79

    -- general fictitious example using a real table
    SELECT rid, ST_Value(rast, 3, sometable.geom) As b3pval
    FROM sometable
    WHERE ST_Intersects(rast,sometable.geom);

    SELECT rid, ST_Value(rast, 1, 1, 1) As b1pval,
        ST_Value(rast, 2, 1, 1) As b2pval, ST_Value(rast, 3, 1, 1) As b3pval
    FROM dummy_rast
    WHERE rid=2;

     rid | b1pval | b2pval | b3pval
    -----+--------+--------+--------
       2 |    253 |     78 |     70

    --- Get all values in bands 1,2,3 of each pixel --
    SELECT x, y, ST_Value(rast, 1, x, y) As b1val,
    	ST_Value(rast, 2, x, y) As b2val, ST_Value(rast, 3, x, y) As b3val
    FROM dummy_rast CROSS JOIN
    generate_series(1, 1000) As x CROSS JOIN generate_series(1, 1000) As y
    WHERE rid =  2 AND x <= ST_Width(rast) AND y <= ST_Height(rast);

     x | y | b1val | b2val | b3val
    ---+---+-------+-------+-------
     1 | 1 |   253 |    78 |    70
     1 | 2 |   253 |    96 |    80
     1 | 3 |   250 |    99 |    90
     1 | 4 |   251 |    89 |    77
     1 | 5 |   252 |    79 |    62
     2 | 1 |   254 |    98 |    86
     2 | 2 |   254 |   118 |   108
     :
     :

    --- Get all values in bands 1,2,3 of each pixel same as above but returning the upper left point point of each pixel --
    SELECT ST_AsText(ST_SetSRID(
    	ST_Point(ST_UpperLeftX(rast) + ST_ScaleX(rast)*x,
    		ST_UpperLeftY(rast) + ST_ScaleY(rast)*y),
    		ST_SRID(rast))) As uplpt
        , ST_Value(rast, 1, x, y) As b1val,
    	ST_Value(rast, 2, x, y) As b2val, ST_Value(rast, 3, x, y) As b3val
    FROM dummy_rast CROSS JOIN
    generate_series(1,1000) As x CROSS JOIN generate_series(1,1000) As y
    WHERE rid =  2 AND x <= ST_Width(rast) AND y <= ST_Height(rast);

                uplpt            | b1val | b2val | b3val
    -----------------------------+-------+-------+-------
     POINT(3427929.25 5793245.5) |   253 |    78 |    70
     POINT(3427929.25 5793247)   |   253 |    96 |    80
     POINT(3427929.25 5793248.5) |   250 |    99 |    90
    :

    --- Get a polygon formed by union of all pixels
    	that fall in a particular value range and intersect particular polygon --
    SELECT ST_AsText(ST_Union(pixpolyg)) As shadow
    FROM (SELECT ST_Translate(ST_MakeEnvelope(
    		ST_UpperLeftX(rast), ST_UpperLeftY(rast),
    			ST_UpperLeftX(rast) + ST_ScaleX(rast),
    			ST_UpperLeftY(rast) + ST_ScaleY(rast), 0
    			), ST_ScaleX(rast)*x, ST_ScaleY(rast)*y
    		) As pixpolyg, ST_Value(rast, 2, x, y) As b2val
    	FROM dummy_rast CROSS JOIN
    generate_series(1,1000) As x CROSS JOIN generate_series(1,1000) As y
    WHERE rid =  2
    	AND x <= ST_Width(rast) AND y <= ST_Height(rast)) As foo
    WHERE
    	ST_Intersects(
    		pixpolyg,
    		ST_GeomFromText('POLYGON((3427928 5793244,3427927.75 5793243.75,3427928 5793243.75,3427928 5793244))',0)
    		) AND b2val != 254;

    		shadow
    ------------------------------------------------------------------------------------
     MULTIPOLYGON(((3427928 5793243.9,3427928 5793243.85,3427927.95 5793243.85,3427927.95 5793243.9,
     3427927.95 5793243.95,3427928 5793243.95,3427928.05 5793243.95,3427928.05 5793243.9,3427928 5793243.9)),((3427927.95 5793243.9,3427927.95 579324
    3.85,3427927.9 5793243.85,3427927.85 5793243.85,3427927.85 5793243.9,3427927.9 5793243.9,3427927.9 5793243.95,
    3427927.95 5793243.95,3427927.95 5793243.9)),((3427927.85 5793243.75,3427927.85 5793243.7,3427927.8 5793243.7,3427927.8 5793243.75
    ,3427927.8 5793243.8,3427927.8 5793243.85,3427927.85 5793243.85,3427927.85 5793243.8,3427927.85 5793243.75)),
    ((3427928.05 5793243.75,3427928.05 5793243.7,3427928 5793243.7,3427927.95 5793243.7,3427927.95 5793243.75,3427927.95 5793243.8,3427
    927.95 5793243.85,3427928 5793243.85,3427928 5793243.8,3427928.05 5793243.8,
    3427928.05 5793243.75)),((3427927.95 5793243.75,3427927.95 5793243.7,3427927.9 5793243.7,3427927.85 5793243.7,
    3427927.85 5793243.75,3427927.85 5793243.8,3427927.85 5793243.85,3427927.9 5793243.85,
    3427927.95 5793243.85,3427927.95 5793243.8,3427927.95 5793243.75)))

    --- Checking all the pixels of a large raster tile can take a long time.
    --- You can dramatically improve speed at some lose of precision by orders of magnitude
    --  by sampling pixels using the step optional parameter of generate_series.
    --  This next example does the same as previous but by checking 1 for every 4 (2x2) pixels and putting in the last checked
    --  putting in the checked pixel as the value for subsequent 4

    SELECT ST_AsText(ST_Union(pixpolyg)) As shadow
    FROM (SELECT ST_Translate(ST_MakeEnvelope(
    		ST_UpperLeftX(rast), ST_UpperLeftY(rast),
    			ST_UpperLeftX(rast) + ST_ScaleX(rast)*2,
    			ST_UpperLeftY(rast) + ST_ScaleY(rast)*2, 0
    			), ST_ScaleX(rast)*x, ST_ScaleY(rast)*y
    		) As pixpolyg, ST_Value(rast, 2, x, y) As b2val
    	FROM dummy_rast CROSS JOIN
    generate_series(1,1000,2) As x CROSS JOIN generate_series(1,1000,2) As y
    WHERE rid =  2
    	AND x <= ST_Width(rast)  AND y <= ST_Height(rast)  ) As foo
    WHERE
    	ST_Intersects(
    		pixpolyg,
    		ST_GeomFromText('POLYGON((3427928 5793244,3427927.75 5793243.75,3427928 5793243.75,3427928 5793244))',0)
    		) AND b2val != 254;

    		shadow
    ------------------------------------------------------------------------------------
     MULTIPOLYGON(((3427927.9 5793243.85,3427927.8 5793243.85,3427927.8 5793243.95,
     3427927.9 5793243.95,3427928 5793243.95,3427928.1 5793243.95,3427928.1 5793243.85,3427928 5793243.85,3427927.9 5793243.85)),
     ((3427927.9 5793243.65,3427927.8 5793243.65,3427927.8 5793243.75,3427927.8 5793243.85,3427927.9 5793243.85,
     3427928 5793243.85,3427928 5793243.75,3427928.1 5793243.75,3427928.1 5793243.65,3427928 5793243.65,3427927.9 5793243.65)))

## See Also

ST_DumpAsPolygons, ST_NumBands, ST_PixelAsPolygon, ST_ScaleX, , ST_ScaleY, ST_UpperLeftX, ST_UpperLeftY, ST_SRID, ST_AsText, , ST_Point, ST_MakeEnvelope, ST_Intersects, ST_Intersection

## Name

ST_SetValue — Returns modified raster resulting from setting the value of a given band in a given columnx, rowy pixel or at a pixel that intersects a particular geometric point. Band numbers start at 1 and assumed to be 1 if not specified.

## Synopsis

`raster ST_SetValue(`raster rast, geometry pt, double precision newvalue`)`;

`raster ST_SetValue(`raster rast, integer bandnum, geometry pt, double precision newvalue`)`;

`raster ST_SetValue(`raster rast, integer columnx, integer rowy, double precision newvalue`)`;

`raster ST_SetValue(`raster rast, integer bandnum, integer columnx, integer rowy, double precision newvalue`)`;

## Description

Returns modified raster resulting from setting the specified pixel value to new value for the designed band given the row column location or a geometric point location. If no band is specified, then band 1 is assumed.

Setting by geometry currently only works for points.

## Examples

    				-- Geometry example
    SELECT (foo.geomval).val, ST_AsText(ST_Union((foo.geomval).geom))
    FROM (SELECT ST_DumpAsPolygons(
    		ST_SetValue(rast,1,
    				ST_Point(3427927.75, 5793243.95),
    				50)
    			) As geomval
    FROM dummy_rast
    where rid = 2) As foo
    WHERE (foo.geomval).val < 250
    GROUP BY (foo.geomval).val;

     val |                                                     st_astext
    -----+-------------------------------------------------------------------
      50 | POLYGON((3427927.75 5793244,3427927.75 5793243.95,3427927.8 579324 ...
     249 | POLYGON((3427927.95 5793243.95,3427927.95 5793243.85,3427928 57932 ...

    -- Store the changed raster --
    	UPDATE dummy_rast SET rast = ST_SetValue(rast,1, ST_Point(3427927.75, 5793243.95),100)
    		WHERE rid = 2   ;

## See Also

ST_Value, ST_DumpAsPolygons

## 9.7. Raster Editors

## Name

ST_SetGeoReference — Set Georeference 6 georeference parameters in a single call. Numbers should be separated by white space. Accepts inputs in GDAL or ESRI format. Default is GDAL.

## Synopsis

`raster ST_SetGeoReference(`raster rast, text georefcoords, text format=GDAL`)`;

## Description

Set Georeference 6 georeference parameters in a single call. Accepts inputs in 'GDAL' or 'ESRI' format. Default is GDAL. If 6 coordinates are not provided will return null.

Difference between format representations is as follows:

`GDAL`:

    scalex skewy skewx scaley upperleftx upperlefty

`ESRI`:

    scalex skewy skewx scaley upperleftx + scalex*0.5 upperlefty + scaley*0.5

## Examples

    UPDATE dummy_rast SET rast = ST_SetGeoReference(rast, '2 0 0 3 0.5 0.5','GDAL')
    	WHERE rid=1;

    -- same coordinates set in 'ESRI' format
    UPDATE dummy_rast SET rast = ST_SetGeoReference(rast, '2 0 0 3 1.5 2','ESRI')
    	WHERE rid=1;

## See Also

ST_GeoReference, ST_ScaleX, ST_ScaleY, ST_UpperLeftX, ST_UpperLeftY

## Name

ST_SetRotation — Set the rotation of the raster in radian.

## Synopsis

`float8 ST_SetRotation(`raster rast, float8 rotation`)`;

## Description

Uniformly rotate the raster. Rotation is in radian. Refer to World File for more details.

## Examples

    SELECT
      ST_ScaleX(rast1), ST_ScaleY(rast1), ST_SkewX(rast1), ST_SkewY(rast1),
      ST_ScaleX(rast2), ST_ScaleY(rast2), ST_SkewX(rast2), ST_SkewY(rast2)
    FROM (
      SELECT ST_SetRotation(rast, 15) AS rast1, rast as rast2 FROM dummy_rast
    ) AS foo;
          st_scalex      |      st_scaley      |      st_skewx      |      st_skewy      | st_scalex | st_scaley | st_skewx | st_skewy
    ---------------------+---------------------+--------------------+--------------------+-----------+-----------+----------+----------
       -1.51937582571764 |   -2.27906373857646 |   1.95086352047135 |   1.30057568031423 |         2 |         3 |        0 |        0
     -0.0379843956429411 | -0.0379843956429411 | 0.0325143920078558 | 0.0325143920078558 |      0.05 |     -0.05 |        0 |        0

## See Also

ST_Rotation, ST_ScaleX, ST_ScaleY, ST_SkewX, ST_SkewY

## Name

ST_SetScale — Sets the X and Y size of pixels in units of coordinate reference system. Number units/pixel width/height.

## Synopsis

`raster ST_SetScale(`raster rast, float8 xy`)`;

`raster ST_SetScale(`raster rast, float8 x, float8 y`)`;

## Description

Sets the X and Y size of pixels in units of coordinate reference system. Number units/pixel width/height. If only one unit passed in, assumed X and Y are the same number.

ST_SetScale is different from ST_Rescale in that ST_SetScale do not resample the raster to match the raster extent. It only changes the metadata (or georeference) of the raster to correct an originally mis-specified scaling. ST_Rescale results in a raster having different width and height computed to fit the geographic extent of the input raster. ST_SetScale do not modify the width, nor the height of the raster.

Changed: 2.0.0 In WKTRaster versions this was called ST_SetPixelSize. This was changed in 2.0.0.

## Examples

    UPDATE dummy_rast
    	SET rast = ST_SetScale(rast, 1.5)
    WHERE rid = 2;

    SELECT ST_ScaleX(rast) As pixx, ST_ScaleY(rast) As pixy, Box3D(rast) As newbox
    FROM dummy_rast
    WHERE rid = 2;

     pixx | pixy |                    newbox
    ------+------+----------------------------------------------
      1.5 |  1.5 | BOX(3427927.75 5793244 0, 3427935.25 5793251.5 0)

    UPDATE dummy_rast
    	SET rast = ST_SetScale(rast, 1.5, 0.55)
    WHERE rid = 2;

    SELECT ST_ScaleX(rast) As pixx, ST_ScaleY(rast) As pixy, Box3D(rast) As newbox
    FROM dummy_rast
    WHERE rid = 2;

     pixx | pixy |                   newbox
    ------+------+--------------------------------------------
      1.5 | 0.55 | BOX(3427927.75 5793244 0,3427935.25 5793247 0)

## See Also

ST_ScaleX, ST_ScaleY, Box3D

## Name

ST_SetSkew — Sets the georeference X and Y skew (or rotation parameter). If only one is passed in, sets X and Y to the same value.

## Synopsis

`raster ST_SetSkew(`raster rast, float8 skewxy`)`;

`raster ST_SetSkew(`raster rast, float8 skewx, float8 skewy`)`;

## Description

Sets the georeference X and Y skew (or rotation parameter). If only one is passed in, sets X and Y to the same value. Refer to World File for more details.

## Examples

    -- Example 1
    UPDATE dummy_rast SET rast = ST_SetSkew(rast,1,2) WHERE rid = 1;
    SELECT rid, ST_SkewX(rast) As skewx, ST_SkewY(rast) As skewy,
        ST_GeoReference(rast) as georef
    FROM dummy_rast WHERE rid = 1;

    rid | skewx | skewy |    georef
    ----+-------+-------+--------------
      1 |     1 |     2 | 2.0000000000
                        : 2.0000000000
                        : 1.0000000000
                        : 3.0000000000
                        : 0.5000000000
                        : 0.5000000000

    -- Example 2 set both to same number:
    UPDATE dummy_rast SET rast = ST_SetSkew(rast,0) WHERE rid = 1;
    SELECT rid, ST_SkewX(rast) As skewx, ST_SkewY(rast) As skewy,
        ST_GeoReference(rast) as georef
    FROM dummy_rast WHERE rid = 1;

     rid | skewx | skewy |    georef
    -----+-------+-------+--------------
       1 |     0 |     0 | 2.0000000000
                         : 0.0000000000
                         : 0.0000000000
                         : 3.0000000000
                         : 0.5000000000
                         : 0.5000000000

## See Also

ST_GeoReference, ST_SetGeoReference, ST_SkewX, ST_SkewY

## Name

ST_SetSRID — Sets the SRID of a raster to a particular integer srid defined in the spatial_ref_sys table.

## Synopsis

`raster ST_SetSRID(`raster rast, integer srid`)`;

## Description

Sets the SRID on a raster to a particular integer value.

This function does not transform the raster in any way - it simply sets meta data defining the spatial ref of the coordinate reference system that it's currently in. Useful for transformations later.

## See Also

Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems”, ST_SRID

## Name

ST_SetUpperLeft — Sets the value of the upper left corner of the pixel to projected X and Y coordinates.

## Synopsis

`raster ST_SetUpperLeft(`raster rast, double precision x, double precision y`)`;

## Description

Set the value of the upper left corner of raster to the projected X coordinates

## Examples

    SELECT ST_SetUpperLeft(rast,-71.01,42.37)
    FROM dummy_rast
    WHERE rid = 2;

## See Also

ST_UpperLeftX, ST_UpperLeftY

## Name

ST_Resample — Resample a raster using a specified resampling algorithm, new dimensions, an arbitrary grid corner and a set of raster georeferencing attributes defined or borrowed from another raster. New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.

## Synopsis

`raster ST_Resample(`raster rast, integer width, integer height, integer srid=same_as_rast, double precision gridx=NULL, double precision gridy=NULL, double precision skewx=0, double precision skewy=0, text algorithm=NearestNeighbour, double precision maxerr=0.125`)`;

`raster ST_Resample(`raster rast, integer srid=NULL, double precision scalex=0, double precision scaley=0, double precision gridx=NULL, double precision gridy=NULL, double precision skewx=0, double precision skewy=0, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

`raster ST_Resample(`raster rast, raster ref, text algorithm=NearestNeighbour, double precision maxerr=0.125, boolean usescale=true`)`;

`raster ST_Resample(`raster rast, raster ref, boolean usescale, text algorithm=NearestNeighbour, double precision maxerr=0.125`)`;

## Description

Resample a raster using a specified resampling algorithm, new dimensions (width & height), a grid corner (gridx & gridy) and a set of raster georeferencing attributes (scalex, scaley, skewx & skewy) defined or borrowed from another raster.

New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor which is the fastest but produce the worst interpolation.

A maxerror percent of 0.125 is used if no `maxerr` is specified.

Only works if raster is in a known spatial reference system (SRID).

Refer to: GDAL Warp resampling methods for more details.

Availability: 2.0.0 Requires GDAL 1.6.1+

## Examples

    SELECT ST_Width(orig) As orig_width, ST_Width(reduce_100) As new_width
     FROM (
     SELECT rast As orig, ST_Resample(rast,100,100) As reduce_100
      FROM aerials.boston
    	WHERE ST_Intersects(rast,
    	  ST_Transform(
    	    ST_MakeEnvelope(-71.128, 42.2392,-71.1277, 42.2397, 4326),26986) )
    	        limit 1 ) As foo;
     orig_width | new_width
    ------------+-------------
            200 |         100

## See Also

ST_Rescale, ST_Transform

## Name

ST_Rescale — Resample a raster by adjusting only its scale (or pixel size). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.

## Synopsis

`raster ST_Rescale(`raster rast, double precision scalexy, text algorithm=NearestNeighbour, double precision maxerr=0.125`)`;

`raster ST_Rescale(`raster rast, double precision scalex, double precision scaley, text algorithm=NearestNeighbour, double precision maxerr=0.125`)`;

## Description

Resample a raster by adjusting only its scale (or pixel size). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. The default is NearestNeighbor which is the fastest but results in the worst interpolation.

`scalex` and `scaley` define the new pixel size. scaley must often be negative to get well oriented raster.

When the new scalex or scaley is not a divisor of the raster width or height, the extent of the resulting raster is expanded to encompass the extent of the provided raster.

A maxerror percent of 0.125 is used if no `maxerr` is specified.

Refer to: GDAL Warp resampling methods for more details.

Only works if raster is in a known spatial reference system (SRID).

ST_Rescale is different from ST_SetScale in that ST_SetScale do not resample the raster to match the raster extent. ST_SetScale only changes the metadata (or georeference) of the raster to correct an originally mis-specified scaling. ST_Rescale results in a raster having different width and height computed to fit the geographic extent of the input raster. ST_SetScale do not modify the width, nor the height of the raster.

Availability: 2.0.0 Requires GDAL 1.6.1+

## Examples

A simple example rescaling a raster from a pixel size of 0.001 degree to a pixel size of 0.0015 degree.

    -- the original raster pixel size
    SELECT ST_PixelWidth(ST_AddBand(ST_MakeEmptyRaster(100, 100, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0)) width

       width
    ----------
    0.001

    -- the rescaled raster raster pixel size
    SELECT ST_PixelWidth(ST_Rescale(ST_AddBand(ST_MakeEmptyRaster(100, 100, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0), 0.0015)) width

       width
    ----------
    0.0015

## See Also

ST_SetScale, ST_ScaleX, ST_ScaleY, ST_Resample, ST_Transform

## Name

ST_Reskew — Resample a raster by adjusting only its skew (or rotation parameters). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.

## Synopsis

`raster ST_Reskew(`raster rast, double precision skewxy, text algorithm=NearestNeighbour, double precision maxerr=0.125`)`;

`raster ST_Reskew(`raster rast, double precision skewx, double precision skewy, text algorithm=NearestNeighbour, double precision maxerr=0.125`)`;

## Description

Resample a raster by adjusting only its skew (or rotation parameters). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. The default is NearestNeighbor which is the fastest but results in the worst interpolation.

`skewx` and `skewy` define the new skew.

The extent of the new raster will encompass the extent of the provided raster.

A maxerror percent of 0.125 if no `maxerr` is specified.

Only works if raster is in a known spatial reference system (SRID).

Refer to: GDAL Warp resampling methods for more details.

ST_Reskew is different from ST_SetSkew in that ST_SetSkew do not resample the raster to match the raster extent. ST_SetSkew only changes the metadata (or georeference) of the raster to correct an originally mis-specified skew. ST_Reskew results in a raster having different width and height computed to fit the geographic extent of the input raster. ST_SetSkew do not modify the width, nor the height of the raster.

Availability: 2.0.0 Requires GDAL 1.6.1+

## Examples

A simple example reskewing a raster from a skew of 0.0 to a skew of 0.0015.

    -- the original raster pixel size
    SELECT ST_Rotation(ST_AddBand(ST_MakeEmptyRaster(100, 100, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0))

    -- the rescaled raster raster pixel size
    SELECT ST_Rotation(ST_Reskew(ST_AddBand(ST_MakeEmptyRaster(100, 100, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0), 0.0015))

## See Also

ST_Resample, ST_Rescale, ST_SetSkew, ST_SetRotation, ST_SkewX, ST_SkewY, ST_Transform

## Name

ST_SnapToGrid — Resample a raster by snapping it to a grid. New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.

## Synopsis

`raster ST_SnapToGrid(`raster rast, double precision gridx, double precision gridy, text algorithm=NearestNeighbour, double precision maxerr=0.125, double precision scalex=DEFAULT 0, double precision scaley=DEFAULT 0`)`;

`raster ST_SnapToGrid(`raster rast, double precision gridx, double precision gridy, double precision scalex, double precision scaley, text algorithm=NearestNeighbour, double precision maxerr=0.125`)`;

`raster ST_SnapToGrid(`raster rast, double precision gridx, double precision gridy, double precision scalexy, text algorithm=NearestNeighbour, double precision maxerr=0.125`)`;

## Description

Resample a raster by snapping it to a grid defined by an arbitrary pixel corner (gridx & gridy) and optionally a pixel size (scalex & scaley). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. The default is NearestNeighbor which is the fastest but results in the worst interpolation.

`gridx` and `gridy` define any arbitrary pixel corner of the new grid. This is not necessarily the upper left corner of the new raster and it does not have to be inside or on the edge of the new raster extent.

You can optionnal define the pixel size of the new grid with `scalex` and `scaley`.

The extent of the new raster will encompass the extent of the provided raster.

A maxerror percent of 0.125 if no `maxerr` is specified.

Only works if raster is in a known spatial reference system (SRID).

Refer to: GDAL Warp resampling methods for more details.

Use ST_Resample if you need more control over the grid parameters.

Availability: 2.0.0 Requires GDAL 1.6.1+

## Examples

A simple example snapping a raster to a slightly different grid.

    -- the original raster pixel size
    SELECT ST_UpperLeftX(ST_AddBand(ST_MakeEmptyRaster(10, 10, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0))

    -- the rescaled raster raster pixel size
    SELECT ST_UpperLeftX(ST_SnapToGrid(ST_AddBand(ST_MakeEmptyRaster(10, 10, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0), 0.0002, 0.0002))

## See Also

ST_Resample, ST_Rescale, ST_UpperLeftX, ST_UpperLeftY

## Name

ST_Transform — Reprojects a raster in a known spatial reference system to another known spatial reference system using specified resampling algorithm. Options are NearestNeighbor, Bilinear, Cubic, CubicSpline, Lanczos defaulting to NearestNeighbor.

## Synopsis

`raster ST_Transform(`raster rast, integer srid, double precision scalex, double precision scaley, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

`raster ST_Transform(`raster rast, integer srid, text algorithm=NearestNeighbor, double precision maxerr=0.125, double precision scalex, double precision scaley`)`;

## Description

Reprojects a raster in a known spatial reference system to another known spatial reference system using specified pixel warping algorithm. Uses 'NearestNeighbor' if no algorithm is specified and maxerror percent of 0.125 if no maxerr is specified.

Algorithm options are: 'NearestNeighbor', 'Bilinear', 'Cubic', 'CubicSpline', and 'Lanczos'. Refer to: GDAL Warp resampling methods for more details.

Availability: 2.0.0 Requires GDAL 1.6.1+

If you find your transformation support is not working right, you may need to set the environment variable PROJSO to the .so or .dll projection library your PostGIS is using. This just needs to have the name of the file. So for example on windows, you would in Control Panel -> System -> Environment Variables add a system variable called `PROJSO` and set it to `libproj.dll` (if you are using proj 4.6.1). You'll have to restart your PostgreSQL service/daemon after this change.

## Examples

    SELECT ST_Width(mass_stm) As w_before, ST_Width(wgs_84) As w_after,
      ST_Height(mass_stm) As h_before, ST_Height(wgs_84) As h_after
    	FROM
    	( SELECT rast As mass_stm, ST_Transform(rast,4326) As wgs_84
      ,  ST_Transform(rast,4326, 'Bilinear') AS wgs_84_bilin
    		FROM aerials.o_2_boston
    			WHERE ST_Intersects(rast,
    				ST_Transform(ST_MakeEnvelope(-71.128, 42.2392,-71.1277, 42.2397, 4326),26986) )
    		LIMIT 1) As foo;

     w_before | w_after | h_before | h_after
    ----------+---------+----------+---------
          200 |     228 |      200 |     170

original mass state plane meters (mass_stm) | After transform to wgs 84 long lat (wgs_84) | After transform to wgs 84 long lat with bilinear algorithm instead of NN default (wgs_84_bilin)

## See Also

ST_Transform, ST_SetSRID

## 9.8. Raster Band Editors

## Name

ST_SetBandNoDataValue — Sets the value for the given band that represents no data. Band 1 is assumed if no band is specified. To mark a band as having no nodata value, set the nodata value = NULL.

## Synopsis

`raster ST_SetBandNoDataValue(`raster rast, double precision nodatavalue`)`;

`raster ST_SetBandNoDataValue(`raster rast, integer band, double precision nodatavalue, boolean forcechecking=false`)`;

## Description

Sets the value that represents no data for the band. Band 1 is assumed if not specified. This will effect ST_Polygon and ST_ConvexHull results.

## Examples

    -- change just first band no data value
    UPDATE dummy_rast
    	SET rast = ST_SetBandNoDataValue(rast,1, 254)
    WHERE rid = 2;

    -- change no data band value of bands 1,2,3
    UPDATE dummy_rast
    	SET rast =
    		ST_SetBandNoDataValue(
    			ST_SetBandNoDataValue(
    				ST_SetBandNoDataValue(
    					rast,1, 254)
    				,2,99),
    				3,108)
    		WHERE rid = 2;

    -- wipe out the nodata value this will ensure all pixels are considered for all processing functions
    UPDATE dummy_rast
    	SET rast = ST_SetBandNoDataValue(rast,1, NULL)
    WHERE rid = 2;

## See Also

ST_BandNoDataValue, ST_NumBands

## Name

ST_SetBandIsNoData — Sets the isnodata flag of the band to TRUE. You may want to call this function if ST_BandIsNoData(rast, band) != ST_BandIsNodata(rast, band, TRUE). This is, if the isnodata flag is dirty. Band 1 is assumed if no band is specified.

## Synopsis

`integer ST_SetBandIsNoData(`raster rast, integer band=1`)`;

## Description

Sets the isnodata flag for the band to true. Band 1 is assumed if not specified. This function should be called only when the flag is considered dirty. This is, when the result calling ST_BandIsNoData is different using TRUE as last argument and without using it

Availability: 2.0.0

Currently, the loader (raster2pgsql.py) is not able to set the isnodata flag for bands. So, this is the fastest way to set it to TRUE, without changing any other band value

## Examples

    -- Create dummy table with one raster column
    create table dummy_rast (rid integer, rast raster);

    -- Add raster with two bands, one pixel/band. In the first band, nodatavalue = pixel value = 3.
    -- In the second band, nodatavalue = 13, pixel value = 4
    insert into dummy_rast values(1,
    (
    '01' -- little endian (uint8 ndr)
    ||
    '0000' -- version (uint16 0)
    ||
    '0200' -- nBands (uint16 0)
    ||
    '17263529ED684A3F' -- scaleX (float64 0.000805965234044584)
    ||
    'F9253529ED684ABF' -- scaleY (float64 -0.00080596523404458)
    ||
    '1C9F33CE69E352C0' -- ipX (float64 -75.5533328537098)
    ||
    '718F0E9A27A44840' -- ipY (float64 49.2824585505576)
    ||
    'ED50EB853EC32B3F' -- skewX (float64 0.000211812383858707)
    ||
    '7550EB853EC32B3F' -- skewY (float64 0.000211812383858704)
    ||
    'E6100000' -- SRID (int32 4326)
    ||
    '0100' -- width (uint16 1)
    ||
    '0100' -- height (uint16 1)
    ||
    '4' -- hasnodatavalue set to true, isnodata value set to false (when it should be true)
    ||
    '2' -- first band type (4BUI)
    ||
    '03' -- novalue==3
    ||
    '03' -- pixel(0,0)==3 (same that nodata)
    ||
    '0' -- hasnodatavalue set to false
    ||
    '5' -- second band type (16BSI)
    ||
    '0D00' -- novalue==13
    ||
    '0400' -- pixel(0,0)==4
    )::raster
    );

    select st_bandisnodata(rast, 1) from dummy_rast where rid = 1; -- Expected false
    select st_bandisnodata(rast, 1, TRUE) from dummy_rast where rid = 1; -- Expected true

    -- The isnodata flag is dirty. We are going to set it to true
    update dummy_rast set rast = st_setbandisnodata(rast, 1) where rid = 1;

    select st_bandisnodata(rast, 1) from dummy_rast where rid = 1; -- Expected true

## See Also

ST_BandNoDataValue, ST_NumBands, ST_SetBandNoDataValue, ST_BandIsNoData

## 9.9. Raster Band Statistics and Analytics

## Name

ST_Count — Returns the number of pixels in a given band of a raster or raster coverage. If no band is specified defaults to band 1. If exclude_nodata_value is set to true, will only count pixels that are not equal to the nodata value.

## Synopsis

`bigint ST_Count(`raster rast, integer nband=1, boolean exclude_nodata_value=true`)`;

`bigint ST_Count(`raster rast, boolean exclude_nodata_value`)`;

`bigint ST_Count(`text rastertable, text rastercolumn, integer nband=1, boolean exclude_nodata_value=true`)`;

`bigint ST_Count(`text rastertable, text rastercolumn, boolean exclude_nodata_value`)`;

## Description

Returns the number of pixels in a given band of a raster or raster coverage. If no band is specified `nband` defaults to 1.

If `exclude_nodata_value` is set to true, will only count pixels with value not equal to the `nodata` value of the raster. Set `exclude_nodata_value` to false to get count all pixels

Availability: 2.0.0

## Examples

    --example will count all pixels not 249 and one will count all pixels.  --
    SELECT rid, ST_Count(ST_SetBandNoDataValue(rast,249)) As exclude_nodata,
            ST_Count(ST_SetBandNoDataValue(rast,249),false) As include_nodata
        FROM dummy_rast WHERE rid=2;

    rid | exclude_nodata | include_nodata
    -----+----------------+----------------
       2 |             23 |             25

## See Also

ST_SetBandNoDataValue

## Name

ST_Histogram — Returns a set of histogram summarizing a raster or raster coverage data distribution separate bin ranges. Number of bins are autocomputed if not specified.

## Synopsis

`SETOF histogram ST_Histogram(`raster rast, integer nband=1, boolean exclude_nodata_value=true, integer bins=autocomputed, double precision[] width=NULL, boolean right=false`)`;

`SETOF histogram ST_Histogram(`raster rast, integer nband, integer bins, double precision[] width=NULL, boolean right=false`)`;

`SETOF histogram ST_Histogram(`raster rast, integer nband, boolean exclude_nodata_value, integer bins, boolean right`)`;

`SETOF histogram ST_Histogram(`raster rast, integer nband, integer bins, boolean right`)`;

`SETOF histogram ST_Histogram(`text rastertable, text rastercolumn, integer nband, integer bins, boolean right`)`;

`SETOF histogram ST_Histogram(`text rastertable, text rastercolumn, integer nband, boolean exclude_nodata_value, integer bins, boolean right`)`;

`SETOF histogram ST_Histogram(`text rastertable, text rastercolumn, integer nband=1, boolean exclude_nodata_value=true, integer bins=autocomputed, double precision[] width=NULL, boolean right=false`)`;

`SETOF histogram ST_Histogram(`text rastertable, text rastercolumn, integer nband=1, integer bins, double precision[] width=NULL, boolean right=false`)`;

## Description

Returns set of `histogram` records consisting of min,max, count, percent for a given raster band for each bin. If no band is specified `nband` defaults to 1.

By default only considers pixel values not equal to the `nodata` value . Set `exclude_nodata_value` to false to get count all pixels.

`width` double precision[]

  width: an array indicating the width of each category/bin. If the number of bins is greater than the number of widths, the widths are repeated.

  Example: 9 bins, widths are [a, b, c] will have the output be [a, b, c, a, b, c, a, b, c]

`bins` integer

  Number of breakouts -- this is the number of records you'll get back from the function if specified. If not specified then the number of breakouts is autocomputed.

`right` boolean

  compute the histogram from the right rather than from the left (default). This changes the criteria for evaluating a value x from [a, b) to (a, b]

Availability: 2.0.0

## Example: Single raster tile - compute histograms for bands 1, 2, 3 and autocompute bins

    SELECT band, (stats).*
    FROM (SELECT rid, band, ST_Histogram(rast, band) As stats
        FROM dummy_rast CROSS JOIN generate_series(1,3) As band
         WHERE rid=2) As foo;

     band |  min  |  max  | count | percent
    ------+-------+-------+-------+---------
        1 |   249 |   250 |     2 |    0.08
        1 |   250 |   251 |     2 |    0.08
        1 |   251 |   252 |     1 |    0.04
        1 |   252 |   253 |     2 |    0.08
        1 |   253 |   254 |    18 |    0.72
        2 |    78 | 113.2 |    11 |    0.44
        2 | 113.2 | 148.4 |     4 |    0.16
        2 | 148.4 | 183.6 |     4 |    0.16
        2 | 183.6 | 218.8 |     1 |    0.04
        2 | 218.8 |   254 |     5 |     0.2
        3 |    62 | 100.4 |    11 |    0.44
        3 | 100.4 | 138.8 |     5 |     0.2
        3 | 138.8 | 177.2 |     4 |    0.16
        3 | 177.2 | 215.6 |     1 |    0.04
        3 | 215.6 |   254 |     4 |    0.16

## Example: Just band 2 but for 6 bins

    SELECT (stats).*
    FROM (SELECT rid, ST_Histogram(rast, 2,6) As stats
        FROM dummy_rast
         WHERE rid=2) As foo;

        min     |    max     | count | percent
    ------------+------------+-------+---------
             78 | 107.333333 |     9 |    0.36
     107.333333 | 136.666667 |     6 |    0.24
     136.666667 |        166 |     0 |       0
            166 | 195.333333 |     4 |    0.16
     195.333333 | 224.666667 |     1 |    0.04
     224.666667 |        254 |     5 |     0.2
    (6 rows)

    -- Same as previous but we explicitly control the pixel value range of each bin.
    SELECT (stats).*
    FROM (SELECT rid, ST_Histogram(rast, 2,6,ARRAY[0.5,1,4,100,5]) As stats
        FROM dummy_rast
         WHERE rid=2) As foo;

      min  |  max  | count | percent
    -------+-------+-------+----------
        78 |  78.5 |     1 |     0.08
      78.5 |  79.5 |     1 |     0.04
      79.5 |  83.5 |     0 |        0
      83.5 | 183.5 |    17 |   0.0068
     183.5 | 188.5 |     0 |        0
     188.5 |   254 |     6 | 0.003664
    (6 rows)

## See Also

histogram, ST_Count, ST_SummaryStats

## Name

ST_Quantile — Compute quantiles for a raster or raster table coverage in the context of the sample or population. Thus, a value could be examined to be at the raster's 25%, 50%, 75% percentile.

## Synopsis

`SETOF quantile ST_Quantile(`raster rast, integer nband=1, boolean exclude_nodata_value=true, double precision[] quantiles=NULL`)`;

`SETOF quantile ST_Quantile(`raster rast, double precision[] quantiles`)`;

`SETOF quantile ST_Quantile(`raster rast, integer nband, double precision[] quantiles`)`;

`double precision ST_Quantile(`raster rast, double precision quantile`)`;

`double precision ST_Quantile(`raster rast, boolean exclude_nodata_value, double precision quantile=NULL`)`;

`double precision ST_Quantile(`raster rast, integer nband, double precision quantile`)`;

`double precision ST_Quantile(`raster rast, integer nband, boolean exclude_nodata_value, double precision quantile`)`;

`double precision ST_Quantile(`raster rast, integer nband, double precision quantile`)`;

`setof quantile ST_Quantile(`text rastertable, text rastercolumn, integer nband=1, boolean exclude_nodata_value=true, double precision[] quantiles=NULL`)`;

`setof quantile ST_Quantile(`text rastertable, text rastercolumn, integer nband, double precision[] quantiles`)`;

## Description

Compute quantiles for a raster or raster table coverage in the context of the sample or population. Thus, a value could be examined to be at the raster's 25%, 50%, 75% percentile.

If `exclude_nodata_value` is set to false, will also count pixels with no data.

Availability: 2.0.0

## Examples

    UPDATE dummy_rast SET rast = ST_SetBandNoDataValue(rast,249) WHERE rid=2;
    --Example will consider only pixels of band 1 that are not 249 and in named quantiles --

    SELECT (pvq).*
    FROM (SELECT ST_Quantile(rast, ARRAY[0.25,0.75]) As pvq
        FROM dummy_rast WHERE rid=2) As foo
        ORDER BY (pvq).quantile;

     quantile | value
    ----------+-------
         0.25 |   253
         0.75 |   254

    SELECT ST_Quantile(rast, 0.75) As value
        FROM dummy_rast WHERE rid=2;

    value
    ------
      254

    --real live example.  Quantile of all pixels in band 2 intersecting a geometry
    SELECT rid, (ST_Quantile(rast,2)).* As pvc
        FROM o_4_boston
            WHERE ST_Intersects(rast,
                ST_GeomFromText('POLYGON((224486 892151,224486 892200,224706 892200,224706 892151,224486 892151))',26986)
                )
    ORDER BY value, quantile,rid
    ;

     rid | quantile | value
    -----+----------+-------
       1 |        0 |     0
       2 |        0 |     0
      14 |        0 |     1
      15 |        0 |     2
      14 |     0.25 |    37
       1 |     0.25 |    42
      15 |     0.25 |    47
       2 |     0.25 |    50
      14 |      0.5 |    56
       1 |      0.5 |    64
      15 |      0.5 |    66
       2 |      0.5 |    77
      14 |     0.75 |    81
      15 |     0.75 |    87
       1 |     0.75 |    94
       2 |     0.75 |   106
      14 |        1 |   199
       1 |        1 |   244
       2 |        1 |   255
      15 |        1 |   255

## See Also

ST_Count, ST_SetBandNoDataValue

## Name

ST_SummaryStats — Returns summary stats consisting of count,sum,mean,stddev,min,max for a given raster band of a raster or raster coverage. Band 1 is assumed is no band is specified.

## Synopsis

`summarystats ST_SummaryStats(`text rastertable, text rastercolumn, boolean exclude_nodata_value`)`;

`summarystats ST_SummaryStats(`raster rast, boolean exclude_nodata_value`)`;

`summarystats ST_SummaryStats(`text rastertable, text rastercolumn, integer nband=1, boolean exclude_nodata_value=true`)`;

`summarystats ST_SummaryStats(`raster rast, integer nband, boolean exclude_nodata_value`)`;

## Description

Returns `summarystats` consisting of count, sum, mean, stddev, min, max for a given raster band of a raster or raster coverage. If no band is specified `nband` defaults to 1.

By default only considers pixel values not equal to the `nodata` value. Set `exclude_nodata_value` to false to get count of all pixels.

By default will sample all pixels. To get faster response, set `sample_percent` to lower than 1

Availability: 2.0.0

## Example: Single raster tile

    SELECT rid, band, (stats).*
    FROM (SELECT rid, band, ST_SummaryStats(rast, band) As stats
        FROM dummy_rast CROSS JOIN generate_series(1,3) As band
         WHERE rid=2) As foo;

     rid | band | count | sum  |    mean    |  stddev   | min | max
    -----+------+-------+------+------------+-----------+-----+-----
       2 |    1 |    23 | 5821 | 253.086957 |  1.248061 | 250 | 254
       2 |    2 |    25 | 3682 |     147.28 | 59.862188 |  78 | 254
       2 |    3 |    25 | 3290 |      131.6 | 61.647384 |  62 | 254

## Example: Summarize pixels that intersect buildings of interest

This example took 574ms on PostGIS windows 64-bit with all of Boston Buildings and aerial Tiles (tiles each 150x150 pixels ~ 134,000 tiles), ~102,000 building records

    WITH
    -- our features of interest
       feat AS (SELECT gid As building_id, geom_26986 As geom FROM buildings AS b
        WHERE gid IN(100, 103,150)
       ),
    -- clip band 2 of raster tiles to boundaries of builds
    -- then get stats for these clipped regions
       b_stats AS
    	(SELECT  building_id, (stats).*
    FROM (SELECT building_id, ST_SummaryStats(ST_Clip(rast,2,geom)) As stats
        FROM aerials.boston
    		INNER JOIN feat
    	ON ST_Intersects(feat.geom,rast)
     ) As foo
     )
    -- finally summarize stats
    SELECT building_id, SUM(count) As num_pixels
      , MIN(min) As min_pval
      ,  MAX(max) As max_pval
      , SUM(mean*count)/SUM(count) As avg_pval
    	FROM b_stats
     WHERE count > 0
    	GROUP BY building_id
    	ORDER BY building_id;
     building_id | num_pixels | min_pval | max_pval |     avg_pval
    -------------+------------+----------+----------+------------------
             100 |       1090 |        1 |      255 | 61.0697247706422
             103 |        655 |        7 |      182 | 70.5038167938931
             150 |        895 |        2 |      252 | 185.642458100559

## Example: Raster coverage

    -- stats for each band --
    SELECT band, (stats).*
    FROM (SELECT band, ST_SummaryStats('o_4_boston','rast', band) As stats
        FROM generate_series(1,3) As band) As foo;

     band |  count  |  sum   |       mean       |      stddev      | min | max
    ------+---------+--------+------------------+------------------+-----+-----
        1 | 8450000 | 725799 | 82.7064349112426 | 45.6800222638537 |   0 | 255
        2 | 8450000 | 700487 | 81.4197705325444 | 44.2161184161765 |   0 | 255
        3 | 8450000 | 575943 |  74.682739408284 | 44.2143885481407 |   0 | 255

    -- For a table -- will get better speed if set sampling to less than 100%
    -- Here we set to 25% and get a much faster answer
    SELECT band, (stats).*
    FROM (SELECT band, ST_SummaryStats('o_4_boston','rast', band,true,0.25) As stats
        FROM generate_series(1,3) As band) As foo;

     band |  count  |  sum   |       mean       |      stddev      | min | max
    ------+---------+--------+------------------+------------------+-----+-----
        1 | 2112500 | 180686 | 82.6890480473373 | 45.6961043857248 |   0 | 255
        2 | 2112500 | 174571 |  81.448503668639 | 44.2252623171821 |   0 | 255
        3 | 2112500 | 144364 | 74.6765884023669 | 44.2014869384578 |   0 | 255

## See Also

ST_Count, summarystats, ST_Clip

## Name

ST_ValueCount — Returns a set of records containing a pixel band value and count of the number of pixels in a given band of a raster (or a raster coverage) that have a given set of values. If no band is specified defaults to band 1. By default nodata value pixels are not counted. and all other values in the pixel are output and pixel band values are rounded to the nearest integer.

## Synopsis

`SETOF record ST_ValueCount(`raster rast, integer nband=1, boolean exclude_nodata_value=true, double precision[] searchvalues=NULL, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`SETOF record ST_ValueCount(`raster rast, integer nband, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`SETOF record ST_ValueCount(`raster rast, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`bigint ST_ValueCount(`raster rast, double precision searchvalue, double precision roundto=0`)`;

`bigint ST_ValueCount(`raster rast, integer nband, boolean exclude_nodata_value, double precision searchvalue, double precision roundto=0`)`;

`bigint ST_ValueCount(`raster rast, integer nband, double precision searchvalue, double precision roundto=0`)`;

`SETOF record ST_ValueCount(`text rastertable, text rastercolumn, integer nband=1, boolean exclude_nodata_value=true, double precision[] searchvalues=NULL, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`SETOF record ST_ValueCount(`text rastertable, text rastercolumn, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`SETOF record ST_ValueCount(`text rastertable, text rastercolumn, integer nband, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`bigintST_ValueCount(`text rastertable, text rastercolumn, integer nband, boolean exclude_nodata_value, double precision searchvalue, double precision roundto=0`)`;

`bigint ST_ValueCount(`text rastertable, text rastercolumn, double precision searchvalue, double precision roundto=0`)`;

`bigint ST_ValueCount(`text rastertable, text rastercolumn, integer nband, double precision searchvalue, double precision roundto=0`)`;

## Description

Returns a set of records with columns `value` `count` which contain the pixel band value and count of pixels in the raster tile or raster coverage of selected band.

If no band is specified `nband` defaults to 1. If no `searchvalues` are specified, will return all pixel values found in the raster or raster coverage. If one searchvalue is given, will return an integer instead of records denoting the count of pixels having that pixel band value

If `exclude_nodata_value` is set to false, will also count pixels with no data.

Availability: 2.0.0

## Examples

    UPDATE dummy_rast SET rast = ST_SetBandNoDataValue(rast,249) WHERE rid=2;
    --Example will count only pixels of band 1 that are not 249. --

    SELECT (pvc).*
    FROM (SELECT ST_ValueCount(rast) As pvc
        FROM dummy_rast WHERE rid=2) As foo
        ORDER BY (pvc).value;

     value | count
    -------+-------
       250 |     2
       251 |     1
       252 |     2
       253 |     6
       254 |    12

    -- Example will coount all pixels of band 1 including 249 --
    SELECT (pvc).*
    FROM (SELECT ST_ValueCount(rast,1,false) As pvc
        FROM dummy_rast WHERE rid=2) As foo
        ORDER BY (pvc).value;

     value | count
    -------+-------
       249 |     2
       250 |     2
       251 |     1
       252 |     2
       253 |     6
       254 |    12

    -- Example will count only non-nodata value pixels of band 2
    SELECT (pvc).*
    FROM (SELECT ST_ValueCount(rast,2) As pvc
        FROM dummy_rast WHERE rid=2) As foo
        ORDER BY (pvc).value;
     value | count
    -------+-------
        78 |     1
        79 |     1
        88 |     1
        89 |     1
        96 |     1
        97 |     1
        98 |     1
        99 |     2
       112 |     2
    :

    --real live example.  Count all the pixels in an aerial raster tile band 2 intersecting a geometry
    -- and return only the pixel band values that have a count > 500
    SELECT (pvc).value, SUM((pvc).count) As total
    FROM (SELECT ST_ValueCount(rast,2) As pvc
        FROM o_4_boston
            WHERE ST_Intersects(rast,
                ST_GeomFromText('POLYGON((224486 892151,224486 892200,224706 892200,224706 892151,224486 892151))',26986)
                 )
            ) As foo
        GROUP BY (pvc).value
        HAVING SUM((pvc).count) > 500
        ORDER BY (pvc).value;

     value | total
    -------+-----
        51 | 502
        54 | 521

    -- Just return count of pixels in each raster tile that have value of 100 of tiles that intersect  a specific geometry --
    SELECT rid, ST_ValueCount(rast,2,100) As count
        FROM o_4_boston
            WHERE ST_Intersects(rast,
                ST_GeomFromText('POLYGON((224486 892151,224486 892200,224706 892200,224706 892151,224486 892151))',26986)
                 ) ;

     rid | count
    -----+-------
       1 |    56
       2 |    95
      14 |    37
      15 |    64

## See Also

ST_Count, ST_SetBandNoDataValue

## 9.10. Raster Outputs

## Name

ST_AsBinary — Return the Well-Known Binary (WKB) representation of the raster without SRID meta data.

## Synopsis

`bytea ST_AsBinary(`raster rast`)`;

## Description

Returns the Binary representation of the raster. There are 2 variants of the function. The first variant takes no endian encoding parameter and defaults to little endian. The second variant takes a second argument denoting the encoding - using little-endian ('NDR') or big-endian ('XDR') encoding.

This is useful in binary cursors to pull data out of the database without converting it to a string representation.

## Examples

    SELECT ST_AsBinary(rast) As rastbin
    FROM dummy_rast WHERE rid=1;

    					 rastbin
    ---------------------------------------------------------------------------------
    \001\000\000\000\000\000\000\000\000\000\000\000@\000\000\000\000\000\000\010@\
    000\000\000\000\000\000\340?\000\000\000\000\000\000\340?\000\000\000\000\000\00
    0\000\000\000\000\000\000\000\000\000\000\012\000\000\000\012\000\024\000

## Name

ST_AsGDALRaster — Return the raster tile in the designated GDAL Raster format. Raster formats are one of those supported by your compiled library. Use ST_GDALRasters() to get a list of formats supported by your library.

## Synopsis

`bytea ST_AsGDALRaster(`raster rast, text format, text[] options=NULL, integer srid=sameassource`)`;

## Description

Returns the raster tile in the designated format. Arguments are itemized below:

- `format` format to output. This is dependent on the drivers compiled in your libgdal library. Generally available are 'JPEG', 'GTIff', 'PNG'. Use ST_GDALDrivers to get a list of formats supported by your library.

- `options` text array of GDAL options. Valid options are dependent on the format. Refer to GDAL Raster format options for more details.

- `srs` The proj4text or srtext (from spatial_ref_sys) to embed in the image

Availability: 2.0.0 - requires GDAL >= 1.6.0.

## JPEG Output Examples

    SELECT ST_AsGDALRaster(rast, 'JPEG') As rastjpg
    FROM dummy_rast WHERE rid=1;

    SELECT ST_AsGDALRaster(rast, 'JPEG', ARRAY!['QUALITY=50']) As rastjpg
    FROM dummy_rast WHERE rid=2;

## GTIFF Output Examples

    SELECT ST_AsGDALRaster(rast, 'GTiff') As rastjpg
    FROM dummy_rast WHERE rid=2;

    -- Out GeoTiff with jpeg compression, 90% quality
    SELECT ST_AsGDALRaster(rast, 'GTiff',
      ARRAY['COMPRESS=JPEG', 'JPEG_QUALITY=90'],
      4269) As rasttiff
    FROM dummy_rast WHERE rid=2;

## See Also

Section 5.3, “Building Custom Applications with PostGIS Raster”, ST_GDALDrivers, ST_SRID

## Name

ST_AsJPEG — Return the raster tile selected bands as a single Joint Photographic Exports Group (JPEG) image (byte array). If no band is specified and 1 or more than 3 bands, then only the first band is used. If only 3 bands then all 3 bands are used and mapped to RGB.

## Synopsis

`bytea ST_AsJPEG(`raster rast, text[] options=NULL`)`;

`bytea ST_AsJPEG(`raster rast, integer nband, integer quality`)`;

`bytea ST_AsJPEG(`raster rast, integer nband, text[] options=NULL`)`;

`bytea ST_AsJPEG(`raster rast, integer[] nbands, text[] options=NULL`)`;

`bytea ST_AsJPEG(`raster rast, integer[] nbands, integer quality`)`;

## Description

Returns the selected bands of the raster as a single Joint Photographic Exports Group Image (JPEG). Use ST_AsGDALRaster if you need to export as less common raster types. If no band is specified and 1 or more than 3 bands, then only the first band is used. If 3 bands then all 3 bands are used. There are many variants of the function with many options. These are itemized below:

- `nband` is for single band exports.

- `nbands` is an array of bands to export (note that max is 3 for JPEG) and the order of the bands is RGB. e.g ARRAY[3,2,1] means map band 3 to Red, band 2 to green and band 1 to blue

- `quality` number from 0 to 100. The higher the number the crisper the image.

- `options` text Array of GDAL options as defined for JPEG (look at create_options for JPEG ST_GDALDrivers). For JPEG valid ones are `PROGRESSIVE` ON or OFF and `QUALITY` a range from 0 to 100 and default to 75. Refer to GDAL Raster format options for more details.

Availability: 2.0.0 - requires GDAL >= 1.6.0.

## Examples: Output

    -- output first 3 bands 75% quality
    SELECT ST_AsJPEG(rast) As rastjpg
        FROM dummy_rast WHERE rid=2;

    -- output only first band as 90% quality
    SELECT ST_AsJPEG(rast,1,90) As rastjpg
        FROM dummy_rast WHERE rid=2;

    -- output first 3 bands (but make band 2 Red, band 1 green, and band 3 blue, progressive and 90% quality
    SELECT ST_AsJPEG(rast,ARRAY[2,1,3],ARRAY['QUALITY=90','PROGRESSIVE=ON']) As rastjpg
        FROM dummy_rast WHERE rid=2;

## See Also

Section 5.3, “Building Custom Applications with PostGIS Raster”, ST_GDALDrivers, ST_AsGDALRaster, ST_AsPNG, ST_AsTIFF

## Name

ST_AsPNG — Return the raster tile selected bands as a single portable network graphics (PNG) image (byte array). If 1, 3, or 4 bands in raster and no bands are specified, then all bands are used. If more 2 or more than 4 bands and no bands specified, then only band 1 is used. Bands are mapped to RGB or RGBA space.

## Synopsis

`bytea ST_AsPNG(`raster rast, text[] options=NULL`)`;

`bytea ST_AsPNG(`raster rast, integer nband, integer compression`)`;

`bytea ST_AsPNG(`raster rast, integer nband, text[] options=NULL`)`;

`bytea ST_AsPNG(`raster rast, integer[] nbands, integer compression`)`;

`bytea ST_AsPNG(`raster rast, integer[] nbands, text[] options=NULL`)`;

## Description

Returns the selected bands of the raster as a single Portable Network Graphics Image (PNG). Use ST_AsGDALRaster if you need to export as less common raster types. If no band is specified, then the first 3 bands are exported. There are many variants of the function with many options. If no `srid` is specified then then srid of the raster is used. These are itemized below:

- `nband` is for single band exports.

- `nbands` is an array of bands to export (note that max is 3 for PNG) and the order of the bands is RGB. e.g ARRAY[3,2,1] means map band 3 to Red, band 2 to green and band 1 to blue

- `compression` number from 1 to 9. The higher the number the greater the compression.

- `options` text Array of GDAL options as defined for PNG (look at create_options for PNG of ST_GDALDrivers). For PNG valid one is only ZLEVEL (amount of time to spend on compression -- default 6) e.g. ARRAY['ZLEVEL=9']. WORLDFILE is not allowed since the function would have to output two outputs. Refer to GDAL Raster format options for more details.

Availability: 2.0.0 - requires GDAL >= 1.6.0.

## Examples

    SELECT ST_AsPNG(rast) As rastpng
    FROM dummy_rast WHERE rid=2;

    -- export the first 3 bands and map band 3 to Red, band 1 to Green, band 2 to blue
    SELECT ST_AsPNG(rast, ARRAY[3,1,2]) As rastpng
    FROM dummy_rast WHERE rid=2;

## See Also

ST_GDALDrivers, ST_AsGDALRaster, Section 5.3, “Building Custom Applications with PostGIS Raster”

## Name

ST_AsTIFF — Return the raster selected bands as a single TIFF image (byte array). If no band is specified, then will try to use all bands.

## Synopsis

`bytea ST_AsTIFF(`raster rast, text[] options='', integer srid=sameassource`)`;

`bytea ST_AsTIFF(`raster rast, text compression='', integer srid=sameassource`)`;

`bytea ST_AsTIFF(`raster rast, integer[] nbands, text compression='', integer srid=sameassource`)`;

`bytea ST_AsTIFF(`raster rast, integer[] nbands, text[] options, integer srid=sameassource`)`;

## Description

Returns the selected bands of the raster as a single Tagged Image File Format (TIFF). If no band is specified, will try to use all bands. This is a wrapper around ST_AsGDALRaster. Use ST_AsGDALRaster if you need to export as less common raster types. There are many variants of the function with many options. If no spatial reference SRS text is present, the spatial reference of the raster is used. These are itemized below:

- `nbands` is an array of bands to export (note that max is 3 for PNG) and the order of the bands is RGB. e.g ARRAY[3,2,1] means map band 3 to Red, band 2 to green and band 1 to blue

- `compression` Compression expression -- JPEG90 (or some other percent), LZW, JPEG, DEFLATE9.

- `options` text Array of GDAL create options as defined for GTiff (look at create_options for GTiff of ST_GDALDrivers). or refer to GDAL Raster format options for more details.

- `srid` srid of spatial_ref_sys of the raster. This is used to populate the georeference information

Availability: 2.0.0 - requires GDAL >= 1.6.0.

## Examples: Use jpeg compression 90%

    SELECT ST_AsTIFF(rast, 'JPEG90') As rasttiff
    FROM dummy_rast WHERE rid=2;

## See Also

ST_GDALDrivers, ST_AsGDALRaster, ST_SRID

## 9.11. Raster Processing

## Name

Box3D — Returns the box 3d representation of the enclosing box of the raster.

## Synopsis

`box3d Box3D(`raster rast`)`;

## Description

Returns the box representing the extent of the raster.

The polygon is defined by the corner points of the bounding box ((`MINX`, `MINY`), (`MAXX`, `MAXY`))

Changed: 2.0.0 In pre-2.0 versions, there used to be a box2d instead of box3d. Since box2d is a deprecated type, this was changed to box3d.

## Examples

    SELECT rid, Box3D(rast) As rastbox
    FROM dummy_rast;

    rid |        rastbox
    ----+-------------------------------------------------
    1   | BOX3D(0.5 0.5 0,20.5 60.5 0)
    2   | BOX3D(3427927.75 5793243.5 0,3427928 5793244 0)

## See Also

ST_Envelope

## Name

ST_Clip — Returns the raster clipped by the input geometry. If no band is specified all bands are returned. If `crop` is not specified, true is assumed meaning the output raster is cropped.

## Synopsis

`raster ST_Clip(`raster rast, geometry geom, double precision[] nodataval=NULL, boolean crop=true`)`;

`raster ST_Clip(`raster rast, geometry geom, boolean crop`)`;

`raster ST_Clip(`raster rast, integer band, geometry geom, boolean crop`)`;

## Description

Returns a raster that is clipped by the input geometry `geom`. If no band is specified all bands are returned.

Rasters resulting from ST_Clip must have a nodata value assigned for areas clipped, one for each band. If none are provided and the input raster do not have a nodata value defined, nodata values of the resulting raster are set to ST_MinPossibleValue(ST_BandPixelType(rast, band)). When the number of nodata value in the array is smaller than the number of band, the last one in the array is used for the remaining bands. If the number of nodata value is greater than the number of band, the extra nodata values are ignored. All variants accepting an array of nodata values also accept a single value which will be assigned to each band.

If `crop` is not specified, true is assumed meaning the output raster is cropped to the intersection of the `geom`and `rast` extents. If `crop` is set to false, the new raster gets the same extent as `rast`.

Availability: 2.0.0

Examples here use Massachusetts aerial data available on MassGIS site MassGIS Aerial Orthos. Coordinates are in Massachusetts State Plane Meters.

## Examples: 1 band clipping

    -- Clip the first band of an aerial tile by a 20 meter buffer.
    SELECT ST_Clip(rast, 1,
    		ST_Buffer(ST_Centroid(ST_Envelope(rast)),20)
    	) from aerials.boston
    WHERE rid = 4;

    -- Demonstrate effect of crop on final dimensions of raster
    -- Note how final extent is clipped to that of the geometry
    -- if crop = true
    SELECT ST_XMax(ST_Envelope(ST_Clip(rast, 1, clipper, true))) As xmax_w_trim,
    	ST_XMax(clipper) As xmax_clipper,
    	ST_XMax(ST_Envelope(ST_Clip(rast, 1, clipper, false))) As xmax_wo_trim,
    	ST_XMax(ST_Envelope(rast)) As xmax_rast_orig
    FROM (SELECT rast, ST_Buffer(ST_Centroid(ST_Envelope(rast)),6) As clipper
    	FROM aerials.boston
    WHERE rid = 6) As foo;

       xmax_w_trim    |   xmax_clipper   |   xmax_wo_trim   |  xmax_rast_orig
    ------------------+------------------+------------------+------------------
     230657.436173996 | 230657.436173996 | 230666.436173996 | 230666.436173996

Full raster tile before clipping | After Clipping

## Examples: 1 band clipping with no crop and add back other bands unchanged

    -- Same example as before, but we need to set crop to false to be able to use ST_AddBand
    -- because ST_AddBand requires all bands be the same Width and height
    SELECT ST_AddBand(ST_Clip(rast, 1,
    		ST_Buffer(ST_Centroid(ST_Envelope(rast)),20),false
    	), ARRAY[ST_Band(rast,2),ST_Band(rast,3)] ) from aerials.boston
    WHERE rid = 6;

Full raster tile before clipping | After Clipping - surreal

## Examples: Clip all bands

    -- Clip all bands of an aerial tile by a 20 meter buffer.
    -- Only difference is we don't specify a specific band to clip
    -- so all bands are clipped
    SELECT ST_Clip(rast,
    	  ST_Buffer(ST_Centroid(ST_Envelope(rast)), 20),
    	  false
    	) from aerials.boston
    WHERE rid = 4;

Full raster tile before clipping | After Clipping

## See Also

ST_AddBand, ST_Intersection

## Name

ST_ConvexHull — Return the convex hull geometry of the raster including pixel values equal to BandNoDataValue. For regular shaped and non-skewed rasters, this gives the same result as ST_Envelope so only useful for irregularly shaped or skewed rasters.

## Synopsis

`geometry ST_ConvexHull(`raster rast`)`;

## Description

Return the convex hull geometry of the raster including the NoDataBandValue band pixels. For regular shaped and non-skewed rasters, this gives more or less the same result as ST_Envelope so only useful for irregularly shaped or skewed rasters.

ST_Envelope floors the coordinates and hence add a little buffer around the raster so the answer is subtly different from ST_ConvexHull which does not floor.

## Examples

Refer to PostGIS Raster Specification for a diagram of this.

    -- Note envelope and convexhull are more or less the same
    SELECT ST_AsText(ST_ConvexHull(rast)) As convhull,
    	ST_AsText(ST_Envelope(rast)) As env
    FROM dummy_rast WHERE rid=1;

                            convhull                        |                env

    --------------------------------------------------------+-----------------------
     POLYGON((0.5 0.5,20.5 0.5,20.5 60.5,0.5 60.5,0.5 0.5)) | POLYGON((0 0,20 0,20 60,0 60,0 0))
    -- now we skew the raster
    -- note how the convex hull and envelope are now different
    SELECT ST_AsText(ST_ConvexHull(rast)) As convhull,
    	ST_AsText(ST_Envelope(rast)) As env
    FROM (SELECT ST_SetRotation(rast, 0.1, 0.1) As rast
    	FROM dummy_rast WHERE rid=1) As foo;

                            convhull                        |                env

    --------------------------------------------------------+------------------------------------
     POLYGON((0.5 0.5,20.5 1.5,22.5 61.5,2.5 60.5,0.5 0.5)) | POLYGON((0 0,22 0,22 61,0 61,0 0))

## See Also

ST_Envelope, ST_ConvexHull, ST_AsText

## Name

ST_DumpAsPolygons — Returns a set of geomval (geom,val) rows, from a given raster band. If no band number is specified, band num defaults to 1.

## Synopsis

`setof geomval ST_DumpAsPolygons(`raster rast, integer band_num=1`)`;

## Description

This is a set-returning function (SRF). It returns a set of geomval rows, formed by a geometry (geom) and a pixel band value (val). Each polygon is the union of all pixels for that band that have the same pixel value denoted by val.

ST_DumpAsPolygon is useful for polygonizing rasters. It is the reverse of a GROUP BY in that it creates new rows. For example it can be used to expand a single raster into multiple POLYGONS/MULTIPOLYGONS.

Availability: Requires GDAL 1.7 or higher.

If there is a no data value set for a band, pixels with that value will not be returned.

If you only care about count of pixels with a given value in a raster, it is faster to use ST_ValueCount.

## Examples

    SELECT val, ST_AsText(geom) As geomwkt
    FROM (
    SELECT (ST_DumpAsPolygons(rast)).*
    FROM dummy_rast
    WHERE rid = 2
    ) As foo
    WHERE val BETWEEN 249 and 251
    ORDER BY val;

     val |                                                       geomwkt
    -----+--------------------------------------------------------------------------
     249 | POLYGON((3427927.95 5793243.95,3427927.95 5793243.85,3427928 5793243.85,
     		3427928 5793243.95,3427927.95 5793243.95))
     250 | POLYGON((3427927.75 5793243.9,3427927.75 5793243.85,3427927.8 5793243.85,
     		3427927.8 5793243.9,3427927.75 5793243.9))
     250 | POLYGON((3427927.8 5793243.8,3427927.8 5793243.75,3427927.85 5793243.75,
     		3427927.85 5793243.8, 3427927.8 5793243.8))
     251 | POLYGON((3427927.75 5793243.85,3427927.75 5793243.8,3427927.8 5793243.8,
     		3427927.8 5793243.85,3427927.75 5793243.85))

## See Also

geomval, ST_Value, ST_Polygon, ST_ValueCount

## Name

ST_Envelope — Returns the polygon representation of the extent of the raster.

## Synopsis

`geometry ST_Envelope(`raster rast`)`;

## Description

Returns the polygon representation of the extent of the raster in spatial coordinate units defined by srid. It is a float8 minimum bounding box represented as a polygon.

The polygon is defined by the corner points of the bounding box ((`MINX`, `MINY`), (`MINX`, `MAXY`), (`MAXX`, `MAXY`), (`MAXX`, `MINY`), (`MINX`, `MINY`))

## Examples

    SELECT rid, ST_AsText(ST_Envelope(rast)) As envgeomwkt
    FROM dummy_rast;

     rid |                                         envgeomwkt
    -----+--------------------------------------------------------------------
       1 | POLYGON((0 0,20 0,20 60,0 60,0 0))
       2 | POLYGON((3427927 5793243,3427928 5793243,
       		3427928 5793244,3427927 5793244, 3427927 5793243))

## See Also

ST_Envelope, ST_AsText, ST_SRID

## Name

ST_HillShade — Returns the hypothetical illumination of an elevation raster band using provided azimuth, altitude, brightness and elevation scale inputs. Useful for visualizing terrain.

## Synopsis

`raster ST_HillShade(`raster rast, integer band, text pixeltype, double precision azimuth, double precision altitude, double precision max_bright=255, double precision elevation_scale=1`)`;

## Description

Returns the hypothetical illumination of an elevation raster band using the azimuth, altitude, brightness, and elevation scale inputs. Utilizes map algebra and applies the hill shade equation to neighboring pixels.

The hill shade equation is:

    max_bright * ( (cos(zenith)*cos(slope)) + (sin(zenith)*sin(slope)*cos(azimuth - aspect)) )

.

Availability: 2.0.0

## Examples - coming soon

    coming soon

## See Also

ST_MapAlgebraFctNgb

ST_Aspect

ST_Slope

## Name

ST_Aspect — Returns the surface aspect of an elevation raster band. Useful for analyzing terrain.

## Synopsis

`raster ST_Aspect(`raster rast, integer band, text pixeltype`)`;

## Description

Returns the surface aspect of an elevation raster band. Utilizes map algebra and applies the aspect equation to neighboring pixels.

Given the following representation of a 3x3 neighborhood of pixels:

A | B | C
D | E | F
G | H | I

The equation for the pixel aspect of cell E is: atan2((((G + 2H + I) - (A + 2B + C)) / 8), -(((C + 2F + I) - (A + 2D + G)) / 8))

Availability: 2.0.0

## Examples - coming soon

    coming soon

## See Also

ST_MapAlgebraFctNgb

ST_HillShade

ST_Slope

## Name

ST_Slope — Returns the surface slope of an elevation raster band. Useful for analyzing terrain.

## Synopsis

`raster ST_Slope(`raster rast, integer band, text pixeltype`)`;

## Description

Returns the surface slope of an elevation raster band. Utilizes map algebra and applies the slope equation to neighboring pixels.

Given the following representation of a 3x3 neighborhood of pixels:

A | B | C
D | E | F
G | H | I

The equation for the pixel slope of cell E is: atan(sqrt(((c + 2f + i) - (a + 2d + g) / 8)^2 + (((g + 2h + i) - (a + 2b + c)) / 8) ^ 2))

Availability: 2.0.0

## Examples - coming soon

    coming soon

## See Also

ST_MapAlgebraFctNgb

ST_HillShade

ST_Aspect

## Name

ST_Intersection — Returns a raster or a set of geometry-pixelvalue pairs representing the shared portion of two rasters or the geometrical intersection of a vectorization of the raster and a geometry.

## Synopsis

`setof geomval ST_Intersection(`geometry geom, raster rast, integer band_num=1`)`;

`setof geomval ST_Intersection(`raster rast, geometry geom`)`;

`setof geomval ST_Intersection(`raster rast, integer band_num, geometry geom`)`;

`raster ST_Intersection(`raster rast1, raster rast2, double precision[] nodataval`)`;

`raster ST_Intersection(`raster rast1, raster rast2, text returnband='BOTH', double precision[] nodataval=NULL`)`;

`raster ST_Intersection(`raster rast1, integer band_num1, raster rast2, integer band_num2, double precision[] nodataval`)`;

`raster ST_Intersection(`raster rast1, integer band_num1, raster rast2, integer band_num2, text returnband='BOTH', double precision[] nodataval=NULL`)`;

## Description

Returns a raster or a set of geometry-pixelvalue pairs representing the shared portion of two rasters or the geometrical intersection of a vectorization of the raster and a geometry.

The first three variants, returning a setof geomval, works in vector space. The raster is first vectorized (using ST_DumpAsPolygon) into a set of geomval rows and those rows are then intersected with the geometry using the ST_Intersection(geometry, geometry) PostGIS function. Geometries intersecting only with a nodata value area of a raster returns an empty geometry. They are normally excluded from the results by the proper usage of ST_Intersect in the WHERE clause.

You can access the geometry and the value parts of the resulting set of geomval by surrounding them with parenthesis and adding '.geom' or '.val' at the end of the expression. e.g. (ST_Intersection(rast, geom)).geom

The other variants, returning a raster, works in raster space. They are using the two rasters version of ST_MapAlgebraExpr to perform the intersection.

The extent of the resulting raster corresponds to the geometrical intersection of the two raster extents. The resulting raster includes 'BAND1', 'BAND2' or 'BOTH' bands, following what is passed as the `returnband` parameter. Nodata value areas present in any band results in nodata value areas in every bands of the result. In other words, any pixel intersecting with a nodata value pixel becomes a nodata value pixel in the result.

Rasters resulting from ST_Intersection must have a nodata value assigned for areas not intersecting. You can define or replace the nodata value for any resulting band by providing a `nodataval[]` array of one or two nodata values depending if you request 'BAND1', 'BAND2' or 'BOTH' bands. The first value in the array replace the nodata value in the first band and the second value replace the nodata value in the second band. If one input band do not have a nodata value defined and none are provided as an array, one is chosen using the ST_MinPossibleValue function. All variant accepting an array of nodata value can also accept a single value which will be assigned to each requested band.

In all variants, if no band number is specified band 1 is assumed.

To get more control on the resulting extent or on what to return when encountering a nodata value, use the two rasters version of ST_MapAlgebraExpr.

To compute the intersection of a raster band with a geometry in raster space, use ST_Clip. ST_Clip works on multiple bands rasters and does not return a band corresponding to the rasterized geometry.

ST_Intersection should be used in conjunction with ST_Intersects and an index on the raster column and/or the geometry column.

Enhanced: 2.0.0 - Intersection in the raster space was introduced. In earlier pre-2.0.0 versions, only intersection performed in vector space were supported.

## Examples: Geometry, Raster -- resulting in geometry vals

    SELECT foo.rid, foo.gid,
       ST_AsText((foo.geomval).geom) As geomwkt, (foo.geomval).val
    FROM
    	(
    SELECT A.rid, g.gid , ST_Intersection(A.rast, g.geom) As geomval
     FROM dummy_rast AS A CROSS JOIN
    	(VALUES (1, ST_Point(3427928, 5793243.85) ) ,
    		(2, ST_GeomFromText('LINESTRING(3427927.85 5793243.75,3427927.8 5793243.75,3427927.8 5793243.8)') ),
    		(3, ST_GeomFromText('LINESTRING(1 2, 3 4)') )
    		) As g(gid,geom)
    WHERE A.rid =2 ) As foo;

     rid | gid |      geomwkt												| val
    -----+-----+---------------------------------------------------------------------------------------------
       2 |   1 | POINT(3427928 5793243.85)									| 249
       2 |   1 | POINT(3427928 5793243.85)									| 253
       2 |   2 | POINT(3427927.85 5793243.75)								| 254
       2 |   2 | POINT(3427927.8 5793243.8)									| 251
       2 |   2 | POINT(3427927.8 5793243.8)									| 253
       2 |   2 | LINESTRING(3427927.8 5793243.75,3427927.8 5793243.8)   	| 252
       2 |   2 | MULTILINESTRING((3427927.8 5793243.8,3427927.8 5793243.75),...) | 250
       2 |   3 | GEOMETRYCOLLECTION EMPTY

## Example: Raster, Geometry -- resulting is a raster

Examples coming soon

## See Also

geomval, ST_Intersects, ST_MapAlgebraExpr, ST_Clip, ST_AsText

## Name

ST_MapAlgebraExpr — 1 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the input raster band and of pixeltype provided. Band 1 is assumed if no band is specified.

## Synopsis

`raster ST_MapAlgebraExpr(`raster rast, integer band, text pixeltype, text expression, double precision nodataval=NULL`)`;

`raster ST_MapAlgebraExpr(`raster rast, text pixeltype, text expression, double precision nodataval=NULL`)`;

## Description

Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation defined by the `expression` on the input raster (`rast`). If no `band` is specified band 1 is assumed. The new raster will have the same georeference, width, and height as the original raster but will only have one band.

If `pixeltype` is passed in, then the new raster will have a band of that pixeltype. If pixeltype is passed NULL, then the new raster band will have the same pixeltype as the input `rast` band.

In the expression you can use the term `[rast]` to refer to the pixel value of the original band, `[rast.x]` to refer to the 1-based pixel column index, `[rast.y]` to refer to the 1-based pixel row index.

Availability: 2.0.0

## Examples

Create a new 1 band raster from our original that is a function of modulo 2 of the original raster band.

    ALTER TABLE dummy_rast ADD COLUMN map_rast raster;
    UPDATE dummy_rast SET map_rast = ST_MapAlgebraExpr(rast,NULL,'mod([rast],2)') WHERE rid = 2;

    SELECT ST_Value(rast,1,i,j) As origval, ST_Value(map_rast, 1, i, j) As mapval
    FROM dummy_rast CROSS JOIN generate_series(1, 3) AS i CROSS JOIN generate_series(1,3) AS j
    WHERE rid = 2;

     origval | mapval
    ---------+--------
         253 |      1
         254 |      0
         253 |      1
         253 |      1
         254 |      0
         254 |      0
         250 |      0
         254 |      0
         254 |      0

Create a new 1 band raster of pixel-type 2BUI from our original that is reclassified and set the nodata value to be 0.

    ALTER TABLE dummy_rast ADD COLUMN map_rast2 raster;
    UPDATE dummy_rast SET map_rast2 = ST_MapAlgebraExpr(rast,'2BUI','CASE WHEN [rast] BETWEEN 100 and 250 THEN 1
    WHEN [rast] = 252 THEN 2
    WHEN [rast] BETWEEN 253 and 254 THEN 3 ELSE 0 END', '0') WHERE rid = 2;

    SELECT DISTINCT ST_Value(rast,1,i,j) As origval, ST_Value(map_rast2, 1, i, j) As mapval
    FROM dummy_rast CROSS JOIN generate_series(1, 5) AS i CROSS JOIN generate_series(1,5) AS j
    WHERE rid = 2;

     origval | mapval
    ---------+--------
         249 |      1
         250 |      1
         251 |
         252 |      2
         253 |      3
         254 |      3

    SELECT ST_BandPixelType(map_rast2) As b1pixtyp
    FROM dummy_rast WHERE rid = 2;

     b1pixtyp
    ----------
     2BUI

original (column rast-view) | rast_view_ma

Create a new 3 band raster same pixel type from our original 3 band raster with first band altered by map algebra and remaining 2 bands unaltered.

    SELECT ST_AddBand(
    ST_AddBand(
    	ST_AddBand(
    		ST_MakeEmptyRaster(rast_view),
    			ST_MapAlgebraExpr(rast_view,1,NULL,'tan([rast])*[rast]')
    			),
    		ST_Band(rast_view,2)
    			),
    	ST_Band(rast_view, 3) As rast_view_ma
    )
    FROM wind
    WHERE rid=167;

## See Also

ST_MapAlgebraExpr, ST_MapAlgebraFct, ST_BandPixelType, ST_GeoReference, ST_Value

## Name

ST_MapAlgebraExpr — 2 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the two input raster bands and of pixeltype provided. band 1 of each raster is assumed if no band numbers are specified. The resulting raster will be aligned (scale, skew and pixel corners) on the grid defined by the first raster and have its extent defined by the "extenttype" parameter. Values for "extenttype" can be: INTERSECTION, UNION, FIRST, SECOND.

## Synopsis

`raster ST_MapAlgebraExpr(`raster rast1, raster rast2, text expression, text pixeltype=same_as_rast1_band, text extenttype=INTERSECTION, text nodata1expr=NULL, text nodata2expr=NULL, double precision nodatanodataval=NULL`)`;

`raster ST_MapAlgebraExpr(`raster rast1, integer band1, raster rast2, integer band2, text expression, text pixeltype=same_as_rast1_band, text extenttype=INTERSECTION, text nodata1expr=NULL, text nodata2expr=NULL, double precision nodatanodataval=NULL`)`;

## Description

Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation to the two bands defined by the `expression` on the two input raster bands `rast1`, (`rast2`). If no `band1`, `band2` is specified band 1 is assumed. The resulting raster will be aligned (scale, skew and pixel corners) on the grid defined by the first raster. The resulting raster will have the extent defined by the `extenttype` parameter.

expression

  A PostgreSQL algebraic expression involving the two rasters and PostgreSQL defined functions/operators that will define the pixel value when pixels intersect. e.g. (([rast1] + [rast2])/2.0)::integer

pixeltype

  The resulting pixel type of the output raster. Must be one listed in ST_BandPixelType, left out or set to NULL. If not passed in or set to NULL, will default to the pixeltype of the first raster.

extenttype

  Controls the extent of resulting raster

  1. `INTERSECTION` - The extent of the new raster is the intersection of the two rasters. This is the default.

  2. `UNION` - The extent of the new raster is the union of the two rasters.

  3. `FIRST` - The extent of the new raster is the same as the one of the first raster.

  4. `SECOND` - The extent of the new raster is the same as the one of the second raster.

nodata1expr

  An algebraic expression involving only `rast2` or a constant that defines what to return when pixels of `rast1` are nodata values and spatially corresponding rast2 pixels have values.

nodata2expr

  An algebraic expression involving only `rast1` or a constant that defines what to return when pixels of `rast2` are nodata values and spatially corresponding rast1 pixels have values.

nodatanodataval

  A numeric constant to return when spatially corresponding rast1 and rast2 pixels are both nodata values.

If `pixeltype` is passed in, then the new raster will have a band of that pixeltype. If pixeltype is passed NULL or no pixel type specified, then the new raster band will have the same pixeltype as the input `rast1` band.

Use the term `[rast1.val]` `[rast2.val]` to refer to the pixel value of the original raster bands and `[rast1.x]`, `[rast1.y]` etc. to refer to the column / row positions of the pixels.

Availability: 2.0.0

## Example: 2 Band Intersection and Union

Create a new 1 band raster from our original that is a function of modulo 2 of the original raster band.

    --Create a cool set of rasters --
    DROP TABLE IF EXISTS fun_shapes;
    CREATE TABLE fun_shapes(rid serial PRIMARY KEY, fun_name text, rast raster);

    -- Insert some cool shapes around Boston in Massachusetts state plane meters --
    INSERT INTO fun_shapes(fun_name, rast)
    VALUES ('ref', ST_AsRaster(ST_MakeEnvelope(235229, 899970, 237229, 901930,26986),200,200,'8BUI',0,0));

    INSERT INTO fun_shapes(fun_name,rast)
    WITH ref(rast) AS (SELECT rast FROM fun_shapes WHERE fun_name = 'ref' )
    SELECT 'area' AS fun_name, ST_AsRaster(ST_Buffer(ST_SetSRID(ST_Point(236229, 900930),26986), 1000),
    			ref.rast,'8BUI', 10, 0) As rast
    FROM ref
    UNION ALL
    SELECT 'rand bubbles',
    		 	ST_AsRaster(
    		 	(SELECT ST_Collect(geom)
    	FROM (SELECT ST_Buffer(ST_SetSRID(ST_Point(236229 + i*random()*100, 900930 + j*random()*100),26986), random()*20) As geom
    			FROM generate_series(1,10) As i, generate_series(1,10) As j
    			) As foo ), ref.rast,'8BUI', 200, 0)
    FROM ref;

    --map them -
    SELECT  ST_MapAlgebraExpr(
    		area.rast, bub.rast, '[rast2.val]', '8BUI', 'INTERSECTION', '[rast2.val]', '[rast1.val]') As interrast,
    		ST_MapAlgebraExpr(
    			area.rast, bub.rast, '[rast2.val]', '8BUI', 'UNION', '[rast2.val]', '[rast1.val]') As unionrast
    FROM
      (SELECT rast FROM fun_shapes WHERE
     fun_name = 'area') As area
    CROSS JOIN  (SELECT rast
    FROM fun_shapes WHERE
     fun_name = 'rand bubbles') As bub

mapalgebra intersection | map algebra union

## Example: Overlaying rasters on a canvas as separate bands

    -- we use ST_AsPNG to render the image so all single band ones look grey --
    WITH mygeoms
        AS ( SELECT 2 As bnum, ST_Buffer(ST_Point(1,5),10) As geom
                UNION ALL
                SELECT 3 AS bnum,
                    ST_Buffer(ST_GeomFromText('LINESTRING(50 50,150 150,150 50)'), 10,'join=bevel') As geom
                UNION ALL
                SELECT 1 As bnum,
                    ST_Buffer(ST_GeomFromText('LINESTRING(60 50,150 150,150 50)'), 5,'join=bevel') As geom
                ),
       -- define our canvas to be 1 to 1 pixel to geometry
       canvas
        AS (SELECT ST_AddBand(ST_MakeEmptyRaster(200,
            200,
            ST_XMin(e)::integer, ST_YMax(e)::integer, 1, -1, 0, 0) , '8BUI'::text,0) As rast
            FROM (SELECT ST_Extent(geom) As e,
                        Max(ST_SRID(geom)) As srid
                        from mygeoms
                        ) As foo
                ),
       rbands AS (SELECT ARRAY(SELECT ST_MapAlgebraExpr(canvas.rast, ST_AsRaster(m.geom, canvas.rast, '8BUI', 100),
                     '[rast2.val]', '8BUI', 'FIRST', '[rast2.val]', '[rast1.val]') As rast
                    FROM mygeoms AS m CROSS JOIN canvas
                    ORDER BY m.bnum) As rasts
                    )
              SELECT rasts[1] As rast1 , rasts[2] As rast2, rasts[3] As rast3, ST_AddBand(
                        ST_AddBand(rasts[1],rasts[2]), rasts[3]) As final_rast
                FROM rbands;

rast1 | rast2
rast3 | final_rast

## Example: Overlay 2 meter boundary of select parcels over an aerial imagery

    -- Create new 3 band raster composed of first 2 clipped bands, and overlay of 3rd band with our geometry
    -- This query took 3.6 seconds on PostGIS windows 64-bit install
    WITH pr AS
    -- Note the order of operation: we clip all the rasters to dimensions of our region
    (SELECT ST_Clip(rast,ST_Expand(geom,50) ) As rast, g.geom
    	FROM aerials.o_2_boston AS r INNER JOIN
    -- union our parcels of interest so they form a single geometry we can later intersect with
    		(SELECT ST_Union(ST_Transform(the_geom,26986)) AS geom
    		  FROM landparcels WHERE pid IN('0303890000', '0303900000')) As g
    		ON ST_Intersects(rast::geometry, ST_Expand(g.geom,50))
    ),
    -- we then union the raster shards together
    -- ST_Union on raster is kinda of slow but much faster the smaller you can get the rasters
    -- therefore we want to clip first and then union
    prunion AS
    (SELECT ST_AddBand(NULL, ARRAY[ST_Union(rast,1),ST_Union(rast,2),ST_Union(rast,3)] ) As clipped,geom
    FROM pr
    GROUP BY geom)
    -- return our final raster which is the unioned shard with
    -- with the overlay of our parcel boundaries
    -- add first 2 bands, then mapalgebra of 3rd band + geometry
    SELECT ST_AddBand(ST_Band(clipped,ARRAY[1,2])
    	, ST_MapAlgebraExpr(ST_Band(clipped,3), ST_AsRaster(ST_Buffer(ST_Boundary(geom),2),clipped, '8BUI',250),
    	 '[rast2.val]', '8BUI', 'FIRST', '[rast2.val]', '[rast1.val]') ) As rast
    FROM prunion;

The blue lines are the boundaries of select parcels

## See Also

ST_MapAlgebraExpr, ST_AddBand, ST_AsPNG, ST_AsRaster, ST_MapAlgebraFct, ST_BandPixelType, ST_GeoReference, ST_Value , ST_Union, ST_Union

## Name

ST_MapAlgebraFct — 1 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the input raster band and of pixeltype prodived. Band 1 is assumed if no band is specified.

## Synopsis

`raster ST_MapAlgebraFct(`raster rast, regprocedure onerasteruserfunc`)`;

`raster ST_MapAlgebraFct(`raster rast, regprocedure onerasteruserfunc, text[] VARIADIC args`)`;

`raster ST_MapAlgebraFct(`raster rast, text pixeltype, regprocedure onerasteruserfunc`)`;

`raster ST_MapAlgebraFct(`raster rast, text pixeltype, regprocedure onerasteruserfunc, text[] VARIADIC args`)`;

`raster ST_MapAlgebraFct(`raster rast, integer band, regprocedure onerasteruserfunc`)`;

`raster ST_MapAlgebraFct(`raster rast, integer band, regprocedure onerasteruserfunc, text[] VARIADIC args`)`;

`raster ST_MapAlgebraFct(`raster rast, integer band, text pixeltype, regprocedure onerasteruserfunc`)`;

`raster ST_MapAlgebraFct(`raster rast, integer band, text pixeltype, regprocedure onerasteruserfunc, text[] VARIADIC args`)`;

## Description

Creates a new one band raster formed by applying a valid PostgreSQL function specified by the `onerasteruserfunc` on the input raster (`rast`). If no `band` is specified, band 1 is assumed. The new raster will have the same georeference, width, and height as the original raster but will only have one band.

If `pixeltype` is passed in, then the new raster will have a band of that pixeltype. If pixeltype is passed NULL, then the new raster band will have the same pixeltype as the input `rast` band.

The `onerasteruserfunc` parameter must be the name and signature of a SQL or PL/pgSQL function, cast to a regprocedure. A very simple and quite useless PL/pgSQL function example is:

    CREATE OR REPLACE FUNCTION simple_function(pixel FLOAT, pos INTEGER[], VARIADIC args TEXT[])
        RETURNS FLOAT
        AS $$ BEGIN
            RETURN 0.0;
        END; $$
        LANGUAGE 'plpgsql' IMMUTABLE;

The `userfunction` may accept two or three arguments: a float value, an optional integer array, and a variadic text array. The first argument is the value of an individual raster cell (regardless of the raster datatype). The second argument is the position of the current processing cell in the form '{x,y}'. The third argument indicates that all remaining parameters to ST_MapAlgebraFct shall be passed through to the `userfunction`.

Passing a regprodedure argument to a SQL function requires the full function signature to be passed, then cast to a regprocedure type. To pass the above example PL/pgSQL function as an argument, the SQL for the argument is:

    'simple_function(float,integer[],text[])'::regprocedure

Note that the argument contains the name of the function, the types of the function arguments, quotes around the name and argument types, and a cast to a regprocedure.

The third argument to the `userfunction` is a variadic text array. All trailing text arguments to any ST_MapAlgebraFct call are passed through to the specified `userfunction`, and are contained in the `args` argument.

For more information about the VARIADIC keyword, please refer to the PostgreSQL documentation and the "SQL Functions with Variable Numbers of Arguments" section of Query Language (SQL) Functions.

The text[] argument to the `userfunction` is required, regardless of whether you choose to pass any arguments to your user function for processing or not.

Availability: 2.0.0

## Examples

Create a new 1 band raster from our original that is a function of modulo 2 of the original raster band.

    ALTER TABLE dummy_rast ADD COLUMN map_rast raster;
    CREATE FUNCTION mod_fct(pixel float, pos integer[], variadic args text[])
    RETURNS float
    AS $$
    BEGIN
        RETURN pixel::integer % 2;
    END;
    $$
    LANGUAGE 'plpgsql' IMMUTABLE;

    UPDATE dummy_rast SET map_rast = ST_MapAlgebraFct(rast,NULL,'mod_fct(float,integer[],text[])'::regprocedure) WHERE rid = 2;

    SELECT ST_Value(rast,1,i,j) As origval, ST_Value(map_rast, 1, i, j) As mapval
    FROM dummy_rast CROSS JOIN generate_series(1, 3) AS i CROSS JOIN generate_series(1,3) AS j
    WHERE rid = 2;

     origval | mapval
    ---------+--------
         253 |      1
         254 |      0
         253 |      1
         253 |      1
         254 |      0
         254 |      0
         250 |      0
         254 |      0
         254 |      0

Create a new 1 band raster of pixel-type 2BUI from our original that is reclassified and set the nodata value to a passed parameter to the user function (0).

    ALTER TABLE dummy_rast ADD COLUMN map_rast2 raster;
    CREATE FUNCTION classify_fct(pixel float, pos integer[], variadic args text[])
    RETURNS float
    AS
    $$
    DECLARE
        nodata float := 0;
    BEGIN
        IF NOT args[1] IS NULL THEN
            nodata := args[1];
        END IF;
        IF pixel < 251 THEN
            RETURN 1;
        ELSIF pixel = 252 THEN
            RETURN 2;
        ELSIF pixel > 252 THEN
            RETURN 3;
        ELSE
            RETURN nodata;
        END IF;
    END;
    $$
    LANGUAGE 'plpgsql';
    UPDATE dummy_rast SET map_rast2 = ST_MapAlgebraFct(rast,'2BUI','classify_fct(float,integer[],text[])'::regprocedure, '0') WHERE rid = 2;

    SELECT DISTINCT ST_Value(rast,1,i,j) As origval, ST_Value(map_rast2, 1, i, j) As mapval
    FROM dummy_rast CROSS JOIN generate_series(1, 5) AS i CROSS JOIN generate_series(1,5) AS j
    WHERE rid = 2;

     origval | mapval
    ---------+--------
         249 |      1
         250 |      1
         251 |
         252 |      2
         253 |      3
         254 |      3

    SELECT ST_BandPixelType(map_rast2) As b1pixtyp
    FROM dummy_rast WHERE rid = 2;

     b1pixtyp
    ----------
     2BUI

original (column rast-view) | rast_view_ma

Create a new 3 band raster same pixel type from our original 3 band raster with first band altered by map algebra and remaining 2 bands unaltered.

    CREATE FUNCTION rast_plus_tan(pixel float, pos integer[], variadic args text[])
    RETURNS float
    AS
    $$
    BEGIN
    	RETURN tan(pixel) * pixel;
    END;
    $$
    LANGUAGE 'plpgsql';

    SELECT ST_AddBand(
    	ST_AddBand(
    		ST_AddBand(
    			ST_MakeEmptyRaster(rast_view),
    			ST_MapAlgebraFct(rast_view,1,NULL,'rast_plus_tan(float,integer[],text[])'::regprocedure)
    		),
    		ST_Band(rast_view,2)
    	),
    	ST_Band(rast_view, 3) As rast_view_ma
    )
    FROM wind
    WHERE rid=167;

## See Also

ST_MapAlgebraExpr, ST_BandPixelType, ST_GeoReference, ST_SetValue

## Name

ST_MapAlgebraFct — 2 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the 2 input raster bands and of pixeltype prodived. Band 1 is assumed if no band is specified. Extent type defaults to INTERSECTION if not specified.

## Synopsis

`raster ST_MapAlgebraFct(`raster rast1, raster rast2, regprocedure tworastuserfunc, text pixeltype=same_as_rast1, text extenttype=INTERSECTION, text[] VARIADIC userargs`)`;

`raster ST_MapAlgebraFct(`raster rast1, integer band1, raster rast2, integer band2, regprocedure tworastuserfunc, text pixeltype=same_as_rast1, text extenttype=INTERSECTION, text[] VARIADIC userargs`)`;

## Description

Creates a new one band raster formed by applying a valid PostgreSQL function specified by the `tworastuserfunc` on the input raster `rast1`, `rast2`. If no `band1` or `band2` is specified, band 1 is assumed. The new raster will have the same georeference, width, and height as the original rasters but will only have one band.

If `pixeltype` is passed in, then the new raster will have a band of that pixeltype. If pixeltype is passed NULL or left out, then the new raster band will have the same pixeltype as the input `rast1` band.

The `tworastuserfunc` parameter must be the name and signature of an SQL or PL/pgSQL function, cast to a regprocedure. An example PL/pgSQL function example is:

    CREATE OR REPLACE FUNCTION simple_function_for_two_rasters(pixel1 FLOAT, pixel2 FLOAT, pos INTEGER[], VARIADIC args TEXT[])
        RETURNS FLOAT
        AS $$ BEGIN
            RETURN 0.0;
        END; $$
        LANGUAGE 'plpgsql' IMMUTABLE;

The `tworastuserfunc` may accept three or four arguments: a double precision value, a double precision value, an optional integer array, and a variadic text array. The first argument is the value of an individual raster cell in `rast1` (regardless of the raster datatype). The second argument is an individual raster cell value in `rast2`. The third argument is the position of the current processing cell in the form '{x,y}'. The fourth argument indicates that all remaining parameters to ST_MapAlgebraFct shall be passed through to the `tworastuserfunc`.

Passing a regprodedure argument to a SQL function requires the full function signature to be passed, then cast to a regprocedure type. To pass the above example PL/pgSQL function as an argument, the SQL for the argument is:

    'simple_function(double precision, double precision, integer[], text[])'::regprocedure

Note that the argument contains the name of the function, the types of the function arguments, quotes around the name and argument types, and a cast to a regprocedure.

The third argument to the `tworastuserfunc` is a variadic text array. All trailing text arguments to any ST_MapAlgebraFct call are passed through to the specified `tworastuserfunc`, and are contained in the `userargs` argument.

For more information about the VARIADIC keyword, please refer to the PostgreSQL documentation and the "SQL Functions with Variable Numbers of Arguments" section of Query Language (SQL) Functions.

The text[] argument to the `tworastuserfunc` is required, regardless of whether you choose to pass any arguments to your user function for processing or not.

Availability: 2.0.0

## Example: Overlaying rasters on a canvas as separate bands

    -- define our user defined function --
    CREATE OR REPLACE FUNCTION raster_mapalgebra_union(
    	rast1 double precision,
    	rast2 double precision,
        pos integer[],
    	VARIADIC userargs text[]
    )
    	RETURNS double precision
    	AS $$
    	DECLARE
    	BEGIN
    		CASE
    			WHEN rast1 IS NOT NULL AND rast2 IS NOT NULL THEN
    				RETURN ((rast1 + rast2)/2.);
    			WHEN rast1 IS NULL AND rast2 IS NULL THEN
    				RETURN NULL;
    			WHEN rast1 IS NULL THEN
    				RETURN rast2;
    			ELSE
    				RETURN rast1;
    		END CASE;

    		RETURN NULL;
    	END;
    	$$ LANGUAGE 'plpgsql' IMMUTABLE COST 1000;

    -- prep our test table of rasters
    DROP TABLE IF EXISTS map_shapes;
    CREATE TABLE map_shapes(rid serial PRIMARY KEY, rast raster, bnum integer, descrip text);
    INSERT INTO map_shapes(rast,bnum, descrip)
    WITH mygeoms
        AS ( SELECT 2 As bnum, ST_Buffer(ST_Point(90,90),30) As geom, 'circle' As descrip
                UNION ALL
                SELECT 3 AS bnum,
                    ST_Buffer(ST_GeomFromText('LINESTRING(50 50,150 150,150 50)'), 15) As geom, 'big road' As descrip
                UNION ALL
                SELECT 1 As bnum,
                    ST_Translate(ST_Buffer(ST_GeomFromText('LINESTRING(60 50,150 150,150 50)'), 8,'join=bevel'), 10,-6) As geom, 'small road' As descrip
                ),
       -- define our canvas to be 1 to 1 pixel to geometry
       canvas
        AS ( SELECT ST_AddBand(ST_MakeEmptyRaster(250,
            250,
            ST_XMin(e)::integer, ST_YMax(e)::integer, 1, -1, 0, 0 ) , '8BUI'::text,0) As rast
            FROM (SELECT ST_Extent(geom) As e,
                        Max(ST_SRID(geom)) As srid
                        from mygeoms
                        ) As foo
                )
    -- return our rasters aligned with our canvas
    SELECT ST_AsRaster(m.geom, canvas.rast, '8BUI', 240) As rast, bnum, descrip
                    FROM mygeoms AS m CROSS JOIN canvas
    UNION ALL
    SELECT canvas.rast, 4, 'canvas'
    FROM canvas;

    -- Map algebra on single band rasters and then collect with ST_AddBand
    INSERT INTO map_shapes(rast,bnum,descrip)
    SELECT ST_AddBand(ST_AddBand(rasts[1], rasts[2]),rasts[3]), 4, 'map bands overlay fct union (canvas)'
    	FROM (SELECT ARRAY(SELECT ST_MapAlgebraFct(m1.rast, m2.rast,
    			'raster_mapalgebra_union(double precision, double precision, integer[], text[])'::regprocedure, '8BUI', 'FIRST')
                    FROM map_shapes As m1 CROSS JOIN map_shapes As m2
                    	WHERE m1.descrip = 'canvas' AND m2.descrip <> 'canvas' ORDER BY m2.bnum) As rasts) As foo;

map bands overlay (canvas) (R: small road, G: circle, B: big road)

## User Defined function that takes extra args

    CREATE OR REPLACE FUNCTION raster_mapalgebra_userargs(
    	rast1 double precision,
    	rast2 double precision,
        pos integer[],
    	VARIADIC userargs text[]
    )
    	RETURNS double precision
    	AS $$
    	DECLARE
    	BEGIN
    		CASE
    			WHEN rast1 IS NOT NULL AND rast2 IS NOT NULL THEN
    				RETURN least(userargs[1]::integer,(rast1 + rast2)/2.);
    			WHEN rast1 IS NULL AND rast2 IS NULL THEN
    				RETURN userargs[2]::integer;
    			WHEN rast1 IS NULL THEN
    				RETURN greatest(rast2,random()*userargs[3]::integer)::integer;
    			ELSE
    				RETURN greatest(rast1, random()*userargs[4]::integer)::integer;
    		END CASE;

    		RETURN NULL;
    	END;
    	$$ LANGUAGE 'plpgsql' VOLATILE COST 1000;

    SELECT ST_MapAlgebraFct(m1.rast, 1, m1.rast, 3,
    			'raster_mapalgebra_userargs(double precision, double precision, integer[], text[])'::regprocedure,
    				'8BUI', 'INTERSECT', '100','200','200','0')
                    FROM map_shapes As m1
                    	WHERE m1.descrip = 'map bands overlay fct union (canvas)';

user defined with extra args and different bands from same raster

## See Also

ST_MapAlgebraExpr, ST_BandPixelType, ST_GeoReference, ST_SetValue

## Name

ST_MapAlgebraFctNgb — 1-band version: Map Algebra Nearest Neighbor using user-defined PostgreSQL function. Return a raster which values are the result of a PLPGSQL user function involving a neighborhood of values from the input raster band.

## Synopsis

`raster ST_MapAlgebraFctNgb(`raster rast, integer band, text pixeltype, integer ngbwidth, integer ngbheight, regprocedure onerastngbuserfunc, text nodatamode, text[] VARIADIC args`)`;

## Description

(one raster version) Return a raster which values are the result of a PLPGSQL user function involving a neighborhood of values from the input raster band. The user function takes the neighborhood of pixel values as an array of numbers, for each pixel, returns the result from the user function, replacing pixel value of currently inspected pixel with the function result.

rast

  Raster on which the user function is evaluated.

band

  Band number of the raster to be evaluated. Default to 1.

pixeltype

  The resulting pixel type of the output raster. Must be one listed in ST_BandPixelType or left out or set to NULL. If not passed in or set to NULL, will default to the pixeltype of the `rast`. Results are truncated if they are larger than what is allowed for the pixeltype.

ngbwidth

  The width of the neighborhood, in cells.

ngbheight

  The height of the neighborhood, in cells.

onerastngbuserfunc

  PLPGSQL/psql user function to apply to neighborhood pixels of a single band of a raster. The first element is a 2-dimensional array of numbers representing the rectangular pixel neighborhood

nodatamode

  Defines what value to pass to the function for a neighborhood pixel that is nodata or NULL

  'ignore': any NODATA values encountered in the neighborhood are ignored by the computation -- this flag must be sent to the user callback function, and the user function decides how to ignore it.

  'NULL': any NODATA values encountered in the neighborhood will cause the resulting pixel to be NULL -- the user callback function is skipped in this case.

  'value': any NODATA values encountered in the neighborhood are replaced by the reference pixel (the one in the center of the neighborhood). Note that if this value is NODATA, the behavior is the same as 'NULL' (for the affected neighborhood)

args

  Arguments to pass into the user function.

Availability: 2.0.0

## Examples

Examples utilize the katrina raster loaded as a single tile described in http://trac.osgeo.org/gdal/wiki/frmts_wtkraster.html and then prepared in the ST_Rescale examples

    --
    -- A simple 'callback' user function that averages up all the values in a neighborhood.
    --
    CREATE OR REPLACE FUNCTION rast_avg(matrix float[][], nodatamode text, variadic args text[])
        RETURNS float AS
        $$
        DECLARE
    		_matrix float[][];
            x1 integer;
            x2 integer;
            y1 integer;
            y2 integer;
            sum float;
        BEGIN
    		_matrix := matrix;
            sum := 0;
            FOR x in array_lower(matrix, 1)..array_upper(matrix, 1) LOOP
                FOR y in array_lower(matrix, 2)..array_upper(matrix, 2) LOOP
                    sum := sum + _matrix[x][y];
                END LOOP;
            END LOOP;
            RETURN (sum*1.0/(array_upper(matrix,1)*array_upper(matrix,2) ))::integer ;
        END;
        $$
    LANGUAGE 'plpgsql' IMMUTABLE COST 1000;

    -- now we apply to our raster averaging pixels within 2 pixels of each other in X and Y direction --
    SELECT ST_MapAlgebraFctNgb(rast, 1,  '8BUI', 4,4,
    		'rast_avg(float[][], text, text[])'::regprocedure, 'NULL', NULL) As nn_with_border
    	FROM katrinas_rescaled
    	limit 1;

First band of our raster | new raster after averaging pixels withing 4x4 pixels of each other

## See Also

ST_MapAlgebraFct, ST_MapAlgebraExpr, ST_Rescale

## Name

ST_Polygon — Returns a polygon geometry formed by the union of pixels that have a pixel value that is not no data value. If no band number is specified, band num defaults to 1.

## Synopsis

`geometry ST_Polygon(`raster rast, integer band_num=1`)`;

## Description

Availability: Requires GDAL 1.7 or higher.

## Examples

    -- by default no data band value is 0 or not set, so polygon will return a square polygon
    SELECT ST_AsText(ST_Polygon(rast)) As geomwkt
    FROM dummy_rast
    WHERE rid = 2;

    geomwkt
    --------------------------------------------
    POLYGON((3427927.8 5793243.75,3427927.75 5793243.75,3427927.75 5793243.8,3427927.75 5793243.85,3427927.75 5793243.9,
    3427927.75 5793244,3427927.8 5793244,3427927.85 5793244,3427927.9 5793244,3427928 5793244,3427928 5793243.95,
    3427928 5793243.85,3427928 5793243.8,3427928 5793243.75,3427927.85 5793243.75,3427927.8 5793243.75))

    -- now we change the no data value of first band
    UPDATE dummy_rast SET rast = ST_SetBandNoDataValue(rast,1,254)
    WHERE rid = 2;
    SELECt rid, ST_BandNoDataValue(rast)
    from dummy_rast where rid = 2;

    -- ST_Polygon excludes the pixel value 254 and returns a multipolygon
    SELECT ST_AsText(ST_Polygon(rast)) As geomwkt
    FROM dummy_rast
    WHERE rid = 2;

    geomwkt
    ---------------------------------------------------------
    MULTIPOLYGON(((3427927.9 5793243.95,3427927.85 5793243.95,3427927.85 5793244,3427927.9 5793244,3427927.9 5793243.95)),
    ((3427928 5793243.85,3427928 5793243.8,3427927.95 5793243.8,3427927.95 5793243.85,3427927.9 5793243.85,3427927.9 5793243.9,3427927.9 5793243.95,3427927.95 5793243.95,3427928 5793243.95,3427928 5793243.85)),
    ((3427927.8 5793243.75,3427927.75 5793243.75,3427927.75 5793243.8,3427927.75 5793243.85,3427927.75 5793243.9,3427927.75 5793244,3427927.8 5793244,
    3427927.8 5793243.9,3427927.8 5793243.85,3427927.85 5793243.85,3427927.85 5793243.8,3427927.85 5793243.75,3427927.8 5793243.75)))

    -- Or if you want the no data value different for just one time

    SELECT ST_AsText(
    	ST_Polygon(
    		ST_SetBandNoDataValue(rast,1,252)
    		)
    	) As geomwkt
    FROM dummy_rast
    WHERE rid =2;

    geomwkt
    ---------------------------------
    POLYGON((3427928 5793243.85,3427928 5793243.8,3427928 5793243.75,3427927.85 5793243.75,3427927.8 5793243.75,3427927.8 5793243.8,3427927.75 5793243.8,3427927.75 5793243.85,3427927.75 5793243.9,3427927.75 5793244,3427927.8 5793244,3427927.85 5793244,3427927.9 5793244,3427928 5793244,3427928 5793243.95,3427928 5793243.85),
    (3427927.9 5793243.9,3427927.9 5793243.85,3427927.95 5793243.85,3427927.95 5793243.9,3427927.9 5793243.9))

## See Also

ST_Value, ST_DumpAsPolygons

## Name

ST_Reclass — Creates a new raster composed of band types reclassified from original. The nband is the band to be changed. If nband is not specified assumed to be 1. All other bands are returned unchanged. Use case: convert a 16BUI band to a 8BUI and so forth for simpler rendering as viewable formats.

## Synopsis

`raster ST_Reclass(`raster rast, integer nband, text reclassexpr, text pixeltype, double precision nodataval=NULL`)`;

`raster ST_Reclass(`raster rast, reclassarg[] VARIADIC reclassargset`)`;

`raster ST_Reclass(`raster rast, text reclassexpr, text pixeltype`)`;

## Description

Creates a new raster formed by applying a valid PostgreSQL algebraic operation defined by the `reclassexpr` on the input raster (`rast`). If no `band` is specified band 1 is assumed. The new raster will have the same georeference, width, and height as the original raster. Bands not designated will come back unchanged. Refer to reclassarg for description of valid reclassification expressions.

The bands of the new raster will have pixel type of `pixeltype`. If `reclassargset` is passed in then each reclassarg defines behavior of each band generated.

Availability: 2.0.0

## Examples Basic

Create a new raster from the original where band 2 is converted from 8BUI to 4BUI and all values from 101-254 are set to nodata value.

    ALTER TABLE dummy_rast ADD COLUMN reclass_rast raster;
    UPDATE dummy_rast SET reclass_rast = ST_Reclass(rast,2,'0-87:1-10, 88-100:11-15, 101-254:0-0', '4BUI',0) WHERE rid = 2;

    SELECT i as col, j as row, ST_Value(rast,2,i,j) As origval,
        ST_Value(reclass_rast, 2, i, j) As reclassval,
        ST_Value(reclass_rast, 2, i, j, false) As reclassval_include_nodata
    FROM dummy_rast CROSS JOIN generate_series(1, 3) AS i CROSS JOIN generate_series(1,3) AS j
    WHERE rid = 2;

     col | row | origval | reclassval | reclassval_include_nodata
    -----+-----+---------+------------+---------------------------
       1 |   1 |      78 |          9 |                         9
       2 |   1 |      98 |         14 |                        14
       3 |   1 |     122 |            |                         0
       1 |   2 |      96 |         14 |                        14
       2 |   2 |     118 |            |                         0
       3 |   2 |     180 |            |                         0
       1 |   3 |      99 |         15 |                        15
       2 |   3 |     112 |            |                         0
       3 |   3 |     169 |            |                         0

## Example: Advanced using multiple reclassargs

Create a new raster from the original where band 1,2,3 is converted to 1BB,4BUI, 4BUI respectively and reclassified. Note this uses the variadic `reclassarg` argument which can take as input an indefinite number of reclassargs (theoretically as many bands as you have)

    UPDATE dummy_rast SET reclass_rast =
        ST_Reclass(rast,
            ROW(2,'0-87]:1-10, (87-100]:11-15, (101-254]:0-0', '4BUI',NULL)::reclassarg,
            ROW(1,'0-253]:1, 254:0', '1BB', NULL)::reclassarg,
            ROW(3,'0-70]:1, (70-86:2, [86-150):3, [150-255:4', '4BUI', NULL)::reclassarg
            ) WHERE rid = 2;

    SELECT i as col, j as row,ST_Value(rast,1,i,j) As ov1,  ST_Value(reclass_rast, 1, i, j) As rv1,
        ST_Value(rast,2,i,j) As ov2, ST_Value(reclass_rast, 2, i, j) As rv2,
        ST_Value(rast,3,i,j) As ov3, ST_Value(reclass_rast, 3, i, j) As rv3
    FROM dummy_rast CROSS JOIN generate_series(1, 3) AS i CROSS JOIN generate_series(1,3) AS j
    WHERE rid = 2;

    col | row | ov1 | rv1 | ov2 | rv2 | ov3 | rv3
    ----+-----+-----+-----+-----+-----+-----+-----
      1 |   1 | 253 |   1 |  78 |   9 |  70 |   1
      2 |   1 | 254 |   0 |  98 |  14 |  86 |   3
      3 |   1 | 253 |   1 | 122 |   0 | 100 |   3
      1 |   2 | 253 |   1 |  96 |  14 |  80 |   2
      2 |   2 | 254 |   0 | 118 |   0 | 108 |   3
      3 |   2 | 254 |   0 | 180 |   0 | 162 |   4
      1 |   3 | 250 |   1 |  99 |  15 |  90 |   3
      2 |   3 | 254 |   0 | 112 |   0 | 108 |   3
      3 |   3 | 254 |   0 | 169 |   0 | 175 |   4

## Example: Advanced Map a single band 32BF raster to multiple viewable bands

Create a new 3 band (8BUI,8BUI,8BUI viewable raster) from a raster that has only one 32bf band

    ALTER TABLE wind ADD COLUMN rast_view raster;
    UPDATE wind
    	set rast_view = ST_AddBand( NULL,
            ARRAY[
            	ST_Reclass(rast, 1,'0.1-10]:1-10,9-10]:11,(11-33:0'::text, '8BUI'::text,0),
            	ST_Reclass(rast,1, '11-33):0-255,[0-32:0,(34-1000:0'::text, '8BUI'::text,0),
            	ST_Reclass(rast,1,'0-32]:0,(32-100:100-255'::text, '8BUI'::text,0)
            	]
            	) ;

## See Also

ST_AddBand, ST_Band, ST_BandPixelType, ST_MakeEmptyRaster, reclassarg, ST_Value

## Name

ST_Union — Returns the union of a set of raster tiles into a single raster composed of 1 band. If no band is specified for unioning, band num 1 is assumed. The resulting raster's extent is the extent of the whole set. In the case of intersection, the resulting value is defined by p_expression which is one of the following: LAST - the default when none is specified, MEAN, SUM, FIRST, MAX, MIN.

## Synopsis

`raster ST_Union(`setof raster rast`)`;

`raster ST_Union(`raster set rast, integer band_num`)`;

`raster ST_Union(`raster set rast, text p_expression`)`;

`raster ST_Union(`raster set rast, integer band_num, text p_expression`)`;

## Description

Returns the union of a set of raster tiles into a single raster composed of 1 band. If no band is specified for unioning, band num 1 is assumed. The resulting raster's extent is the extent of the whole set. In the case of intersection, the resulting value is defined by p_expression which is one of the following: LAST - the default when none is specified, MEAN, SUM, FIRST, MAX, MIN

There are several other variants of this function not installed by default in PostGIS 2.0.0 -- these can be found in the raster/scripts/plpgsql/st_union.sql file of postgis source code.

The ST_Union function in 2.0.0 is currently implemented predominantly in plpgsql. Because of the memory copying needed to copy between the C and plpgsql layer, this function is much much slower than it needs to be. Future 2.0 releases will have this function implemented in C, so you should witness significant improvements in speed when that happens. As a general rule of thumb you want to minimize the size of the rasters, that ST_Union works with. One approach is to clip first and then union the clipped versions. Refer to select parcels example in ST_MapAlgebraExpr. That example if unioning is done before clipping takes about 4 times longer. With the higher res imagery the timing the ratio between is even higher.

Availability: 2.0.0

## Examples: Reconstitute a single band chunked raster tile

    -- this creates a single band from first band of raster tiles
    -- that form the original file system tile
    SELECT filename, ST_Union(rast) As file_rast
    FROM sometable WHERE filename IN('dem01', 'dem02') GROUP BY filename;

## Examples: Return a multi-band raster that is the union of tiles intersecting geometry

    -- this creates a multi band raster collecting all the tiles that intersect a line
    SELECT ST_AddBand(NULL,ARRAY[ST_Union(rast,1), ST_Union(rast,2), ST_Union(rast,3) ])
    FROM aerials.boston
    WHERE ST_Intersects(rast,  ST_GeomFromText('LINESTRING(230486 887771, 230500 88772)',26986) );

## See Also

ST_Envelope, ST_ConvexHull, , ST_MapAlgebraExpr

## 9.12. Raster Processing Builtin Functions

## Name

ST_Min4ma — Raster processing function that calculates the minimum pixel value in a neighborhood.

## Synopsis

`float8 ST_Min4ma(`float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

## Description

Calculate the minimum pixel value in a neighborhood of pixels.

This function is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Availability: 2.0.0

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_min4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid | st_value
    -----+----------
       2 |      250
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_Max4ma, ST_Sum4ma, ST_Mean4ma, ST_Range4ma, ST_Distinct4ma ST_StdDev4ma

## Name

ST_Max4ma — Raster processing function that calculates the maximum pixel value in a neighborhood.

## Synopsis

`float8 ST_Max4ma(`float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

## Description

Calculate the maximum pixel value in a neighborhood of pixels.

This function is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Availability: 2.0.0

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_max4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid | st_value
    -----+----------
       2 |      254
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_Min4ma, ST_Sum4ma, ST_Mean4ma, ST_Range4ma, ST_Distinct4ma ST_StdDev4ma

## Name

ST_Sum4ma — Raster processing function that calculates the sum of all pixel values in a neighborhood.

## Synopsis

`float8 ST_Sum4ma(`float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

## Description

Calculate the sum of all pixel values in a neighborhood of pixels.

This function is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Availability: 2.0.0

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, '32BF', 1, 1, 'st_sum4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid | st_value
    -----+----------
       2 |     2279
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_Min4ma, ST_Max4ma, ST_Mean4ma, ST_Range4ma, ST_Distinct4ma ST_StdDev4ma

## Name

ST_Mean4ma — Raster processing function that calculates the mean pixel value in a neighborhood.

## Synopsis

`float8 ST_Mean4ma(`float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

## Description

Calculate the mean pixel value in a neighborhood of pixels.

This function is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Availability: 2.0.0

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, '32BF', 1, 1, 'st_mean4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid |     st_value
    -----+------------------
       2 | 253.222229003906
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_Min4ma, ST_Max4ma, ST_Sum4ma, ST_Range4ma, ST_StdDev4ma

## Name

ST_Range4ma — Raster processing function that calculates the range of pixel values in a neighborhood.

## Synopsis

`float8 ST_Range4ma(`float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

## Description

Calculate the range of pixel values in a neighborhood of pixels.

This function is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Availability: 2.0.0

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_range4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid | st_value
    -----+----------
       2 |        4
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_Min4ma, ST_Max4ma, ST_Sum4ma, ST_Mean4ma, ST_Distinct4ma ST_StdDev4ma

## Name

ST_Distinct4ma — Raster processing function that calculates the number of unique pixel values in a neighborhood.

## Synopsis

`float8 ST_Distinct4ma(`float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

## Description

Calculate the number of unique pixel values in a neighborhood of pixels.

This function is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Availability: 2.0.0

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_distinct4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid | st_value
    -----+----------
       2 |        3
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_Min4ma, ST_Max4ma, ST_Sum4ma, ST_Mean4ma, ST_Distinct4ma ST_StdDev4ma

## Name

ST_StdDev4ma — Raster processing function that calculates the standard deviation of pixel values in a neighborhood.

## Synopsis

`float8 ST_StdDev4ma(`float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

## Description

Calculate the standard deviation of pixel values in a neighborhood of pixels.

This function is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Availability: 2.0.0

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, '32BF', 1, 1, 'st_stddev4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid |     st_value
    -----+------------------
       2 | 1.30170822143555
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_Min4ma, ST_Max4ma, ST_Sum4ma, ST_Mean4ma, ST_Distinct4ma ST_StdDev4ma

## 9.13. Raster Operators

## Name

&& — Returns `TRUE` if A's bounding box overlaps B's.

## Synopsis

`boolean &&(` raster A , raster B `)`;

## Description

The `&&` operator returns `TRUE` if the bounding box of raster A overlaps the bounding box of raster B.

This operand will make use of any indexes that may be available on the rasters.

## Examples

    SELECT A.rid As a_rid, B.rid As b_rid, A.rast && B.rast As overlap
     FROM dummy_rast AS A CROSS JOIN dummy_rast AS B LIMIT 3;

     a_rid | b_rid | overlap
    -------+-------+---------
         2 |     2 | t
         2 |     3 | f
         2 |     1 | f

## Name

&< — Returns `TRUE` if A's bounding box is to the left of B's.

## Synopsis

`boolean &<(` raster A , raster B `)`;

## Description

The `&<` operator returns `TRUE` if the bounding box of raster A overlaps or is to the left of the bounding box of raster B, or more accurately, overlaps or is NOT to the right of the bounding box of raster B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT A.rid As a_rid, B.rid As b_rid, A.rast &< B.rast As overleft
     FROM dummy_rast AS A CROSS JOIN dummy_rast AS B;

    a_rid | b_rid | overleft
    ------+-------+----------
        2 |     2 | t
        2 |     3 | f
        2 |     1 | f
        3 |     2 | t
        3 |     3 | t
        3 |     1 | f
        1 |     2 | t
        1 |     3 | t
        1 |     1 | t

## Name

&> — Returns `TRUE` if A's bounding box is to the right of B's.

## Synopsis

`boolean &>(` raster A , raster B `)`;

## Description

The `&>` operator returns `TRUE` if the bounding box of raster A overlaps or is to the right of the bounding box of raster B, or more accurately, overlaps or is NOT to the left of the bounding box of raster B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT A.rid As a_rid, B.rid As b_rid, A.rast &> B.rast As overright
     FROM dummy_rast AS A CROSS JOIN dummy_rast AS B;

     a_rid | b_rid | overright
    -------+-------+----------
         2 |     2 | t
         2 |     3 | t
         2 |     1 | t
         3 |     2 | f
         3 |     3 | t
         3 |     1 | f
         1 |     2 | f
         1 |     3 | t
         1 |     1 | t

## 9.14. Raster and Raster Band Spatial Relationships

## Name

ST_Intersects — Return true if the raster spatially intersects a separate raster or geometry. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

## Synopsis

`boolean ST_Intersects(` raster rasta , integer nbanda , raster rastb , integer nbandb `)`;

`boolean ST_Intersects(` raster rasta , raster rastb `)`;

`boolean ST_Intersects(` raster rast , integer nband , geometry geommin `)`;

`boolean ST_Intersects(` raster rast , geometry geommin , integer nband=NULL `)`;

`boolean ST_Intersects(` geometry geommin , raster rast , integer nband=NULL `)`;

## Description

Return true if the raster spatially intersects a separate raster or geometry. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

Depending on the order that the raster and geometry is passed to ST_Intersects(), the test will operate in either raster-space or geometry-space. If ST_Intersects(raster, ....), the test is in raster-space (the geometry is converted to a raster). If ST_Intersects(geometry, ...), the test is in geometry-space (the raster is converted to a set of pixel polygons).

This operand will make use of any indexes that may be available on the geometries / rasters.

Enhanced: 2.0.0 support raster/raster intersects was introduced.

## Examples

    SELECT A.rid, g.gid , ST_Intersects(A.rast, g.geom) As inter
    FROM dummy_rast AS A CROSS JOIN
    	(VALUES (1, ST_Point(3427928, 5793243.85) ) ,
    		(2, ST_GeomFromText('LINESTRING(3427927.85 5793243.75,3427927.8 5793243.75,3427927.8 5793243.8)') ),
    		(3, ST_GeomFromText('LINESTRING(1 2, 3 4)') )
    		) As g(gid,geom)
    WHERE A.rid =2 ;

     rid | gid | inter
    -----+-----+-------
       2 |   1 | t
       2 |   2 | t
       2 |   3 | f

## See Also

ST_Intersection

## Name

ST_SameAlignment — Returns true if rasters have same skew, scale, spatial ref and false if they don't with notice detailing issue.

## Synopsis

`boolean ST_SameAlignment(` raster rastA , raster rastB `)`;

`boolean ST_SameAlignment(` double precision ulx1 , double precision uly1 , double precision scalex1 , double precision scaley1 , double precision skewx1 , double precision skewy1 , double precision ulx2 , double precision uly2 , double precision scalex2 , double precision scaley2 , double precision skewx2 , double precision skewy2 `)`;

## Description

Returns true if the raster have same skew scale etc. Returns false if they don't and a NOTICE detailing the alignment issue.

Availability: 2.0.0

## Examples: Rasters

    SELECT ST_SameAlignment(
    	ST_MakeEmptyRaster(1, 1, 0, 0, 1, 1, 0, 0),
    	ST_MakeEmptyRaster(1, 1, 0, 0, 1, 1, 0, 0)
    ) as sm;

    sm
    ----
    t

    SELECT ST_SameAlignment(A.rast,b.rast)
     FROM dummy_rast AS A CROSS JOIN dummy_rast AS B;

     NOTICE:  The two rasters provided have different SRIDs
    NOTICE:  The two rasters provided have different SRIDs
     st_samealignment
    ------------------
     t
     f
     f
     f

## See Also

Section 5.1, “Loading and Creating Rasters”, ST_MakeEmptyRaster

## Chapter 10. PostGIS Raster Frequently Asked Questions

10.1. Where can I find out more about the PostGIS Raster Project?
10.2. Are there any books or tutorials to get me started with this wonderful invention?
10.3. How do I install Raster support in my PostGIS database?
10.4. I get error could not load library "C:/Program Files/PostgreSQL/8.4/lib/rtpostgis.dll": The specified module could not be found. or could not load library on Linux when trying to run rtpostgis.sql
10.5. How do I load Raster data into PostGIS?
10.6. What kind of raster file formats can I load into my database?
10.7. Can I export my PostGIS raster data to other raster formats?
10.8. Are their binaries of GDAL available already compiled with PostGIS Raster suppport?
10.9. What tools can I use to view PostGIS raster data?
10.10. How can I add a PostGIS raster layer to my MapServer map?
10.11. What functions can I currently use with my raster data?
10.12. I am getting error ERROR: function st_intersects(raster, unknown) is not unique or st_union(geometry,text) is not unique. How do I fix?
10.13. How is PostGIS Raster different from Oracle GeoRaster (SDO_GEORASTER) and SDO_RASTER types?

10.1. | Where can I find out more about the PostGIS Raster Project?
| Refer to the PostGIS Raster home page.
10.2. | Are there any books or tutorials to get me started with this wonderful invention?
| There is a full length beginner tutorial Intersecting vector buffers with large raster coverage using PostGIS Raster. Jorge has a series of blog articles on PostGIS Raster that demonstrate how to load raster data as well as cross compare to same tasks in Oracle GeoRaster. Check out Jorge's PostGIS Raster / Oracle GeoRaster Series. There is a whole chapter (more than 35 pages of content) dedicated to PostGIS Raster with free code and data downloads at PostGIS in Action - Raster chapter. You can buy PostGIS in Action now from Manning in hard-copy (significant discounts for bulk purchases) or just the E-book format. You can also buy from Amazon and various other book distributors. All hard-copy books come with a free coupon to download the E-book version. Here is a review from a PostGIS Raster user PostGIS raster applied to land classification urban forestry
10.3. | How do I install Raster support in my PostGIS database?
| The easiest is to download binaries for PostGIS and Raster which are currently available for windows and latest versions of Mac OSX. First you need a working PostGIS 2.0.0 or above and be running PostgreSQL 8.4, 9.0, or 9.1. Note in PostGIS 2.0 PostGIS Raster is fully integrated, so it will be compiled when you compile PostGIS. Instructions for installing and running under windows are available at How to Install and Configure PostGIS raster on windows If you are on windows, you can compile yourself, or use the pre-compiled PostGIS Raster windows binaries. If you are on Mac OSX Leopard or Snow Leopard, there are binaries available at Kyng Chaos Mac OSX PostgreSQL/GIS binaries. Then to enable raster support in your database, run the rtpostgis.sql file in your database. To upgrade an existing install use rtpostgis_upgrade_minor..sql instead of rtpostgis.sql For other platforms, you generally need to compile yourself. Dependencies are PostGIS and GDAL. For more details about compiling from source, please refer to Installing PostGIS Raster from source (in prior versions of PostGIS)
10.4. | I get error could not load library "C:/Program Files/PostgreSQL/8.4/lib/rtpostgis.dll": The specified module could not be found. or could not load library on Linux when trying to run rtpostgis.sql
| rtpostgis.so/dll is built with dependency on libgdal.dll/so. Make sure for Windows you have libgdal-1.dll in the bin folder of your PostgreSQL install. For Linux libgdal has to be in your path or bin folder. You may also run into different errors if you don't have PostGIS installed in your database. Make sure to install PostGIS first in your database before trying to install the raster support.
10.5. | How do I load Raster data into PostGIS?
| The latest version of PostGIS comes packaged with a `raster2pgsql` raster loader executable capable of loading many kinds of rasters and also generating lower resolution overviews without any additional software. Please refer to Section 5.1.1, “Using raster2pgsql to load rasters” for more details. Pre-2.0 versions came with a `raster2pgsql.py` that required python with numpy and GDAL. This is no longer needed.
10.6. | What kind of raster file formats can I load into my database?
| Any that your GDAL library supports. GDAL supported formats are documented GDAL File Formats. Your particular GDAL install may not support all formats. To verify the ones supported by your particular GDAL install, you can use
    raster2pgsql -G
10.7. | Can I export my PostGIS raster data to other raster formats?
| Yes GDAL 1.7+ has a PostGIS raster driver, but is only compiled in if you choose to compile with PostgreSQL support. The driver currently doesn't support irregularly blocked rasters, although you can store irregularly blocked rasters in PostGIS raster data type. If you are compiling from source, you need to include in your configure
    --with-pg=path/to/pg_config
to enable the driver. Refer to GDAL Build Hints for tips on building GDAL against in various OS platforms. If your version of GDAL is compiled with the PostGIS Raster driver you should see PostGIS Raster in list when you do
    gdalinfo --formats
To get a summary about your raster via GDAL use gdalinfo:
    gdalinfo  "PG:host=localhost port=5432 dbname='mygisdb' user='postgres' password='whatever' schema='someschema' table=sometable"
To export data to other raster formats, use gdal_translate the below will export all data from a table to a PNG file at 10% size. Depending on your pixel band types, some translations may not work if the export format does not support that Pixel type. For example floating point band types and 32 bit unsigned ints will not translate easily to JPG or some others. Here is an example simple translation
    gdal_translate -of PNG -outsize 10% 10% "PG:host=localhost dbname='mygisdb' user='postgres' password=whatever' schema='someschema' table=sometable" C:\somefile.png
You can also use SQL where clauses in your export using the where=... in your driver connection string. Below are some using a where clause
    gdal_translate -of PNG -outsize 10% 10% "PG:host=localhost dbname='mygisdb' user='postgres' password=whatever' schema='someschema' table=sometable where="owner='jimmy'" " C:\somefile.png
    gdal_translate -of PNG -outsize 10% 10% "PG:host=localhost dbname='mygisdb' user='postgres' password=whatever' schema='someschema' table=sometable where='ST_Intersects(rast, ST_SetSRID(ST_Point(-71.032,42.3793),4326) )' " C:\intersectregion.png
To see more examples and syntax refer to Reading Raster Data of PostGIS Raster section
10.8. | Are their binaries of GDAL available already compiled with PostGIS Raster suppport?
| Yes. Check out the page GDAL Binaries page. Any compiled with PostgreSQL support should have PostGIS Raster in them. We know for sure the following windows binaries have PostGIS Raster built in. FWTools latest stable version for Windows is compiled with Raster support. PostGIS Raster is undergoing many changes. If you want to get the latest nightly build for Windows -- then check out the Tamas Szekeres nightly builds built with Visual Studio which contain GDAL trunk, Python Bindings and MapServer executables and PostGIS Raster driver built-in. Just click the SDK bat and run your commands from there. http://vbkto.dyndns.org/sdk/. Also available are VS project files.
10.9. | What tools can I use to view PostGIS raster data?
| You can use MapServer compiled with GDAL 1.7+ and PostGIS Raster driver support to view Raster data. QuantumGIS (QGIS) now supports viewing of PostGIS Raster if you have PostGIS raster driver installed. In theory any tool that renders data using GDAL can support PostGIS raster data or support it with fairly minimal effort. Again for Windows, Tamas' binaries http://vbkto.dyndns.org/sdk/ are a good choice if you don't want the hassle of having to setup to compile your own.
10.10. | How can I add a PostGIS raster layer to my MapServer map?
| First you need GDAL 1.7 or higher compiled with PostGIS raster support. GDAL 1.8 or above is preferred since many issues have been fixed in 1.8 and more PostGIS raster issues fixed in trunk version. You can much like you can with any other raster. Refer to MapServer Raster processing options for list of various processing functions you can use with MapServer raster layers. What makes PostGIS raster data particularly interesting, is that since each tile can have various standard database columns, you can segment it in your data source Below is an example of how you would define a PostGIS raster layer in MapServer.
The mode=2 is required for tiled rasters and was added in PostGIS 2.0 and GDAL 1.8 drivers. This does not exist in GDAL 1.7 drivers.
    -- displaying raster with standard raster options
    LAYER
    	NAME coolwktraster
    	TYPE raster
    	STATUS ON
    	DATA "PG:host=localhost port=5432 dbname='somedb' user='someuser' password='whatever'
    		schema='someschema' table='cooltable' mode='2'"
    	PROCESSING "NODATA=0"
    	PROCESSING "SCALE=AUTO"
    	#... other standard raster processing functions here
    	#... classes are optional but useful for 1 band data
    	CLASS
    		NAME "boring"
    		EXPRESSION ([pixel] < 20)
    		COLOR 250 250 250
    	END
    	CLASS
    		NAME "mildly interesting"
    		EXPRESSION ([pixel] > 20 AND [pixel] < 1000)
    		COLOR 255 0 0
    	END
    	CLASS
    		NAME "very interesting"
    		EXPRESSION ([pixel] >= 1000)
    		COLOR 0 255 0
    	END
    END
    -- displaying raster with standard raster options and a where clause
    LAYER
    	NAME soil_survey2009
    	TYPE raster
    	STATUS ON
    	DATA "PG:host=localhost port=5432 dbname='somedb' user='someuser' password='whatever'
    		schema='someschema' table='cooltable' where='survey_year=2009' mode='2'"
    	PROCESSING "NODATA=0"
    	#... other standard raster processing functions here
    	#... classes are optional but useful for 1 band data
    END
10.11. | What functions can I currently use with my raster data?
| Refer to the list of Chapter 9, Raster Reference. There are more, but this is still a work in progress. Refer to the PostGIS Raster roadmap page for details of what you can expect in the future.
10.12. | I am getting error ERROR: function st_intersects(raster, unknown) is not unique or st_union(geometry,text) is not unique. How do I fix?
| The function is not unique error happens if one of your arguments is a textual representation of a geometry instead of a geometry. In these cases, PostgreSQL marks the textual representation as an unknown type, which means it can fall into the st_intersects(raster, geometry) or st_intersects(raster,raster) thus resulting in a non-unique case since both functions can in theory support your request. To prevent this, you need to cast the geometry to a geometry. For example if your code looks like this:
    SELECT rast
     FROM my_raster
       WHERE ST_Intersects(rast, 'SRID=4326;POINT(-10 10)');
Cast the textual geometry representation to a geometry by changing your code to this:
    SELECT rast
     FROM my_raster
       WHERE ST_Intersects(rast, 'SRID=4326;POINT(-10 10)'::geometry);
10.13. | How is PostGIS Raster different from Oracle GeoRaster (SDO_GEORASTER) and SDO_RASTER types?
| For a more extensive discussion on this topic, check out Jorge Arévalo Oracle GeoRaster and PostGIS Raster: First impressions The major advantage of one-georeference-by-raster over one-georeference-by-layer is to allow: * coverages to be not necessarily rectangular (which is often the case of raster coverage covering large extents. See the possible raster arrangements in the documentation) * rasters to overlaps (which is necessary to implement lossless vector to raster conversion) These arrangements are possible in Oracle as well, but they imply the storage of multiple SDO_GEORASTER objects linked to as many SDO_RASTER tables. A complex coverage can lead to hundreds of tables in the database. With PostGIS Raster you can store a similar raster arrangement into a unique table. It's a bit like if PostGIS would force you to store only full rectangular vector coverage without gaps or overlaps (a perfect rectangular topological layer). This is very practical in some applications but practice has shown that it is not realistic or desirable for most geographical coverages. Vector structures needs the flexibility to store discontinuous and non-rectangular coverages. We think it is a big advantage that raster structure should benefit as well.

## Chapter 11. Topology

The PostGIS Topology types and functions are used to manage topological objects such as faces, edges and nodes.

Sandro Santilli's presentation at PostGIS Day Paris 2011 conference gives a good synopsis of PostGIS Topology and where it is headed Topology with PostGIS 2.0 slide deck.

Vincent Picavet provides a good synopsis and overview of what is Topology, how is it used, and various FOSS4G tools that support it in State of the art of FOSS4G for topology and network analysis.

An example of a topologically based GIS database is the US Census Topologically Integrated Geographic Encoding and Reference System (TIGER) database. If you want to experiment with PostGIS topology and need some data, check out Topology_Load_Tiger.

The PostGIS topology module has existed in prior versions of PostGIS but was never part of the Official PostGIS documentation. In PostGIS 2.0.0 major cleanup is going on to remove use of all deprecated functions in it, fix known usability issues, better document the features and functions, add new functions, and enhance to closer conform to SQL-MM standards.

Details of this project can be found at PostGIS Topology Wiki

All functions and tables associated with this module are installed in a schema called `topology`.

Functions that are defined in SQL/MM standard are prefixed with ST_ and functions specific to PostGIS are not prefixed.

To build PostGIS 2.0 with topology support, compile with the --with-topology option as described in Chapter 2, Installation. Some functions depend on GEOS 3.3+ so you should compile with GEOS 3.3+ to fully utilize the topology support.

## 11.1. Topology Types

Abstract

This section lists the PostgreSQL data types installed by PostGIS Topology. Note we describe the casting behavior of these which is very important especially when designing your own functions.

## Name

getfaceedges_returntype — A composite type that consists of a sequence number and edge number. This is the return type for `ST_GetFaceEdges`

## Description

A composite type that consists of a sequence number and edge number. This is the return type for `ST_GetFaceEdges` function.

1. `sequence` is an integer: Refers to a topology defined in the topology.topology table which defines the topology schema and srid.

2. `edge` is an integer: The identifier of an edge.

## Name

topogeometry — A composite type that refers to a topology geometry in a specific topology, layer, having specific type (1:[multi]point, 2:[multi]line, 3:[multi]poly, 4:collection) with specific identifier id in the topology. The id uniquely defines the topogeometry in the topology.

## Description

A composite type that refers to a topology geometry in a specific topology, layer, having specific type with specific id. The elements of a topogeometry are the properties: topology_id,layer_id,id integer,type integer.

1. `topology_id` is an integer: Refers to a topology defined in the topology.topology table which defines the topology schema and srid.

2. `layer_id` is an integer: The layer_id in the layers table that hte topogeometry belongs to. The combination of topology_id, layer_id provides a unique reference in the topology.layers table.

3. `type` integer between 1 - 4 that defines the geometry type: 1:[multi]point, 2:[multi]line, 3:[multi]poly, 4:collection

4. `id` is an integer: The id is the autogenerated sequence number that uniquely defines the topogeometry in the respective topology.

## Casting Behavior

This section lists the automatic as well as explicit casts allowed for this data type

Cast To | Behavior
geometry | automatic

## See Also

CreateTopoGeom

## Name

validatetopology_returntype — A composite type that consists of an error message and id1 and id2 to denote location of error. This is the return type for `ValidateTopology`

## Description

A composite type that consists of an error message and two integers. The ValidateTopology function returns a set of these to denote validation errors and the id1 and id2 to denote the ids of the topology objects involved in the error.

1. `error` is varchar: Denotes type of error.

   Current error descriptors are: coincident nodes, edge crosses node, edge not simple, edge end node geometry mis-match, edge start node geometry mismatch, face overlaps face,face within face,

2. `id1` is an integer: Denotes identifier of edge / face / nodes in error.

3. `id2` is an integer: For errors that involve 2 objects denotes the secondary edge / or node

## See Also

ValidateTopology

## 11.2. Topology Domains

Abstract

This section lists the PostgreSQL domains installed by PostGIS Topology. Domains can be used like object types as return objects of functions or table columns. The distinction between a domain and a type is that a domain is an existing type with a check constraint bound to it.

## Name

TopoElement — An array of 2 integers generally used to identify a TopoGeometry component.

## Description

An array of 2 integers used to represent the id and type of a topology primitive or the id and layer of a TopoGeometry. Sets of such pairs are used to define TopoGeometry objects (either simple or hierarchical).

## Examples

    SELECT ARRAY[1,2]::topology.topoelement;
      te
    -------
     {1,2}

    --Example of what happens when you try to case a 3 element array to topoelement
    -- NOTE: topoement has to be a 2 element array so fails dimension check
    SELECT ARRAY[1,2,3]::topology.topoelement;
    ERROR:  value for domain topology.topoelement violates check constraint "dimensions"

## See Also

GetTopoGeomElements

## Name

topoelementarray — An array of element_id,element_type values. a bidimensional array of integers: '{{id,type}, {id,type}, ...}'

## Description

An array of 1 or more topoelements ( a bidimensional array of integers: '{{id,type}, {id,type}, ...}'). So an array of 1 or more arrays each having 2 integers generally used to return an array of sets of element id and element type of a topology relation.

For types currrently only 3 types are supported: `node`=1, `edge`=2, `face`=3

## Examples

    SELECT '{{1,2},{4,3}}'::topology.topoelementarray As tea;
      tea
    -------
    {{1,2},{4,3}}

    -- more verbose equivalent --
    SELECT ARRAY[ARRAY[1,2], ARRAY[4,3]]::topology.topoelementarray As tea;

      tea
    -------
    {{1,2},{4,3}}

    --using the array agg function packaged with topology --
    SELECT topology.TopoElementArray_Agg(ARRAY[e,t]) As tea
      FROM generate_series(1,4) As e CROSS JOIN generate_series(1,3) As t;
      tea
    --------------------------------------------------------------------------
    {{1,1},{1,2},{1,3},{2,1},{2,2},{2,3},{3,1},{3,2},{3,3},{4,1},{4,2},{4,3}}

    SELECT '{{1,2,4},{3,4,5}}'::topology.topoelementarray As tea;
    ERROR:  value for domain topology.topoelementarray violates check constraint "dimensions"

## See Also

GetTopoGeomElementArray, TopoElementArray_Agg

## 11.3. Topology and TopoGeometry Management

Abstract

This section lists the Topology functions for building new Topology schemas, validating topologies, and managing TopoGeometry Columns

## Name

AddTopoGeometryColumn — Adds a topogeometry column to an existing table, registers this new column as a layer in topology.layer and returns the new layer_id.

## Synopsis

`text AddTopoGeometryColumn(`varchar topology_name, varchar schema_name, varchar table_name, varchar column_name, varchar feature_type`)`;

`text AddTopoGeometryColumn(`varchar topology_name, varchar schema_name, varchar table_name, varchar column_name, varchar feature_type, integer child_layer`)`;

## Description

Each TopoGeometry object belongs to a specific Layer of a specific Topology. Before creating a TopoGeometry object you need to create its TopologyLayer. A Topology Layer is an association of a feature-table with the topology. It also contain type and hierarchy information. We create a layer using the AddTopoGeometryColumn() function:

This function will both add the requested column to the table and add a record to the topology.layer table with all the given info.

If you don't specify [child_layer] (or set it to NULL) this layer would contain Basic TopoGeometries (composed by primitive topology elements). Otherwise this layer will contain hierarchical TopoGeometries (composed by TopoGeometries from the child_layer).

Once the layer is created (it's id is returned by the AddTopoGeometryColumn function) you're ready to construct TopoGeometry objects in it

Valid `feature_type`s are: POINT, LINE, POLYGON, COLLECTION

Availability: 1.?

## Examples

    -- Note for this example we created our new table in the ma_topo schema
    -- though we could have created it in a different schema -- in which case topology_name and schema_name would be different
    CREATE SCHEMA ma;
    CREATE TABLE ma.parcels(gid serial, parcel_id varchar(20) PRIMARY KEY, address text);
    SELECT topology.AddTopoGeometryColumn('ma_topo', 'ma', 'parcels', 'topo', 'POLYGON');

    CREATE SCHEMA ri;
    CREATE TABLE ri.roads(gid serial PRIMARY KEY, road_name text);
    SELECT topology.AddTopoGeometryColumn('ri_topo', 'ri', 'roads', 'topo', 'LINE');

## See Also

CreateTopology, CreateTopoGeom

## Name

DropTopology — Use with caution: Drops a topology schema and deletes its reference from topology.topology table and references to tables in that schema from the geometry_columns table.

## Synopsis

`integer DropTopology(`varchar topology_schema_name`)`;

## Description

Drops a topology schema and deletes its reference from topology.topology table and references to tables in that schema from the geometry_columns table. This function should be USED WITH CAUTION, as it could destroy data you care about. If the schema does not exist, it just removes reference entries the named schema.

Availability: 1.?

## Examples

Cascade drops the ma_topo schema and removes all references to it in topology.topology and geometry_columns.

    SELECT topology.DropTopology('ma_topo');

## See Also

## Name

DropTopoGeometryColumn — Drops the topogeometry column from the table named `table_name` in schema `schema_name` and unregisters the columns from topology.layer table.

## Synopsis

`text DropTopoGeometryColumn(`varchar schema_name, varchar table_name, varchar column_name`)`;

## Description

Drops the topogeometry column from the table named `table_name` in schema `schema_name` and unregisters the columns from topology.layer table. Returns summary of drop status. NOTE: it first sets all values to NULL before dropping to bypass referential integrity checks.

Availability: 1.?

## Examples

    SELECT topology.DropTopoGeometryColumn('ma_topo', 'parcel_topo', 'topo');

## See Also

AddTopoGeometryColumn

## Name

TopologySummary — Takes a topology name and provides summary totals of types of objects in topology

## Synopsis

`text TopologySummary(`varchar topology_schema_name`)`;

## Description

Takes a topology name and provides summary totals of types of objects in topology.

Availability: 2.0.0

## Examples

    SELECT topology.topologysummary('city_data');
                        topologysummary
    --------------------------------------------------------
     Topology city_data (329), SRID 4326, precision: 0
     22 nodes, 24 edges, 10 faces, 29 topogeoms in 5 layers
     Layer 1, type Polygonal (3), 9 topogeoms
      Deploy: features.land_parcels.feature
     Layer 2, type Puntal (1), 8 topogeoms
      Deploy: features.traffic_signs.feature
     Layer 3, type Lineal (2), 8 topogeoms
      Deploy: features.city_streets.feature
     Layer 4, type Polygonal (3), 3 topogeoms
      Hierarchy level 1, child layer 1
      Deploy: features.big_parcels.feature
     Layer 5, type Puntal (1), 1 topogeoms
      Hierarchy level 1, child layer 2
      Deploy: features.big_signs.feature

## See Also

Topology_Load_Tiger

## Name

ValidateTopology — Returns a set of validatetopology_returntype objects detailing issues with topology

## Synopsis

`setof validatetopology_returntype ValidateTopology(`varchar topology_schema_name`)`;

## Description

Returns a set of validatetopology_returntype objects detailing issues with topology. Refer to validatetopology_returntype for listing of possible errors.

Availability: 1.?

Enhanced: 2.0.0 more efficient edge crossing detection and fixes for false positives that were existent in prior versions.

## Examples

    SELECT * FROM  topology.ValidateTopology('ma_topo');
          error        | id1 | id2
    -------------------+-----+-----
    face without edges |   0 |

## See Also

validatetopology_returntype, Topology_Load_Tiger

## 11.4. Topology Constructors

Abstract

This section covers the topology functions for creating new topologies.

## Name

CreateTopology — Creates a new topology schema and registers this new schema in the topology.topology table.

## Synopsis

`integer CreateTopology(`varchar topology_schema_name`)`;

`integer CreateTopology(`varchar topology_schema_name, integer srid`)`;

`integer CreateTopology(`varchar topology_schema_name, integer srid, double precision tolerance`)`;

`integer CreateTopology(`varchar topology_schema_name, integer srid, double precision tolerance, boolean hasz`)`;

## Description

Creates a new schema with name `topology_name` consisting of tables (`edge_data`,`face`,`node`, `relation` and registers this new topology in the topology.topology table. It returns the id of the topology in the topology table. The srid is the spatial reference identified as defined in spatial_ref_sys table for that topology. Topologies must be uniquely named. The tolerance is measured in the units of the spatial reference system. If the tolerance is not specified defaults to 0.

This is similar to the SQL/MM ST_InitTopoGeo but a bit more functional. `hasz` defaults to false if not specified.

Availability: 1.?

## Examples

This example creates a new schema called ma_topo that will store edges, faces, and relations in Massachusetts State Plane meters. The tolerance represents 1/2 meter since the spatial reference system is a meter based spatial reference system

    SELECT topology.CreateTopology('ma_topo',26986, 0.5);

Create Rhode Island topology in State Plane ft

    SELECT topology.CreateTopology('ri_topo',3438) As topoid;
    topoid
    ------
    2

## See Also

Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems”, ST_InitTopoGeo, Topology_Load_Tiger

## Name

CopyTopology — Makes a copy of a topology structure (nodes, edges, faces, layers and TopoGeometries).

## Synopsis

`integer CopyTopology(`varchar existing_topology_name, varchar new_name`)`;

## Description

Creates a new topology with name `new_topology_name` and SRID and precision taken from `existing_topology_name`, copies all nodes, edges and faces in there, copies layers and their TopoGeometries too.

The new rows in topology.layer will contain synthesized values for schema_name, table_name and feature_column. This is because the TopoGeometry will only exist as a definition but won't be available in any user-level table yet.

Availability: 2.0.0

## Examples

This example makes a backup of a topology called ma_topo

    SELECT topology.CopyTopology('ma_topo', 'ma_topo_bakup');

## See Also

Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems”, CreateTopology

## Name

ST_InitTopoGeo — Creates a new topology schema and registers this new schema in the topology.topology table and details summary of process.

## Synopsis

`text ST_InitTopoGeo(`varchar topology_schema_name`)`;

## Description

This is an SQL-MM equivalent of CreateTopology but lacks the spatial reference and tolerance options of CreateTopology and outputs a text description of creation instead of topology id.

Availability: 1.?

This method implements the SQL/MM specification. SQL-MM 3 Topo-Geo and Topo-Net 3: Routine Details: X.3.17

## Examples

    SELECT topology.ST_InitTopoGeo('topo_schema_to_create') AS topocreation;
                          astopocreation
    ------------------------------------------------------------
     Topology-Geometry 'topo_schema_to_create' (id:7) created.

## See Also

CreateTopology

## Name

ST_CreateTopoGeo — Adds a collection of geometries to a given empty topology and returns a message detailing success.

## Synopsis

`text ST_CreateTopoGeo(`varchar atopology, geometry acollection`)`;

## Description

Adds a collection of geometries to a given empty topology and returns a message detailing success.

Useful for populating an empty topology.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details -- X.3.18

## Examples

    -- Populate topology --
    SELECT topology.ST_CreateTopoGeo('ri_topo',
     ST_GeomFromText('MULTILINESTRING((384744 236928,384750 236923,384769 236911,384799 236895,384811 236890,384833 236884,
      384844 236882,384866 236881,384879 236883,384954 236898,385087 236932,385117 236938,
      385167 236938,385203 236941,385224 236946,385233 236950,385241 236956,385254 236971,
      385260 236979,385268 236999,385273 237018,385273 237037,385271 237047,385267 237057,
      385225 237125,385210 237144,385192 237161,385167 237192,385162 237202,385159 237214,
      385159 237227,385162 237241,385166 237256,385196 237324,385209 237345,385234 237375,
      385237 237383,385238 237399,385236 237407,385227 237419,385213 237430,385193 237439,
      385174 237451,385170 237455,385169 237460,385171 237475,385181 237503,385190 237521,
      385200 237533,385206 237538,385213 237541,385221 237542,385235 237540,385242 237541,
      385249 237544,385260 237555,385270 237570,385289 237584,385292 237589,385291 237596,385284 237630))',3438)
      );

          st_createtopogeo
    ----------------------------
     Topology ri_topo populated

    -- create tables and topo geometries --
    CREATE TABLE ri.roads(gid serial PRIMARY KEY, road_name text);

    SELECT topology.AddTopoGeometryColumn('ri_topo', 'ri', 'roads', 'topo', 'LINE');

## See Also

AddTopoGeometryColumn, CreateTopology, DropTopology

## Name

TopoGeo_AddPoint — Adds a point to an existing topology using a tolerance and possibly splitting an existing edge.

## Synopsis

`integer TopoGeo_AddPoint(`varchar toponame, geometry apoint, float8 tolerance`)`;

## Description

Adds a point to an existing topology and return its identifier. The given point will snap to existing nodes or edges within given tolerance. An existing edge may be split by the snapped point.

Availability: 2.0.0

## See Also

TopoGeo_AddLineString, TopoGeo_AddPolygon, AddNode, CreateTopology

## Name

TopoGeo_AddLineString — Adds a linestring to an existing topology using a tolerance and possibly splitting existing edges/faces.

## Synopsis

`integer TopoGeo_AddLineString(`varchar toponame, geometry aline, float8 tolerance`)`;

## Description

Adds a linestring to an existing topology and return a set of edge identifiers forming it up. The given line will snap to existing nodes or edges within given tolerance. Existing edges and faces may be split by the line.

Availability: 2.0.0

## See Also

TopoGeo_AddPoint, TopoGeo_AddPolygon, AddEdge, CreateTopology

## Name

TopoGeo_AddPolygon — Adds a polygon to an existing topology using a tolerance and possibly splitting existing edges/faces.

## Synopsis

`integer TopoGeo_AddPolygon(`varchar atopology, geometry aline, float8 atolerance`)`;

## Description

Adds a polygon to an existing topology and return a set of face identifiers forming it up. The boundary of the given polygon will snap to existing nodes or edges within given tolerance. Existing edges and faces may be split by the boundary of the new polygon.

Availability: 2.0.0

## See Also

TopoGeo_AddPoint, TopoGeo_AddLineString, AddFace, CreateTopology

## 11.5. Topology Editors

Abstract

This section covers topology functions for adding, moving, deleting, and splitting edges, faces, and nodes. All of these functions are defined by ISO SQL/MM.

## Name

ST_AddIsoNode — Adds an isolated node to a face in a topology and returns the nodeid of the new node. If face is null, the node is still created.

## Synopsis

`integer ST_AddIsoNode(`varchar atopology, integer aface, geometry apoint`)`;

## Description

Adds an isolated node with point location `apoint` to an existing face with faceid `aface` to a topology `atopology` and returns the nodeid of the new node.

If the spatial reference system (srid) of the point geometry is not the same as the topology, the `apoint` is not a point geometry, the point is null, or the point intersects an existing edge (even at the boundaries) then an exception is thrown. If the point already exists as a node, an exception is thrown.

If `aface` is not null and the `apoint` is not within the face, then an exception is thrown.

Availability: 1.?

This method implements the SQL/MM specification. SQL-MM: Topo-Net Routines: X+1.3.1

## Examples

## See Also

AddNode, CreateTopology, DropTopology, ST_Intersects

## Name

ST_AddIsoEdge — Adds an isolated edge defined by geometry `alinestring` to a topology connecting two existing isolated nodes `anode` and `anothernode` and returns the edge id of the new edge.

## Synopsis

`integer ST_AddIsoEdge(`varchar atopology, integer anode, integer anothernode, geometry alinestring`)`;

## Description

Adds an isolated edge defined by geometry `alinestring` to a topology connecting two existing isolated nodes `anode` and `anothernode` and returns the edge id of the new edge.

If the spatial reference system (srid) of the `alinestring` geometry is not the same as the topology, any of the input arguments are null, or the nodes are contained in more than one face, or the nodes are start or end nodes of an existing edge, then an exception is thrown.

If the `alinestring` is not within the face of the face the `anode` and `anothernode` belong to, then an exception is thrown.

If the `anode` and `anothernode` are not the start and end points of the `alinestring` then an exception is thrown.

Availability: 1.?

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.4

## Examples

## See Also

ST_AddIsoNode, ST_IsSimple, ST_Within

## Name

ST_AddEdgeNewFaces — Add a new edge and, if in doing so it splits a face, delete the original face and replace it with two new faces.

## Synopsis

`integer ST_AddEdgeNewFaces(`varchar atopology, integer anode, integer anothernode, geometry acurve`)`;

## Description

Add a new edge and, if in doing so it splits a face, delete the original face and replace it with two new faces. Returns the id of the newly added edge.

Updates all existing joined edges and relationships accordingly.

If any arguments are null, the given nodes are unknown (must already exist in the `node` table of the topology schema) , the `acurve` is not a `LINESTRING`, the `anode` and `anothernode` are not the start and endpoints of `acurve` then an error is thrown.

If the spatial reference system (srid) of the `acurve` geometry is not the same as the topology an exception is thrown.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.12

## Examples

## See Also

ST_RemEdgeNewFace

ST_AddEdgeModFace

## Name

ST_AddEdgeModFace — Add a new edge and, if in doing so it splits a face, modify the original face and add a new face.

## Synopsis

`integer ST_AddEdgeModFace(`varchar atopology, integer anode, integer anothernode, geometry acurve`)`;

## Description

Add a new edge and, if in doing so it splits a face, modify the original face and add a new face. Unless the face being split is the Universal Face, the new face will be on the right side of the newly added edge. Returns the id of the newly added edge.

Updates all existing joined edges and relationships accordingly.

If any arguments are null, the given nodes are unknown (must already exist in the `node` table of the topology schema) , the `acurve` is not a `LINESTRING`, the `anode` and `anothernode` are not the start and endpoints of `acurve` then an error is thrown.

If the spatial reference system (srid) of the `acurve` geometry is not the same as the topology an exception is thrown.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.13

## Examples

## See Also

ST_RemEdgeModFace

ST_AddEdgeNewFaces

## Name

ST_RemEdgeNewFace — Removes an edge and, if the removed edge separated two faces, delete the original faces and replace them with a new face.

## Synopsis

`integer ST_RemEdgeNewFace(`varchar atopology, integer anedge`)`;

## Description

Removes an edge and, if the removed edge separated two faces, delete the original faces and replace them with a new face.

Returns the id of a newly created face or NULL, if no new face is created. No new face is created when the removed edge is dangling or isolated or confined with the universe face (possibly making the universe flood into the face on the other side).

Updates all existing joined edges and relationships accordingly.

Refuses to remove an edge partecipating in the definition of an existing TopoGeometry. Refuses to heal two faces if any TopoGeometry is defined by only one of them (and not the other).

If any arguments are null, the given edge is unknown (must already exist in the `edge` table of the topology schema), the topology name is invalid then an error is thrown.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.14

## Examples

## See Also

ST_RemEdgeModFace

ST_AddEdgeNewFaces

## Name

ST_RemEdgeModFace — Removes an edge and, if the removed edge separated two faces, delete one of the them and modify the other to take the space of both.

## Synopsis

`integer ST_RemEdgeModFace(`varchar atopology, integer anedge`)`;

## Description

Removes an edge and, if the removed edge separated two faces, delete one of the them and modify the other to take the space of both. Preferentially keeps the face on the right, to be symmetric with ST_AddEdgeModFace also keeping it. Returns the id of the face remaining in place of the removed edge.

Updates all existing joined edges and relationships accordingly.

Refuses to remove an edge partecipating in the definition of an existing TopoGeometry. Refuses to heal two faces if any TopoGeometry is defined by only one of them (and not the other).

If any arguments are null, the given edge is unknown (must already exist in the `edge` table of the topology schema), the topology name is invalid then an error is thrown.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.15

## Examples

## See Also

ST_AddEdgeModFace

ST_RemEdgeNewFace

## Name

ST_ChangeEdgeGeom — Changes the shape of an edge without affecting the topology structure.

## Synopsis

`integer ST_ChangeEdgeGeom(`varchar atopology, integer anedge, geometry acurve`)`;

## Description

Changes the shape of an edge without affecting the topology structure.

If any arguments are null, the given edge does not exist in the `node` table of the topology schema, the `acurve` is not a `LINESTRING`, the `anode` and `anothernode` are not the start and endpoints of `acurve` or the modification would change the underlying topology then an error is thrown.

If the spatial reference system (srid) of the `acurve` geometry is not the same as the topology an exception is thrown.

If the new `acurve` is not simple, then an error is thrown.

If moving the edge from old to new position would hit an obstacle then an error is thrown.

Availability: 1.1.0

Enhanced: 2.0.0 adds topological consistency enforcement

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details X.3.6

## Examples

    SELECT topology.ST_ChangeEdgeGeom('ma_topo', 1,
    		ST_GeomFromText('LINESTRING(227591.9 893900.4,227622.6 893844.3,227641.6 893816.6, 227704.5 893778.5)', 26986) );
     ----
     Edge 1 changed

## See Also

ST_AddEdgeModFace

ST_RemEdgeModFace

ST_ModEdgeSplit

## Name

ST_ModEdgeSplit — Split an edge by creating a new node along an existing edge, modifying the original edge and adding a new edge.

## Synopsis

`text ST_ModEdgeSplit(`varchar atopology, integer anedge, geometry apoint`)`;

## Description

Split an edge by creating a new node along an existing edge, modifying the original edge and adding a new edge. Updates all existing joined edges and relationships accordingly.

Availability: 1.?

Changed: 2.0 - In prior versions, this was misnamed ST_ModEdgesSplit

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.9

## Examples

    -- Add an edge --
     SELECT topology.AddEdge('ma_topo', ST_GeomFromText('LINESTRING(227592 893910, 227600 893910)', 26986) ) As edgeid;

    -- edgeid-
    3

    -- Split the edge  --
    SELECT topology.ST_ModEdgeSplit('ma_topo',  3, ST_SetSRID(ST_Point(227594,893910),26986)  ) As result;
             result
    -------------------------
    7

## See Also

ST_NewEdgesSplit, ST_ModEdgeHeal, ST_NewEdgeHeal, AddEdge

## Name

ST_ModEdgeHeal — Heal two edges by deleting the node connecting them, modifying the first edge and deleting the second edge. Returns the id of the deleted node.

## Synopsis

`int ST_ModEdgeHeal(`varchar atopology, integer anedge, integer anotheredge`)`;

## Description

Heal two edges by deleting the node connecting them, modifying the first edge and deleting the second edge. Returns the id of the deleted node. Updates all existing joined edges and relationships accordingly.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.9

## See Also

ST_ModEdgeSplit ST_NewEdgesSplit

## Name

ST_NewEdgeHeal — Heal two edges by deleting the node connecting them, deleting both edges, and replacing them with an edge whose direction is the same as the first edge provided.

## Synopsis

`int ST_NewEdgeHeal(`varchar atopology, integer anedge, integer anotheredge`)`;

## Description

Heal two edges by deleting the node connecting them, deleting both edges, and replacing them with an edge whose direction is the same as the first edge provided. Returns the id of the new edge replacing the healed ones. Updates all existing joined edges and relationships accordingly.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.9

## See Also

ST_ModEdgeHeal ST_ModEdgeSplit ST_NewEdgesSplit

## Name

ST_MoveIsoNode — Moves an isolated node in a topology from one point to another. If new `apoint` geometry exists as a node an error is thrown. REturns description of move.

## Synopsis

`text ST_MoveIsoNode(`varchar atopology, integer anedge, geometry apoint`)`;

## Description

Moves an isolated node in a topology from one point to another. If new `apoint` geometry exists as a node an error is thrown.

If any arguments are null, the `apoint` is not a point, the existing node is not isolated (is a start or end point of an existing edge), new node location intersects an existing edge (even at the end points) then an exception is thrown.

If the spatial reference system (srid) of the point geometry is not the same as the topology an exception is thrown.

Availability: 1.?

This method implements the SQL/MM specification. SQL-MM: Topo-Net Routines: X.3.2

## Examples

    -- Add an isolated node with no face  --
    SELECT topology.ST_AddIsoNode('ma_topo',  NULL, ST_GeomFromText('POINT(227579 893916)', 26986) ) As nodeid;
     nodeid
    --------
          7
    -- Move the new node --
    SELECT topology.ST_MoveIsoNode('ma_topo', 7,  ST_GeomFromText('POINT(227579.5 893916.5)', 26986) ) As descrip;
                          descrip
    ----------------------------------------------------
    Isolated Node 7 moved to location 227579.5,893916.5

## See Also

ST_AddIsoNode

## Name

ST_NewEdgesSplit — Split an edge by creating a new node along an existing edge, deleting the original edge and replacing it with two new edges. Returns the id of the new node created that joins the new edges.

## Synopsis

`integer ST_NewEdgesSplit(`varchar atopology, integer anedge, geometry apoint`)`;

## Description

Split an edge with edge id `anedge` by creating a new node with point location `apoint` along current edge, deleting the original edge and replacing it with two new edges. Returns the id of the new node created that joins the new edges. Updates all existing joined edges and relationships accordingly.

If the spatial reference system (srid) of the point geometry is not the same as the topology, the `apoint` is not a point geometry, the point is null, the point already exists as a node, the edge does not correspond to an existing edge or the point is not within the edge then an exception is thrown.

Availability: 1.?

This method implements the SQL/MM specification. SQL-MM: Topo-Net Routines: X.3.8

## Examples

    -- Add an edge  --
    SELECT topology.AddEdge('ma_topo', ST_GeomFromText('LINESTRING(227575 893917,227592 893900)', 26986) ) As edgeid;
    -- result-
    edgeid
    ------
    	2
    -- Split the new edge --
    SELECT topology.ST_NewEdgesSplit('ma_topo', 2,  ST_GeomFromText('POINT(227578.5 893913.5)', 26986) ) As newnodeid;
     newnodeid
    ---------
           6

## See Also

ST_ModEdgeSplit ST_ModEdgeHeal ST_NewEdgeHeal AddEdge

## Name

ST_RemoveIsoNode — Removes an isolated node and returns description of action. If the node is not isolated (is start or end of an edge), then an exception is thrown.

## Synopsis

`text ST_RemoveIsoNode(`varchar atopology, integer anode`)`;

## Description

Removes an isolated node and returns description of action. If the node is not isolated (is start or end of an edge), then an exception is thrown.

Availability: 1.?

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X+1.3.3

## Examples

    -- Add an isolated node with no face  --
    SELECT topology.ST_RemoveIsoNode('ma_topo',  7 ) As result;
             result
    -------------------------
     Isolated node 7 removed

## See Also

ST_AddIsoNode

## 11.6. Topology Accessors

## Name

GetEdgeByPoint — Find the edge-id of an edge that intersects a given point

## Synopsis

`integer GetEdgeByPoint(`varchar atopology, geometry apoint, float8 tol`)`;

## Retrieve the id of an edge that intersects a Point

The function returns an integer (id-edge) given a topology, a POINT and a tolerance. If tolerance = 0 then the point has to intersect the edge.

If the point is the location of a node, then an exception is thrown. To avoid this run the GetNodeByPoint function.

If the point doesn't intersect an edge, returns 0 (zero).

If use tolerance > 0 and there is more than one edge near the point then an exception is thrown.

If tolerance = 0, the function use ST_Intersects otherwise uses ST_DWithin.

Availability: 2.0.0 - requires GEOS >= 3.3.0.

## Examples

These examples use edges we created in AddEdge

    SELECT topology.GetEdgeByPoint('ma_topo',geom, 1) As with1mtol, topology.GetEdgeByPoint('ma_topo',geom,0) As withnotol
    FROM ST_GeomFromEWKT('SRID=26986;POINT(227622.6 893843)') As geom;
     with1mtol | withnotol
    -----------+-----------
             2 |         0

    SELECT topology.GetEdgeByPoint('ma_topo',geom, 1) As nearnode
    FROM ST_GeomFromEWKT('SRID=26986;POINT(227591.9 893900.4)') As geom;

    -- get error --
    ERROR:  Two or more edges found

## See Also

AddEdge, GetNodeByPoint

## Name

GetFaceByPoint — Find the face-id of a face that intersects a given point

## Synopsis

`integer GetFaceByPoint(`varchar atopology, geometry apoint, float8 tol`)`;

## Description

Retrieve the id of a face that intersects a Point.

The function returns an integer (id-face) given a topology, a POINT and a tolerance. If tolerance = 0 then the point has to intersect the face.

If the point is the location of a node, then an exception is thrown. To avoid this run the GetNodeByPoint function.

If the point doesn't intersect a face, returns 0 (zero).

If use tolerance > 0 and there is more than one face near the point then an exception is thrown.

If tolerance = 0, the function uses ST_Intersects otherwise uses ST_DWithin.

Availability: 2.0.0 - requires GEOS >= 3.3.0.

## Examples

These examples use edges faces created in AddFace

    SELECT topology.GetFaceByPoint('ma_topo',geom, 10) As with1mtol, topology.GetFaceByPoint('ma_topo',geom,0) As withnotol
    	FROM ST_GeomFromEWKT('POINT(234604.6 899382.0)') As geom;

    	 with1mtol | withnotol
    	-----------+-----------
    			 1 |         0

    SELECT topology.GetFaceByPoint('ma_topo',geom, 1) As nearnode
    	FROM ST_GeomFromEWKT('POINT(227591.9 893900.4)') As geom;

    -- get error --
    ERROR:  Two or more faces found

## See Also

AddFace, GetNodeByPoint, GetEdgeByPoint

## Name

GetNodeByPoint — Find the id of a node at a point location

## Synopsis

`integer GetNodeByPoint(`varchar atopology, geometry point, float8 tol`)`;

## Retrieve the id of a node at a point location

The function return an integer (id-node) given a topology, a POINT and a tolerance. If tolerance = 0 mean exactly intersection otherwise retrieve the node from an interval.

If there isn't a node at the point, it return 0 (zero).

If use tolerance > 0 and near the point there are more than one node it throw an exception.

If tolerance = 0, the function use ST_Intersects otherwise will use ST_DWithin.

Availability: 2.0.0 - requires GEOS >= 3.3.0.

## Examples

These examples use edges we created in AddEdge

    SELECT topology.GetNodeByPoint('ma_topo',geom, 1) As nearnode
     FROM ST_GeomFromEWKT('SRID=26986;POINT(227591.9 893900.4)') As geom;
      nearnode
    ----------
            2

    SELECT topology.GetNodeByPoint('ma_topo',geom, 1000) As too_much_tolerance
     FROM ST_GeomFromEWKT('SRID=26986;POINT(227591.9 893900.4)') As geom;

     ----get error--
     ERROR:  Two or more nodes found

## See Also

AddEdge, GetEdgeByPoint

## Name

GetTopologyID — Returns the id of a topology in the topology.topology table given the name of the topology.

## Synopsis

`integer GetTopologyID(`varchar toponame`)`;

## Description

Returns the id of a topology in the topology.topology table given the name of the topology.

Availability: 1.?

## Examples

    SELECT topology.GetTopologyID('ma_topo') As topo_id;
     topo_id
    ---------
           1

## See Also

CreateTopology, DropTopology, GetTopologyName, GetTopologySRID

## Name

GetTopologySRID — Returns the SRID of a topology in the topology.topology table given the name of the topology.

## Synopsis

`integer GetTopologyID(`varchar toponame`)`;

## Description

Returns the spatial reference id of a topology in the topology.topology table given the name of the topology.

Availability: 2.0.0

## Examples

    SELECT topology.GetTopologySRID('ma_topo') As SRID;
     SRID
    -------
      4326

## See Also

CreateTopology, DropTopology, GetTopologyName, GetTopologyID

## Name

GetTopologyName — Returns the name of a topology (schema) given the id of the topology.

## Synopsis

`varchar GetTopologyName(`integer topology_id`)`;

## Description

Returns the topology name (schema) of a topology from the topology.topology table given the topology id of the topology.

Availability: 1.?

## Examples

    SELECT topology.GetTopologyName(1) As topo_name;
     topo_name
    -----------
     ma_topo

## See Also

CreateTopology, DropTopology, GetTopologyID, GetTopologySRID

## Name

ST_GetFaceEdges — Returns a set of ordered edges that bound `aface` includes the sequence order.

## Synopsis

`getfaceedges_returntype ST_GetFaceEdges(`varchar atopology, integer aface`)`;

## Description

Returns a set of ordered edges that bound `aface` includes the sequence order. Each output consists of a sequence and edgeid. Sequence numbers start with value 1.

Enumeration of each ring edges start from the edge with smallest identifier.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM 3 Topo-Geo and Topo-Net 3: Routine Details: X.3.5

## Examples

    -- Returns the edges bounding face 1
    SELECT (topology.ST_GetFaceEdges('tt', 1)).*;
    -- result --
     sequence | edge
    ----------+------
            1 |   -4
            2 |    5
            3 |    7
            4 |   -6
            5 |    1
            6 |    2
            7 |    3
    (7 rows)

    -- Returns the sequenc, edge id
    -- , and geometry of the edges that bound face 1
    -- If you just need geom and seq, can use ST_GetFaceGeometry
    SELECT t.seq, t.edge, geom
    FROM topology.ST_GetFaceEdges('tt',1) As t(seq,edge)
    	INNER JOIN tt.edge AS e ON abs(t.edge) = e.edge_id;

## See Also

GetRingEdges, AddFace, ST_GetFaceGeometry

## Name

ST_GetFaceGeometry — Returns the polygon in the given topology with the specified face id.

## Synopsis

`geometry ST_GetFaceGeometry(`varchar atopology, integer aface`)`;

## Description

Returns the polygon in the given topology with the specified face id. Builds the polygon from the edges making up the face.

Availability: 1.?

This method implements the SQL/MM specification. SQL-MM 3 Topo-Geo and Topo-Net 3: Routine Details: X.3.16

## Examples

    -- Returns the wkt of the polygon added with AddFace
    SELECT ST_AsText(topology.ST_GetFaceGeometry('ma_topo', 1)) As facegeomwkt;
    -- result --
                   facegeomwkt

    --------------------------------------------------------------------------------
     POLYGON((234776.9 899563.7,234896.5 899456.7,234914 899436.4,234946.6 899356.9,
    234872.5 899328.7,234891 899285.4,234992.5 899145,234890.6 899069,
    234755.2 899255.4,234612.7 899379.4,234776.9 899563.7))

## See Also

AddFace

## Name

GetRingEdges — Returns an ordered set of edges forming a ring with the given edge .

## Synopsis

`getfaceedges_returntype GetRingEdges(`varchar atopology, integer aring, integer max_edges=null`)`;

## Description

Returns an ordered set of edges forming a ring with the given edge. Each output consists of a sequence and a signed edge id. Sequence numbers start with value 1. A negative edge identifier means that the given edge is taken backward. You can pass a negative edge id to start walking backward.

If `max_edges` is not null no more than those records are returned by that function. This is meant to be a safety parameter when dealing with possibly invalid topologies.

Availability: 2.0

## See Also

ST_GetFaceEdges, GetNodeEdges

## Name

GetNodeEdges — Returns an ordered set of edges incident to the given node.

## Synopsis

`getfaceedges_returntype GetNodeEdges(`varchar atopology, integer anode`)`;

## Description

Returns an ordered set of edges incident to the given node. Each output consists of a sequence and a signed edge id. Sequence numbers start with value 1. A positive edge starts at the given node. A negative edge ends into the given node. Closed edges will appear twice (with both signs). Order is clockwise starting from northbound.

This function computes ordering rather than deriving from metadata and is thus usable to build edge ring linking.

Availability: 2.0

## See Also

GetRingEdges, ST_Azimuth

## 11.7. Topology Processing

Abstract

This section covers the functions for processing topologies in non-standard ways.

## Name

Polygonize — Find and register all faces defined by topology edges

## Synopsis

`text Polygonize(`varchar toponame`)`;

## Description

Register all faces that can be built out a topology edge primitives.

The target topology is assumed to contain no self-intersecting edges.

Already known faces are recognized, so it is safe to call Polygonize multiple times on the same topology.

This function does not use nor set the next_left_edge and next_right_edge fields of the edge table.

Availability: 2.0.0

## See Also

AddFace, ST_Polygonize

## Name

AddNode — Adds a point node to the node table in the specified topology schema and returns the nodeid of new node. If point already exists as node, the existing nodeid is returned.

## Synopsis

`integer AddNode(`varchar toponame, geometry apoint, boolean allowEdgeSplitting=false, boolean computeContainingFace=false`)`;

## Description

Adds a point node to the node table in the specified topology schema. The AddEdge function automatically adds start and end points of an edge when called so not necessary to explicitly add nodes of an edge.

If any edge crossing the node is found either an exception is raised or the edge is splitted, depending on the `allowEdgeSplitting` parameter value.

If `computeContainingFace` is true a newly added node would get the correct containing face computed.

If the `apoint` geometry already exists as a node, the node is not added but the existing nodeid is returned.

Availability: 2.0.0

## Examples

    SELECT topology.AddNode('ma_topo', ST_GeomFromText('POINT(227641.6 893816.5)', 26986) ) As nodeid;
    -- result --
    nodeid
    --------
     4

## See Also

AddEdge, CreateTopology

## Name

AddEdge — Adds a linestring edge to the edge table and associated start and end points to the point nodes table of the specified topology schema using the specified linestring geometry and returns the edgeid of the new (or existing) edge.

## Synopsis

`integer AddEdge(`varchar toponame, geometry aline`)`;

## Description

Adds an edge to the edge table and associated nodes to the nodes table of the specified `toponame` schema using the specified linestring geometry and returns the edgeid of the new or existing record. The newly added edge has "universe" face on both sides and links to itself.

If the `aline` geometry crosses, overlaps, contains or is contained by an existing linestring edge, then an error is thrown and the edge is not added.

The geometry of `aline` must have the same `srid` as defined for the topology otherwise an invalid spatial reference sys error will be thrown.

Availability: 2.0.0 requires GEOS >= 3.3.0.

## Examples

    SELECT topology.AddEdge('ma_topo', ST_GeomFromText('LINESTRING(227575.8 893917.2,227591.9 893900.4)', 26986) ) As edgeid;
    -- result-
    edgeid
    --------
     1

    SELECT topology.AddEdge('ma_topo', ST_GeomFromText('LINESTRING(227591.9 893900.4,227622.6 893844.2,227641.6 893816.5,
     227704.5 893778.5)', 26986) ) As edgeid;
    -- result --
    edgeid
    --------
     2

     SELECT topology.AddEdge('ma_topo', ST_GeomFromText('LINESTRING(227591.2 893900, 227591.9 893900.4,
      227704.5 893778.5)', 26986) ) As edgeid;
     -- gives error --
     ERROR:  Edge intersects (not on endpoints) with existing edge 1

## See Also

CreateTopology, Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems”

## Name

AddFace — Registers a face primitive to a topology and get it's identifier.

## Synopsis

`integer AddFace(`varchar toponame, geometry apolygon, boolean force_new=false`)`;

## Description

Registers a face primitive to a topology and get it's identifier.

For a newly added face, the edges forming its boundaries and the ones contained in the face will be updated to have correct values in the left_face and right_face fields. Isolated nodes contained in the face will also be updated to have a correct containing_face field value.

This function does not use nor set the next_left_edge and next_right_edge fields of the edge table.

The target topology is assumed to be valid (containing no self-intersecting edges). An exception is raised if: The polygon boundary is not fully defined by existing edges or the polygon overlaps an existing face.

If the `apolygon` geometry already exists as a face, then: if `force_new` is false (the default) the face id of the existing face is returned; if `force_new` is true a new id will be assigned to the newly registered face.

When a new registration of an existing face is performed (force_new=true), no action will be taken to resolve dangling references to the existing face in the edge, node an relation tables, nor will the MBR field of the existing face record be updated. It is up to the caller to deal with that.

The `apolygon` geometry must have the same `srid` as defined for the topology otherwise an invalid spatial reference sys error will be thrown.

Availability: 2.0.0

## Examples

    -- first add the edges we use generate_series as an iterator (the below
    -- will only work for polygons with < 10000 points because of our max in gs)
    SELECT topology.AddEdge('ma_topo', ST_MakeLine(ST_PointN(geom,i), ST_PointN(geom, i + 1) )) As edgeid
        FROM (SELECT  ST_NPoints(geom) AS npt, geom
                FROM
                    (SELECT ST_Boundary(ST_GeomFromText('POLYGON((234896.5 899456.7,234914 899436.4,234946.6 899356.9,234872.5 899328.7,
                    234891 899285.4,234992.5 899145, 234890.6 899069,234755.2 899255.4,
                    234612.7 899379.4,234776.9 899563.7,234896.5 899456.7))', 26986) )  As geom
                )  As geoms) As facen CROSS JOIN generate_series(1,10000) As i
             WHERE i < npt;
    -- result --
     edgeid
    --------
          3
          4
          5
          6
          7
          8
          9
         10
         11
         12
    (10 rows)
    -- then add the face -

    SELECT topology.AddFace('ma_topo',
        ST_GeomFromText('POLYGON((234896.5 899456.7,234914 899436.4,234946.6 899356.9,234872.5 899328.7,
        234891 899285.4,234992.5 899145, 234890.6 899069,234755.2 899255.4,
        234612.7 899379.4,234776.9 899563.7,234896.5 899456.7))', 26986) ) As faceid;
    -- result --
    faceid
    --------
     1

## See Also

AddEdge, CreateTopology, Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems”

## 11.8. TopoGeometry Constructors

Abstract

This section covers the topology functions for creating new topogeometries.

## Name

CreateTopoGeom — Creates a new topo geometry object from topo element array - tg_type: 1:[multi]point, 2:[multi]line, 3:[multi]poly, 4:collection

## Synopsis

`topogeometry CreateTopoGeom(`varchar toponame, integer tg_type, integer layer_id, topoelementarray tg_objs`)`;

`topogeometry CreateTopoGeom(`varchar toponame, integer tg_type, integer layer_id`)`;

## Description

Creates a topogeometry object for layer denoted by layer_id and registers it in the relations table in the `toponame` schema.

tg_type is an integer: 1:[multi]point (punctal), 2:[multi]line (lineal), 3:[multi]poly (areal), 4:collection. layer_id is the layer id in the topology.layer table.

punctal layers are formed from set of nodes, lineal layers are formed from a set of edges, areal layers are formed from a set of faces, and collections can be formed from a mixture of nodes, edges, and faces.

Omitting the array of components generates an empty TopoGeometry object.

Availability: 1.?

## Examples: Form from existing edges

Create a topogeom in ri_topo schema for layer 2 (our ri_roads), of type (2) LINE, for the first edge (we loaded in `ST_CreateTopoGeo`.

    INSERT INTO ri.ri_roads(road_name, topo) VALUES('Unknown', topology.CreateTopoGeom('ri_topo',2,2,'{{1,2}}'::topology.topoelementarray);

## Examples: Convert an areal geometry to best guess topogeometry

Lets say we have geometries that should be formed from a collection of faces. We have for example blockgroups table and want to know the topo geometry of each block group. If our data was perfectly aligned, we could do this:

    -- create our topo geometry column --
    SELECT topology.AddTopoGeometryColumn(
    	'topo_boston',
    	'boston', 'blockgroups', 'topo', 'POLYGON');

    -- addtopgeometrycolumn --
    1

    -- update our column assuming
    -- everything is perfectly aligned with our edges
    UPDATE boston.blockgroups AS bg
    	SET topo = topology.CreateTopoGeom('topo_boston'
            ,3,1
            , foo.bfaces)
    FROM (SELECT b.gid,  topology.TopoElementArray_Agg(ARRAY[f.face_id,3]) As bfaces
    	FROM boston.blockgroups As b
                INNER JOIN topo_boston.face As f ON b.geom && f.mbr
            WHERE ST_Covers(b.geom, topology.ST_GetFaceGeometry('topo_boston', f.face_id))
                GROUP BY b.gid) As foo
    WHERE foo.gid = bg.gid;

    --the world is rarely perfect allow for some error
    --count the face if 50% of it falls
    -- within what we think is our blockgroup boundary
    UPDATE boston.blockgroups AS bg
    	SET topo = topology.CreateTopoGeom('topo_boston'
            ,3,1
            , foo.bfaces)
    FROM (SELECT b.gid,  topology.TopoElementArray_Agg(ARRAY[f.face_id,3]) As bfaces
    	FROM boston.blockgroups As b
                INNER JOIN topo_boston.face As f ON b.geom && f.mbr
            WHERE ST_Covers(b.geom, topology.ST_GetFaceGeometry('topo_boston', f.face_id))
            	OR
     (  ST_Intersects(b.geom, topology.ST_GetFaceGeometry('topo_boston', f.face_id))
                AND ST_Area(ST_Intersection(b.geom, topology.ST_GetFaceGeometry('topo_boston', f.face_id) ) ) >
                    ST_Area(topology.ST_GetFaceGeometry('topo_boston', f.face_id))*0.5
                    )
                GROUP BY b.gid) As foo
    WHERE foo.gid = bg.gid;

    -- and if we wanted to convert our topogeometry back
    -- to a denomalized geometry aligned with our faces and edges
    -- cast the topo to a geometry
    -- The really cool thing is my new geometries
    -- are now aligned with my tiger street centerlines
    UPDATE boston.blockgroups SET new_geom = topo::geometry;

## See Also

AddTopoGeometryColumn, toTopoGeom ST_CreateTopoGeo, ST_GetFaceGeometry, topoelementarray, TopoElementArray_Agg

## Name

toTopoGeom — Creates a new topo geometry from a simple geometry

## Synopsis

`topogeometry toTopoGeom(`geometry geom, varchar toponame, integer layer_id, float8 tolerance`)`;

## Description

Creates a topogeometry object for layer denoted by layer_id and registers it in the relations table in the `toponame` schema.

Topological primitives required to represent the input geometry will be added, possibly splitting existing ones. Pre-existing TopoGeometry objects will retain their shapes.

When `tolerance` is given it will be used to snap the input geometry to existing primitives.

Availability: 2.0

## Examples

This is a full self-contained workflow

     -- do this if you don't have a topology setup already
    -- creates topology not allowing any tolerance
    SELECT topology.CreateTopology('topo_boston_test', 2249);
    -- create a new table
    CREATE TABLE nei_topo(gid serial primary key, nei varchar(30));
    --add a topogeometry column to it
    SELECT topology.AddTopoGeometryColumn('topo_boston_test', 'public', 'nei_topo', 'topo', 'MULTIPOLYGON') As new_layer_id;
    new_layer_id
    -----------
    1

    --use new layer id in populating the new topogeometry column
    -- we add the topogeoms to the new layer with 0 tolerance
    INSERT INTO nei_topo(nei, topo)
    SELECT nei,  topology.toTopoGeom(geom, 'topo_boston_test', 1)
    FROM neighborhoods
    WHERE gid BETWEEN 1 and 15;

    --use to verify what has happened --
    SELECT * FROM
        topology.TopologySummary('topo_boston_test');

    -- summary--
    Topology topo_boston_test (5), SRID 2249, precision 0
    61 nodes, 87 edges, 35 faces, 15 topogeoms in 1 layers
    Layer 1, type Polygonal (3), 15 topogeoms
     Deploy: public.nei_topo.topo

## See Also

CreateTopology,AddTopoGeometryColumn, CreateTopoGeom, TopologySummary

## Name

TopoElementArray_Agg — Returns a `topoelementarray` for a set of element_id, type arrays (topoelements)

## Synopsis

`topoelementarray TopoElementArray_Agg(`topoelement set tefield`)`;

## Description

Used to create a topoelementarray from a set of TopoElement.

Availability: 2.0.0

## Examples

    SELECT topology.TopoElementArray_Agg(ARRAY[e,t]) As tea
      FROM generate_series(1,3) As e CROSS JOIN generate_series(1,4) As t;
      tea
    --------------------------------------------------------------------------
    {{1,1},{1,2},{1,3},{1,4},{2,1},{2,2},{2,3},{2,4},{3,1},{3,2},{3,3},{3,4}}

## See Also

TopoElement, topoelementarray

## 11.9. TopoGeometry Accessors

## Name

GetTopoGeomElementArray — Returns a `topoelementarray` (an array of topoelements) containing the topological elements and type of the given TopoGeometry (primitive elements)

## Synopsis

`topoelementarray GetTopoGeomElementArray(`varchar toponame, integer layer_id, integer tg_id`)`;

`topoelementarray topoelement GetTopoGeomElementArray(`topogeometry tg`)`;

## Description

Returns a topoelementarray containing the topological elements and type of the given TopoGeometry (primitive elements). This is similar to GetTopoGeomElements except it returns the elements as an array rather than as a dataset.

tg_id is the topogeometry id of the topogeometry object in the topology in the layer denoted by `layer_id` in the topology.layer table.

Availability: 1.?

## Examples

## See Also

GetTopoGeomElements, topoelementarray

## Name

GetTopoGeomElements — Returns a set of `topoelement` objects containing the topological element_id,element_type of the given TopoGeometry (primitive elements)

## Synopsis

`setof topoelement GetTopoGeomElements(`varchar toponame, integer layer_id, integer tg_id`)`;

`setof topoelement GetTopoGeomElements(`topogeometry tg`)`;

## Description

Returns a set of element_id,element_type (topoelements) for a given topogeometry object in `toponame` schema.

tg_id is the topogeometry id of the topogeometry object in the topology in the layer denoted by `layer_id` in the topology.layer table.

Availability: 1.?

## Examples

## See Also

GetTopoGeomElementArray, TopoElement

## 11.10. TopoGeometry Outputs

## Name

AsGML — Returns the GML representation of a topogeometry.

## Synopsis

`text AsGML(`topogeometry tg`)`;

`text AsGML(`topogeometry tg, text nsprefix_in`)`;

`text AsGML(`topogeometry tg, regclass visitedTable`)`;

`text AsGML(`topogeometry tg, regclass visitedTable, text nsprefix`)`;

`text AsGML(`topogeometry tg, text nsprefix_in, integer precision, integer options`)`;

`text AsGML(`topogeometry tg, text nsprefix_in, integer precision, integer options, regclass visitedTable`)`;

`text AsGML(`topogeometry tg, text nsprefix_in, integer precision, integer options, regclass visitedTable, text idprefix`)`;

`text AsGML(`topogeometry tg, text nsprefix_in, integer precision, integer options, regclass visitedTable, text idprefix, int gmlversion`)`;

## Description

Returns the GML representation of a topogeometry in version GML3 format. If no `nsprefix_in` is specified then `gml` is used. Pass in an empty string for nsprefix to get a non-qualified name space. The precision (default: 15) and options (default 1) parameters, if given, are passed untouched to the underlying call to ST_AsGML.

The `visitedTable` parameter, if given, is used for keeping track of the visited Node and Edge elements so to use cross-references (xlink:xref) rather than duplicating definitions. The table is expected to have (at least) two integer fields: 'element_type' and 'element_id'. The calling user must have both read and write privileges on the given table. For best performance, an index should be defined on `element_type` and `element_id`, in that order. Such index would be created automatically by adding a unique constraint to the fields. Example:

    CREATE TABLE visited (
      element_type integer, element_id integer,
      unique(element_type, element_id)
    );

The `idprefix` parameter, if given, will be prepended to Edge and Node tag identifiers.

The `gmlver` parameter, if given, will be passed to the underlying ST_AsGML. Defaults to 3.

Availability: 2.0.0

## Examples

This uses the topo geometry we created in CreateTopoGeom

    SELECT topology.AsGML(topo) As rdgml
      FROM ri.roads
      WHERE road_name = 'Unknown';

    -- rdgml--
    <gml:TopoCurve>
        <gml:directedEdge>
            <gml:Edge gml:id="E1">
                <gml:directedNode orientation="-">
                    <gml:Node gml:id="N1"/>
                </gml:directedNode>
                <gml:directedNode></gml:directedNode>
                <gml:curveProperty>
                    <gml:Curve srsName="urn:ogc:def:crs:EPSG::3438">
                        <gml:segments>
                            <gml:LineStringSegment>
                                <gml:posList srsDimension="2">384744 236928 384750 236923 384769 236911 384799 236895 384811 236890
                                384833 236884 384844 236882 384866 236881 384879 236883 384954 236898 385087 236932 385117 236938
                                385167 236938 385203 236941 385224 236946 385233 236950 385241 236956 385254 236971
                                385260 236979 385268 236999 385273 237018 385273 237037 385271 237047 385267 237057 385225 237125
                                385210 237144 385192 237161 385167 237192 385162 237202 385159 237214 385159 237227 385162 237241
                                385166 237256 385196 237324 385209 237345 385234 237375 385237 237383 385238 237399 385236 237407
                                385227 237419 385213 237430 385193 237439 385174 237451 385170 237455 385169 237460 385171 237475
                                385181 237503 385190 237521 385200 237533 385206 237538 385213 237541 385221 237542 385235 237540 385242 237541
                                385249 237544 385260 237555 385270 237570 385289 237584 385292 237589 385291 237596 385284 237630</gml:posList>
                            </gml:LineStringSegment>
                        </gml:segments>
                    </gml:Curve>
                </gml:curveProperty>
            </gml:Edge>
        </gml:directedEdge>
    </gml:TopoCurve>

Same exercise as previous without namespace

    SELECT topology.AsGML(topo,'') As rdgml
      FROM ri.roads
      WHERE road_name = 'Unknown';

    -- rdgml--
    <TopoCurve>
        <directedEdge>
            <Edge id="E1">
                <directedNode orientation="-">
                    <Node id="N1"/>
                </directedNode>
                <directedNode></directedNode>
                <curveProperty>
                    <Curve srsName="urn:ogc:def:crs:EPSG::3438">
                        <segments>
                            <LineStringSegment>
                                <posList srsDimension="2">384744 236928 384750 236923 384769 236911 384799 236895 384811 236890
                                384833 236884 384844 236882 384866 236881 384879 236883 384954 236898 385087 236932 385117 236938
                                385167 236938 385203 236941 385224 236946 385233 236950 385241 236956 385254 236971
                                385260 236979 385268 236999 385273 237018 385273 237037 385271 237047 385267 237057 385225 237125
                                385210 237144 385192 237161 385167 237192 385162 237202 385159 237214 385159 237227 385162 237241
                                385166 237256 385196 237324 385209 237345 385234 237375 385237 237383 385238 237399 385236 237407
                                385227 237419 385213 237430 385193 237439 385174 237451 385170 237455 385169 237460 385171 237475
                                385181 237503 385190 237521 385200 237533 385206 237538 385213 237541 385221 237542 385235 237540 385242 237541
                                385249 237544 385260 237555 385270 237570 385289 237584 385292 237589 385291 237596 385284 237630</posList>
                             </LineStringSegment>
                        </segments>
                    </Curve>
                </curveProperty>
            </Edge>
        </directedEdge>
    </TopoCurve>

## See Also

CreateTopoGeom, ST_CreateTopoGeo

## Chapter 12. PostGIS Extras

This chapter documents features found in the extras folder of the PostGIS source tarballs and source repository. These are not always packaged with PostGIS binary releases, but are usually plpgsql based or standard shell scripts that can be run as is.

## 12.1. Tiger Geocoder

Abstract

A plpgsql based geocoder written to work with the TIGER (Topologically Integrated Geographic Encoding and Referencing system ) / Line and Master Address database export released by the US Census Bureau. In prior versions the TIGER files were released in ASCII format. The older geocoder used to work with that format is in `extras/tiger_geocoder/tiger_2006andbefore`.

There are four components to the geocoder: the data loader functions, the address normalizer, the address geocoder, and the reverse geocoder. The latest version updated to use the TIGER 2010 census data is located in the `extras/tiger_geocoder/tiger_2010` folder.

Although it is designed specifically for the US, a lot of the concepts and functions are applicable and can be adapted to work with other country address and road networks.

The script builds a schema called `tiger` to house all the tiger related functions, reusable lookup data such as road type prefixes, suffixes, states, various control tables for managing data load, and skeleton base tables from which all the tiger loaded tables inherit from.

Another schema called `tiger_data` is also created which houses all the census data for each state that the loader downloads from Census site and loads into the database. In the current model, each set of state tables is prefixed with the state code e.g ma_addr, ca_edges etc with constraints to enforce only that state data. Each of these tables inherits from the base addr, faces, edges, etc located in the tiger schema.

All the geocode functions only reference the base tables, so there is no requirement that the data schema be called `tiger_data` or that data can't be further partitioned into other schemas -- e.g a different schema for each state, as long as all the tables inherit from the tables in the `tiger` schema.

If you are using a prerelease version of PostGIS 2.0.0 tiger geocoder, you can upgrade the scripts using the accompanying upgrade_geocoder.bat / .sh scripts in tiger_2010. We'll be refining the upgrade scripts until release.

Design:

The goal of this project is to build a fully functional geocoder that can process an arbitrary address string and using normalized TIGER census data, produce a point geometry and rating reflecting the location of the given address and likeliness of the location.

The `reverse_geocode` function, introduced in PostGIS 2.0.0 is useful for deriving the street address and cross streets of a GPS location.

The geocoder should be simple for anyone familiar with PostGIS to install and use, and should be easily installable and usable on all platforms supported by PostGIS.

It should be robust enough to function properly despite formatting and spelling errors.

It should be extensible enough to be used with future data updates, or alternate data sources with a minimum of coding changes.

The `tiger` schema must be added to the database search path for the functions to work properly.

There is another geocoder for PostGIS gaining in popularity and more suitable for international use. It is called Nominatim and uses OpenStreetMap gazeteer formatted data. It requires osm2pgsql for loading the data, PostgreSQL 8.4+ and PostGIS 1.5+ to function. It is packaged as a webservice interface and seems designed to be called as a webservice. Just like the tiger geocoder, it has both a geocoder and a reverse geocoder component. From the documentation, it is unclear if it has a pure SQL interface like the tiger geocoder, or if a good deal of the logic is implemented in the web interface.

## Name

Drop_Indexes_Generate_Script — Generates a script that drops all non-primary key and non-unique indexes on tiger schema and user specified schema. Defaults schema to `tiger_data` if no schema is specified.

## Synopsis

`text Drop_Indexes_Generate_Script(`text param_schema=tiger_data`)`;

## Description

Generates a script that drops all non-primary key and non-unique indexes on tiger schema and user specified schema. Defaults schema to `tiger_data` if no schema is specified.

This is useful for minimizing index bloat that may confuse the query planner or take up unnecessary space. Use in combination with Install_Missing_Indexes to add just the indexes used by the geocoder.

Availability: 2.0.0

## Examples

    SELECT drop_indexes_generate_script() As actionsql;
    actionsql
    ---------------------------------------------------------
    DROP INDEX tiger.idx_tiger_countysub_lookup_lower_name;
    DROP INDEX tiger.idx_tiger_edges_countyfp;
    DROP INDEX tiger.idx_tiger_faces_countyfp;
    DROP INDEX tiger.tiger_place_the_geom_gist;
    DROP INDEX tiger.tiger_edges_the_geom_gist;
    DROP INDEX tiger.tiger_state_the_geom_gist;
    DROP INDEX tiger.idx_tiger_addr_least_address;
    DROP INDEX tiger.idx_tiger_addr_tlid;
    DROP INDEX tiger.idx_tiger_addr_zip;
    DROP INDEX tiger.idx_tiger_county_countyfp;
    DROP INDEX tiger.idx_tiger_county_lookup_lower_name;
    DROP INDEX tiger.idx_tiger_county_lookup_snd_name;
    DROP INDEX tiger.idx_tiger_county_lower_name;
    DROP INDEX tiger.idx_tiger_county_snd_name;
    DROP INDEX tiger.idx_tiger_county_the_geom_gist;
    DROP INDEX tiger.idx_tiger_countysub_lookup_snd_name;
    DROP INDEX tiger.idx_tiger_cousub_countyfp;
    DROP INDEX tiger.idx_tiger_cousub_cousubfp;
    DROP INDEX tiger.idx_tiger_cousub_lower_name;
    DROP INDEX tiger.idx_tiger_cousub_snd_name;
    DROP INDEX tiger.idx_tiger_cousub_the_geom_gist;
    DROP INDEX tiger_data.idx_tiger_data_ma_addr_least_address;
    DROP INDEX tiger_data.idx_tiger_data_ma_addr_tlid;
    DROP INDEX tiger_data.idx_tiger_data_ma_addr_zip;
    DROP INDEX tiger_data.idx_tiger_data_ma_county_countyfp;
    DROP INDEX tiger_data.idx_tiger_data_ma_county_lookup_lower_name;
    DROP INDEX tiger_data.idx_tiger_data_ma_county_lookup_snd_name;
    DROP INDEX tiger_data.idx_tiger_data_ma_county_lower_name;
    DROP INDEX tiger_data.idx_tiger_data_ma_county_snd_name;
    :
    :

## See Also

Install_Missing_Indexes, Missing_Indexes_Generate_Script

## Name

Drop_State_Tables_Generate_Script — Generates a script that drops all tables in the specified schema that are prefixed with the state abbreviation. Defaults schema to `tiger_data` if no schema is specified.

## Synopsis

`text Drop_State_Tables_Generate_Script(`text param_state, text param_schema=tiger_data`)`;

## Description

Generates a script that drops all tables in the specified schema that are prefixed with the state abbreviation. Defaults schema to `tiger_data` if no schema is specified. This function is useful for dropping tables of a state just before you reload a state in case something went wrong during your previous load.

Availability: 2.0.0

## Examples

    SELECT drop_state_tables_generate_script('PA');
    DROP TABLE tiger_data.pa_addr;
    DROP TABLE tiger_data.pa_county;
    DROP TABLE tiger_data.pa_county_lookup;
    DROP TABLE tiger_data.pa_cousub;
    DROP TABLE tiger_data.pa_edges;
    DROP TABLE tiger_data.pa_faces;
    DROP TABLE tiger_data.pa_featnames;
    DROP TABLE tiger_data.pa_place;
    DROP TABLE tiger_data.pa_state;
    DROP TABLE tiger_data.pa_zip_lookup_base;
    DROP TABLE tiger_data.pa_zip_state;
    DROP TABLE tiger_data.pa_zip_state_loc;

## See Also

Loader_Generate_Script

## Name

Geocode — Takes in an address as a string (or other normalized address) and outputs a set of possible locations which include a point geometry in NAD 83 long lat, a normalized address for each, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Can optionally pass in maximum results, defaults to 10, and restrict_region (defaults to NULL)

## Synopsis

`setof record geocode(`varchar address, integer max_results=10, geometry restrict_region=NULL, norm_addy OUT addy, geometry OUT geomout, integer OUT rating`)`;

`setof record geocode(`norm_addy in_addy, integer max_results=10, geometry restrict_region=NULL, norm_addy OUT addy, geometry OUT geomout, integer OUT rating`)`;

## Description

Takes in an address as a string (or already normalized address) and outputs a set of possible locations which include a point geometry in NAD 83 long lat, a `normalized_address` (addy) for each, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Uses Tiger data (edges,faces,addr), PostgreSQL fuzzy string matching (soundex,levenshtein) and PostGIS line interpolation functions to interpolate address along the Tiger edges. The higher the rating the less likely the geocode is right. The geocoded point is defaulted to offset 10 meters from center-line off to side (L/R) of street address is located on.

Enhanced: 2.0.0 to support Tiger 2010 structured data and revised some logic to improve speed, accuracy of geocoding, and to offset point from centerline to side of street address is located on. New parameter max_results useful for specifying ot just return the best result.

## Examples: Basic

The below examples timings are on a 3.0 GHZ single processor Windows 7 machine with 2GB ram running PostgreSQL 9.1rc1/PostGIS 2.0 loaded with all of MA,MN,CA, RI state Tiger data loaded.

Exact matches are faster to compute (61ms)

    SELECT g.rating, ST_X(g.geomout) As lon, ST_Y(g.geomout) As lat,
    	(addy).address As stno, (addy).streetname As street,
    	(addy).streettypeabbrev As styp, (addy).location As city, (addy).stateabbrev As st,(addy).zip
    	FROM geocode('75 State Street, Boston MA 02109') As g;
     rating |        lon        |       lat        | stno | street | styp |  city  | st |  zip
    --------+-------------------+------------------+------+--------+------+--------+----+-------
          0 | -71.0556722990239 | 42.3589914927049 |   75 | State  | St   | Boston | MA | 02109

Even if zip is not passed in the geocoder can guess (took about 122-150 ms)

    SELECT g.rating, ST_AsText(ST_SnapToGrid(g.geomout,0.00001)) As wktlonlat,
    	(addy).address As stno, (addy).streetname As street,
    	(addy).streettypeabbrev As styp, (addy).location As city, (addy).stateabbrev As st,(addy).zip
    	FROM geocode('226 Hanover Street, Boston, MA',1) As g;
     rating |         wktlonlat         | stno | street  | styp |  city  | st |  zip
    --------+---------------------------+------+---------+------+--------+----+-------
          1 | POINT(-71.05528 42.36316) |  226 | Hanover | St   | Boston | MA | 02113

Can handle misspellings and provides more than one possible solution with ratings and takes longer (500ms).

    SELECT g.rating, ST_AsText(ST_SnapToGrid(g.geomout,0.00001)) As wktlonlat,
        (addy).address As stno, (addy).streetname As street,
    	(addy).streettypeabbrev As styp, (addy).location As city, (addy).stateabbrev As st,(addy).zip
    	FROM geocode('31 - 37 Stewart Street, Boston, MA 02116') As g;
     rating |         wktlonlat         | stno | street | styp |  city  | st |  zip
    --------+---------------------------+------+--------+------+--------+----+-------
         70 | POINT(-71.06459 42.35113) |   31 | Stuart | St   | Boston | MA | 02116

Using to do a batch geocode of addresses. Easiest is to set `max_results=1`. Only process those not yet geocoded (have no rating).

    CREATE TABLE addresses_to_geocode(addid serial PRIMARY KEY, address text,
    		lon numeric, lat numeric, new_address text, rating integer);

    INSERT INTO addresses_to_geocode(address)
    VALUES ('529 Main Street, Boston MA, 02129'),
     ('77 Massachusetts Avenue, Cambridge, MA 02139'),
     ('25 Wizard of Oz, Walaford, KS 99912323'),
     ('26 Capen Street, Medford, MA'),
     ('124 Mount Auburn St, Cambridge, Massachusetts 02138'),
     ('950 Main Street, Worcester, MA 01610');

    -- only update the first 3 addresses (323-704 ms -  there are caching and shared memory effects so first geocode you do is always slower) --
    -- for large numbers of addresses you don't want to update all at once
    -- since the whole geocode must commit at once
    -- For this example we rejoin with LEFT JOIN
    -- and set to rating to -1 rating if no match
    -- to ensure we don't regeocode a bad address
    UPDATE addresses_to_geocode
      SET  (rating, new_address, lon, lat)
    	= ( COALESCE((g.geo).rating,-1), pprint_addy((g.geo).addy),
    	   ST_X((g.geo).geomout)::numeric(8,5), ST_Y((g.geo).geomout)::numeric(8,5) )
    FROM (SELECT addid
    	FROM addresses_to_geocode
    	WHERE rating IS NULL ORDER BY addid LIMIT 3) As a
    	LEFT JOIN (SELECT addid, (geocode(address,1)) As geo
        FROM addresses_to_geocode As ag
    	WHERE ag.rating IS NULL ORDER BY addid LIMIT 3) As g ON a.addid = g.addid
    WHERE a.addid = addresses_to_geocode.addid;

    result
    -----
    Query returned successfully: 3 rows affected, 480 ms execution time.

    SELECT * FROM addresses_to_geocode WHERE rating is not null;

     addid |                   address                    |    lon    |   lat    |                new_address                | rating
    -------+----------------------------------------------+-----------+----------+-------------------------------------------+--------
         1 | 529 Main Street, Boston MA, 02129            | -71.07181 | 42.38359 | 529 Main St, Boston, MA 02129             |      0
         2 | 77 Massachusetts Avenue, Cambridge, MA 02139 | -71.09428 | 42.35988 | 77 Massachusetts Ave, Cambridge, MA 02139 |      0
         3 | 25 Wizard of Oz, Walaford, KS 99912323       |           |          |                                           |     -1

## Examples: Using Geometry filter

    SELECT g.rating, ST_AsText(ST_SnapToGrid(g.geomout,0.00001)) As wktlonlat,
        (addy).address As stno, (addy).streetname As street,
    	(addy).streettypeabbrev As styp,
    	(addy).location As city, (addy).stateabbrev As st,(addy).zip
      FROM geocode('100 Federal Street, MA',
    		3,
    		(SELECT ST_Union(the_geom)
    			FROM place WHERE statefp = '25' AND name = 'Lynn')::geometry
    		) As g;

     rating |        wktlonlat         | stno | street  | styp | city | st |  zip
    --------+--------------------------+------+---------+------+------+----+-------
          8 | POINT(-70.96796 42.4659) |  100 | Federal | St   | Lynn | MA | 01905
    Total query runtime: 245 ms.

## See Also

Normalize_Address, Pprint_Addy, ST_AsText, ST_SnapToGrid, ST_X, ST_Y

## Name

Geocode_Intersection — Takes in 2 streets that intersect and a state, city, zip, and outputs a set of possible locations on the first cross street that is at the intersection, also includes a point geometry in NAD 83 long lat, a normalized address for each location, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Can optionally pass in maximum results, defaults to 10

## Synopsis

`setof record geocode_intersection(`text roadway1, text roadway2, text in_state, text in_city, text in_zip, integer max_results=10, norm_addy OUT addy, geometry OUT geomout, integer OUT rating`)`;

## Description

Takes in 2 streets that intersect and a state, city, zip, and outputs a set of possible locations on the first cross street that is at the intersection, also includes a point geometry in NAD 83 long lat, a normalized address for each location, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Can optionally pass in maximum results, defaults to 10. Returns `normalized_address` (addy) for each, geomout as the point location in nad 83 long lat, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Uses Tiger data (edges,faces,addr), PostgreSQL fuzzy string matching (soundex,levenshtein)

Availability: 2.0.0

## Examples: Basic

The below examples timings are on a 3.0 GHZ single processor Windows 7 machine with 2GB ram running PostgreSQL 9.0/PostGIS 1.5 loaded with all of MA state Tiger data loaded. Currently a bit slow (3000 ms)

Testing on Windows 2003 64-bit 8GB on PostGIS 2.0 PostgreSQL 64-bit Tiger 2011 data loaded -- (41ms)

    SELECT pprint_addy(addy), st_astext(geomout),rating
    			FROM geocode_intersection( 'Haverford St','Germania St', 'MA', 'Boston', '02130',1);
               pprint_addy            |         st_astext          | rating
    ----------------------------------+----------------------------+--------
    98 Haverford St, Boston, MA 02130 | POINT(-71.101375 42.31376) |      0

Even if zip is not passed in the geocoder can guess (took about 3500 ms on the windows 7 box), on the windows 2003 64-bit 741 ms

    SELECT pprint_addy(addy), st_astext(geomout),rating
    				FROM geocode_intersection('Weld', 'School', 'MA', 'Boston');
              pprint_addy          |        st_astext         | rating
    -------------------------------+--------------------------+--------
     98 Weld Ave, Boston, MA 02119 | POINT(-71.099 42.314234) |      3
     99 Weld Ave, Boston, MA 02119 | POINT(-71.099 42.314234) |      3

## See Also

Geocode, Pprint_Addy, ST_AsText

## Name

Get_Tract — Returns census tract or field from tract table of where the geometry is located. Default to returning short name of tract.

## Synopsis

`text get_tract(`geometry loc_geom, text output_field='name'`)`;

## Description

Given a geometry will return the census tract location of that geometry. NAD 83 long lat is assumed if no spatial ref sys is specified.

Availability: 2.0.0

## Examples: Basic

    SELECT get_tract(ST_Point(-71.101375, 42.31376) ) As tract_name;
    tract_name
    ---------
    1203.01

    --this one returns the tiger geoid
    SELECT get_tract(ST_Point(-71.101375, 42.31376), 'tract_id' ) As tract_id;
    tract_id
    ---------
    25025120301

## See Also

Geocode>

## Name

Install_Missing_Indexes — Finds all tables with key columns used in geocoder joins and filter conditions that are missing used indexes on those columns and will add them.

## Synopsis

`boolean Install_Missing_Indexes(``)`;

## Description

Finds all tables in `tiger` and `tiger_data` schemas with key columns used in geocoder joins and filters that are missing indexes on those columns and will output the SQL DDL to define the index for those tables and then execute the generated script. This is a helper function that adds new indexes needed to make queries faster that may have been missing during the load process. This function is a companion to Missing_Indexes_Generate_Script that in addition to generating the create index script, also executes it. It is called as part of the `update_geocode.sql` upgrade script.

Availability: 2.0.0

## Examples

    SELECT install_missing_indexes();
    		 install_missing_indexes
    -------------------------
     t

## See Also

Loader_Generate_Script, Missing_Indexes_Generate_Script

## Name

Loader_Generate_Script — Generates a shell script for the specified platform for the specified states that will download Tiger data, stage and load into `tiger_data` schema. Each state script is returned as a separate record. Latest version supports Tiger 2010 structural changes and also loads census tract, block groups, and blocks tables.

## Synopsis

`setof text loader_generate_script(`text[] param_states, text os`)`;

## Description

Generates a shell script for the specified platform for the specified states that will download Tiger data, stage and load into `tiger_data` schema. Each state script is returned as a separate record.

It uses unzip on Linux (7-zip on Windows by default) and wget to do the downloading. It uses Section 4.4.2, “Using the Loader” to load in the data. Note the smallest unit it does is a whole state, but you can overwrite this by downloading the files yourself. It will only process the files in the staging and temp folders.

It uses the following control tables to control the process and different OS shell syntax variations.

1. `loader_variables` keeps track of various variables such as census site, year, data and staging schemas

2. `loader_platform` profiles of various platforms and where the various executables are located. Comes with windows and linux. More can be added.

3. `loader_lookuptables` each record defines a kind of table (state, county), whether to process records in it and how to load them in. Defines the steps to import data, stage data, add, removes columns, indexes, and constraints for each. Each table is prefixed with the state and inherits from a table in the tiger schema. e.g. creates `tiger_data.ma_faces` which inherits from `tiger.faces`

Availability: 2.0.0 to support Tiger 2010 structured data and load census tract (tract), block groups (bg), and blocks (tabblocks) tables .

## Examples

Generate script to load up data for 2 states in Windows shell script format.

    SELECT loader_generate_script(ARRAY['MA','RI'], 'windows') AS result;
    -- result --
    set STATEDIR="\gisdata\www2.census.gov\geo\pvs\tiger2010st\44_Rhode_Island"
    set TMPDIR=\gisdata\temp\
    set UNZIPTOOL="C:\Program Files\7-Zip\7z.exe"
    set WGETTOOL="C:\wget\wget.exe"
    set PGBIN=C:\Program Files\PostgreSQL\8.4\bin\
    set PGPORT=5432
    set PGHOST=localhost
    set PGUSER=postgres
    set PGPASSWORD=yourpasswordhere
    set PGDATABASE=geocoder
    set PSQL="%PGBIN%psql"
    set SHP2PGSQL="%PGBIN%shp2pgsql"

    %WGETTOOL% http://www2.census.gov/geo/pvs/tiger2010st/44_Rhode_Island/ --no-parent --relative --recursive --level=2 --accept=zip,txt --mirror --reject=html
    :
    :

Generate sh script

    SELECT loader_generate_script(ARRAY['MA','RI'], 'sh') AS result;
    -- result --
    STATEDIR="/gisdata/www2.census.gov/geo/pvs/tiger2010st/44_Rhode_Island"
    TMPDIR="/gisdata/temp/"
    UNZIPTOOL=unzip
    PGPORT=5432
    PGHOST=localhost
    PGUSER=postgres
    PGPASSWORD=yourpasswordhere
    PGDATABASE=geocoder
    PSQL=psql
    SHP2PGSQ=shp2pgsql

    wget http://www2.census.gov/geo/pvs/tiger2010st/44_Rhode_Island/ --no-parent --relative --recursive --level=2 --accept=zip,txt --mirror --reject=html
    :
    :

## See Also

## Name

Loader_Generate_Census_Script — Generates a shell script for the specified platform for the specified states that will download Tiger census state tract, bg, and tabblocks data tables, stage and load into `tiger_data` schema. Each state script is returned as a separate record.

## Synopsis

`setof text loader_generate_census_script(`text[] param_states, text os`)`;

## Description

Generates a shell script for the specified platform for the specified states that will download Tiger data census state `tract`, block groups `bg`, and `tabblocks` data tables, stage and load into `tiger_data` schema. Each state script is returned as a separate record.

It uses unzip on Linux (7-zip on Windows by default) and wget to do the downloading. It uses Section 4.4.2, “Using the Loader” to load in the data. Note the smallest unit it does is a whole state. It will only process the files in the staging and temp folders.

It uses the following control tables to control the process and different OS shell syntax variations.

1. `loader_variables` keeps track of various variables such as census site, year, data and staging schemas

2. `loader_platform` profiles of various platforms and where the various executables are located. Comes with windows and linux. More can be added.

3. `loader_lookuptables` each record defines a kind of table (state, county), whether to process records in it and how to load them in. Defines the steps to import data, stage data, add, removes columns, indexes, and constraints for each. Each table is prefixed with the state and inherits from a table in the tiger schema. e.g. creates `tiger_data.ma_faces` which inherits from `tiger.faces`

Availability: 2.0.0

Loader_Generate_Script includes this logic, but if you installed tiger geocoder prior to PostGIS 2.0.0 alpha5, you'll need to run this on the states you have already done to get these additional tables.

## Examples

Generate script to load up data for select states in Windows shell script format.

    SELECT loader_generate_census_script(ARRAY['MA'], 'windows');
    -- result --
    set STATEDIR="\gisdata\www2.census.gov\geo\pvs\tiger2010st\25_Massachusetts"
    set TMPDIR=\gisdata\temp\
    set UNZIPTOOL="C:\Program Files\7-Zip\7z.exe"
    set WGETTOOL="C:\wget\wget.exe"
    set PGBIN=C:\projects\pg\pg91win\bin\
    set PGPORT=5432
    set PGHOST=localhost
    set PGUSER=postgres
    set PGPASSWORD=yourpasswordhere
    set PGDATABASE=tiger_postgis20
    set PSQL="%PGBIN%psql"
    set SHP2PGSQL="%PGBIN%shp2pgsql"
    cd \gisdata

    %WGETTOOL% http://www2.census.gov/geo/pvs/tiger2010st/25_Massachusetts/25/ --no-parent --relative --accept=*bg10.zip,*tract10.zip,*tabblock10.zip --mirror --reject=html
    del %TMPDIR%\*.* /Q
    %PSQL% -c "DROP SCHEMA tiger_staging CASCADE;"
    %PSQL% -c "CREATE SCHEMA tiger_staging;"
    cd %STATEDIR%
    for /r %%z in (*.zip) do %UNZIPTOOL% e %%z  -o%TMPDIR%
    cd %TMPDIR%
    %PSQL% -c "CREATE TABLE tiger_data.MA_tract(CONSTRAINT pk_MA_tract PRIMARY KEY (tract_id) ) INHERITS(tiger.tract); "
    %SHP2PGSQL% -c -s 4269 -g the_geom   -W "latin1" tl_2010_25_tract10.dbf tiger_staging.ma_tract10 | %PSQL%
    %PSQL% -c "ALTER TABLE tiger_staging.MA_tract10 RENAME geoid10 TO tract_id;  SELECT loader_load_staged_data(lower('MA_tract10'), lower('MA_tract')); "
    %PSQL% -c "CREATE INDEX tiger_data_MA_tract_the_geom_gist ON tiger_data.MA_tract USING gist(the_geom);"
    %PSQL% -c "VACUUM ANALYZE tiger_data.MA_tract;"
    %PSQL% -c "ALTER TABLE tiger_data.MA_tract ADD CONSTRAINT chk_statefp CHECK (statefp = '25');"
    :

Generate sh script

    STATEDIR="/gisdata/www2.census.gov/geo/pvs/tiger2010st/25_Massachusetts"
    TMPDIR="/gisdata/temp/"
    UNZIPTOOL=unzip
    WGETTOOL="/usr/bin/wget"
    export PGBIN=/usr/pgsql-9.0/bin
    export PGPORT=5432
    export PGHOST=localhost
    export PGUSER=postgres
    export PGPASSWORD=yourpasswordhere
    export PGDATABASE=geocoder
    PSQL=${PGBIN}/psql
    SHP2PGSQL=${PGBIN}/shp2pgsql
    cd /gisdata

    wget http://www2.census.gov/geo/pvs/tiger2010st/25_Massachusetts/25/ --no-parent --relative --accept=*bg10.zip,*tract10.zip,*tabblock10.zip --mirror --reject=html
    rm -f ${TMPDIR}/*.*
    ${PSQL} -c "DROP SCHEMA tiger_staging CASCADE;"
    ${PSQL} -c "CREATE SCHEMA tiger_staging;"
    cd $STATEDIR
    for z in *.zip; do $UNZIPTOOL -o -d $TMPDIR $z; done
    :
    :

## See Also

Loader_Generate_Script

## Name

Missing_Indexes_Generate_Script — Finds all tables with key columns used in geocoder joins that are missing indexes on those columns and will output the SQL DDL to define the index for those tables.

## Synopsis

`text Missing_Indexes_Generate_Script(``)`;

## Description

Finds all tables in `tiger` and `tiger_data` schemas with key columns used in geocoder joins that are missing indexes on those columns and will output the SQL DDL to define the index for those tables. This is a helper function that adds new indexes needed to make queries faster that may have been missing during the load process. As the geocoder is improved, this function will be updated to accommodate new indexes being used. If this function outputs nothing, it means all your tables have what we think are the key indexes already in place.

Availability: 2.0.0

## Examples

    SELECT missing_indexes_generate_script();
    -- output: This was run on a database that was created before many corrections were made to the loading script ---
    CREATE INDEX idx_tiger_county_countyfp ON tiger.county USING btree(countyfp);
    CREATE INDEX idx_tiger_cousub_countyfp ON tiger.cousub USING btree(countyfp);
    CREATE INDEX idx_tiger_edges_tfidr ON tiger.edges USING btree(tfidr);
    CREATE INDEX idx_tiger_edges_tfidl ON tiger.edges USING btree(tfidl);
    CREATE INDEX idx_tiger_zip_lookup_all_zip ON tiger.zip_lookup_all USING btree(zip);
    CREATE INDEX idx_tiger_data_ma_county_countyfp ON tiger_data.ma_county USING btree(countyfp);
    CREATE INDEX idx_tiger_data_ma_cousub_countyfp ON tiger_data.ma_cousub USING btree(countyfp);
    CREATE INDEX idx_tiger_data_ma_edges_countyfp ON tiger_data.ma_edges USING btree(countyfp);
    CREATE INDEX idx_tiger_data_ma_faces_countyfp ON tiger_data.ma_faces USING btree(countyfp);

## See Also

Loader_Generate_Script, Install_Missing_Indexes

## Name

Normalize_Address — Given a textual street address, returns a composite `norm_addy` type that has road suffix, prefix and type standardized, street, streetname etc. broken into separate fields. This function will work with just the lookup data packaged with the tiger_geocoder (no need for tiger census data).

## Synopsis

`norm_addy normalize_address(`varchar in_address`)`;

## Description

Given a textual street address, returns a composite `norm_addy` type that has road suffix, prefix and type standardized, street, streetname etc. broken into separate fields. This is the first step in the geocoding process to get all addresses into normalized postal form. No other data is required aside from what is packaged with the geocoder.

This function just uses the various direction/state/suffix lookup tables preloaded with the tiger_geocoder and located in the `tiger` schema, so it doesn't need you to download tiger census data or any other additional data to make use of it. You may find the need to add more abbreviations or alternative namings to the various lookup tables in the `tiger` schema.

It uses various control lookup tables located in `tiger` schema to normalize the input address.

Fields in the `norm_addy` type object returned by this function in this order where () indicates a field required by the geocoder, [] indicates an optional field:

(address) [predirAbbrev] (streetName) [streetTypeAbbrev] [postdirAbbrev] [internal] [location] [stateAbbrev] [zip]

1. `address` is an integer: The street number

2. `predirAbbrev` is varchar: Directional prefix of road such as N, S, E, W etc. These are controlled using the `direction_lookup` table.

3. `streetName` varchar

4. `streetTypeAbbrev` varchar abbreviated version of street type: e.g. St, Ave, Cir. These are controlled using the `street_type_lookup` table.

5. `postdirAbbrev` varchar abbreviated directional suffice of road N, S, E, W etc. These are controlled using the `direction_lookup` table.

6. `internal` varchar internal address such as an apartment or suite number.

7. `location` varchar usually a city or governing province.

8. `stateAbbrev` varchar two character US State. e.g MA, NY, MI. These are controlled by the `state_lookup` table.

9. `zip` varchar 5-digit zipcode. e.g. 02109.

10. `parsed` boolean - denotes if addess was formed from normalize process. The normalize_address function sets this to true before returning the address.

## Examples

Output select fields. Use Pprint_Addy if you want a pretty textual output.

    SELECT address As orig, (g.na).streetname, (g.na).streettypeabbrev
     FROM (SELECT address, normalize_address(address) As na
            FROM addresses_to_geocode) As g;

                            orig                         |  streetname   | streettypeabbrev
    -----------------------------------------------------+---------------+------------------
     28 Capen Street, Medford, MA                        | Capen         | St
     124 Mount Auburn St, Cambridge, Massachusetts 02138 | Mount Auburn  | St
     950 Main Street, Worcester, MA 01610                | Main          | St
     529 Main Street, Boston MA, 02129                   | Main          | St
     77 Massachusetts Avenue, Cambridge, MA 02139        | Massachusetts | Ave
     25 Wizard of Oz, Walaford, KS 99912323              | Wizard of Oz  |

## See Also

Geocode, Pprint_Addy

## Name

Pprint_Addy — Given a `norm_addy` composite type object, returns a pretty print representation of it. Usually used in conjunction with normalize_address.

## Synopsis

`varchar pprint_addy(`norm_addy in_addy`)`;

## Description

Given a `norm_addy` composite type object, returns a pretty print representation of it. No other data is required aside from what is packaged with the geocoder.

Usually used in conjunction with Normalize_Address.

## Examples

Pretty print a single address

    SELECT pprint_addy(normalize_address('202 East Fremont Street, Las Vegas, Nevada 89101')) As pretty_address;
                pretty_address
    ---------------------------------------
     202 E Fremont St, Las Vegas, NV 89101

Pretty print address a table of addresses

    SELECT address As orig, pprint_addy(normalize_address(address)) As pretty_address
            FROM addresses_to_geocode;

                            orig                         |              pretty_address
    -----------------------------------------------------+-------------------------------------------
     529 Main Street, Boston MA, 02129                   | 529 Main St, Boston MA, 02129
     77 Massachusetts Avenue, Cambridge, MA 02139        | 77 Massachusetts Ave, Cambridge, MA 02139
     28 Capen Street, Medford, MA                        | 28 Capen St, Medford, MA
     124 Mount Auburn St, Cambridge, Massachusetts 02138 | 124 Mount Auburn St, Cambridge, MA 02138
     950 Main Street, Worcester, MA 01610                | 950 Main St, Worcester, MA 01610

## See Also

Normalize_Address

## Name

Reverse_Geocode — Takes a geometry point in a known spatial ref sys and returns a record containing an array of theoretically possible addresses and an array of cross streets. If include_strnum_range = true, includes the street range in the cross streets.

## Synopsis

`record Reverse_Geocode(`geometry pt, boolean include_strnum_range=false, geometry[] OUT intpt, norm_addy[] OUT addy, varchar[] OUT street`)`;

## Description

Takes a geometry point in a known spatial ref and returns a record containing an array of theoretically possible addresses and an array of cross streets. If include_strnum_range = true, includes the street range in the cross streets. include_strnum_range defaults to false if not passed in. Addresses are sorted according to which road a point is closest to so first address is most likely the right one.

Why do we say theoretical instead of actual addresses. The Tiger data doesn't have real addresses, but just street ranges. As such the theoretical address is an interpolated address based on the street ranges. Like for example interpolating one of my addresses returns a 26 Court St. and 26 Court Sq., though there is no such place as 26 Court Sq. This is because a point may be at a corner of 2 streets and thus the logic interpolates along both streets. The logic also assumes addresses are equally spaced along a street, which of course is wrong since you can have a municipal building taking up a good chunk of the street range and the rest of the buildings are clustered at the end.

Note: Hmm this function relies on Tiger data. If you have not loaded data covering the region of this point, then hmm you will get a record filled with NULLS.

Returned elements of the record are as follows:

1. `intpt` is an array of points: These are the center line points on the street closest to the input point. There are as many points as there are addresses.

2. `addy` is an array of norm_addy (normalized addresses): These are an array of possible addresses that fit the input point. The first one in the array is most likely. Generally there should be only one, except in the case when a point is at the corner of 2 or 3 streets, or the point is somewhere on the road and not off to the side.

3. `street` an array of varchar: These are cross streets (or the street) (streets that intersect or are the street the point is projected to be on).

Availability: 2.0.0

## Examples

Example of a point at the corner of two streets, but closest to one. This is approximate location of MIT: 77 Massachusetts Ave, Cambridge, MA 02139 Note that although we don't have 3 streets, PostgreSQL will just return null for entries above our upper bound so safe to use. This includes street ranges

    SELECT pprint_addy(r.addy[1]) As st1, pprint_addy(r.addy[2]) As st2, pprint_addy(r.addy[3]) As st3,
            	array_to_string(r.street, ',') As cross_streets
            FROM reverse_geocode(ST_GeomFromText('POINT(-71.093902 42.359446)',4269),true) As r;

     result
     ------
          st1                                  | st2 | st3 |               cross_streets
    -------------------------------------------+-----+-----+----------------------------------------------
     67 Massachusetts Ave, Cambridge, MA 02139 |     |     | 67 - 127 Massachusetts Ave,32 - 88 Vassar St

Here we choose not to include the address ranges for the cross streets and picked a location really really close to a corner of 2 streets thus could be known by two different addresses.

    SELECT pprint_addy(r.addy[1]) As st1, pprint_addy(r.addy[2]) As st2,
    pprint_addy(r.addy[3]) As st3, array_to_string(r.street, ',') As cross_str
    FROM reverse_geocode(ST_GeomFromText('POINT(-71.06941 42.34225)',4269)) As r;

    result
    --------
                   st1               |               st2               | st3 | cross_str
    ---------------------------------+---------------------------------+-----+------------------------
     5 Bradford St, Boston, MA 02118 | 49 Waltham St, Boston, MA 02118 |     | Waltham St

For this one we reuse our geocoded example from Geocode and we only want the primary address and at most 2 cross streets.

    SELECT actual_addr, lon, lat, pprint_addy((rg).addy[1]) As int_addr1,
    	(rg).street[1] As cross1, (rg).street[2] As cross2
    FROM (SELECT address As actual_addr, lon, lat,
        reverse_geocode( ST_SetSRID(ST_Point(lon,lat),4326) ) As rg
        FROM addresses_to_geocode WHERE rating > -1) As foo;

                         actual_addr                     |    lon    |   lat    |                 int_addr1                 |     cross1      |   cross2
    -----------------------------------------------------+-----------+----------+-------------------------------------------+-----------------+------------
     529 Main Street, Boston MA, 02129                   | -71.07181 | 42.38359 | 527 Main St, Boston, MA 02129             | Medford St      |
     77 Massachusetts Avenue, Cambridge, MA 02139        | -71.09428 | 42.35988 | 77 Massachusetts Ave, Cambridge, MA 02139 | Vassar St       |
     26 Capen Street, Medford, MA                        | -71.12377 | 42.41101 | 9 Edison Ave, Medford, MA 02155           | Capen St        | Tesla Ave
     124 Mount Auburn St, Cambridge, Massachusetts 02138 | -71.12304 | 42.37328 | 3 University Rd, Cambridge, MA 02138      | Mount Auburn St |
     950 Main Street, Worcester, MA 01610                | -71.82368 | 42.24956 | 3 Maywood St, Worcester, MA 01603         | Main St         | Maywood Pl

## See Also

Pprint_Addy, Geocode

## Name

Topology_Load_Tiger — Loads a defined region of tiger data into a PostGIS Topology and transforming the tiger data to spatial reference of the topology and snapping to the precision tolerance of the topology.

## Synopsis

`text Topology_Load_Tiger(`varchar topo_name, varchar region_type, varchar region_id`)`;

## Description

Loads a defined region of tiger data into a PostGIS Topology. The faces, nodes and edges are transformed to the spatial reference system of the target topology and points are snapped to the tolerance of the target topology. The created faces, nodes, edges maintain the same ids as the original Tiger data faces, nodes, edges so that datasets can be in the future be more easily reconciled with tiger data. Returns summary details about the process.

This would be useful for example for redistricting data where you require the newly formed polygons to follow the center lines of streets and for the resulting polygons not to overlap.

This function relies on Tiger data as well as the installation of the PostGIS topology module. For more information, refer to Chapter 11, Topology and Section 2.4.1, “Configuration”. If you have not loaded data covering the region of interest, then no topology records will be created. This function will also fail if you have not created a topology using the topology functions.

Most topology validation errors are a result of tolerance issues where after transformation the edges points don't quite line up or overlap. To remedy the situation you may want to increase or lower the precision if you get topology validation failures.

Required arguments:

1. `topo_name` The name of an existing PostGIS topology to load data into.

2. `region_type` The type of bounding region. Currently only `place` and `county` are supported. Plan is to have several more. This is the table to look into to define the region bounds. e.g `tiger.place`, `tiger.county`

3. `region_id` This is what TIGER calls the geoid. It is the unique identifier of the region in the table. For place it is the `plcidfp` column in `tiger.place`. For county it is the `cntyidfp` column in `tiger.county`

Availability: 2.0.0

## Example: Boston, Massachusetts Topology

Create a topology for Boston, Massachusetts in Mass State Plane Feet (2249) with tolerance 0.25 feet and then load in Boston city tiger faces, edges, nodes.

    SELECT topology.CreateTopology('topo_boston', 2249, 0.25);
    createtopology
    --------------
       15
    -- 60,902 ms ~ 1 minute on windows 7 desktop running 9.1 (with 5 states tiger data loaded)
    SELECT tiger.topology_load_tiger('topo_boston', 'place', '2507000');
    -- topology_loader_tiger --
    29722 edges holding in temporary. 11108 faces added. 1875 edges of faces added.  20576 nodes added.
    19962 nodes contained in a face.  0 edge start end corrected.  31597 edges added.

    -- 41 ms --
    SELECT topology.TopologySummary('topo_boston');
     -- topologysummary--
    Topology topo_boston (15), SRID 2249, precision 0.25
    20576 nodes, 31597 edges, 11109 faces, 0 topogeoms in 0 layers

    -- 28,797 ms to validate yeh returned no errors --
    SELECT * FROM
        topology.ValidateTopology('topo_boston');

           error       |   id1    |    id2
    -------------------+----------+-----------

## Example: Suffolk, Massachusetts Topology

Create a topology for Suffolk, Massachusetts in Mass State Plane Meters (26986) with tolerance 0.25 meters and then load in Suffolk county tiger faces, edges, nodes.

    SELECT topology.CreateTopology('topo_suffolk', 26986, 0.25);
    -- this took 56,275 ms ~ 1 minute on Windows 7 32-bit with 5 states of tiger loaded
    -- must have been warmed up after loading boston
    SELECT tiger.topology_load_tiger('topo_suffolk', 'county', '25025');
    -- topology_loader_tiger --
     36003 edges holding in temporary. 13518 faces added. 2172 edges of faces added.
     24761 nodes added.  24075 nodes contained in a face.  0 edge start end corrected.  38175 edges added.
    -- 31 ms --
    SELECT topology.TopologySummary('topo_suffolk');
     -- topologysummary--
     Topology topo_suffolk (14), SRID 26986, precision 0.25
    24761 nodes, 38175 edges, 13519 faces, 0 topogeoms in 0 layers

    -- 33,606 ms to validate --
    SELECT * FROM
        topology.ValidateTopology('topo_suffolk');

           error       |   id1    |    id2
    -------------------+----------+-----------
     coincident nodes  | 81045651 |  81064553
     edge crosses node | 81045651 |  85737793
     edge crosses node | 81045651 |  85742215
     edge crosses node | 81045651 | 620628939
     edge crosses node | 81064553 |  85697815
     edge crosses node | 81064553 |  85728168
     edge crosses node | 81064553 |  85733413

## See Also

CreateTopology, CreateTopoGeom, TopologySummary, ValidateTopology

## Chapter 13. PostGIS Special Functions Index

## 13.1. PostGIS Aggregate Functions

The functions given below are spatial aggregate functions provided with PostGIS that can be used just like any other sql aggregate function such as sum, average.

- ST_3DExtent - an aggregate function that returns the box3D bounding box that bounds rows of geometries.
- ST_Accum - Aggregate. Constructs an array of geometries.
- ST_Collect - Return a specified ST_Geometry value from a collection of other geometries.
- ST_Extent - an aggregate function that returns the bounding box that bounds rows of geometries.
- ST_MakeLine - Creates a Linestring from point or line geometries.
- ST_MemUnion - Same as ST_Union, only memory-friendly (uses less memory and more processor time).
- ST_Polygonize - Aggregate. Creates a GeometryCollection containing possible polygons formed from the constituent linework of a set of geometries.
- ST_Union - Returns a geometry that represents the point set union of the Geometries.
- ST_Union - Returns the union of a set of raster tiles into a single raster composed of 1 band. If no band is specified for unioning, band num 1 is assumed. The resulting raster's extent is the extent of the whole set. In the case of intersection, the resulting value is defined by p_expression which is one of the following: LAST - the default when none is specified, MEAN, SUM, FIRST, MAX, MIN.
- ST_Union - Returns the union of a set of raster tiles into a single raster composed of 1 band. If no band is specified for unioning, band num 1 is assumed. The resulting raster's extent is the extent of the whole set. In the case of intersection, the resulting value is defined by p_expression which is one of the following: LAST - the default when none is specified, MEAN, SUM, FIRST, MAX, MIN.
- ST_Union - Returns the union of a set of raster tiles into a single raster composed of 1 band. If no band is specified for unioning, band num 1 is assumed. The resulting raster's extent is the extent of the whole set. In the case of intersection, the resulting value is defined by p_expression which is one of the following: LAST - the default when none is specified, MEAN, SUM, FIRST, MAX, MIN.
- TopoElementArray_Agg - Returns a topoelementarray for a set of element_id, type arrays (topoelements)

## 13.2. PostGIS SQL-MM Compliant Functions

The functions given below are PostGIS functions that conform to the SQL/MM 3 standard

SQL-MM defines the default SRID of all geometry constructors as 0. PostGIS uses a default SRID of -1.

- ST_3DDWithin - For 3d (z) geometry type Returns true if two geometries 3d distance is within number of units. This method implements the SQL/MM specification. SQL-MM ?
- ST_3DDistance - For geometry type Returns the 3-dimensional cartesian minimum distance (based on spatial ref) between two geometries in projected units. This method implements the SQL/MM specification. SQL-MM ?
- ST_3DIntersects - Returns TRUE if the Geometries "spatially intersect" in 3d - only for points and linestrings This method implements the SQL/MM specification. SQL-MM 3: ?
- ST_AddEdgeModFace - Add a new edge and, if in doing so it splits a face, modify the original face and add a new face. This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.13
- ST_AddEdgeNewFaces - Add a new edge and, if in doing so it splits a face, delete the original face and replace it with two new faces. This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.12
- ST_AddIsoEdge - Adds an isolated edge defined by geometry alinestring to a topology connecting two existing isolated nodes anode and anothernode and returns the edge id of the new edge. This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.4
- ST_AddIsoNode - Adds an isolated node to a face in a topology and returns the nodeid of the new node. If face is null, the node is still created. This method implements the SQL/MM specification. SQL-MM: Topo-Net Routines: X+1.3.1
- ST_Area - Returns the area of the surface if it is a polygon or multi-polygon. For "geometry" type area is in SRID units. For "geography" area is in square meters. This method implements the SQL/MM specification. SQL-MM 3: 8.1.2, 9.5.3
- ST_AsBinary - Return the Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data. This method implements the SQL/MM specification. SQL-MM 3: 5.1.37
- ST_AsText - Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata. This method implements the SQL/MM specification. SQL-MM 3: 5.1.25
- ST_Boundary - Returns the closure of the combinatorial boundary of this Geometry. This method implements the SQL/MM specification. SQL-MM 3: 5.1.14
- ST_Buffer - (T) For geometry: Returns a geometry that represents all points whose distance from this Geometry is less than or equal to distance. Calculations are in the Spatial Reference System of this Geometry. For geography: Uses a planar transform wrapper. Introduced in 1.5 support for different end cap and mitre settings to control shape. buffer_style options: quad_segs=#,endcap=round|flat|square,join=round|mitre|bevel,mitre_limit=#.# This method implements the SQL/MM specification. SQL-MM 3: 5.1.17
- ST_Centroid - Returns the geometric center of a geometry. This method implements the SQL/MM specification. SQL-MM 3: 8.1.4, 9.5.5
- ST_ChangeEdgeGeom - Changes the shape of an edge without affecting the topology structure. This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details X.3.6
- ST_Contains - Returns true if and only if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A. This method implements the SQL/MM specification. SQL-MM 3: 5.1.31
- ST_ConvexHull - The convex hull of a geometry represents the minimum convex geometry that encloses all geometries within the set. This method implements the SQL/MM specification. SQL-MM 3: 5.1.16
- ST_CoordDim - Return the coordinate dimension of the ST_Geometry value. This method implements the SQL/MM specification. SQL-MM 3: 5.1.3
- ST_CreateTopoGeo - Adds a collection of geometries to a given empty topology and returns a message detailing success. This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details -- X.3.18
- ST_Crosses - Returns TRUE if the supplied geometries have some, but not all, interior points in common. This method implements the SQL/MM specification. SQL-MM 3: 5.1.29
- ST_CurveToLine - Converts a CIRCULARSTRING/CURVEDPOLYGON to a LINESTRING/POLYGON This method implements the SQL/MM specification. SQL-MM 3: 7.1.7
- ST_Difference - Returns a geometry that represents that part of geometry A that does not intersect with geometry B. This method implements the SQL/MM specification. SQL-MM 3: 5.1.20
- ST_Dimension - The inherent dimension of this Geometry object, which must be less than or equal to the coordinate dimension. This method implements the SQL/MM specification. SQL-MM 3: 5.1.2
- ST_Disjoint - Returns TRUE if the Geometries do not "spatially intersect" - if they do not share any space together. This method implements the SQL/MM specification. SQL-MM 3: 5.1.26
- ST_Distance - For geometry type Returns the 2-dimensional cartesian minimum distance (based on spatial ref) between two geometries in projected units. For geography type defaults to return spheroidal minimum distance between two geographies in meters. This method implements the SQL/MM specification. SQL-MM 3: 5.1.23
- ST_EndPoint - Returns the last point of a LINESTRING geometry as a POINT. This method implements the SQL/MM specification. SQL-MM 3: 7.1.4
- ST_Envelope - Returns a geometry representing the double precision (float8) bounding box of the supplied geometry. This method implements the SQL/MM specification. SQL-MM 3: 5.1.15
- ST_Equals - Returns true if the given geometries represent the same geometry. Directionality is ignored. This method implements the SQL/MM specification. SQL-MM 3: 5.1.24
- ST_ExteriorRing - Returns a line string representing the exterior ring of the POLYGON geometry. Return NULL if the geometry is not a polygon. Will not work with MULTIPOLYGON This method implements the SQL/MM specification. SQL-MM 3: 8.2.3, 8.3.3
- ST_GMLToSQL - Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML This method implements the SQL/MM specification. SQL-MM 3: 5.1.50 (except for curves support).
- ST_GeomCollFromText - Makes a collection Geometry from collection WKT with the given SRID. If SRID is not give, it defaults to -1. This method implements the SQL/MM specification.
- ST_GeomFromText - Return a specified ST_Geometry value from Well-Known Text representation (WKT). This method implements the SQL/MM specification. SQL-MM 3: 5.1.40
- ST_GeomFromWKB - Creates a geometry instance from a Well-Known Binary geometry representation (WKB) and optional SRID. This method implements the SQL/MM specification. SQL-MM 3: 5.1.41
- ST_GeometryFromText - Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText This method implements the SQL/MM specification. SQL-MM 3: 5.1.40
- ST_GeometryN - Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL. This method implements the SQL/MM specification. SQL-MM 3: 9.1.5
- ST_GeometryType - Return the geometry type of the ST_Geometry value. This method implements the SQL/MM specification. SQL-MM 3: 5.1.4
- ST_GetFaceEdges - Returns a set of ordered edges that bound aface includes the sequence order. This method implements the SQL/MM specification. SQL-MM 3 Topo-Geo and Topo-Net 3: Routine Details: X.3.5
- ST_GetFaceGeometry - Returns the polygon in the given topology with the specified face id. This method implements the SQL/MM specification. SQL-MM 3 Topo-Geo and Topo-Net 3: Routine Details: X.3.16
- ST_InitTopoGeo - Creates a new topology schema and registers this new schema in the topology.topology table and details summary of process. This method implements the SQL/MM specification. SQL-MM 3 Topo-Geo and Topo-Net 3: Routine Details: X.3.17
- ST_InteriorRingN - Return the Nth interior linestring ring of the polygon geometry. Return NULL if the geometry is not a polygon or the given N is out of range. This method implements the SQL/MM specification. SQL-MM 3: 8.2.6, 8.3.5
- ST_Intersection - (T) Returns a geometry that represents the shared portion of geomA and geomB. The geography implementation does a transform to geometry to do the intersection and then transform back to WGS84. This method implements the SQL/MM specification. SQL-MM 3: 5.1.18
- ST_Intersects - Returns TRUE if the Geometries/Geography "spatially intersect in 2D" - (share any portion of space) and FALSE if they don't (they are Disjoint). For geography -- tolerance is 0.00001 meters (so any points that close are considered to intersect) This method implements the SQL/MM specification. SQL-MM 3: 5.1.27
- ST_IsClosed - Returns TRUE if the LINESTRING's start and end points are coincident. For Polyhedral surface is closed (volumetric). This method implements the SQL/MM specification. SQL-MM 3: 7.1.5, 9.3.3
- ST_IsEmpty - Returns true if this Geometry is an empty geometrycollection, polygon, point etc. This method implements the SQL/MM specification. SQL-MM 3: 5.1.7
- ST_IsRing - Returns TRUE if this LINESTRING is both closed and simple. This method implements the SQL/MM specification. SQL-MM 3: 7.1.6
- ST_IsSimple - Returns (TRUE) if this Geometry has no anomalous geometric points, such as self intersection or self tangency. This method implements the SQL/MM specification. SQL-MM 3: 5.1.8
- ST_IsValid - Returns true if the ST_Geometry is well formed. This method implements the SQL/MM specification. SQL-MM 3: 5.1.9
- ST_Length - Returns the 2d length of the geometry if it is a linestring or multilinestring. geometry are in units of spatial reference and geography are in meters (default spheroid) This method implements the SQL/MM specification. SQL-MM 3: 7.1.2, 9.3.4
- ST_LineFromText - Makes a Geometry from WKT representation with the given SRID. If SRID is not given, it defaults to -1. This method implements the SQL/MM specification. SQL-MM 3: 7.2.8
- ST_LineFromWKB - Makes a LINESTRING from WKB with the given SRID This method implements the SQL/MM specification. SQL-MM 3: 7.2.9
- ST_LinestringFromWKB - Makes a geometry from WKB with the given SRID. This method implements the SQL/MM specification. SQL-MM 3: 7.2.9
- ST_M - Return the M coordinate of the point, or NULL if not available. Input must be a point. This method implements the SQL/MM specification.
- ST_MLineFromText - Return a specified ST_MultiLineString value from WKT representation. This method implements the SQL/MM specification.SQL-MM 3: 9.4.4
- ST_MPointFromText - Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1. This method implements the SQL/MM specification. SQL-MM 3: 9.2.4
- ST_MPolyFromText - Makes a MultiPolygon Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1. This method implements the SQL/MM specification. SQL-MM 3: 9.6.4
- ST_ModEdgeHeal - Heal two edges by deleting the node connecting them, modifying the first edgeand deleting the second edge. Returns the id of the deleted node. This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.9
- ST_ModEdgeSplit - Split an edge by creating a new node along an existing edge, modifying the original edge and adding a new edge. This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.9
- ST_MoveIsoNode - Moves an isolated node in a topology from one point to another. If new apoint geometry exists as a node an error is thrown. REturns description of move. This method implements the SQL/MM specification. SQL-MM: Topo-Net Routines: X.3.2
- ST_NewEdgeHeal - Heal two edges by deleting the node connecting them, deleting both edges,and replacing them with an edge whose direction is the same as the firstedge provided. This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.9
- ST_NewEdgesSplit - Split an edge by creating a new node along an existing edge, deleting the original edge and replacing it with two new edges. Returns the id of the new node created that joins the new edges. This method implements the SQL/MM specification. SQL-MM: Topo-Net Routines: X.3.8
- ST_NumGeometries - If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for single geometries will return 1, otherwise return NULL. This method implements the SQL/MM specification. SQL-MM 3: 9.1.4
- ST_NumInteriorRing - Return the number of interior rings of the first polygon in the geometry. Synonym to ST_NumInteriorRings. This method implements the SQL/MM specification. SQL-MM 3: 8.2.5
- ST_NumInteriorRings - Return the number of interior rings of the first polygon in the geometry. This will work with both POLYGON and MULTIPOLYGON types but only looks at the first polygon. Return NULL if there is no polygon in the geometry. This method implements the SQL/MM specification. SQL-MM 3: 8.2.5
- ST_NumPatches - Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries. This method implements the SQL/MM specification. SQL-MM 3: ?
- ST_NumPoints - Return the number of points in an ST_LineString or ST_CircularString value. This method implements the SQL/MM specification. SQL-MM 3: 7.2.4
- ST_OrderingEquals - Returns true if the given geometries represent the same geometry and points are in the same directional order. This method implements the SQL/MM specification. SQL-MM 3: 5.1.43
- ST_Overlaps - Returns TRUE if the Geometries share space, are of the same dimension, but are not completely contained by each other. This method implements the SQL/MM specification. SQL-MM 3: 5.1.32
- ST_PatchN - Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Otherwise, return NULL. This method implements the SQL/MM specification. SQL-MM 3: ?
- ST_Perimeter - Return the length measurement of the boundary of an ST_Surface or ST_MultiSurface geometry or geography. (Polygon, Multipolygon). geometry measurement is in units of spatial reference and geography is in meters. This method implements the SQL/MM specification. SQL-MM 3: 8.1.3, 9.5.4
- ST_Point - Returns an ST_Point with the given coordinate values. OGC alias for ST_MakePoint. This method implements the SQL/MM specification. SQL-MM 3: 6.1.2
- ST_PointFromText - Makes a point Geometry from WKT with the given SRID. If SRID is not given, it defaults to unknown. This method implements the SQL/MM specification. SQL-MM 3: 6.1.8
- ST_PointFromWKB - Makes a geometry from WKB with the given SRID This method implements the SQL/MM specification. SQL-MM 3: 6.1.9
- ST_PointN - Return the Nth point in the first linestring or circular linestring in the geometry. Return NULL if there is no linestring in the geometry. This method implements the SQL/MM specification. SQL-MM 3: 7.2.5, 7.3.5
- ST_PointOnSurface - Returns a POINT guaranteed to lie on the surface. This method implements the SQL/MM specification. SQL-MM 3: 8.1.5, 9.5.6. According to the specs, ST_PointOnSurface works for surface geometries (POLYGONs, MULTIPOLYGONS, CURVED POLYGONS). So PostGIS seems to be extending what the spec allows here. Most databases Oracle,DB II, ESRI SDE seem to only support this function for surfaces. SQL Server 2008 like PostGIS supports for all common geometries.
- ST_Polygon - Returns a polygon built from the specified linestring and SRID. This method implements the SQL/MM specification. SQL-MM 3: 8.3.2
- ST_PolygonFromText - Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1. This method implements the SQL/MM specification. SQL-MM 3: 8.3.6
- ST_Relate - Returns true if this Geometry is spatially related to anotherGeometry, by testing for intersections between the Interior, Boundary and Exterior of the two geometries as specified by the values in the intersectionMatrixPattern. If no intersectionMatrixPattern is passed in, then returns the maximum intersectionMatrixPattern that relates the 2 geometries. This method implements the SQL/MM specification. SQL-MM 3: 5.1.25
- ST_RemEdgeModFace - Removes an edge and, if the removed edge separated two faces,delete one of the them and modify the other to take the space of both. This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.15
- ST_RemEdgeNewFace - Removes an edge and, if the removed edge separated two faces,delete the original faces and replace them with a new face. This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.14
- ST_RemoveIsoNode - Removes an isolated node and returns description of action. If the node is not isolated (is start or end of an edge), then an exception is thrown. This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X+1.3.3
- ST_SRID - Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table. This method implements the SQL/MM specification. SQL-MM 3: 5.1.5
- ST_StartPoint - Returns the first point of a LINESTRING geometry as a POINT. This method implements the SQL/MM specification. SQL-MM 3: 7.1.3
- ST_SymDifference - Returns a geometry that represents the portions of A and B that do not intersect. It is called a symmetric difference because ST_SymDifference(A,B) = ST_SymDifference(B,A). This method implements the SQL/MM specification. SQL-MM 3: 5.1.21
- ST_Touches - Returns TRUE if the geometries have at least one point in common, but their interiors do not intersect. This method implements the SQL/MM specification. SQL-MM 3: 5.1.28
- ST_Transform - Returns a new geometry with its coordinates transformed to the SRID referenced by the integer parameter. This method implements the SQL/MM specification. SQL-MM 3: 5.1.6
- ST_Union - Returns a geometry that represents the point set union of the Geometries. This method implements the SQL/MM specification. SQL-MM 3: 5.1.19 the z-index (elevation) when polygons are involved.
- ST_WKBToSQL - Return a specified ST_Geometry value from Well-Known Binary representation (WKB). This is an alias name for ST_GeomFromWKB that takes no srid This method implements the SQL/MM specification. SQL-MM 3: 5.1.36
- ST_WKTToSQL - Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText This method implements the SQL/MM specification. SQL-MM 3: 5.1.34
- ST_Within - Returns true if the geometry A is completely inside geometry B This method implements the SQL/MM specification. SQL-MM 3: 5.1.30
- ST_X - Return the X coordinate of the point, or NULL if not available. Input must be a point. This method implements the SQL/MM specification. SQL-MM 3: 6.1.3
- ST_Y - Return the Y coordinate of the point, or NULL if not available. Input must be a point. This method implements the SQL/MM specification. SQL-MM 3: 6.1.4
- ST_Z - Return the Z coordinate of the point, or NULL if not available. Input must be a point. This method implements the SQL/MM specification.

## 13.3. PostGIS Geography Support Functions

The functions and operators given below are PostGIS functions/operators that take as input or return as output a geography data type object.

Functions with a (T) are not native geodetic functions, and use a ST_Transform call to and from geometry to do the operation. As a result, they may not behave as expected when going over dateline, poles, and for large geometries or geometry pairs that cover more than one UTM zone. Basic tranform - (favoring UTM, Lambert Azimuthal (North/South), and falling back on mercator in worst case scenario)

- ST_Area - Returns the area of the surface if it is a polygon or multi-polygon. For "geometry" type area is in SRID units. For "geography" area is in square meters.
- ST_AsBinary - Return the Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsEWKT - Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
- ST_AsGML - Return the geometry as a GML version 2 or 3 element.
- ST_AsGeoJSON - Return the geometry as a GeoJSON element.
- ST_AsKML - Return the geometry as a KML element. Several variants. Default version=2, default precision=15
- ST_AsSVG - Returns a Geometry in SVG path data given a geometry or geography object.
- ST_AsText - Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.
- ST_Azimuth - Returns the angle in radians from the horizontal of the vector defined by pointA and pointB. Angle is computed clockwise from down-to-up: on the clock: 12=0; 3=PI/2; 6=PI; 9=3PI/2.
- ST_Buffer - (T) For geometry: Returns a geometry that represents all points whose distance from this Geometry is less than or equal to distance. Calculations are in the Spatial Reference System of this Geometry. For geography: Uses a planar transform wrapper. Introduced in 1.5 support for different end cap and mitre settings to control shape. buffer_style options: quad_segs=#,endcap=round|flat|square,join=round|mitre|bevel,mitre_limit=#.#
- ST_CoveredBy - Returns 1 (TRUE) if no point in Geometry/Geography A is outside Geometry/Geography B
- ST_Covers - Returns 1 (TRUE) if no point in Geometry B is outside Geometry A
- ST_DWithin - Returns true if the geometries are within the specified distance of one another. For geometry units are in those of spatial reference and For geography units are in meters and measurement is defaulted to use_spheroid=true (measure around spheroid), for faster check, use_spheroid=false to measure along sphere.
- ST_Distance - For geometry type Returns the 2-dimensional cartesian minimum distance (based on spatial ref) between two geometries in projected units. For geography type defaults to return spheroidal minimum distance between two geographies in meters.
- ST_GeogFromText - Return a specified geography value from Well-Known Text representation or extended (WKT).
- ST_GeogFromWKB - Creates a geography instance from a Well-Known Binary geometry representation (WKB) or extended Well Known Binary (EWKB).
- ST_GeographyFromText - Return a specified geography value from Well-Known Text representation or extended (WKT).
- = - Returns TRUE if A's bounding box is the same as B's. Uses double precision bounding box.
- ST_Intersection - (T) Returns a geometry that represents the shared portion of geomA and geomB. The geography implementation does a transform to geometry to do the intersection and then transform back to WGS84.
- ST_Intersects - Returns TRUE if the Geometries/Geography "spatially intersect in 2D" - (share any portion of space) and FALSE if they don't (they are Disjoint). For geography -- tolerance is 0.00001 meters (so any points that close are considered to intersect)
- ST_Length - Returns the 2d length of the geometry if it is a linestring or multilinestring. geometry are in units of spatial reference and geography are in meters (default spheroid)
- ST_Project - Returns a POINT projected from a start point using a bearing and distance.
- ST_Summary - Returns a text summary of the contents of the geometry.
- && - Returns TRUE if A's 2D bounding box intersects B's 2D bounding box.

## 13.4. PostGIS Raster Support Functions

The functions and operators given below are PostGIS functions/operators that take as input or return as output a raster data type object. Listed in alphabetical order.

- Box3D - Returns the box 3d representation of the enclosing box of the raster.
- &< - Returns TRUE if A's bounding box is to the left of B's.
- &> - Returns TRUE if A's bounding box is to the right of B's.
- && - Returns TRUE if A's bounding box overlaps B's.
- ST_AddBand - Returns a raster with the new band(s) of given type added with given initial value in the given index location. If no index is specified, the band is added to the end.
- ST_AsBinary - Return the Well-Known Binary (WKB) representation of the raster without SRID meta data.
- ST_AsGDALRaster - Return the raster tile in the designated GDAL Raster format. Raster formats are one of those supported by your compiled library. Use ST_GDALRasters() to get a list of formats supported by your library.
- ST_AsJPEG - Return the raster tile selected bands as a single Joint Photographic Exports Group (JPEG) image (byte array). If no band is specified and 1 or more than 3 bands, then only the first band is used. If only 3 bands then all 3 bands are used and mapped to RGB.
- ST_AsPNG - Return the raster tile selected bands as a single portable network graphics (PNG) image (byte array). If 1, 3, or 4 bands in raster and no bands are specified, then all bands are used. If more 2 or more than 4 bands and no bands specified, then only band 1 is used. Bands are mapped to RGB or RGBA space.
- ST_AsRaster - Converts a PostGIS geometry to a PostGIS raster.
- ST_AsTIFF - Return the raster selected bands as a single TIFF image (byte array). If no band is specified, then will try to use all bands.
- ST_Aspect - Returns the surface aspect of an elevation raster band. Useful for analyzing terrain.
- ST_Band - Returns one or more bands of an existing raster as a new raster. Useful for building new rasters from existing rasters.
- ST_BandIsNoData - Returns true if the band is filled with only nodata values.
- ST_BandMetaData - Returns basic meta data for a specific raster band. band num 1 is assumed if none-specified.
- ST_BandNoDataValue - Returns the value in a given band that represents no data. If no band num 1 is assumed.
- ST_BandPath - Returns system file path to a band stored in file system. If no bandnum specified, 1 is assumed.
- ST_BandPixelType - Returns the type of pixel for given band. If no bandnum specified, 1 is assumed.
- ST_Clip - Returns the raster clipped by the input geometry. If no band is specified all bands are returned. If crop is not specified, true is assumed meaning the output raster is cropped.
- ST_ConvexHull - Return the convex hull geometry of the raster including pixel values equal to BandNoDataValue. For regular shaped and non-skewed rasters, this gives the same result as ST_Envelope so only useful for irregularly shaped or skewed rasters.
- ST_Count - Returns the number of pixels in a given band of a raster or raster coverage. If no band is specified defaults to band 1. If exclude_nodata_value is set to true, will only count pixels that are not equal to the nodata value.
- ST_DumpAsPolygons - Returns a set of geomval (geom,val) rows, from a given raster band. If no band number is specified, band num defaults to 1.
- ST_Envelope - Returns the polygon representation of the extent of the raster.
- ST_GeoReference - Returns the georeference meta data in GDAL or ESRI format as commonly seen in a world file. Default is GDAL.
- ST_HasNoBand - Returns true if there is no band with given band number. If no band number is specified, then band number 1 is assumed.
- ST_Height - Returns the height of the raster in pixels.
- ST_HillShade - Returns the hypothetical illumination of an elevation raster band using provided azimuth, altitude, brightness and elevation scale inputs. Useful for visualizing terrain.
- ST_Histogram - Returns a set of histogram summarizing a raster or raster coverage data distribution separate bin ranges. Number of bins are autocomputed if not specified.
- ST_Intersection - Returns a raster or a set of geometry-pixelvalue pairs representing the shared portion of two rasters or the geometrical intersection of a vectorization of the raster and a geometry.
- ST_Intersects - Return true if the raster spatially intersects a separate raster or geometry. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.
- ST_IsEmpty - Returns true if the raster is empty (width = 0 and height = 0). Otherwise, returns false.
- ST_MakeEmptyRaster - Returns an empty raster (having no bands) of given dimensions (width & height), upperleft X and Y, pixel size and rotation (scalex, scaley, skewx & skewy) and reference system (srid). If a raster is passed in, returns a new raster with the same size, alignment and SRID. If srid is left out, the spatial ref is set to unknown (0).
- ST_MapAlgebraExpr - 1 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the input raster band and of pixeltype provided. Band 1 is assumed if no band is specified.
- ST_MapAlgebraExpr - 2 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the two input raster bands and of pixeltype provided. band 1 of each raster is assumed if no band numbers are specified. The resulting raster will be aligned (scale, skew and pixel corners) on the grid defined by the first raster and have its extent defined by the "extenttype" parameter. Values for "extenttype" can be: INTERSECTION, UNION, FIRST, SECOND.
- ST_MapAlgebraFct - 1 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the input raster band and of pixeltype prodived. Band 1 is assumed if no band is specified.
- ST_MapAlgebraFct - 2 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the 2 input raster bands and of pixeltype prodived. Band 1 is assumed if no band is specified. Extent type defaults to INTERSECTION if not specified.
- ST_MapAlgebraFctNgb - 1-band version: Map Algebra Nearest Neighbor using user-defined PostgreSQL function. Return a raster which values are the result of a PLPGSQL user function involving a neighborhood of values from the input raster band.
- ST_MetaData - Returns basic meta data about a raster object such as pixel size, rotation (skew), upper, lower left, etc.
- ST_NumBands - Returns the number of bands in the raster object.
- ST_PixelAsPolygon - Returns the geometry that bounds the pixel for a particular row and column.
- ST_PixelAsPolygons - Returns the geometry that bounds every pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel.
- ST_PixelHeight - Returns the pixel height in geometric units of the spatial reference system.
- ST_PixelWidth - Returns the pixel width in geometric units of the spatial reference system.
- ST_Polygon - Returns a polygon geometry formed by the union of pixels that have a pixel value that is not no data value. If no band number is specified, band num defaults to 1.
- ST_Quantile - Compute quantiles for a raster or raster table coverage in the context of the sample or population. Thus, a value could be examined to be at the raster's 25%, 50%, 75% percentile.
- ST_Raster2WorldCoordX - Returns the geometric X coordinate upper left of a raster, column and row. Numbering of columns and rows starts at 1.
- ST_Raster2WorldCoordY - Returns the geometric Y coordinate upper left corner of a raster, column and row. Numbering of columns and rows starts at 1.
- ST_Reclass - Creates a new raster composed of band types reclassified from original. The nband is the band to be changed. If nband is not specified assumed to be 1. All other bands are returned unchanged. Use case: convert a 16BUI band to a 8BUI and so forth for simpler rendering as viewable formats.
- ST_Resample - Resample a raster using a specified resampling algorithm, new dimensions, an arbitrary grid corner and a set of raster georeferencing attributes defined or borrowed from another raster. New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_Rescale - Resample a raster by adjusting only its scale (or pixel size). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_Reskew - Resample a raster by adjusting only its skew (or rotation parameters). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_Rotation - Returns the rotation of the raster in radian.
- ST_SRID - Returns the spatial reference identifier of the raster as defined in spatial_ref_sys table.
- ST_SameAlignment - Returns true if rasters have same skew, scale, spatial ref and false if they don't with notice detailing issue.
- ST_ScaleX - Returns the X component of the pixel width in units of coordinate reference system.
- ST_ScaleY - Returns the Y component of the pixel height in units of coordinate reference system.
- ST_SetBandIsNoData - Sets the isnodata flag of the band to TRUE. You may want to call this function if ST_BandIsNoData(rast, band) != ST_BandIsNodata(rast, band, TRUE). This is, if the isnodata flag is dirty. Band 1 is assumed if no band is specified.
- ST_SetBandNoDataValue - Sets the value for the given band that represents no data. Band 1 is assumed if no band is specified. To mark a band as having no nodata value, set the nodata value = NULL.
- ST_SetGeoReference - Set Georeference 6 georeference parameters in a single call. Numbers should be separated by white space. Accepts inputs in GDAL or ESRI format. Default is GDAL.
- ST_SetRotation - Set the rotation of the raster in radian.
- ST_SetSRID - Sets the SRID of a raster to a particular integer srid defined in the spatial_ref_sys table.
- ST_SetScale - Sets the X and Y size of pixels in units of coordinate reference system. Number units/pixel width/height.
- ST_SetSkew - Sets the georeference X and Y skew (or rotation parameter). If only one is passed in, sets X and Y to the same value.
- ST_SetUpperLeft - Sets the value of the upper left corner of the pixel to projected X and Y coordinates.
- ST_SetValue - Returns modified raster resulting from setting the value of a given band in a given columnx, rowy pixel or at a pixel that intersects a particular geometric point. Band numbers start at 1 and assumed to be 1 if not specified.
- ST_SkewX - Returns the georeference X skew (or rotation parameter).
- ST_SkewY - Returns the georeference Y skew (or rotation parameter).
- ST_Slope - Returns the surface slope of an elevation raster band. Useful for analyzing terrain.
- ST_SnapToGrid - Resample a raster by snapping it to a grid. New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_SummaryStats - Returns summary stats consisting of count,sum,mean,stddev,min,max for a given raster band of a raster or raster coverage. Band 1 is assumed is no band is specified.
- ST_Transform - Reprojects a raster in a known spatial reference system to another known spatial reference system using specified resampling algorithm. Options are NearestNeighbor, Bilinear, Cubic, CubicSpline, Lanczos defaulting to NearestNeighbor.
- ST_Union - Returns the union of a set of raster tiles into a single raster composed of 1 band. If no band is specified for unioning, band num 1 is assumed. The resulting raster's extent is the extent of the whole set. In the case of intersection, the resulting value is defined by p_expression which is one of the following: LAST - the default when none is specified, MEAN, SUM, FIRST, MAX, MIN.
- ST_UpperLeftX - Returns the upper left X coordinate of raster in projected spatial ref.
- ST_UpperLeftY - Returns the upper left Y coordinate of raster in projected spatial ref.
- ST_Value - Returns the value of a given band in a given columnx, rowy pixel or at a particular geometric point. Band numbers start at 1 and assumed to be 1 if not specified. If exclude_nodata_value is set to false, then all pixels include nodata pixels are considered to intersect and return value. If exclude_nodata_value is not passed in then reads it from metadata of raster.
- ST_ValueCount - Returns a set of records containing a pixel band value and count of the number of pixels in a given band of a raster (or a raster coverage) that have a given set of values. If no band is specified defaults to band 1. By default nodata value pixels are not counted. and all other values in the pixel are output and pixel band values are rounded to the nearest integer.
- ST_Width - Returns the width of the raster in pixels.
- ST_World2RasterCoordX - Returns the column in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw) represented in world spatial reference system of raster.
- ST_World2RasterCoordY - Returns the row in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw) represented in world spatial reference system of raster.

## 13.5. PostGIS Geometry / Geography / Raster Dump Functions

The functions given below are PostGIS functions that take as input or return as output a set of or single geometry_dump or geomval data type object.

- ST_DumpAsPolygons - Returns a set of geomval (geom,val) rows, from a given raster band. If no band number is specified, band num defaults to 1.
- ST_Intersection - Returns a raster or a set of geometry-pixelvalue pairs representing the shared portion of two rasters or the geometrical intersection of a vectorization of the raster and a geometry.
- ST_Dump - Returns a set of geometry_dump (geom,path) rows, that make up a geometry g1.
- ST_DumpPoints - Returns a set of geometry_dump (geom,path) rows of all points that make up a geometry.
- ST_DumpRings - Returns a set of geometry_dump rows, representing the exterior and interior rings of a polygon.

## 13.6. PostGIS Box Functions

The functions given below are PostGIS functions that take as input or return as output the box* family of PostGIS spatial types. The box family of types consists of box2d, and box3d

- Box2D - Returns a BOX2D representing the maximum extents of the geometry.
- Box3D - Returns a BOX3D representing the maximum extents of the geometry.
- Box3D - Returns the box 3d representation of the enclosing box of the raster.
- ST_3DExtent - an aggregate function that returns the box3D bounding box that bounds rows of geometries.
- ST_3DMakeBox - Creates a BOX3D defined by the given 3d point geometries.
- ST_Estimated_Extent - Return the 'estimated' extent of the given spatial table. The estimated is taken from the geometry column's statistics. The current schema will be used if not specified.
- ST_Expand - Returns bounding box expanded in all directions from the bounding box of the input geometry. Uses double-precision
- ST_Extent - an aggregate function that returns the bounding box that bounds rows of geometries.
- ST_MakeBox2D - Creates a BOX2D defined by the given point geometries.
- ST_XMax - Returns X maxima of a bounding box 2d or 3d or a geometry.
- ST_XMin - Returns X minima of a bounding box 2d or 3d or a geometry.
- ST_YMax - Returns Y maxima of a bounding box 2d or 3d or a geometry.
- ST_YMin - Returns Y minima of a bounding box 2d or 3d or a geometry.
- ST_ZMax - Returns Z minima of a bounding box 2d or 3d or a geometry.
- ST_ZMin - Returns Z minima of a bounding box 2d or 3d or a geometry.

## 13.7. PostGIS Functions that support 3D

The functions given below are PostGIS functions that do not throw away the Z-Index.

- AddGeometryColumn - Adds a geometry column to an existing table of attributes. By default uses type modifier to define rather than constraints. Pass in false for use_typmod to get old check constraint based behavior
- Box3D - Returns a BOX3D representing the maximum extents of the geometry.
- DropGeometryColumn - Removes a geometry column from a spatial table.
- GeometryType - Returns the type of the geometry as a string. Eg: 'LINESTRING', 'POLYGON', 'MULTIPOINT', etc.
- ST_3DClosestPoint - Returns the 3-dimensional point on g1 that is closest to g2. This is the first point of the 3D shortest line.
- ST_3DDFullyWithin - Returns true if all of the 3D geometries are within the specified distance of one another.
- ST_3DDWithin - For 3d (z) geometry type Returns true if two geometries 3d distance is within number of units.
- ST_3DDistance - For geometry type Returns the 3-dimensional cartesian minimum distance (based on spatial ref) between two geometries in projected units.
- ST_3DExtent - an aggregate function that returns the box3D bounding box that bounds rows of geometries.
- ST_3DIntersects - Returns TRUE if the Geometries "spatially intersect" in 3d - only for points and linestrings
- ST_3DLength - Returns the 3-dimensional or 2-dimensional length of the geometry if it is a linestring or multi-linestring.
- ST_3DLength_Spheroid - Calculates the length of a geometry on an ellipsoid, taking the elevation into account. This is just an alias for ST_Length_Spheroid.
- ST_3DLongestLine - Returns the 3-dimensional longest line between two geometries
- ST_3DMakeBox - Creates a BOX3D defined by the given 3d point geometries.
- ST_3DMaxDistance - For geometry type Returns the 3-dimensional cartesian maximum distance (based on spatial ref) between two geometries in projected units.
- ST_3DPerimeter - Returns the 3-dimensional perimeter of the geometry, if it is a polygon or multi-polygon.
- ST_3DShortestLine - Returns the 3-dimensional shortest line between two geometries
- ST_Accum - Aggregate. Constructs an array of geometries.
- ST_AddMeasure - Return a derived geometry with measure elements linearly interpolated between the start and end points. If the geometry has no measure dimension, one is added. If the geometry has a measure dimension, it is over-written with new values. Only LINESTRINGS and MULTILINESTRINGS are supported.
- ST_AddPoint - Adds a point to a LineString before point <position> (0-based index).
- ST_Affine - Applies a 3d affine transformation to the geometry to do things like translate, rotate, scale in one step.
- ST_AsBinary - Return the Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsEWKB - Return the Well-Known Binary (WKB) representation of the geometry with SRID meta data.
- ST_AsEWKT - Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
- ST_AsGML - Return the geometry as a GML version 2 or 3 element.
- ST_AsGeoJSON - Return the geometry as a GeoJSON element.
- ST_AsHEXEWKB - Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding.
- ST_AsKML - Return the geometry as a KML element. Several variants. Default version=2, default precision=15
- ST_AsX3D - Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML
- ST_Boundary - Returns the closure of the combinatorial boundary of this Geometry.
- ST_Collect - Return a specified ST_Geometry value from a collection of other geometries.
- ST_ConvexHull - The convex hull of a geometry represents the minimum convex geometry that encloses all geometries within the set.
- ST_CoordDim - Return the coordinate dimension of the ST_Geometry value.
- ST_CurveToLine - Converts a CIRCULARSTRING/CURVEDPOLYGON to a LINESTRING/POLYGON
- ST_Difference - Returns a geometry that represents that part of geometry A that does not intersect with geometry B.
- ST_Dump - Returns a set of geometry_dump (geom,path) rows, that make up a geometry g1.
- ST_DumpPoints - Returns a set of geometry_dump (geom,path) rows of all points that make up a geometry.
- ST_DumpRings - Returns a set of geometry_dump rows, representing the exterior and interior rings of a polygon.
- ST_EndPoint - Returns the last point of a LINESTRING geometry as a POINT.
- ST_ExteriorRing - Returns a line string representing the exterior ring of the POLYGON geometry. Return NULL if the geometry is not a polygon. Will not work with MULTIPOLYGON
- ST_FlipCoordinates - Returns a version of the given geometry with X and Y axis flipped. Useful for people who have built latitude/longitude features and need to fix them.
- ST_ForceRHR - Forces the orientation of the vertices in a polygon to follow the Right-Hand-Rule.
- ST_Force_2D - Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X and Y coordinates.
- ST_Force_3D - Forces the geometries into XYZ mode. This is an alias for ST_Force_3DZ.
- ST_Force_3DZ - Forces the geometries into XYZ mode. This is a synonym for ST_Force_3D.
- ST_Force_4D - Forces the geometries into XYZM mode.
- ST_Force_Collection - Converts the geometry into a GEOMETRYCOLLECTION.
- ST_GeomFromEWKB - Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).
- ST_GeomFromEWKT - Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).
- ST_GeomFromGML - Takes as input GML representation of geometry and outputs a PostGIS geometry object
- ST_GeomFromGeoJSON - Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object
- ST_GeomFromKML - Takes as input KML representation of geometry and outputs a PostGIS geometry object
- ST_GeometryN - Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL.
- ST_GeometryType - Return the geometry type of the ST_Geometry value.
- ST_HasArc - Returns true if a geometry or geometry collection contains a circular string
- ST_InteriorRingN - Return the Nth interior linestring ring of the polygon geometry. Return NULL if the geometry is not a polygon or the given N is out of range.
- ST_InterpolatePoint - Return the value of the measure dimension of a geometry at the point closed to the provided point.
- ST_IsClosed - Returns TRUE if the LINESTRING's start and end points are coincident. For Polyhedral surface is closed (volumetric).
- ST_IsCollection - Returns TRUE if the argument is a collection (MULTI*, GEOMETRYCOLLECTION, ...)
- ST_IsSimple - Returns (TRUE) if this Geometry has no anomalous geometric points, such as self intersection or self tangency.
- ST_Length_Spheroid - Calculates the 2D or 3D length of a linestring/multilinestring on an ellipsoid. This is useful if the coordinates of the geometry are in longitude/latitude and a length is desired without reprojection.
- ST_LineFromMultiPoint - Creates a LineString from a MultiPoint geometry.
- ST_LineToCurve - Converts a LINESTRING/POLYGON to a CIRCULARSTRING, CURVED POLYGON
- ST_Line_Interpolate_Point - Returns a point interpolated along a line. Second argument is a float8 between 0 and 1 representing fraction of total length of linestring the point has to be located.
- ST_Line_Substring - Return a linestring being a substring of the input one starting and ending at the given fractions of total 2d length. Second and third arguments are float8 values between 0 and 1.
- ST_LocateBetweenElevations - Return a derived geometry (collection) value with elements that intersect the specified range of elevations inclusively. Only 3D, 4D LINESTRINGS and MULTILINESTRINGS are supported.
- ST_M - Return the M coordinate of the point, or NULL if not available. Input must be a point.
- ST_MakeLine - Creates a Linestring from point or line geometries.
- ST_MakePoint - Creates a 2D,3DZ or 4D point geometry.
- ST_MakePolygon - Creates a Polygon formed by the given shell. Input geometries must be closed LINESTRINGS.
- ST_MakeValid - Attempts to make an invalid geometry valid w/out loosing vertices.
- ST_MemUnion - Same as ST_Union, only memory-friendly (uses less memory and more processor time).
- ST_Mem_Size - Returns the amount of space (in bytes) the geometry takes.
- ST_NDims - Returns coordinate dimension of the geometry as a small int. Values are: 2,3 or 4.
- ST_NPoints - Return the number of points (vertexes) in a geometry.
- ST_NRings - If the geometry is a polygon or multi-polygon returns the number of rings.
- ST_Node - Node a set of linestrings.
- ST_NumGeometries - If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for single geometries will return 1, otherwise return NULL.
- ST_NumPatches - Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.
- ST_PatchN - Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Otherwise, return NULL.
- ST_PointFromWKB - Makes a geometry from WKB with the given SRID
- ST_PointN - Return the Nth point in the first linestring or circular linestring in the geometry. Return NULL if there is no linestring in the geometry.
- ST_PointOnSurface - Returns a POINT guaranteed to lie on the surface.
- ST_Polygon - Returns a polygon built from the specified linestring and SRID.
- ST_RemovePoint - Removes point from a linestring. Offset is 0-based.
- ST_RemoveRepeatedPoints - Returns a version of the given geometry with duplicated points removed.
- ST_Rotate - Rotate a geometry rotRadians counter-clockwise about an origin.
- ST_RotateX - Rotate a geometry rotRadians about the X axis.
- ST_RotateY - Rotate a geometry rotRadians about the Y axis.
- ST_RotateZ - Rotate a geometry rotRadians about the Z axis.
- ST_Scale - Scales the geometry to a new size by multiplying the ordinates with the parameters. Ie: ST_Scale(geom, Xfactor, Yfactor, Zfactor).
- ST_SetPoint - Replace point N of linestring with given point. Index is 0-based.
- ST_Shift_Longitude - Reads every point/vertex in every component of every feature in a geometry, and if the longitude coordinate is <0, adds 360 to it. The result would be a 0-360 version of the data to be plotted in a 180 centric map
- ST_SnapToGrid - Snap all points of the input geometry to a regular grid.
- ST_StartPoint - Returns the first point of a LINESTRING geometry as a POINT.
- ST_SymDifference - Returns a geometry that represents the portions of A and B that do not intersect. It is called a symmetric difference because ST_SymDifference(A,B) = ST_SymDifference(B,A).
- ST_TransScale - Translates the geometry using the deltaX and deltaY args, then scales it using the XFactor, YFactor args, working in 2D only.
- ST_Translate - Translates the geometry to a new location using the numeric parameters as offsets. Ie: ST_Translate(geom, X, Y) or ST_Translate(geom, X, Y,Z).
- ST_UnaryUnion - Like ST_Union, but working at the geometry component level.
- ST_X - Return the X coordinate of the point, or NULL if not available. Input must be a point.
- ST_XMax - Returns X maxima of a bounding box 2d or 3d or a geometry.
- ST_XMin - Returns X minima of a bounding box 2d or 3d or a geometry.
- ST_Y - Return the Y coordinate of the point, or NULL if not available. Input must be a point.
- ST_YMax - Returns Y maxima of a bounding box 2d or 3d or a geometry.
- ST_YMin - Returns Y minima of a bounding box 2d or 3d or a geometry.
- ST_Z - Return the Z coordinate of the point, or NULL if not available. Input must be a point.
- ST_ZMax - Returns Z minima of a bounding box 2d or 3d or a geometry.
- ST_ZMin - Returns Z minima of a bounding box 2d or 3d or a geometry.
- ST_Zmflag - Returns ZM (dimension semantic) flag of the geometries as a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d.
- UpdateGeometrySRID - Updates the SRID of all features in a geometry column, geometry_columns metadata and srid table constraint
- geometry_overlaps_nd - Returns TRUE if A's 3D bounding box intersects B's 3D bounding box.

## 13.8. PostGIS Curved Geometry Support Functions

The functions given below are PostGIS functions that can use CIRCULARSTRING, CURVEDPOLYGON, and other curved geometry types

- AddGeometryColumn - Adds a geometry column to an existing table of attributes. By default uses type modifier to define rather than constraints. Pass in false for use_typmod to get old check constraint based behavior
- Box2D - Returns a BOX2D representing the maximum extents of the geometry.
- Box3D - Returns a BOX3D representing the maximum extents of the geometry.
- DropGeometryColumn - Removes a geometry column from a spatial table.
- GeometryType - Returns the type of the geometry as a string. Eg: 'LINESTRING', 'POLYGON', 'MULTIPOINT', etc.
- PostGIS_AddBBox - Add bounding box to the geometry.
- PostGIS_DropBBox - Drop the bounding box cache from the geometry.
- PostGIS_HasBBox - Returns TRUE if the bbox of this geometry is cached, FALSE otherwise.
- ST_3DExtent - an aggregate function that returns the box3D bounding box that bounds rows of geometries.
- ST_Accum - Aggregate. Constructs an array of geometries.
- ST_Affine - Applies a 3d affine transformation to the geometry to do things like translate, rotate, scale in one step.
- ST_AsBinary - Return the Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsEWKB - Return the Well-Known Binary (WKB) representation of the geometry with SRID meta data.
- ST_AsEWKT - Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
- ST_AsHEXEWKB - Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding.
- ST_AsText - Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.
- ST_Collect - Return a specified ST_Geometry value from a collection of other geometries.
- ST_CoordDim - Return the coordinate dimension of the ST_Geometry value.
- ST_CurveToLine - Converts a CIRCULARSTRING/CURVEDPOLYGON to a LINESTRING/POLYGON
- ST_Dump - Returns a set of geometry_dump (geom,path) rows, that make up a geometry g1.
- ST_DumpPoints - Returns a set of geometry_dump (geom,path) rows of all points that make up a geometry.
- ST_Estimated_Extent - Return the 'estimated' extent of the given spatial table. The estimated is taken from the geometry column's statistics. The current schema will be used if not specified.
- ST_FlipCoordinates - Returns a version of the given geometry with X and Y axis flipped. Useful for people who have built latitude/longitude features and need to fix them.
- ST_Force_2D - Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X and Y coordinates.
- ST_Force_3D - Forces the geometries into XYZ mode. This is an alias for ST_Force_3DZ.
- ST_Force_3DM - Forces the geometries into XYM mode.
- ST_Force_3DZ - Forces the geometries into XYZ mode. This is a synonym for ST_Force_3D.
- ST_Force_4D - Forces the geometries into XYZM mode.
- ST_Force_Collection - Converts the geometry into a GEOMETRYCOLLECTION.
- ST_GeoHash - Return a GeoHash representation (geohash.org) of the geometry.
- ST_GeogFromWKB - Creates a geography instance from a Well-Known Binary geometry representation (WKB) or extended Well Known Binary (EWKB).
- ST_GeomFromEWKB - Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).
- ST_GeomFromEWKT - Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).
- ST_GeomFromText - Return a specified ST_Geometry value from Well-Known Text representation (WKT).
- ST_GeomFromWKB - Creates a geometry instance from a Well-Known Binary geometry representation (WKB) and optional SRID.
- ST_GeometryN - Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL.
- = - Returns TRUE if A's bounding box is the same as B's. Uses double precision bounding box.
- &<| - Returns TRUE if A's bounding box overlaps or is below B's.
- ST_HasArc - Returns true if a geometry or geometry collection contains a circular string
- ST_IsClosed - Returns TRUE if the LINESTRING's start and end points are coincident. For Polyhedral surface is closed (volumetric).
- ST_IsCollection - Returns TRUE if the argument is a collection (MULTI*, GEOMETRYCOLLECTION, ...)
- ST_IsEmpty - Returns true if this Geometry is an empty geometrycollection, polygon, point etc.
- ST_LineToCurve - Converts a LINESTRING/POLYGON to a CIRCULARSTRING, CURVED POLYGON
- ST_Mem_Size - Returns the amount of space (in bytes) the geometry takes.
- ST_NPoints - Return the number of points (vertexes) in a geometry.
- ST_NRings - If the geometry is a polygon or multi-polygon returns the number of rings.
- ST_PointFromWKB - Makes a geometry from WKB with the given SRID
- ST_PointN - Return the Nth point in the first linestring or circular linestring in the geometry. Return NULL if there is no linestring in the geometry.
- ST_Rotate - Rotate a geometry rotRadians counter-clockwise about an origin.
- ST_RotateZ - Rotate a geometry rotRadians about the Z axis.
- ST_SRID - Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table.
- ST_Scale - Scales the geometry to a new size by multiplying the ordinates with the parameters. Ie: ST_Scale(geom, Xfactor, Yfactor, Zfactor).
- ST_SetSRID - Sets the SRID on a geometry to a particular integer value.
- ST_TransScale - Translates the geometry using the deltaX and deltaY args, then scales it using the XFactor, YFactor args, working in 2D only.
- ST_Transform - Returns a new geometry with its coordinates transformed to the SRID referenced by the integer parameter.
- ST_Translate - Translates the geometry to a new location using the numeric parameters as offsets. Ie: ST_Translate(geom, X, Y) or ST_Translate(geom, X, Y,Z).
- ST_XMax - Returns X maxima of a bounding box 2d or 3d or a geometry.
- ST_XMin - Returns X minima of a bounding box 2d or 3d or a geometry.
- ST_YMax - Returns Y maxima of a bounding box 2d or 3d or a geometry.
- ST_YMin - Returns Y minima of a bounding box 2d or 3d or a geometry.
- ST_ZMax - Returns Z minima of a bounding box 2d or 3d or a geometry.
- ST_ZMin - Returns Z minima of a bounding box 2d or 3d or a geometry.
- ST_Zmflag - Returns ZM (dimension semantic) flag of the geometries as a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d.
- UpdateGeometrySRID - Updates the SRID of all features in a geometry column, geometry_columns metadata and srid table constraint
- && - Returns TRUE if A's 2D bounding box intersects B's 2D bounding box.
- &&& - Returns TRUE if A's 3D bounding box intersects B's 3D bounding box.

## 13.9. PostGIS Polyhedral Surface Support Functions

The functions given below are PostGIS functions that can use POLYHEDRALSURFACE, POLYHEDRALSURFACEM geometries

- Box2D - Returns a BOX2D representing the maximum extents of the geometry.
- Box3D - Returns a BOX3D representing the maximum extents of the geometry.
- GeometryType - Returns the type of the geometry as a string. Eg: 'LINESTRING', 'POLYGON', 'MULTIPOINT', etc.
- ST_3DClosestPoint - Returns the 3-dimensional point on g1 that is closest to g2. This is the first point of the 3D shortest line.
- ST_3DDFullyWithin - Returns true if all of the 3D geometries are within the specified distance of one another.
- ST_3DDWithin - For 3d (z) geometry type Returns true if two geometries 3d distance is within number of units.
- ST_3DDistance - For geometry type Returns the 3-dimensional cartesian minimum distance (based on spatial ref) between two geometries in projected units.
- ST_3DExtent - an aggregate function that returns the box3D bounding box that bounds rows of geometries.
- ST_3DIntersects - Returns TRUE if the Geometries "spatially intersect" in 3d - only for points and linestrings
- ST_3DLongestLine - Returns the 3-dimensional longest line between two geometries
- ST_3DMaxDistance - For geometry type Returns the 3-dimensional cartesian maximum distance (based on spatial ref) between two geometries in projected units.
- ST_3DShortestLine - Returns the 3-dimensional shortest line between two geometries
- ST_Accum - Aggregate. Constructs an array of geometries.
- ST_Affine - Applies a 3d affine transformation to the geometry to do things like translate, rotate, scale in one step.
- ST_Area - Returns the area of the surface if it is a polygon or multi-polygon. For "geometry" type area is in SRID units. For "geography" area is in square meters.
- ST_AsBinary - Return the Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsEWKB - Return the Well-Known Binary (WKB) representation of the geometry with SRID meta data.
- ST_AsEWKT - Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
- ST_AsGML - Return the geometry as a GML version 2 or 3 element.
- ST_AsX3D - Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML
- ST_CoordDim - Return the coordinate dimension of the ST_Geometry value.
- ST_Dimension - The inherent dimension of this Geometry object, which must be less than or equal to the coordinate dimension.
- ST_Dump - Returns a set of geometry_dump (geom,path) rows, that make up a geometry g1.
- ST_DumpPoints - Returns a set of geometry_dump (geom,path) rows of all points that make up a geometry.
- ST_Expand - Returns bounding box expanded in all directions from the bounding box of the input geometry. Uses double-precision
- ST_Extent - an aggregate function that returns the bounding box that bounds rows of geometries.
- ST_FlipCoordinates - Returns a version of the given geometry with X and Y axis flipped. Useful for people who have built latitude/longitude features and need to fix them.
- ST_ForceRHR - Forces the orientation of the vertices in a polygon to follow the Right-Hand-Rule.
- ST_Force_2D - Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X and Y coordinates.
- ST_Force_3D - Forces the geometries into XYZ mode. This is an alias for ST_Force_3DZ.
- ST_Force_3DZ - Forces the geometries into XYZ mode. This is a synonym for ST_Force_3D.
- ST_Force_Collection - Converts the geometry into a GEOMETRYCOLLECTION.
- ST_GeomFromEWKB - Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).
- ST_GeomFromEWKT - Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).
- ST_GeomFromGML - Takes as input GML representation of geometry and outputs a PostGIS geometry object
- ST_GeometryN - Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL.
- ST_GeometryType - Return the geometry type of the ST_Geometry value.
- = - Returns TRUE if A's bounding box is the same as B's. Uses double precision bounding box.
- &<| - Returns TRUE if A's bounding box overlaps or is below B's.
- ~= - Returns TRUE if A's bounding box is the same as B's.
- ST_IsClosed - Returns TRUE if the LINESTRING's start and end points are coincident. For Polyhedral surface is closed (volumetric).
- ST_Mem_Size - Returns the amount of space (in bytes) the geometry takes.
- ST_NPoints - Return the number of points (vertexes) in a geometry.
- ST_NumGeometries - If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for single geometries will return 1, otherwise return NULL.
- ST_NumPatches - Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.
- ST_PatchN - Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Otherwise, return NULL.
- ST_RemoveRepeatedPoints - Returns a version of the given geometry with duplicated points removed.
- ST_Rotate - Rotate a geometry rotRadians counter-clockwise about an origin.
- ST_RotateX - Rotate a geometry rotRadians about the X axis.
- ST_RotateY - Rotate a geometry rotRadians about the Y axis.
- ST_RotateZ - Rotate a geometry rotRadians about the Z axis.
- ST_Scale - Scales the geometry to a new size by multiplying the ordinates with the parameters. Ie: ST_Scale(geom, Xfactor, Yfactor, Zfactor).
- ST_Shift_Longitude - Reads every point/vertex in every component of every feature in a geometry, and if the longitude coordinate is <0, adds 360 to it. The result would be a 0-360 version of the data to be plotted in a 180 centric map
- ST_Transform - Returns a new geometry with its coordinates transformed to the SRID referenced by the integer parameter.
- && - Returns TRUE if A's 2D bounding box intersects B's 2D bounding box.
- &&& - Returns TRUE if A's 3D bounding box intersects B's 3D bounding box.

## 13.10. PostGIS Function Support Matrix

Below is an alphabetical listing of spatial specific functions in PostGIS and the kinds of spatial types they work with or OGC/SQL compliance they try to conform to.

- A means the function works with the type or subtype natively.
- A means it works but with a transform cast built-in using cast to geometry, transform to a "best srid" spatial ref and then cast back. Results may not be as expected for large areas or areas at poles and may accumulate floating point junk.
- A means the function works with the type because of a auto-cast to another such as to box3d rather than direct type support.
- geom - Basic 2D geometry support (x,y).
- geog - Basic 2D geography support (x,y).
- 2.5D - basic 2D geometries in 3 D/4D space (has Z or M coord).
- PS - Polyhedral surfaces
- T - Triangles and Triangulated Irregular Network surfaces (TIN)

Function | geom | geog | 2.5D | Curves | SQL MM | PS | T
--- | --- | --- | --- | --- | --- | --- | ---
Box2D |  |  |  |  |  |  |
Box3D |  |  |  |  |  |  |
Find_SRID |  |  |  |  |  |  |
GeometryType |  |  |  |  |  |  |
ST_3DClosestPoint |  |  |  |  |  |  |
ST_3DDFullyWithin |  |  |  |  |  |  |
ST_3DDWithin |  |  |  |  |  |  |
ST_3DDistance |  |  |  |  |  |  |
ST_3DExtent |  |  |  |  |  |  |
ST_3DIntersects |  |  |  |  |  |  |
ST_3DLength |  |  |  |  |  |  |
ST_3DLength_Spheroid |  |  |  |  |  |  |
ST_3DLongestLine |  |  |  |  |  |  |
ST_3DMakeBox |  |  |  |  |  |  |
ST_3DMaxDistance |  |  |  |  |  |  |
ST_3DPerimeter |  |  |  |  |  |  |
ST_3DShortestLine |  |  |  |  |  |  |
ST_Accum |  |  |  |  |  |  |
ST_AddMeasure |  |  |  |  |  |  |
ST_AddPoint |  |  |  |  |  |  |
ST_Affine |  |  |  |  |  |  |
ST_Area |  |  |  |  |  |  |
ST_AsBinary |  |  |  |  |  |  |
ST_AsEWKB |  |  |  |  |  |  |
ST_AsEWKT |  |  |  |  |  |  |
ST_AsGML |  |  |  |  |  |  |
ST_AsGeoJSON |  |  |  |  |  |  |
ST_AsHEXEWKB |  |  |  |  |  |  |
ST_AsKML |  |  |  |  |  |  |
ST_AsLatLonText |  |  |  |  |  |  |
ST_AsSVG |  |  |  |  |  |  |
ST_AsText |  |  |  |  |  |  |
ST_AsX3D |  |  |  |  |  |  |
ST_Azimuth |  |  |  |  |  |  |
ST_BdMPolyFromText |  |  |  |  |  |  |
ST_BdPolyFromText |  |  |  |  |  |  |
ST_Boundary |  |  |  |  |  |  |
ST_Buffer |  |  |  |  |  |  |
ST_BuildArea |  |  |  |  |  |  |
ST_Centroid |  |  |  |  |  |  |
ST_ClosestPoint |  |  |  |  |  |  |
ST_Collect |  |  |  |  |  |  |
ST_CollectionExtract |  |  |  |  |  |  |
ST_CollectionHomogenize |  |  |  |  |  |  |
ST_ConcaveHull |  |  |  |  |  |  |
ST_Contains |  |  |  |  |  |  |
ST_ContainsProperly |  |  |  |  |  |  |
ST_ConvexHull |  |  |  |  |  |  |
ST_CoordDim |  |  |  |  |  |  |
ST_CoveredBy |  |  |  |  |  |  |
ST_Covers |  |  |  |  |  |  |
ST_Crosses |  |  |  |  |  |  |
ST_CurveToLine |  |  |  |  |  |  |
ST_DFullyWithin |  |  |  |  |  |  |
ST_DWithin |  |  |  |  |  |  |
ST_Difference |  |  |  |  |  |  |
ST_Dimension |  |  |  |  |  |  |
ST_Disjoint |  |  |  |  |  |  |
ST_Distance |  |  |  |  |  |  |
ST_Distance_Sphere |  |  |  |  |  |  |
ST_Distance_Spheroid |  |  |  |  |  |  |
ST_Dump |  |  |  |  |  |  |
ST_DumpPoints |  |  |  |  |  |  |
ST_DumpRings |  |  |  |  |  |  |
ST_EndPoint |  |  |  |  |  |  |
ST_Envelope |  |  |  |  |  |  |
ST_Equals |  |  |  |  |  |  |
ST_Estimated_Extent |  |  |  |  |  |  |
ST_Expand |  |  |  |  |  |  |
ST_Extent |  |  |  |  |  |  |
ST_ExteriorRing |  |  |  |  |  |  |
ST_FlipCoordinates |  |  |  |  |  |  |
ST_ForceRHR |  |  |  |  |  |  |
ST_Force_2D |  |  |  |  |  |  |
ST_Force_3D |  |  |  |  |  |  |
ST_Force_3DM |  |  |  |  |  |  |
ST_Force_3DZ |  |  |  |  |  |  |
ST_Force_4D |  |  |  |  |  |  |
ST_Force_Collection |  |  |  |  |  |  |
ST_GMLToSQL |  |  |  |  |  |  |
ST_GeoHash |  |  |  |  |  |  |
ST_GeogFromText |  |  |  |  |  |  |
ST_GeogFromWKB |  |  |  |  |  |  |
ST_GeographyFromText |  |  |  |  |  |  |
ST_GeomCollFromText |  |  |  |  |  |  |
ST_GeomFromEWKB |  |  |  |  |  |  |
ST_GeomFromEWKT |  |  |  |  |  |  |
ST_GeomFromGML |  |  |  |  |  |  |
ST_GeomFromGeoJSON |  |  |  |  |  |  |
ST_GeomFromKML |  |  |  |  |  |  |
ST_GeomFromText |  |  |  |  |  |  |
ST_GeomFromWKB |  |  |  |  |  |  |
ST_GeometryFromText |  |  |  |  |  |  |
ST_GeometryN |  |  |  |  |  |  |
ST_GeometryType |  |  |  |  |  |  |
|>> |  |  |  |  |  |  |
<<| |  |  |  |  |  |  |
~ |  |  |  |  |  |  |
@ |  |  |  |  |  |  |
= |  |  |  |  |  |  |
<< |  |  |  |  |  |  |
|&> |  |  |  |  |  |  |
&<| |  |  |  |  |  |  |
&< |  |  |  |  |  |  |
&> |  |  |  |  |  |  |
>> |  |  |  |  |  |  |
~= |  |  |  |  |  |  |
ST_HasArc |  |  |  |  |  |  |
ST_HausdorffDistance |  |  |  |  |  |  |
ST_InteriorRingN |  |  |  |  |  |  |
ST_InterpolatePoint |  |  |  |  |  |  |
ST_Intersection |  |  |  |  |  |  |
ST_Intersects |  |  |  |  |  |  |
ST_IsClosed |  |  |  |  |  |  |
ST_IsCollection |  |  |  |  |  |  |
ST_IsEmpty |  |  |  |  |  |  |
ST_IsRing |  |  |  |  |  |  |
ST_IsSimple |  |  |  |  |  |  |
ST_IsValid |  |  |  |  |  |  |
ST_IsValidDetail |  |  |  |  |  |  |
ST_IsValidReason |  |  |  |  |  |  |
ST_Length |  |  |  |  |  |  |
ST_Length2D |  |  |  |  |  |  |
ST_Length2D_Spheroid |  |  |  |  |  |  |
ST_Length_Spheroid |  |  |  |  |  |  |
ST_LineCrossingDirection |  |  |  |  |  |  |
ST_LineFromMultiPoint |  |  |  |  |  |  |
ST_LineFromText |  |  |  |  |  |  |
ST_LineFromWKB |  |  |  |  |  |  |
ST_LineMerge |  |  |  |  |  |  |
ST_LineToCurve |  |  |  |  |  |  |
ST_Line_Interpolate_Point |  |  |  |  |  |  |
ST_Line_Locate_Point |  |  |  |  |  |  |
ST_Line_Substring |  |  |  |  |  |  |
ST_LinestringFromWKB |  |  |  |  |  |  |
ST_LocateAlong |  |  |  |  |  |  |
ST_LocateBetween |  |  |  |  |  |  |
ST_LocateBetweenElevations |  |  |  |  |  |  |
ST_LongestLine |  |  |  |  |  |  |
ST_M |  |  |  |  |  |  |
ST_MLineFromText |  |  |  |  |  |  |
ST_MPointFromText |  |  |  |  |  |  |
ST_MPolyFromText |  |  |  |  |  |  |
ST_MakeBox2D |  |  |  |  |  |  |
ST_MakeEnvelope |  |  |  |  |  |  |
ST_MakeLine |  |  |  |  |  |  |
ST_MakePoint |  |  |  |  |  |  |
ST_MakePointM |  |  |  |  |  |  |
ST_MakePolygon |  |  |  |  |  |  |
ST_MakeValid |  |  |  |  |  |  |
ST_MaxDistance |  |  |  |  |  |  |
ST_MemUnion |  |  |  |  |  |  |
ST_Mem_Size |  |  |  |  |  |  |
ST_MinimumBoundingCircle |  |  |  |  |  |  |
ST_Multi |  |  |  |  |  |  |
ST_NDims |  |  |  |  |  |  |
ST_NPoints |  |  |  |  |  |  |
ST_NRings |  |  |  |  |  |  |
ST_Node |  |  |  |  |  |  |
ST_NumGeometries |  |  |  |  |  |  |
ST_NumInteriorRing |  |  |  |  |  |  |
ST_NumInteriorRings |  |  |  |  |  |  |
ST_NumPatches |  |  |  |  |  |  |
ST_NumPoints |  |  |  |  |  |  |
ST_OffsetCurve |  |  |  |  |  |  |
ST_OrderingEquals |  |  |  |  |  |  |
ST_Overlaps |  |  |  |  |  |  |
ST_PatchN |  |  |  |  |  |  |
ST_Perimeter |  |  |  |  |  |  |
ST_Perimeter2D |  |  |  |  |  |  |
ST_Point |  |  |  |  |  |  |
ST_PointFromText |  |  |  |  |  |  |
ST_PointFromWKB |  |  |  |  |  |  |
ST_PointN |  |  |  |  |  |  |
ST_PointOnSurface |  |  |  |  |  |  |
ST_Point_Inside_Circle |  |  |  |  |  |  |
ST_Polygon |  |  |  |  |  |  |
ST_PolygonFromText |  |  |  |  |  |  |
ST_Polygonize |  |  |  |  |  |  |
ST_Project |  |  |  |  |  |  |
ST_Relate |  |  |  |  |  |  |
ST_RelateMatch |  |  |  |  |  |  |
ST_RemovePoint |  |  |  |  |  |  |
ST_RemoveRepeatedPoints |  |  |  |  |  |  |
ST_Reverse |  |  |  |  |  |  |
ST_Rotate |  |  |  |  |  |  |
ST_RotateX |  |  |  |  |  |  |
ST_RotateY |  |  |  |  |  |  |
ST_RotateZ |  |  |  |  |  |  |
ST_SRID |  |  |  |  |  |  |
ST_Scale |  |  |  |  |  |  |
ST_Segmentize |  |  |  |  |  |  |
ST_SetPoint |  |  |  |  |  |  |
ST_SetSRID |  |  |  |  |  |  |
ST_SharedPaths |  |  |  |  |  |  |
ST_Shift_Longitude |  |  |  |  |  |  |
ST_ShortestLine |  |  |  |  |  |  |
ST_Simplify |  |  |  |  |  |  |
ST_SimplifyPreserveTopology |  |  |  |  |  |  |
ST_Snap |  |  |  |  |  |  |
ST_SnapToGrid |  |  |  |  |  |  |
ST_Split |  |  |  |  |  |  |
ST_StartPoint |  |  |  |  |  |  |
ST_Summary |  |  |  |  |  |  |
ST_SymDifference |  |  |  |  |  |  |
ST_Touches |  |  |  |  |  |  |
ST_TransScale |  |  |  |  |  |  |
ST_Transform |  |  |  |  |  |  |
ST_Translate |  |  |  |  |  |  |
ST_UnaryUnion |  |  |  |  |  |  |
ST_Union |  |  |  |  |  |  |
ST_WKBToSQL |  |  |  |  |  |  |
ST_WKTToSQL |  |  |  |  |  |  |
ST_Within |  |  |  |  |  |  |
ST_X |  |  |  |  |  |  |
ST_XMax |  |  |  |  |  |  |
ST_XMin |  |  |  |  |  |  |
ST_Y |  |  |  |  |  |  |
ST_YMax |  |  |  |  |  |  |
ST_YMin |  |  |  |  |  |  |
ST_Z |  |  |  |  |  |  |
ST_ZMax |  |  |  |  |  |  |
ST_ZMin |  |  |  |  |  |  |
ST_Zmflag |  |  |  |  |  |  |
<#> |  |  |  |  |  |  |
<-> |  |  |  |  |  |  |
&& |  |  |  |  |  |  |
&&& |  |  |  |  |  |  |

## 13.11. New, Enhanced or changed PostGIS Functions

### 13.11.1. PostGIS Functions new, behavior changed, or enhanced in 2.0

The functions given below are PostGIS functions that were added, enhanced, or have Section 13.11.2, “PostGIS Functions changed behavior in 2.0” breaking changes in 2.0 releases.

New geometry types: TIN and Polyhedral surfaces was introduced in 2.0

Greatly improved support for Topology. Please refer to Chapter 11, Topology for more details.

In PostGIS 2.0, raster type and raster functionality has been integrated. There are way too many new raster functions to list here and all are new so please refer to Chapter 9, Raster Reference for more details of the raster functions available. Earlier pre-2.0 versions had raster_columns/raster_overviews as real tables. These were changed to views before release. Functions such as `ST_AddRasterColumn` were removed and replaced with AddRasterConstraints, DropRasterConstraints as a result some apps that created raster tables may need changing.

Tiger Geocoder upgraded to work with TIGER 2010 census data and now included in the core PostGIS documentation. A reverse geocoder function was also added. Please refer to Section 12.1, “Tiger Geocoder” for more details.

- &&& - Availability: 2.0.0 Returns TRUE if A's 3D bounding box intersects B's 3D bounding box.
- <#> - Availability: 2.0.0 only available for PostgreSQL 9.1+ Returns the distance between bounding box of 2 geometries. For point / point checks it's almost the same as distance (though may be different since the bounding box is at floating point accuracy and geometries are double precision). Useful for doing distance ordering and nearest neighbor limits using KNN gist functionality.
- <-> - Availability: 2.0.0 only available for PostgreSQL 9.1+ Returns the distance between two points. For point / point checks it uses floating point accuracy (as opposed to the double precision accuracy of the underlying point geometry). For other geometry types the distance between the floating point bounding box centroids is returned. Useful for doing distance ordering and nearest neighbor limits using KNN gist functionality.
- AddEdge - Availability: 2.0.0 requires GEOS >= 3.3.0. Adds a linestring edge to the edge table and associated start and end points to the point nodes table of the specified topology schema using the specified linestring geometry and returns the edgeid of the new (or existing) edge.
- AddFace - Availability: 2.0.0 Registers a face primitive to a topology and get it's identifier.
- AddNode - Availability: 2.0.0 Adds a point node to the node table in the specified topology schema and returns the nodeid of new node. If point already exists as node, the existing nodeid is returned.
- AddRasterConstraints - Availability: 2.0.0 Adds raster constraints to a loaded raster table for a specific column that constrains spatial ref, scaling, blocksize, alignment, bands, band type and a flag to denote if raster column is regularly blocked. The table must be loaded with data for the constraints to be inferred. Returns true of the constraint setting was accomplished and if issues a notice.
- AsGML - Availability: 2.0.0 Returns the GML representation of a topogeometry.
- CopyTopology - Availability: 2.0.0 Makes a copy of a topology structure (nodes, edges, faces, layers and TopoGeometries).
- DropRasterConstraints - Availability: 2.0.0 Drops PostGIS raster constraints that refer to a raster table column. Useful if you need to reload data or update your raster column data.
- Drop_Indexes_Generate_Script - Availability: 2.0.0 Generates a script that drops all non-primary key and non-unique indexes on tiger schema and user specified schema. Defaults schema to tiger_data if no schema is specified.
- Drop_State_Tables_Generate_Script - Availability: 2.0.0 Generates a script that drops all tables in the specified schema that are prefixed with the state abbreviation. Defaults schema to tiger_data if no schema is specified.
- Geocode_Intersection - Availability: 2.0.0 Takes in 2 streets that intersect and a state, city, zip, and outputs a set of possible locations on the first cross street that is at the intersection, also includes a point geometry in NAD 83 long lat, a normalized address for each location, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Can optionally pass in maximum results, defaults to 10
- GetEdgeByPoint - Availability: 2.0.0 - requires GEOS >= 3.3.0. Find the edge-id of an edge that intersects a given point
- GetFaceByPoint - Availability: 2.0.0 - requires GEOS >= 3.3.0. Find the face-id of a face that intersects a given point
- GetNodeByPoint - Availability: 2.0.0 - requires GEOS >= 3.3.0. Find the id of a node at a point location
- GetNodeEdges - Availability: 2.0 Returns an ordered set of edges incident to the given node.
- GetRingEdges - Availability: 2.0 Returns an ordered set of edges forming a ring with the given edge .
- GetTopologySRID - Availability: 2.0.0 Returns the SRID of a topology in the topology.topology table given the name of the topology.
- Get_Tract - Availability: 2.0.0 Returns census tract or field from tract table of where the geometry is located. Default to returning short name of tract.
- Install_Missing_Indexes - Availability: 2.0.0 Finds all tables with key columns used in geocoder joins and filter conditions that are missing used indexes on those columns and will add them.
- Loader_Generate_Census_Script - Availability: 2.0.0 Generates a shell script for the specified platform for the specified states that will download Tiger census state tract, bg, and tabblocks data tables, stage and load into tiger_data schema. Each state script is returned as a separate record.
- Loader_Generate_Script - Availability: 2.0.0 to support Tiger 2010 structured data and load census tract (tract), block groups (bg), and blocks (tabblocks) tables . Generates a shell script for the specified platform for the specified states that will download Tiger data, stage and load into tiger_data schema. Each state script is returned as a separate record. Latest version supports Tiger 2010 structural changes and also loads census tract, block groups, and blocks tables.
- Missing_Indexes_Generate_Script - Availability: 2.0.0 Finds all tables with key columns used in geocoder joins that are missing indexes on those columns and will output the SQL DDL to define the index for those tables.
- Polygonize - Availability: 2.0.0 Find and register all faces defined by topology edges
- Reverse_Geocode - Availability: 2.0.0 Takes a geometry point in a known spatial ref sys and returns a record containing an array of theoretically possible addresses and an array of cross streets. If include_strnum_range = true, includes the street range in the cross streets.
- ST_3DClosestPoint - Availability: 2.0.0 Returns the 3-dimensional point on g1 that is closest to g2. This is the first point of the 3D shortest line.
- ST_3DDFullyWithin - Availability: 2.0.0 Returns true if all of the 3D geometries are within the specified distance of one another.
- ST_3DDWithin - Availability: 2.0.0 For 3d (z) geometry type Returns true if two geometries 3d distance is within number of units.
- ST_3DDistance - Availability: 2.0.0 For geometry type Returns the 3-dimensional cartesian minimum distance (based on spatial ref) between two geometries in projected units.
- ST_3DIntersects - Availability: 2.0.0 Returns TRUE if the Geometries "spatially intersect" in 3d - only for points and linestrings
- ST_3DLongestLine - Availability: 2.0.0 Returns the 3-dimensional longest line between two geometries
- ST_3DMaxDistance - Availability: 2.0.0 For geometry type Returns the 3-dimensional cartesian maximum distance (based on spatial ref) between two geometries in projected units.
- ST_3DShortestLine - Availability: 2.0.0 Returns the 3-dimensional shortest line between two geometries
- ST_AddEdgeModFace - Availability: 2.0 Add a new edge and, if in doing so it splits a face, modify the original face and add a new face.
- ST_AddEdgeNewFaces - Availability: 2.0 Add a new edge and, if in doing so it splits a face, delete the original face and replace it with two new faces.
- ST_AsGDALRaster - Availability: 2.0.0 - requires GDAL >= 1.6.0. Return the raster tile in the designated GDAL Raster format. Raster formats are one of those supported by your compiled library. Use ST_GDALRasters() to get a list of formats supported by your library.
- ST_AsJPEG - Availability: 2.0.0 - requires GDAL >= 1.6.0. Return the raster tile selected bands as a single Joint Photographic Exports Group (JPEG) image (byte array). If no band is specified and 1 or more than 3 bands, then only the first band is used. If only 3 bands then all 3 bands are used and mapped to RGB.
- ST_AsLatLonText - Availability: 2.0 Return the Degrees, Minutes, Seconds representation of the given point.
- ST_AsPNG - Availability: 2.0.0 - requires GDAL >= 1.6.0. Return the raster tile selected bands as a single portable network graphics (PNG) image (byte array). If 1, 3, or 4 bands in raster and no bands are specified, then all bands are used. If more 2 or more than 4 bands and no bands specified, then only band 1 is used. Bands are mapped to RGB or RGBA space.
- ST_AsRaster - Availability: 2.0.0 - requires GDAL >= 1.6.0. Converts a PostGIS geometry to a PostGIS raster.
- ST_AsTIFF - Availability: 2.0.0 - requires GDAL >= 1.6.0. Return the raster selected bands as a single TIFF image (byte array). If no band is specified, then will try to use all bands.
- ST_AsX3D - Availability: 2.0.0: ISO-IEC-19776-1.2-X3DEncodings-XML Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML
- ST_Aspect - Availability: 2.0.0 Returns the surface aspect of an elevation raster band. Useful for analyzing terrain.
- ST_Band - Availability: 2.0.0 Returns one or more bands of an existing raster as a new raster. Useful for building new rasters from existing rasters.
- ST_BandIsNoData - Availability: 2.0.0 Returns true if the band is filled with only nodata values.
- ST_Clip - Availability: 2.0.0 Returns the raster clipped by the input geometry. If no band is specified all bands are returned. If crop is not specified, true is assumed meaning the output raster is cropped.
- ST_CollectionHomogenize - Availability: 2.0.0 Given a geometry collection, returns the "simplest" representation of the contents.
- ST_ConcaveHull - Availability: 2.0.0 The concave hull of a geometry represents a possibly concave geometry that encloses all geometries within the set. You can think of it as shrink wrapping.
- ST_Count - Availability: 2.0.0 Returns the number of pixels in a given band of a raster or raster coverage. If no band is specified defaults to band 1. If exclude_nodata_value is set to true, will only count pixels that are not equal to the nodata value.
- ST_CreateTopoGeo - Availability: 2.0 Adds a collection of geometries to a given empty topology and returns a message detailing success.
- ST_Distinct4ma - Availability: 2.0.0 Raster processing function that calculates the number of unique pixel values in a neighborhood.
- ST_FlipCoordinates - Availability: 2.0.0 Returns a version of the given geometry with X and Y axis flipped. Useful for people who have built latitude/longitude features and need to fix them.
- ST_GDALDrivers - Availability: 2.0.0 - requires GDAL >= 1.6.0. Returns a list of raster formats supported by your lib gdal. These are the formats you can output your raster using ST_AsGDALRaster.
- ST_GeomFromGeoJSON - Availability: 2.0.0 requires - JSON-C >= 0.9 Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object
- ST_GetFaceEdges - Availability: 2.0 Returns a set of ordered edges that bound aface includes the sequence order.
- ST_HasNoBand - Availability: 2.0.0 Returns true if there is no band with given band number. If no band number is specified, then band number 1 is assumed.
- ST_HillShade - Availability: 2.0.0 Returns the hypothetical illumination of an elevation raster band using provided azimuth, altitude, brightness and elevation scale inputs. Useful for visualizing terrain.
- ST_Histogram - Availability: 2.0.0 Returns a set of histogram summarizing a raster or raster coverage data distribution separate bin ranges. Number of bins are autocomputed if not specified.
- ST_InterpolatePoint - Availability: 2.0.0 Return the value of the measure dimension of a geometry at the point closed to the provided point.
- ST_IsValidDetail - Availability: 2.0.0 - requires GEOS >= 3.3.0. Returns a valid_detail (valid,reason,location) row stating if a geometry is valid or not and if not valid, a reason why and a location where.
- ST_IsValidReason - Availability: 2.0 - requires GEOS >= 3.3.0 for the version taking flags. Returns text stating if a geometry is valid or not and if not valid, a reason why.
- ST_MakeLine - Availability: 2.0.0 - Support for linestring input elements was introduced Creates a Linestring from point or line geometries.
- ST_MakeValid - Availability: 2.0.0, requires GEOS-3.3.0 or higher. Attempts to make an invalid geometry valid w/out loosing vertices.
- ST_MapAlgebraExpr - Availability: 2.0.0 1 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the input raster band and of pixeltype provided. Band 1 is assumed if no band is specified.
- ST_MapAlgebraExpr - Availability: 2.0.0 2 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the two input raster bands and of pixeltype provided. band 1 of each raster is assumed if no band numbers are specified. The resulting raster will be aligned (scale, skew and pixel corners) on the grid defined by the first raster and have its extent defined by the "extenttype" parameter. Values for "extenttype" can be: INTERSECTION, UNION, FIRST, SECOND.
- ST_MapAlgebraFct - Availability: 2.0.0 1 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the input raster band and of pixeltype prodived. Band 1 is assumed if no band is specified.
- ST_MapAlgebraFct - Availability: 2.0.0 2 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the 2 input raster bands and of pixeltype prodived. Band 1 is assumed if no band is specified. Extent type defaults to INTERSECTION if not specified.
- ST_MapAlgebraFctNgb - Availability: 2.0.0 1-band version: Map Algebra Nearest Neighbor using user-defined PostgreSQL function. Return a raster which values are the result of a PLPGSQL user function involving a neighborhood of values from the input raster band.
- ST_Max4ma - Availability: 2.0.0 Raster processing function that calculates the maximum pixel value in a neighborhood.
- ST_Mean4ma - Availability: 2.0.0 Raster processing function that calculates the mean pixel value in a neighborhood.
- ST_Min4ma - Availability: 2.0.0 Raster processing function that calculates the minimum pixel value in a neighborhood.
- ST_ModEdgeHeal - Availability: 2.0 Heal two edges by deleting the node connecting them, modifying the first edgeand deleting the second edge. Returns the id of the deleted node.
- ST_NewEdgeHeal - Availability: 2.0 Heal two edges by deleting the node connecting them, deleting both edges,and replacing them with an edge whose direction is the same as the firstedge provided.
- ST_Node - Availability: 2.0.0 - requires GEOS >= 3.3.0. Node a set of linestrings.
- ST_NumPatches - Availability: 2.0.0 Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.
- ST_OffsetCurve - Availability: 2.0 - requires GEOS >= 3.2, improved with GEOS >= 3.3 Return an offset line at a given distance and side from an input line. Useful for computing parallel lines about a center line
- ST_PatchN - Availability: 2.0.0 Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Otherwise, return NULL.
- ST_Quantile - Availability: 2.0.0 Compute quantiles for a raster or raster table coverage in the context of the sample or population. Thus, a value could be examined to be at the raster's 25%, 50%, 75% percentile.
- ST_Range4ma - Availability: 2.0.0 Raster processing function that calculates the range of pixel values in a neighborhood.
- ST_Reclass - Availability: 2.0.0 Creates a new raster composed of band types reclassified from original. The nband is the band to be changed. If nband is not specified assumed to be 1. All other bands are returned unchanged. Use case: convert a 16BUI band to a 8BUI and so forth for simpler rendering as viewable formats.
- ST_RelateMatch - Availability: 2.0.0 - requires GEOS >= 3.3.0. Returns true if intersectionMattrixPattern1 implies intersectionMatrixPattern2
- ST_RemEdgeModFace - Availability: 2.0 Removes an edge and, if the removed edge separated two faces,delete one of the them and modify the other to take the space of both.
- ST_RemEdgeNewFace - Availability: 2.0 Removes an edge and, if the removed edge separated two faces,delete the original faces and replace them with a new face.
- ST_RemoveRepeatedPoints - Availability: 2.0.0 Returns a version of the given geometry with duplicated points removed.
- ST_Resample - Availability: 2.0.0 Requires GDAL 1.6.1+ Resample a raster using a specified resampling algorithm, new dimensions, an arbitrary grid corner and a set of raster georeferencing attributes defined or borrowed from another raster. New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_Rescale - Availability: 2.0.0 Requires GDAL 1.6.1+ Resample a raster by adjusting only its scale (or pixel size). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_Reskew - Availability: 2.0.0 Requires GDAL 1.6.1+ Resample a raster by adjusting only its skew (or rotation parameters). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_SameAlignment - Availability: 2.0.0 Returns true if rasters have same skew, scale, spatial ref and false if they don't with notice detailing issue.
- ST_SetBandIsNoData - Availability: 2.0.0 Sets the isnodata flag of the band to TRUE. You may want to call this function if ST_BandIsNoData(rast, band) != ST_BandIsNodata(rast, band, TRUE). This is, if the isnodata flag is dirty. Band 1 is assumed if no band is specified.
- ST_SharedPaths - Availability: 2.0.0 requires GEOS >= 3.3.0. Returns a collection containing paths shared by the two input linestrings/multilinestrings.
- ST_Slope - Availability: 2.0.0 Returns the surface slope of an elevation raster band. Useful for analyzing terrain.
- ST_Snap - Availability: 2.0.0 requires GEOS >= 3.3.0. Snap segments and vertices of input geometry to vertices of a reference geometry.
- ST_SnapToGrid - Availability: 2.0.0 Requires GDAL 1.6.1+ Resample a raster by snapping it to a grid. New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_Split - Availability: 2.0.0 Returns a collection of geometries resulting by splitting a geometry.
- ST_StdDev4ma - Availability: 2.0.0 Raster processing function that calculates the standard deviation of pixel values in a neighborhood.
- ST_Sum4ma - Availability: 2.0.0 Raster processing function that calculates the sum of all pixel values in a neighborhood.
- ST_SummaryStats - Availability: 2.0.0 Returns summary stats consisting of count,sum,mean,stddev,min,max for a given raster band of a raster or raster coverage. Band 1 is assumed is no band is specified.
- ST_Transform - Availability: 2.0.0 Requires GDAL 1.6.1+ Reprojects a raster in a known spatial reference system to another known spatial reference system using specified resampling algorithm. Options are NearestNeighbor, Bilinear, Cubic, CubicSpline, Lanczos defaulting to NearestNeighbor.
- ST_UnaryUnion - Availability: 2.0.0 - requires GEOS >= 3.3.0. Like ST_Union, but working at the geometry component level.
- ST_Union - Availability: 2.0.0 Returns the union of a set of raster tiles into a single raster composed of 1 band. If no band is specified for unioning, band num 1 is assumed. The resulting raster's extent is the extent of the whole set. In the case of intersection, the resulting value is defined by p_expression which is one of the following: LAST - the default when none is specified, MEAN, SUM, FIRST, MAX, MIN.
- ST_ValueCount - Availability: 2.0.0 Returns a set of records containing a pixel band value and count of the number of pixels in a given band of a raster (or a raster coverage) that have a given set of values. If no band is specified defaults to band 1. By default nodata value pixels are not counted. and all other values in the pixel are output and pixel band values are rounded to the nearest integer.
- TopoElementArray_Agg - Availability: 2.0.0 Returns a topoelementarray for a set of element_id, type arrays (topoelements)
- TopoGeo_AddLineString - Availability: 2.0.0 Adds a linestring to an existing topology using a tolerance and possibly splitting existing edges/faces.
- TopoGeo_AddPoint - Availability: 2.0.0 Adds a point to an existing topology using a tolerance and possibly splitting an existing edge.
- TopoGeo_AddPolygon - Availability: 2.0.0 Adds a polygon to an existing topology using a tolerance and possibly splitting existing edges/faces.
- TopologySummary - Availability: 2.0.0 Takes a topology name and provides summary totals of types of objects in topology
- Topology_Load_Tiger - Availability: 2.0.0 Loads a defined region of tiger data into a PostGIS Topology and transforming the tiger data to spatial reference of the topology and snapping to the precision tolerance of the topology.
- toTopoGeom - Availability: 2.0 Creates a new topo geometry from a simple geometry

The functions given below are PostGIS functions that are enhanced in PostGIS 2.0.

- AddGeometryColumn - Enhanced: 2.0.0 use_typmod argument introduced. Defaults to creating typmod geometry column instead of constraint-based.
- Box2D - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- Box3D - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- Geocode - Enhanced: 2.0.0 to support Tiger 2010 structured data and revised some logic to improve speed, accuracy of geocoding, and to offset point from centerline to side of street address is located on. New parameter max_results useful for specifying ot just return the best result.
- GeometryType - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- Populate_Geometry_Columns - Enhanced: 2.0.0 use_typmod optional argument was introduced that allows controlling if columns are created with typmodifiers or with check constraints.
- ST_Intersection - Enhanced: 2.0.0 - Intersection in the raster space was introduced. In earlier pre-2.0.0 versions, only intersection performed in vector space were supported.
- ST_Intersects - Enhanced: 2.0.0 support raster/raster intersects was introduced.
- ST_Value - Enhanced: 2.0.0 exclude_nodata_value optional argument was added.
- ST_3DExtent - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_Accum - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_Affine - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_Area - Enhanced: 2.0.0 - support for 2D polyhedral surfaces was introduced.
- ST_AsBinary - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_AsBinary - Enhanced: 2.0.0 support for higher coordinate dimensions was introduced.
- ST_AsBinary - Enhanced: 2.0.0 support for specifying endian with geography was introduced.
- ST_AsEWKB - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_AsEWKT - Enhanced: 2.0.0 support for Geography, Polyhedral surfaces, Triangles and TIN was introduced.
- ST_AsGML - Enhanced: 2.0.0 prefix support was introduced. Option 4 for GML3 was introduced to allow using LineString instead of Curve tag for lines. GML3 Support for Polyhedral surfaces and TINS was introduced. Option 32 was introduced to output the box.
- ST_AsKML - Enhanced: 2.0.0 - Add prefix namespace. Default is no prefix
- ST_Azimuth - Enhanced: 2.0.0 support for geography was introduced.
- ST_ChangeEdgeGeom - Enhanced: 2.0.0 adds topological consistency enforcement
- ST_Dimension - Enhanced: 2.0.0 support for Polyhedral surfaces and TINs was introduced. No longer throws an exception if given empty geometry.
- ST_Dump - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_DumpPoints - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_Expand - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_Extent - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_ForceRHR - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.
- ST_Force_2D - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.
- ST_Force_3D - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.
- ST_Force_3DZ - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.
- ST_Force_Collection - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.
- ST_GMLToSQL - Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.
- ST_GMLToSQL - Enhanced: 2.0.0 default srid optional parameter added.
- ST_GeomFromEWKB - Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.
- ST_GeomFromEWKT - Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.
- ST_GeomFromGML - Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.
- ST_GeomFromGML - Enhanced: 2.0.0 default srid optional parameter added.
- ST_GeometryN - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_GeometryType - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.
- ST_IsClosed - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.
- ST_MakeEnvelope - Enhanced: 2.0: Ability to specify an envelope without specifying an SRID was introduced.
- ST_NPoints - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.
- ST_NumGeometries - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_Relate - Enhanced: 2.0.0 - added support for specifying boundary node rule (requires GEOS >= 3.0).
- ST_Rotate - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_Rotate - Enhanced: 2.0.0 additional parameters for specifying the origin of rotation were added.
- ST_RotateX - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_RotateY - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_RotateZ - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_Scale - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
- ST_Shift_Longitude - Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.
- ST_Transform - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.
- ValidateTopology - Enhanced: 2.0.0 more efficient edge crossing detection and fixes for false positives that were existent in prior versions.
- && - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

### 13.11.2. PostGIS Functions changed behavior in 2.0

The functions given below are PostGIS functions that have changed behavior in PostGIS 2.0 and may require application changes.

Most deprecated functions have been removed. These are functions that haven't been documented since 1.2 or some internal functions that were never documented. If you are using a function that you don't see documented, it's probably deprecated, about to be deprecated, or internal and should be avoided. If you have applications or tools that rely on deprecated functions, please refer to ??? for more details.

Bounding boxes of geometries have been changed from float4 to double precision (float8). This has an impact on answers you get using bounding box operators and casting of bounding boxes to geometries. E.g ST_SetSRID(abbox) will often return a different more accurate answer in PostGIS 2.0+ than it did in prior versions which may very well slightly change answers to view port queries.

The arguments hasnodata was replaced with exclude_nodata_value which has the same meaning as the older hasnodata but clearer in purpose.

- AddGeometryColumn - Changed: 2.0.0 This function no longer updates geometry_columns since geometry_columns is a view that reads from system catalogs. It by default also does not create constraints, but instead uses the built in type modifier behavior of PostgreSQL. So for example building a wgs84 POINT column with this function is now equivalent to: ALTER TABLE some_table ADD COLUMN geom geometry(Point,4326);
- AddGeometryColumn - Changed: 2.0.0 If you require the old behavior of constraints use the default use_typmod, but set it to false.
- AddGeometryColumn - Changed: 2.0.0 Views can no longer be manually registered in geometry_columns, however views built against geometry typmod tables geometries and used without wrapper functions will register themselves correctly because they inherit the typmod behavior of their parent table column. Views that use geometry functions that output other geometries will need to be cast to typmod geometries for these view geometry columns to be registered correctly in geometry_columns. Refer to .
- DropGeometryColumn - Changed: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a view against the system catalogs, you can drop a geometry column like any other table column using ALTER TABLE
- DropGeometryTable - Changed: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a view against the system catalogs, you can drop a table with geometry columns like any other table using DROP TABLE
- Populate_Geometry_Columns - Changed: 2.0.0 By default, now uses type modifiers instead of check constraints to constrain geometry types. You can still use check constraint behavior instead by using the new use_typmod and setting it to false.
- Box3D - Changed: 2.0.0 In pre-2.0 versions, there used to be a box2d instead of box3d. Since box2d is a deprecated type, this was changed to box3d.
- ST_ScaleX - Changed: 2.0.0. In WKTRaster versions this was called ST_PixelSizeX.
- ST_ScaleY - Changed: 2.0.0. In WKTRaster versions this was called ST_PixelSizeY.
- ST_SetScale - Changed: 2.0.0 In WKTRaster versions this was called ST_SetPixelSize. This was changed in 2.0.0.
- ST_3DExtent - Changed: 2.0.0 In prior versions this used to be called ST_Extent3D
- ST_3DLength - Changed: 2.0.0 In prior versions this used to be called ST_Length3D
- ST_3DLength_Spheroid - Changed: 2.0.0 In prior versions this used to return 0 for anything that is not a MULTILINESTRING or LINESTRING and in 2.0.0 on returns the perimeter of if given a polgon.
- ST_3DLength_Spheroid - Changed: 2.0.0 In prior versions this used to be called ST_Length3d_Spheroid
- ST_3DMakeBox - Changed: 2.0.0 In prior versions this used to be called ST_MakeBox3D
- ST_3DPerimeter - Changed: 2.0.0 In prior versions this used to be called ST_Perimeter3D
- ST_AsGML - Changed: 2.0.0 use default named args
- ST_AsGeoJSON - Changed: 2.0.0 support default args and named args.
- ST_AsKML - Changed: 2.0.0 - uses default args and supports named args
- ST_AsSVG - Changed: 2.0.0 to use default args and support named args
- ST_EndPoint - Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring. The older behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0 now.
- ST_GeomFromText - Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards. This should now be written as ST_GeomFromText('GEOMETRYCOLLECTION EMPTY')
- ST_GeometryN - Changed: 2.0.0 Prior versions would return NULL for singular geometries. This was changed to return the geometry for ST_GeometryN(..,1) case.
- ST_IsEmpty - Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards
- ST_Length - Changed: 2.0.0 Breaking change -- in prior versions applying this to a MULTI/POLYGON of type geography would give you the perimeter of the POLYGON/MULTIPOLYGON. In 2.0.0 this was changed to return 0 to be in line with geometry behavior. Please use ST_Perimeter if you want the perimeter of a polygon
- ST_LocateAlong - Changed: 2.0.0 in prior versions this used to be called ST_Locate_Along_Measure. The old name has been deprecated and will be removed in the future but is still available.
- ST_LocateBetween - Changed: 2.0.0 - in prior versions this used to be called ST_Locate_Between_Measures. The old name has been deprecated and will be removed in the future but is still available for backward compatibility.
- ST_ModEdgeSplit - Changed: 2.0 - In prior versions, this was misnamed ST_ModEdgesSplit
- ST_NumGeometries - Changed: 2.0.0 In prior versions this would return NULL if the geometry was not a collection/MULTI type. 2.0.0+ now returns 1 for single geometries e.g POLYGON, LINESTRING, POINT.
- ST_StartPoint - Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring. The older behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0 now.

### 13.11.3. PostGIS Functions new, behavior changed, or enhanced in 1.5

The functions given below are PostGIS functions that were introduced or enhanced in this minor release.

- PostGIS_LibXML_Version - Availability: 1.5 Returns the version number of the libxml2 library.
- ST_AddMeasure - Availability: 1.5.0 Return a derived geometry with measure elements linearly interpolated between the start and end points. If the geometry has no measure dimension, one is added. If the geometry has a measure dimension, it is over-written with new values. Only LINESTRINGS and MULTILINESTRINGS are supported.
- ST_AsBinary - Availability: 1.5.0 geography support was introduced. Return the Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsGML - Availability: 1.5.0 geography support was introduced. Return the geometry as a GML version 2 or 3 element.
- ST_AsGeoJSON - Availability: 1.5.0 geography support was introduced. Return the geometry as a GeoJSON element.
- ST_AsText - Availability: 1.5 - support for geography was introduced. Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.
- ST_Buffer - Availability: 1.5 - ST_Buffer was enhanced to support different endcaps and join types. These are useful for example to convert road linestrings into polygon roads with flat or square edges instead of rounded edges. Thin wrapper for geography was added. - requires GEOS >= 3.2 to take advantage of advanced geometry functionality. (T) For geometry: Returns a geometry that represents all points whose distance from this Geometry is less than or equal to distance. Calculations are in the Spatial Reference System of this Geometry. For geography: Uses a planar transform wrapper. Introduced in 1.5 support for different end cap and mitre settings to control shape. buffer_style options: quad_segs=#,endcap=round|flat|square,join=round|mitre|bevel,mitre_limit=#.#
- ST_ClosestPoint - Availability: 1.5.0 Returns the 2-dimensional point on g1 that is closest to g2. This is the first point of the shortest line.
- ST_CollectionExtract - Availability: 1.5.0 Given a (multi)geometry, returns a (multi)geometry consisting only of elements of the specified type.
- ST_Covers - Availability: 1.5 - support for geography was introduced. Returns 1 (TRUE) if no point in Geometry B is outside Geometry A
- ST_DFullyWithin - Availability: 1.5.0 Returns true if all of the geometries are within the specified distance of one another
- ST_DWithin - Availability: 1.5.0 support for geography was introduced Returns true if the geometries are within the specified distance of one another. For geometry units are in those of spatial reference and For geography units are in meters and measurement is defaulted to use_spheroid=true (measure around spheroid), for faster check, use_spheroid=false to measure along sphere.
- ST_Distance - Availability: 1.5.0 geography support was introduced in 1.5. Speed improvements for planar to better handle large or many vertex geometries For geometry type Returns the 2-dimensional cartesian minimum distance (based on spatial ref) between two geometries in projected units. For geography type defaults to return spheroidal minimum distance between two geographies in meters.
- ST_Distance_Sphere - Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points. Returns minimum distance in meters between two lon/lat geometries. Uses a spherical earth and radius of 6370986 meters. Faster than ST_Distance_Spheroid , but less accurate. PostGIS versions prior to 1.5 only implemented for points.
- ST_Distance_Spheroid - Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points. Returns the minimum distance between two lon/lat geometries given a particular spheroid. PostGIS versions prior to 1.5 only support points.
- ST_DumpPoints - Availability: 1.5.0 Returns a set of geometry_dump (geom,path) rows of all points that make up a geometry.
- ST_Envelope - Availability: 1.5.0 behavior changed to output double precision instead of float4 Returns a geometry representing the double precision (float8) bounding box of the supplied geometry.
- ST_GMLToSQL - Availability: 1.5, requires libxml2 1.6+ Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML
- ST_GeomFromGML - Availability: 1.5, requires libxml2 1.6+ Takes as input GML representation of geometry and outputs a PostGIS geometry object
- ST_GeomFromKML - Availability: 1.5,libxml2 2.6+ Takes as input KML representation of geometry and outputs a PostGIS geometry object
- ~= - Availability: 1.5.0 changed behavior Returns TRUE if A's bounding box is the same as B's.
- ST_HausdorffDistance - Availability: 1.5.0 - requires GEOS >= 3.2.0 Returns the Hausdorff distance between two geometries. Basically a measure of how similar or dissimilar 2 geometries are. Units are in the units of the spatial reference system of the geometries.
- ST_Intersection - Availability: 1.5 support for geography data type was introduced. (T) Returns a geometry that represents the shared portion of geomA and geomB. The geography implementation does a transform to geometry to do the intersection and then transform back to WGS84.
- ST_Intersects - Availability: 1.5 support for geography was introduced. Returns TRUE if the Geometries/Geography "spatially intersect in 2D" - (share any portion of space) and FALSE if they don't (they are Disjoint). For geography -- tolerance is 0.00001 meters (so any points that close are considered to intersect)
- ST_Length - Availability: 1.5.0 geography support was introduced in 1.5. Returns the 2d length of the geometry if it is a linestring or multilinestring. geometry are in units of spatial reference and geography are in meters (default spheroid)
- ST_LongestLine - Availability: 1.5.0 Returns the 2-dimensional longest line points of two geometries. The function will only return the first longest line if more than one, that the function finds. The line returned will always start in g1 and end in g2. The length of the line this function returns will always be the same as st_maxdistance returns for g1 and g2.
- ST_MakeEnvelope - Availability: 1.5 Creates a rectangular Polygon formed from the given minimums and maximums. Input values must be in SRS specified by the SRID.
- ST_MaxDistance - Availability: 1.5.0 Returns the 2-dimensional largest distance between two geometries in projected units.
- ST_ShortestLine - Availability: 1.5.0 Returns the 2-dimensional shortest line between two geometries
- && - Availability: 1.5.0 support for geography was introduced. Returns TRUE if A's 2D bounding box intersects B's 2D bounding box.

### 13.11.4. PostGIS Functions new, behavior changed, or enhanced in 1.4

The functions given below are PostGIS functions that were introduced or enhanced in the 1.4 release.

- Populate_Geometry_Columns - Ensures geometry columns are defined with type modifiers or have appropriate spatial constraints This ensures they will be registered correctly in geometry_columns view. By default will convert all geometry columns with no type modifier to ones with type modifiers. To get old behavior set use_typmod=false Availability: 1.4.0
- ST_AsSVG - Returns a Geometry in SVG path data given a geometry or geography object. Availability: 1.2.2. Availability: 1.4.0 Changed in PostGIS 1.4.0 to include L command in absolute path to conform to http://www.w3.org/TR/SVG/paths.html#PathDataBNF
- ST_Collect - Return a specified ST_Geometry value from a collection of other geometries. Availability: 1.4.0 - ST_Collect(geomarray) was introduced. ST_Collect was enhanced to handle more geometries faster.
- ST_ContainsProperly - Returns true if B intersects the interior of A but not the boundary (or exterior). A does not contain properly itself, but does contain itself. Availability: 1.4.0 - requires GEOS >= 3.1.0.
- ST_Extent - an aggregate function that returns the bounding box that bounds rows of geometries. Availability: 1.4.0
- ST_GeoHash - Return a GeoHash representation (geohash.org) of the geometry. Availability: 1.4.0
- ST_IsValidReason - Returns text stating if a geometry is valid or not and if not valid, a reason why. Availability: 1.4 - requires GEOS >= 3.1.0.
- ST_LineCrossingDirection - Given 2 linestrings, returns a number between -3 and 3 denoting what kind of crossing behavior. 0 is no crossing. Availability: 1.4
- ST_LocateBetweenElevations - Return a derived geometry (collection) value with elements that intersect the specified range of elevations inclusively. Only 3D, 4D LINESTRINGS and MULTILINESTRINGS are supported. Availability: 1.4.0
- ST_MakeLine - Creates a Linestring from point or line geometries. Availability: 1.4.0 - ST_MakeLine(geomarray) was introduced. ST_MakeLine aggregate functions was enhanced to handle more points faster.
- ST_MinimumBoundingCircle - Returns the smallest circle polygon that can fully contain a geometry. Default uses 48 segments per quarter circle. Availability: 1.4.0 - requires GEOS
- ST_Union - Returns a geometry that represents the point set union of the Geometries. Availability: 1.4.0 - ST_Union was enhanced. ST_Union(geomarray) was introduced and also faster aggregate collection in PostgreSQL. If you are using GEOS 3.1.0+ ST_Union will use the faster Cascaded Union algorithm described in http://blog.cleverelephant.ca/2009/01/must-faster-unions-in-postgis-14.html

### 13.11.5. PostGIS Functions new in 1.3

The functions given below are PostGIS functions that were introduced in the 1.3 release.

- ST_AsGML - Return the geometry as a GML version 2 or 3 element. Availability: 1.3.2
- ST_AsGeoJSON - Return the geometry as a GeoJSON element. Availability: 1.3.4
- ST_SimplifyPreserveTopology - Returns a "simplified" version of the given geometry using the Douglas-Peucker algorithm. Will avoid creating derived geometries (polygons in particular) that are invalid. Availability: 1.3.3

## Chapter 14. Reporting Problems

## 14.1. Reporting Software Bugs

Reporting bugs effectively is a fundamental way to help PostGIS development. The most effective bug report is that enabling PostGIS developers to reproduce it, so it would ideally contain a script triggering it and every information regarding the environment in which it was detected. Good enough info can be extracted running `SELECT postgis_full_version()` [for postgis] and `SELECT version()` [for postgresql].

If you aren't using the latest release, it's worth taking a look at its release changelog first, to find out if your bug has already been fixed.

Using the PostGIS bug tracker will ensure your reports are not discarded, and will keep you informed on its handling process. Before reporting a new bug please query the database to see if it is a known one, and if it is please add any new information you have about it.

You might want to read Simon Tatham's paper about How to Report Bugs Effectively before filing a new report.

## 14.2. Reporting Documentation Issues

The documentation should accurately reflect the features and behavior of the software. If it doesn't, it could be because of a software bug or because the documentation is in error or deficient.

Documentation issues can also be reported to the PostGIS bug tracker.

If your revision is trivial, just describe it in a new bug tracker issue, being specific about its location in the documentation.

If your changes are more extensive, a Subversion patch is definitely preferred. This is a four step process on Unix (assuming you already have Subversion installed):

1. Check out a copy of PostGIS' Subversion trunk. On Unix, type:

   svn checkout http://svn.osgeo.org/postgis/trunk/

   This will be stored in the directory ./trunk

2. Make your changes to the documentation with your favorite text editor. On Unix, type (for example):

   vim trunk/doc/postgis.xml

   Note that the documentation is written in DocBook XML rather than HTML, so if you are not familiar with it please follow the example of the rest of the documentation.

3. Make a patch file containing the differences from the master copy of the documentation. On Unix, type:

   svn diff trunk/doc/postgis.xml > doc.patch

4. Attach the patch to a new issue in bug tracker.

## Appendix A. Appendix

### Release Notes

## A.1. Release 2.0.1

Release date: 2012/06/22

This is a bug fix release, addressing issues that have been filed since the 2.0.0 release.

### Bug Fixes

#1264, fix st_dwithin(geog, geog, 0).

#1468 shp2pgsql-gui table column schema get shifted

#1694, fix building with clang. (vince)

#1708, improve restore of pre-PostGIS 2.0 backups.

#1714, more robust handling of high topology tolerance.

#1755, ST_GeographyFromText support for higher dimensions.

#1759, loading transformed shapefiles in raster enabled db.

#1761, handling of subdatasets in NetCDF, HDF4 and HDF5 in raster2pgsql.

#1763, topology.toTopoGeom use with custom search_path.

#1766, don't let ST_RemEdge* destroy peripheral TopoGeometry objects.

#1774, Clearer error on setting an edge geometry to an invalid one.

#1775, ST_ChangeEdgeGeom collision detection with 2-vertex target.

#1776, fix ST_SymDifference(empty, geom) to return geom.

#1779, install SQL comment files.

#1782, fix spatial reference string handling in raster.

#1789, fix false edge-node crossing report in ValidateTopology.

#1790, fix toTopoGeom handling of duplicated primitives.

#1791, fix ST_Azimuth with very close but distinct points.

#1797, fix (ValidateTopology(xxx)).* syntax calls.

#1805, put back the 900913 SRID entry.

#1813, Only show readable relations in metadata tables.

#1819, fix floating point issues with ST_World2RasterCoord and ST_Raster2WorldCoord variants.

#1820 compilation on 9.2beta1.

#1822, topology load on PostgreSQL 9.2beta1.

#1825, fix prepared geometry cache lookup

#1829, fix uninitialized read in GeoJSON parser

#1834, revise postgis extension to only backup user specified spatial_ref_sys

#1839, handling of subdatasets in GeoTIFF in raster2pgsql.

#1840, fix logic of when to compute # of tiles in raster2pgsql.

#1851, fix spatial_ref_system parameters for EPSG:3844

#1857, fix failure to detect endpoint mismatch in ST_AddEdge*Face*

#1865, data loss in postgis_restore.pl when data rows have leading dashes.

#1867, catch invalid topology name passed to topogeo_add*

#1872, fix ST_ApproxSummarystats to prevent division by zero

#1873, fix ptarray_locate_point to return interpolated Z/M values for on-the-line case

#1875, ST_SummaryStats returns NULL for all parameters except count when count is zero

### Enhancements

More detailed exception message from topology editing functions.

#1786, improved build dependencies

#1806, speedup of ST_BuildArea, ST_MakeValid and ST_GetFaceGeometry.

#1812, Add lwgeom_normalize in LIBLWGEOM for more stable testing.

## A.2. Release 2.0.0

Release date: 2012/04/03

This is a major release. A hard upgrade is required. Yes this means a full dump reload and some special preparations if you are using obsolete functions. Refer to Section 2.9.2, “Hard upgrade” for details on upgrading. Refer to Section 13.11.1, “PostGIS Functions new, behavior changed, or enhanced in 2.0” for more details and changed/new functions.

### Testers - Our unsung heroes

We are most indebted to the numerous members in the PostGIS community who were brave enough to test out the new features in this release. No major release can be successful without these folk.

Below are those who have been most valiant, provided very detailed and thorough bug reports, and detailed analysis.

Andrea Peri - Lots of testing on topology, checking for correctness
Andreas Forø Tollefsen - raster testing
Chris English - topology stress testing loader functions
Salvatore Larosa - topology robustness testing
Brian Hamlin - Benchmarking (also experimental experimental branches before they are folded into core) , general testing of various pieces including Tiger and Topology. Testing on various server VMs
Mike Pease - Tiger geocoder testing - very detailed reports of issues
Tom van Tilburg - raster testing

### Important / Breaking Changes

#722, #302, Most deprecated functions removed (over 250 functions) (Regina Obe, Paul Ramsey)

Unknown SRID changed from -1 to 0. (Paul Ramsey)

-- (most deprecated in 1.2) removed non-ST variants buffer, length, intersects (and internal functions renamed) etc.

-- If you have been using deprecated functions CHANGE your apps or suffer the consequences. If you don't see a function documented -- it ain't supported or it is an internal function. Some constraints in older tables were built with deprecated functions. If you restore you may need to rebuild table constraints with populate_geometry_columns(). If you have applications or tools that rely on deprecated functions, please refer to ??? for more details.

#944 geometry_columns is now a view instead of a table (Paul Ramsey, Regina Obe) for tables created the old way reads (srid, type, dims) constraints for geometry columns created with type modifiers reads rom column definition

#1081, #1082, #1084, #1088 - Mangement functions support typmod geometry column creation functions now default to typmod creation (Regina Obe)

#1083 probe_geometry_columns(), rename_geometry_table_constraints(), fix_geometry_columns(); removed - now obsolete with geometry_column view (Regina Obe)

#817 Renaming old 3D functions to the convention ST_3D (Nicklas Avén)

#548 (sorta), ST_NumGeometries,ST_GeometryN now returns 1 (or the geometry) instead of null for single geometries (Sandro Santilli, Maxime van Noppen)

### New Features

KNN Gist index based centroid (<->) and box (<#>) distance operators (Paul Ramsey / funded by Vizzuality)

Support for TIN and PolyHedralSurface and enhancement of many functions to support 3D (Olivier Courtin / Oslandia)

Raster support integrated and documented (Pierre Racine, Jorge Arévalo, Mateusz Loskot, Sandro Santilli, David Zwarg, Regina Obe, Bborie Park) (Company developer and funding: University Laval, Deimos Space, CadCorp, Michigan Tech Research Institute, Azavea, Paragon Corporation, UC Davis Center for Vectorborne Diseases)

Making spatial indexes 3D aware - in progress (Paul Ramsey, Mark Cave-Ayland)

Topology support improved (more functions), documented, testing (Sandro Santilli / Faunalia for RT-SIGTA), Andrea Peri, Regina Obe, Jose Carlos Martinez Llari

3D relationship and measurement support functions (Nicklas Avén)

ST_3DDistance, ST_3DClosestPoint, ST_3DIntersects, ST_3DShortestLine and more...

N-Dimensional spatial indexes (Paul Ramsey / OpenGeo)

ST_Split (Sandro Santilli / Faunalia for RT-SIGTA)

ST_IsValidDetail (Sandro Santilli / Faunalia for RT-SIGTA)

ST_MakeValid (Sandro Santilli / Faunalia for RT-SIGTA)

ST_RemoveRepeatedPoints (Sandro Santilli / Faunalia for RT-SIGTA)

ST_GeometryN and ST_NumGeometries support for non-collections (Sandro Santilli)

ST_IsCollection (Sandro Santilli, Maxime van Noppen)

ST_SharedPaths (Sandro Santilli / Faunalia for RT-SIGTA)

ST_Snap (Sandro Santilli)

ST_RelateMatch (Sandro Santilli / Faunalia for RT-SIGTA)

ST_ConcaveHull (Regina Obe and Leo Hsu / Paragon Corporation)

ST_UnaryUnion (Sandro Santilli / Faunalia for RT-SIGTA)

ST_AsX3D (Regina Obe / Arrival 3D funding)

ST_OffsetCurve (Sandro Santilli, Rafal Magda)

ST_GeomFromGeoJSON (Kashif Rasul, Paul Ramsey / Vizzuality funding)

### Enhancements

Made shape file loader tolerant of truncated multibyte values found in some free worldwide shapefiles (Sandro Santilli)

Lots of bug fixes and enhancements to shp2pgsql Beefing up regression tests for loaders Reproject support for both geometry and geography during import (Jeff Adams / Azavea, Mark Cave-Ayland)

pgsql2shp conversion from predefined list (Loic Dachary / Mark Cave-Ayland)

Shp-pgsql GUI loader - support loading multiple files at a time. (Mark Leslie)

Extras - upgraded tiger_geocoder from using old TIGER format to use new TIGER shp and file structure format (Stephen Frost)

Extras - revised tiger_geocoder to work with TIGER census 2010 data, addition of reverse geocoder function, various bug fixes, accuracy enhancements, limit max result return, speed improvements, loading routines. (Regina Obe, Leo Hsu / Paragon Corporation / funding provided by Hunter Systems Group)

Overall Documentation proofreading and corrections. (Kasif Rasul)

Cleanup PostGIS JDBC classes, revise to use Maven build. (Maria Arias de Reyna, Sandro Santilli)

### Bug Fixes

#1335 ST_AddPoint returns incorrect result on Linux (Even Rouault)

### Release specific credits

We thank U.S Department of State Human Information Unit (HIU) and Vizzuality for general monetary support to get PostGIS 2.0 out the door.

## A.3. Release 1.5.4

Release date: 2012/05/07

This is a bug fix release, addressing issues that have been filed since the 1.5.3 release.

### Bug Fixes

#547, ST_Contains memory problems (Sandro Santilli)

#621, Problem finding intersections with geography (Paul Ramsey)

#627, PostGIS/PostgreSQL process die on invalid geometry (Paul Ramsey)

#810, Increase accuracy of area calculation (Paul Ramsey)

#852, improve spatial predicates robustness (Sandro Santilli, Nicklas Avén)

#877, ST_Estimated_Extent returns NULL on empty tables (Sandro Santilli)

#1028, ST_AsSVG kills whole postgres server when fails (Paul Ramsey)

#1056, Fix boxes of arcs and circle stroking code (Paul Ramsey)

#1121, populate_geometry_columns using deprecated functions (Regin Obe, Paul Ramsey)

#1135, improve testsuite predictability (Andreas 'ads' Scherbaum)

#1146, images generator crashes (bronaugh)

#1170, North Pole intersection fails (Paul Ramsey)

#1179, ST_AsText crash with bad value (kjurka)

#1184, honour DESTDIR in documentation Makefile (Bryce L Nordgren)

#1227, server crash on invalid GML

#1252, SRID appearing in WKT (Paul Ramsey)

#1264, st_dwithin(g, g, 0) doesn't work (Paul Ramsey)

#1344, allow exporting tables with invalid geometries (Sandro Santilli)

#1389, wrong proj4text for SRID 31300 and 31370 (Paul Ramsey)

#1406, shp2pgsql crashes when loading into geography (Sandro Santilli)

#1595, fixed SRID redundancy in ST_Line_SubString (Sandro Santilli)

#1596, check SRID in UpdateGeometrySRID (Mike Toews, Sandro Santilli)

#1602, fix ST_Polygonize to retain Z (Sandro Santilli)

#1697, fix crash with EMPTY entries in GiST index (Paul Ramsey)

#1772, fix ST_Line_Locate_Point with collapsed input (Sandro Santilli)

#1799, Protect ST_Segmentize from max_length=0 (Sandro Santilli)

Alter parameter order in 900913 (Paul Ramsey)

Support builds with "gmake" (Greg Troxel)

## A.4. Release 1.5.3

Release date: 2011/06/25

This is a bug fix release, addressing issues that have been filed since the 1.5.2 release. If you are running PostGIS 1.3+, a soft upgrade is sufficient otherwise a hard upgrade is recommended.

### Bug Fixes

#1056, produce correct bboxes for arc geometries, fixes index errors (Paul Ramsey)

#1007, ST_IsValid crash fix requires GEOS 3.3.0+ or 3.2.3+ (Sandro Santilli, reported by Birgit Laggner)

#940, support for PostgreSQL 9.1 beta 1 (Regina Obe, Paul Ramsey, patch submitted by stl)

#845, ST_Intersects precision error (Sandro Santilli, Nicklas Avén) Reported by cdestigter

#884, Unstable results with ST_Within, ST_Intersects (Chris Hodgson)

#779, shp2pgsql -S option seems to fail on points (Jeff Adams)

#666, ST_DumpPoints is not null safe (Regina Obe)

#631, Update NZ projections for grid transformation support (jpalmer)

#630, Peculiar Null treatment in arrays in ST_Collect (Chris Hodgson) Reported by David Bitner

#624, Memory leak in ST_GeogFromText (ryang, Paul Ramsey)

#609, Bad source code in manual section 5.2 Java Clients (simoc, Regina Obe)

#604, shp2pgsql usage touchups (Mike Toews, Paul Ramsey)

#573 ST_Union fails on a group of linestrings Not a PostGIS bug, fixed in GEOS 3.3.0

#457 ST_CollectionExtract returns non-requested type (Nicklas Avén, Paul Ramsey)

#441 ST_AsGeoJson Bbox on GeometryCollection error (Olivier Courtin)

#411 Ability to backup invalid geometries (Sando Santilli) Reported by Regione Toscana

#409 ST_AsSVG - degraded (Olivier Courtin) Reported by Sdikiy

#373 Documentation syntax error in hard upgrade (Paul Ramsey) Reported by psvensso

## A.5. Release 1.5.2

Release date: 2010/09/27

This is a bug fix release, addressing issues that have been filed since the 1.5.1 release. If you are running PostGIS 1.3+, a soft upgrade is sufficient otherwise a hard upgrade is recommended.

### Bug Fixes

Loader: fix handling of empty (0-verticed) geometries in shapefiles. (Sandro Santilli)

#536, Geography ST_Intersects, ST_Covers, ST_CoveredBy and Geometry ST_Equals not using spatial index (Regina Obe, Nicklas Aven)

#573, Improvement to ST_Contains geography (Paul Ramsey)

Loader: Add support for command-q shutdown in Mac GTK build (Paul Ramsey)

#393, Loader: Add temporary patch for large DBF files (Maxime Guillaud, Paul Ramsey)

#507, Fix wrong OGC URN in GeoJSON and GML output (Olivier Courtin)

spatial_ref_sys.sql Add datum conversion for projection SRID 3021 (Paul Ramsey)

Geography - remove crash for case when all geographies are out of the estimate (Paul Ramsey)

#469, Fix for array_aggregation error (Greg Stark, Paul Ramsey)

#532, Temporary geography tables showing up in other user sessions (Paul Ramsey)

#562, ST_Dwithin errors for large geographies (Paul Ramsey)

#513, shape loading GUI tries to make spatial index when loading DBF only mode (Paul Ramsey)

#527, shape loading GUI should always append log messages (Mark Cave-Ayland)

#504, shp2pgsql should rename xmin/xmax fields (Sandro Santilli)

#458, postgis_comments being installed in contrib instead of version folder (Mark Cave-Ayland)

#474, Analyzing a table with geography column crashes server (Paul Ramsey)

#581, LWGEOM-expand produces inconsistent results (Mark Cave-Ayland)

#513, Add dbf filter to shp2pgsql-gui and allow uploading dbf only (Paul Ramsey)

Fix further build issues against PostgreSQL 9.0 (Mark Cave-Ayland)

#572, Password whitespace for Shape File (Mark Cave-Ayland)

#603, shp2pgsql: "-w" produces invalid WKT for MULTI* objects. (Mark Cave-Ayland)

## A.6. Release 1.5.1

Release date: 2010/03/11

This is a bug fix release, addressing issues that have been filed since the 1.4.1 release. If you are running PostGIS 1.3+, a soft upgrade is sufficient otherwise a hard upgrade is recommended.

### Bug Fixes

#410, update embedded bbox when applying ST_SetPoint, ST_AddPoint ST_RemovePoint to a linestring (Paul Ramsey)

#411, allow dumping tables with invalid geometries (Sandro Santilli, for Regione Toscana-SIGTA)

#414, include geography_columns view when running upgrade scripts (Paul Ramsey)

#419, allow support for multilinestring in ST_Line_Substring (Paul Ramsey, for Lidwala Consulting Engineers)

#421, fix computed string length in ST_AsGML() (Olivier Courtin)

#441, fix GML generation with heterogeneous collections (Olivier Courtin)

#443, incorrect coordinate reversal in GML 3 generation (Olivier Courtin)

#450, #451, wrong area calculation for geography features that cross the date line (Paul Ramsey)

Ensure support for upcoming 9.0 PgSQL release (Paul Ramsey)

## A.7. Release 1.5.0

Release date: 2010/02/04

This release provides support for geographic coordinates (lat/lon) via a new GEOGRAPHY type. Also performance enhancements, new input format support (GML,KML) and general upkeep.

### API Stability

The public API of PostGIS will not change during minor (0.0.X) releases.

The definition of the =~ operator has changed from an exact geometric equality check to a bounding box equality check.

### Compatibility

GEOS, Proj4, and LibXML2 are now mandatory dependencies

The library versions below are the minimum requirements for PostGIS 1.5

PostgreSQL 8.3 and higher on all platforms

GEOS 3.1 and higher only (GEOS 3.2+ to take advantage of all features)

LibXML2 2.5+ related to new ST_GeomFromGML/KML functionality

Proj4 4.5 and higher only

### New Features

Section 13.11.3, “PostGIS Functions new, behavior changed, or enhanced in 1.5”

Added Hausdorff distance calculations (#209) (Vincent Picavet)

Added parameters argument to ST_Buffer operation to support one-sided buffering and other buffering styles (Sandro Santilli)

Addition of other Distance related visualization and analysis functions (Nicklas Aven)

- ST_ClosestPoint

- ST_DFullyWithin

- ST_LongestLine

- ST_MaxDistance

- ST_ShortestLine

ST_DumpPoints (Maxime van Noppen)

KML, GML input via ST_GeomFromGML and ST_GeomFromKML (Olivier Courtin)

Extract homogeneous collection with ST_CollectionExtract (Paul Ramsey)

Add measure values to an existing linestring with ST_AddMeasure (Paul Ramsey)

History table implementation in utils (George Silva)

Geography type and supporting functions

- Spherical algorithms (Dave Skea)

- Object/index implementation (Paul Ramsey)

- Selectivity implementation (Mark Cave-Ayland)

- Serializations to KML, GML and JSON (Olivier Courtin)

- ST_Area, ST_Distance, ST_DWithin, ST_GeogFromText, ST_GeogFromWKB, ST_Intersects, ST_Covers, ST_Buffer (Paul Ramsey)

### Enhancements

Performance improvements to ST_Distance (Nicklas Aven)

Documentation updates and improvements (Regina Obe, Kevin Neufeld)

Testing and quality control (Regina Obe)

PostGIS 1.5 support PostgreSQL 8.5 trunk (Guillaume Lelarge)

Win32 support and improvement of core shp2pgsql-gui (Mark Cave-Ayland)

In place 'make check' support (Paul Ramsey)

### Bug fixes

http://trac.osgeo.org/postgis/query?status=closed&milestone=PostGIS+1.5.0&order=priority

## A.8. Release 1.4.0

Release date: 2009/07/24

This release provides performance enhancements, improved internal structures and testing, new features, and upgraded documentation. If you are running PostGIS 1.1+, a soft upgrade is sufficient otherwise a hard upgrade is recommended.

### API Stability

As of the 1.4 release series, the public API of PostGIS will not change during minor releases.

### Compatibility

The versions below are the *minimum* requirements for PostGIS 1.4

PostgreSQL 8.2 and higher on all platforms

GEOS 3.0 and higher only

PROJ4 4.5 and higher only

### New Features

ST_Union() uses high-speed cascaded union when compiled against GEOS 3.1+ (Paul Ramsey)

ST_ContainsProperly() requires GEOS 3.1+

ST_Intersects(), ST_Contains(), ST_Within() use high-speed cached prepared geometry against GEOS 3.1+ (Paul Ramsey / funded by Zonar Systems)

Vastly improved documentation and reference manual (Regina Obe & Kevin Neufeld)

Figures and diagram examples in the reference manual (Kevin Neufeld)

ST_IsValidReason() returns readable explanations for validity failures (Paul Ramsey)

ST_GeoHash() returns a geohash.org signature for geometries (Paul Ramsey)

GTK+ multi-platform GUI for shape file loading (Paul Ramsey)

ST_LineCrossingDirection() returns crossing directions (Paul Ramsey)

ST_LocateBetweenElevations() returns sub-string based on Z-ordinate. (Paul Ramsey)

Geometry parser returns explicit error message about location of syntax errors (Mark Cave-Ayland)

ST_AsGeoJSON() return JSON formatted geometry (Olivier Courtin)

Populate_Geometry_Columns() -- automatically add records to geometry_columns for TABLES and VIEWS (Kevin Neufeld)

ST_MinimumBoundingCircle() -- returns the smallest circle polygon that can encompass a geometry (Bruce Rindahl)

### Enhancements

Core geometry system moved into independent library, liblwgeom. (Mark Cave-Ayland)

New build system uses PostgreSQL "pgxs" build bootstrapper. (Mark Cave-Ayland)

Debugging framework formalized and simplified. (Mark Cave-Ayland)

All build-time #defines generated at configure time and placed in headers for easier cross-platform support (Mark Cave-Ayland)

Logging framework formalized and simplified (Mark Cave-Ayland)

Expanded and more stable support for CIRCULARSTRING, COMPOUNDCURVE and CURVEPOLYGON, better parsing, wider support in functions (Mark Leslie & Mark Cave-Ayland)

Improved support for OpenSolaris builds (Paul Ramsey)

Improved support for MSVC builds (Mateusz Loskot)

Updated KML support (Olivier Courtin)

Unit testing framework for liblwgeom (Paul Ramsey)

New testing framework to comprehensively exercise every PostGIS function (Regine Obe)

Performance improvements to all geometry aggregate functions (Paul Ramsey)

Support for the upcoming PostgreSQL 8.4 (Mark Cave-Ayland, Talha Bin Rizwan)

Shp2pgsql and pgsql2shp re-worked to depend on the common parsing/unparsing code in liblwgeom (Mark Cave-Ayland)

Use of PDF DbLatex to build PDF docs and preliminary instructions for build (Jean David Techer)

Automated User documentation build (PDF and HTML) and Developer Doxygen Documentation (Kevin Neufeld)

Automated build of document images using ImageMagick from WKT geometry text files (Kevin Neufeld)

More attractive CSS for HTML documentation (Dane Springmeyer)

### Bug fixes

http://trac.osgeo.org/postgis/query?status=closed&milestone=PostGIS+1.4.0&order=priority

## A.9. Release 1.3.6

Release date: 2009/05/04

If you are running PostGIS 1.1+, a soft upgrade is sufficient otherwise a hard upgrade is recommended. This release adds support for PostgreSQL 8.4, exporting prj files from the database with shape data, some crash fixes for shp2pgsql, and several small bug fixes in the handling of "curve" types, logical error importing dbf only files, improved error handling of AddGeometryColumns.

## A.10. Release 1.3.5

Release date: 2008/12/15

If you are running PostGIS 1.1+, a soft upgrade is sufficient otherwise a hard upgrade is recommended. This release is a bug fix release to address a failure in ST_Force_Collection and related functions that critically affects using MapServer with LINE layers.

## A.11. Release 1.3.4

Release date: 2008/11/24

This release adds support for GeoJSON output, building with PostgreSQL 8.4, improves documentation quality and output aesthetics, adds function-level SQL documentation, and improves performance for some spatial predicates (point-in-polygon tests).

Bug fixes include removal of crashers in handling circular strings for many functions, some memory leaks removed, a linear referencing failure for measures on vertices, and more. See the NEWS file for details.

## A.12. Release 1.3.3

Release date: 2008/04/12

This release fixes bugs shp2pgsql, adds enhancements to SVG and KML support, adds a ST_SimplifyPreserveTopology function, makes the build more sensitive to GEOS versions, and fixes a handful of severe but rare failure cases.

## A.13. Release 1.3.2

Release date: 2007/12/01

This release fixes bugs in ST_EndPoint() and ST_Envelope, improves support for JDBC building and OS/X, and adds better support for GML output with ST_AsGML(), including GML3 output.

## A.14. Release 1.3.1

Release date: 2007/08/13

This release fixes some oversights in the previous release around version numbering, documentation, and tagging.

## A.15. Release 1.3.0

Release date: 2007/08/09

This release provides performance enhancements to the relational functions, adds new relational functions and begins the migration of our function names to the SQL-MM convention, using the spatial type (SP) prefix.

### Added Functionality

JDBC: Added Hibernate Dialect (thanks to Norman Barker)

Added ST_Covers and ST_CoveredBy relational functions. Description and justification of these functions can be found at http://lin-ear-th-inking.blogspot.com/2007/06/subtleties-of-ogc-covers-spatial.html

Added ST_DWithin relational function.

### Performance Enhancements

Added cached and indexed point-in-polygon short-circuits for the functions ST_Contains, ST_Intersects, ST_Within and ST_Disjoint

Added inline index support for relational functions (except ST_Disjoint)

### Other Changes

Extended curved geometry support into the geometry accessor and some processing functions

Began migration of functions to the SQL-MM naming convention; using a spatial type (ST) prefix.

Added initial support for PostgreSQL 8.3

## A.16. Release 1.2.1

Release date: 2007/01/11

This release provides bug fixes in PostgreSQL 8.2 support and some small performance enhancements.

### Changes

Fixed point-in-polygon shortcut bug in Within().

Fixed PostgreSQL 8.2 NULL handling for indexes.

Updated RPM spec files.

Added short-circuit for Transform() in no-op case.

JDBC: Fixed JTS handling for multi-dimensional geometries (thanks to Thomas Marti for hint and partial patch). Additionally, now JavaDoc is compiled and packaged. Fixed classpath problems with GCJ. Fixed pgjdbc 8.2 compatibility, losing support for jdk 1.3 and older.

## A.17. Release 1.2.0

Release date: 2006/12/08

This release provides type definitions along with serialization/deserialization capabilities for SQL-MM defined curved geometries, as well as performance enhancements.

### Changes

Added curved geometry type support for serialization/deserialization

Added point-in-polygon shortcircuit to the Contains and Within functions to improve performance for these cases.

## A.18. Release 1.1.6

Release date: 2006/11/02

This is a bugfix release, in particular fixing a critical error with GEOS interface in 64bit systems. Includes an updated of the SRS parameters and an improvement in reprojections (take Z in consideration). Upgrade is encouraged.

### Upgrading

If you are upgrading from release 1.0.3 or later follow the soft upgrade procedure.

If you are upgrading from a release between 1.0.0RC6 and 1.0.2 (inclusive) and really want a live upgrade read the upgrade section of the 1.0.3 release notes chapter.

Upgrade from any release prior to 1.0.0RC6 requires an hard upgrade.

### Bug fixes

fixed CAPI change that broke 64-bit platforms

loader/dumper: fixed regression tests and usage output

Fixed setSRID() bug in JDBC, thanks to Thomas Marti

### Other changes

use Z ordinate in reprojections

spatial_ref_sys.sql updated to EPSG 6.11.1

Simplified Version.config infrastructure to use a single pack of version variables for everything.

Include the Version.config in loader/dumper USAGE messages

Replace hand-made, fragile JDBC version parser with Properties

## A.19. Release 1.1.5

Release date: 2006/10/13

This is an bugfix release, including a critical segfault on win32. Upgrade is encouraged.

### Upgrading

If you are upgrading from release 1.0.3 or later follow the soft upgrade procedure.

If you are upgrading from a release between 1.0.0RC6 and 1.0.2 (inclusive) and really want a live upgrade read the upgrade section of the 1.0.3 release notes chapter.

Upgrade from any release prior to 1.0.0RC6 requires an hard upgrade.

### Bug fixes

Fixed MingW link error that was causing pgsql2shp to segfault on Win32 when compiled for PostgreSQL 8.2

fixed nullpointer Exception in Geometry.equals() method in Java

Added EJB3Spatial.odt to fulfill the GPL requirement of distributing the "preferred form of modification"

Removed obsolete synchronization from JDBC Jts code.

Updated heavily outdated README files for shp2pgsql/pgsql2shp by merging them with the manpages.

Fixed version tag in jdbc code that still said "1.1.3" in the "1.1.4" release.

### New Features

Added -S option for non-multi geometries to shp2pgsql

## A.20. Release 1.1.4

Release date: 2006/09/27

This is an bugfix release including some improvements in the Java interface. Upgrade is encouraged.

### Upgrading

If you are upgrading from release 1.0.3 or later follow the soft upgrade procedure.

If you are upgrading from a release between 1.0.0RC6 and 1.0.2 (inclusive) and really want a live upgrade read the upgrade section of the 1.0.3 release notes chapter.

Upgrade from any release prior to 1.0.0RC6 requires an hard upgrade.

### Bug fixes

Fixed support for PostgreSQL 8.2

Fixed bug in collect() function discarding SRID of input

Added SRID match check in MakeBox2d and MakeBox3d

Fixed regress tests to pass with GEOS-3.0.0

Improved pgsql2shp run concurrency.

### Java changes

reworked JTS support to reflect new upstream JTS developers' attitude to SRID handling. Simplifies code and drops build depend on GNU trove.

Added EJB2 support generously donated by the "Geodetix s.r.l. Company" http://www.geodetix.it/

Added EJB3 tutorial / examples donated by Norman Barker <nbarker@ittvis.com>

Reorganized java directory layout a little.

## A.21. Release 1.1.3

Release date: 2006/06/30

This is an bugfix release including also some new functionalities (most notably long transaction support) and portability enhancements. Upgrade is encouraged.

### Upgrading

If you are upgrading from release 1.0.3 or later follow the soft upgrade procedure.

If you are upgrading from a release between 1.0.0RC6 and 1.0.2 (inclusive) and really want a live upgrade read the upgrade section of the 1.0.3 release notes chapter.

Upgrade from any release prior to 1.0.0RC6 requires an hard upgrade.

### Bug fixes / correctness

BUGFIX in distance(poly,poly) giving wrong results.

BUGFIX in pgsql2shp successful return code.

BUGFIX in shp2pgsql handling of MultiLine WKT.

BUGFIX in affine() failing to update bounding box.

WKT parser: forbidden construction of multigeometries with EMPTY elements (still supported for GEOMETRYCOLLECTION).

### New functionalities

NEW Long Transactions support.

NEW DumpRings() function.

NEW AsHEXEWKB(geom, XDR|NDR) function.

### JDBC changes

Improved regression tests: MultiPoint and scientific ordinates

Fixed some minor bugs in jdbc code

Added proper accessor functions for all fields in preparation of making those fields private later

### Other changes

NEW regress test support for loader/dumper.

Added --with-proj-libdir and --with-geos-libdir configure switches.

Support for build Tru64 build.

Use Jade for generating documentation.

Don't link pgsql2shp to more libs then required.

Initial support for PostgreSQL 8.2.

## A.22. Release 1.1.2

Release date: 2006/03/30

This is an bugfix release including some new functions and portability enhancements. Upgrade is encouraged.

### Upgrading

If you are upgrading from release 1.0.3 or later follow the soft upgrade procedure.

If you are upgrading from a release between 1.0.0RC6 and 1.0.2 (inclusive) and really want a live upgrade read the upgrade section of the 1.0.3 release notes chapter.

Upgrade from any release prior to 1.0.0RC6 requires an hard upgrade.

### Bug fixes

BUGFIX in SnapToGrid() computation of output bounding box

BUGFIX in EnforceRHR()

jdbc2 SRID handling fixes in JTS code

Fixed support for 64bit archs

### New functionalities

Regress tests can now be run *before* postgis installation

New affine() matrix transformation functions

New rotate{,X,Y,Z}() function

Old translating and scaling functions now use affine() internally

Embedded access control in estimated_extent() for builds against pgsql >= 8.0.0

### Other changes

More portable ./configure script

Changed ./run_test script to have more sane default behaviour

## A.23. Release 1.1.1

Release date: 2006/01/23

This is an important Bugfix release, upgrade is highly recommended. Previous version contained a bug in postgis_restore.pl preventing hard upgrade procedure to complete and a bug in GEOS-2.2+ connector preventing GeometryCollection objects to be used in topological operations.

### Upgrading

If you are upgrading from release 1.0.3 or later follow the soft upgrade procedure.

If you are upgrading from a release between 1.0.0RC6 and 1.0.2 (inclusive) and really want a live upgrade read the upgrade section of the 1.0.3 release notes chapter.

Upgrade from any release prior to 1.0.0RC6 requires an hard upgrade.

### Bug fixes

Fixed a premature exit in postgis_restore.pl

BUGFIX in geometrycollection handling of GEOS-CAPI connector

Solaris 2.7 and MingW support improvements

BUGFIX in line_locate_point()

Fixed handling of postgresql paths

BUGFIX in line_substring()

Added support for localized cluster in regress tester

### New functionalities

New Z and M interpolation in line_substring()

New Z and M interpolation in line_interpolate_point()

added NumInteriorRing() alias due to OpenGIS ambiguity

## A.24. Release 1.1.0

Release date: 2005/12/21

This is a Minor release, containing many improvements and new things. Most notably: build procedure greatly simplified; transform() performance drastically improved; more stable GEOS connectivity (CAPI support); lots of new functions; draft topology support.

It is highly recommended that you upgrade to GEOS-2.2.x before installing PostGIS, this will ensure future GEOS upgrades won't require a rebuild of the PostGIS library.

### Credits

This release includes code from Mark Cave Ayland for caching of proj4 objects. Markus Schaber added many improvements in his JDBC2 code. Alex Bodnaru helped with PostgreSQL source dependency relief and provided Debian specfiles. Michael Fuhr tested new things on Solaris arch. David Techer and Gerald Fenoy helped testing GEOS C-API connector. Hartmut Tschauner provided code for the azimuth() function. Devrim GUNDUZ provided RPM specfiles. Carl Anderson helped with the new area building functions. See the credits section for more names.

### Upgrading

If you are upgrading from release 1.0.3 or later you DO NOT need a dump/reload. Simply sourcing the new lwpostgis_upgrade.sql script in all your existing databases will work. See the soft upgrade chapter for more information.

If you are upgrading from a release between 1.0.0RC6 and 1.0.2 (inclusive) and really want a live upgrade read the upgrade section of the 1.0.3 release notes chapter.

Upgrade from any release prior to 1.0.0RC6 requires an hard upgrade.

### New functions

scale() and transscale() companion methods to translate()

line_substring()

line_locate_point()

M(point)

LineMerge(geometry)

shift_longitude(geometry)

azimuth(geometry)

locate_along_measure(geometry, float8)

locate_between_measures(geometry, float8, float8)

SnapToGrid by point offset (up to 4d support)

BuildArea(any_geometry)

OGC BdPolyFromText(linestring_wkt, srid)

OGC BdMPolyFromText(linestring_wkt, srid)

RemovePoint(linestring, offset)

ReplacePoint(linestring, offset, point)

### Bug fixes

Fixed memory leak in polygonize()

Fixed bug in lwgeom_as_anytype cast functions

Fixed USE_GEOS, USE_PROJ and USE_STATS elements of postgis_version() output to always reflect library state.

### Function semantic changes

SnapToGrid doesn't discard higher dimensions

Changed Z() function to return NULL if requested dimension is not available

### Performance improvements

Much faster transform() function, caching proj4 objects

Removed automatic call to fix_geometry_columns() in AddGeometryColumns() and update_geometry_stats()

### JDBC2 works

Makefile improvements

JTS support improvements

Improved regression test system

Basic consistency check method for geometry collections

Support for (Hex)(E)wkb

Autoprobing DriverWrapper for HexWKB / EWKT switching

fix compile problems in ValueSetter for ancient jdk releases.

fix EWKT constructors to accept SRID=4711; representation

added preliminary read-only support for java2d geometries

### Other new things

Full autoconf-based configuration, with PostgreSQL source dependency relief

GEOS C-API support (2.2.0 and higher)

Initial support for topology modelling

Debian and RPM specfiles

New lwpostgis_upgrade.sql script

### Other changes

JTS support improvements

Stricter mapping between DBF and SQL integer and string attributes

Wider and cleaner regression test suite

old jdbc code removed from release

obsoleted direct use of postgis_proc_upgrade.pl

scripts version unified with release version

## A.25. Release 1.0.6

Release date: 2005/12/06

Contains a few bug fixes and improvements.

### Upgrading

If you are upgrading from release 1.0.3 or later you DO NOT need a dump/reload.

If you are upgrading from a release between 1.0.0RC6 and 1.0.2 (inclusive) and really want a live upgrade read the upgrade section of the 1.0.3 release notes chapter.

Upgrade from any release prior to 1.0.0RC6 requires an hard upgrade.

### Bug fixes

Fixed palloc(0) call in collection deserializer (only gives problem with --enable-cassert)

Fixed bbox cache handling bugs

Fixed geom_accum(NULL, NULL) segfault

Fixed segfault in addPoint()

Fixed short-allocation in lwcollection_clone()

Fixed bug in segmentize()

Fixed bbox computation of SnapToGrid output

### Improvements

Initial support for postgresql 8.2

Added missing SRID mismatch checks in GEOS ops

## A.26. Release 1.0.5

Release date: 2005/11/25

Contains memory-alignment fixes in the library, a segfault fix in loader's handling of UTF8 attributes and a few improvements and cleanups.

Return code of shp2pgsql changed from previous releases to conform to unix standards (return 0 on success).

### Upgrading

If you are upgrading from release 1.0.3 or later you DO NOT need a dump/reload.

If you are upgrading from a release between 1.0.0RC6 and 1.0.2 (inclusive) and really want a live upgrade read the upgrade section of the 1.0.3 release notes chapter.

Upgrade from any release prior to 1.0.0RC6 requires an hard upgrade.

### Library changes

Fixed memory alignment problems

Fixed computation of null values fraction in analyzer

Fixed a small bug in the getPoint4d_p() low-level function

Speedup of serializer functions

Fixed a bug in force_3dm(), force_3dz() and force_4d()

### Loader changes

Fixed return code of shp2pgsql

Fixed back-compatibility issue in loader (load of null shapefiles)

Fixed handling of trailing dots in dbf numerical attributes

Segfault fix in shp2pgsql (utf8 encoding)

### Other changes

Schema aware postgis_proc_upgrade.pl, support for pgsql 7.2+

New "Reporting Bugs" chapter in manual

## A.27. Release 1.0.4

Release date: 2005/09/09

Contains important bug fixes and a few improvements. In particular, it fixes a memory leak preventing successful build of GiST indexes for large spatial tables.

### Upgrading

If you are upgrading from release 1.0.3 you DO NOT need a dump/reload.

If you are upgrading from a release between 1.0.0RC6 and 1.0.2 (inclusive) and really want a live upgrade read the upgrade section of the 1.0.3 release notes chapter.

Upgrade from any release prior to 1.0.0RC6 requires an hard upgrade.

### Bug fixes

Memory leak plugged in GiST indexing

Segfault fix in transform() handling of proj4 errors

Fixed some proj4 texts in spatial_ref_sys (missing +proj)

Loader: fixed string functions usage, reworked NULL objects check, fixed segfault on MULTILINESTRING input.

Fixed bug in MakeLine dimension handling

Fixed bug in translate() corrupting output bounding box

### Improvements

Documentation improvements

More robust selectivity estimator

Minor speedup in distance()

Minor cleanups

GiST indexing cleanup

Looser syntax acceptance in box3d parser

## A.28. Release 1.0.3

Release date: 2005/08/08

Contains some bug fixes - including a severe one affecting correctness of stored geometries - and a few improvements.

### Upgrading

Due to a bug in a bounding box computation routine, the upgrade procedure requires special attention, as bounding boxes cached in the database could be incorrect.

An hard upgrade procedure (dump/reload) will force recomputation of all bounding boxes (not included in dumps). This is required if upgrading from releases prior to 1.0.0RC6.

If you are upgrading from versions 1.0.0RC6 or up, this release includes a perl script (utils/rebuild_bbox_caches.pl) to force recomputation of geometries' bounding boxes and invoke all operations required to propagate eventual changes in them (geometry statistics update, reindexing). Invoke the script after a make install (run with no args for syntax help). Optionally run utils/postgis_proc_upgrade.pl to refresh postgis procedures and functions signatures (see Soft upgrade).

### Bug fixes

Severe bugfix in lwgeom's 2d bounding box computation

Bugfix in WKT (-w) POINT handling in loader

Bugfix in dumper on 64bit machines

Bugfix in dumper handling of user-defined queries

Bugfix in create_undef.pl script

### Improvements

Small performance improvement in canonical input function

Minor cleanups in loader

Support for multibyte field names in loader

Improvement in the postgis_restore.pl script

New rebuild_bbox_caches.pl util script

## A.29. Release 1.0.2

Release date: 2005/07/04

Contains a few bug fixes and improvements.

### Upgrading

If you are upgrading from release 1.0.0RC6 or up you DO NOT need a dump/reload.

Upgrading from older releases requires a dump/reload. See the upgrading chapter for more informations.

### Bug fixes

Fault tolerant btree ops

Memory leak plugged in pg_error

Rtree index fix

Cleaner build scripts (avoided mix of CFLAGS and CXXFLAGS)

### Improvements

New index creation capabilities in loader (-I switch)

Initial support for postgresql 8.1dev

## A.30. Release 1.0.1

Release date: 2005/05/24

Contains a few bug fixes and some improvements.

### Upgrading

If you are upgrading from release 1.0.0RC6 or up you DO NOT need a dump/reload.

Upgrading from older releases requires a dump/reload. See the upgrading chapter for more informations.

### Library changes

BUGFIX in 3d computation of length_spheroid()

BUGFIX in join selectivity estimator

### Other changes/additions

BUGFIX in shp2pgsql escape functions

better support for concurrent postgis in multiple schemas

documentation fixes

jdbc2: compile with "-target 1.2 -source 1.2" by default

NEW -k switch for pgsql2shp

NEW support for custom createdb options in postgis_restore.pl

BUGFIX in pgsql2shp attribute names unicity enforcement

BUGFIX in Paris projections definitions

postgis_restore.pl cleanups

## A.31. Release 1.0.0

Release date: 2005/04/19

Final 1.0.0 release. Contains a few bug fixes, some improvements in the loader (most notably support for older postgis versions), and more docs.

### Upgrading

If you are upgrading from release 1.0.0RC6 you DO NOT need a dump/reload.

Upgrading from any other precedent release requires a dump/reload. See the upgrading chapter for more informations.

### Library changes

BUGFIX in transform() releasing random memory address

BUGFIX in force_3dm() allocating less memory then required

BUGFIX in join selectivity estimator (defaults, leaks, tuplecount, sd)

### Other changes/additions

BUGFIX in shp2pgsql escape of values starting with tab or single-quote

NEW manual pages for loader/dumper

NEW shp2pgsql support for old (HWGEOM) postgis versions

NEW -p (prepare) flag for shp2pgsql

NEW manual chapter about OGC compliancy enforcement

NEW autoconf support for JTS lib

BUGFIX in estimator testers (support for LWGEOM and schema parsing)

## A.32. Release 1.0.0RC6

Release date: 2005/03/30

Sixth release candidate for 1.0.0. Contains a few bug fixes and cleanups.

### Upgrading

You need a dump/reload to upgrade from precedent releases. See the upgrading chapter for more informations.

### Library changes

BUGFIX in multi()

early return [when noop] from multi()

### Scripts changes

dropped {x,y}{min,max}(box2d) functions

### Other changes

BUGFIX in postgis_restore.pl scrip

BUGFIX in dumper's 64bit support

## A.33. Release 1.0.0RC5

Release date: 2005/03/25

Fifth release candidate for 1.0.0. Contains a few bug fixes and a improvements.

### Upgrading

If you are upgrading from release 1.0.0RC4 you DO NOT need a dump/reload.

Upgrading from any other precedent release requires a dump/reload. See the upgrading chapter for more informations.

### Library changes

BUGFIX (segfaulting) in box3d computation (yes, another!).

BUGFIX (segfaulting) in estimated_extent().

### Other changes

Small build scripts and utilities refinements.

Additional performance tips documented.

## A.34. Release 1.0.0RC4

Release date: 2005/03/18

Fourth release candidate for 1.0.0. Contains bug fixes and a few improvements.

### Upgrading

You need a dump/reload to upgrade from precedent releases. See the upgrading chapter for more informations.

### Library changes

BUGFIX (segfaulting) in geom_accum().

BUGFIX in 64bit architectures support.

BUGFIX in box3d computation function with collections.

NEW subselects support in selectivity estimator.

Early return from force_collection.

Consistency check fix in SnapToGrid().

Box2d output changed back to 15 significant digits.

### Scripts changes

NEW distance_sphere() function.

Changed get_proj4_from_srid implementation to use PL/PGSQL instead of SQL.

### Other changes

BUGFIX in loader and dumper handling of MultiLine shapes

BUGFIX in loader, skipping all but first hole of polygons.

jdbc2: code cleanups, Makefile improvements

FLEX and YACC variables set *after* pgsql Makefile.global is included and only if the pgsql *stripped* version evaluates to the empty string

Added already generated parser in release

Build scripts refinements

improved version handling, central Version.config

improvements in postgis_restore.pl

## A.35. Release 1.0.0RC3

Release date: 2005/02/24

Third release candidate for 1.0.0. Contains many bug fixes and improvements.

### Upgrading

You need a dump/reload to upgrade from precedent releases. See the upgrading chapter for more informations.

### Library changes

BUGFIX in transform(): missing SRID, better error handling.

BUGFIX in memory alignment handling

BUGFIX in force_collection() causing mapserver connector failures on simple (single) geometry types.

BUGFIX in GeometryFromText() missing to add a bbox cache.

reduced precision of box2d output.

prefixed DEBUG macros with PGIS_ to avoid clash with pgsql one

plugged a leak in GEOS2POSTGIS converter

Reduced memory usage by early releasing query-context palloced one.

### Scripts changes

BUGFIX in 72 index bindings.

BUGFIX in probe_geometry_columns() to work with PG72 and support multiple geometry columns in a single table

NEW bool::text cast

Some functions made IMMUTABLE from STABLE, for performance improvement.

### JDBC changes

jdbc2: small patches, box2d/3d tests, revised docs and license.

jdbc2: bug fix and testcase in for pgjdbc 8.0 type autoregistration

jdbc2: Removed use of jdk1.4 only features to enable build with older jdk releases.

jdbc2: Added support for building against pg72jdbc2.jar

jdbc2: updated and cleaned makefile

jdbc2: added BETA support for jts geometry classes

jdbc2: Skip known-to-fail tests against older PostGIS servers.

jdbc2: Fixed handling of measured geometries in EWKT.

### Other changes

new performance tips chapter in manual

documentation updates: pgsql72 requirement, lwpostgis.sql

few changes in autoconf

BUILDDATE extraction made more portable

fixed spatial_ref_sys.sql to avoid vacuuming the whole database.

spatial_ref_sys: changed Paris entries to match the ones distributed with 0.x.

## A.36. Release 1.0.0RC2

Release date: 2005/01/26

Second release candidate for 1.0.0 containing bug fixes and a few improvements.

### Upgrading

You need a dump/reload to upgrade from precedent releases. See the upgrading chapter for more informations.

### Library changes

BUGFIX in pointarray box3d computation

BUGFIX in distance_spheroid definition

BUGFIX in transform() missing to update bbox cache

NEW jdbc driver (jdbc2)

GEOMETRYCOLLECTION(EMPTY) syntax support for backward compatibility

Faster binary outputs

Stricter OGC WKB/WKT constructors

### Scripts changes

More correct STABLE, IMMUTABLE, STRICT uses in lwpostgis.sql

stricter OGC WKB/WKT constructors

### Other changes

Faster and more robust loader (both i18n and not)

Initial autoconf script

## A.37. Release 1.0.0RC1

Release date: 2005/01/13

This is the first candidate of a major postgis release, with internal storage of postgis types redesigned to be smaller and faster on indexed queries.

### Upgrading

You need a dump/reload to upgrade from precedent releases. See the upgrading chapter for more informations.

### Changes

Faster canonical input parsing.

Lossless canonical output.

EWKB Canonical binary IO with PG>73.

Support for up to 4d coordinates, providing lossless shapefile->postgis->shapefile conversion.

New function: UpdateGeometrySRID(), AsGML(), SnapToGrid(), ForceRHR(), estimated_extent(), accum().

Vertical positioning indexed operators.

JOIN selectivity function.

More geometry constructors / editors.

PostGIS extension API.

UTF8 support in loader.