PostGIS is GIS extensions to the PostgreSQL relational database server.

PostGIS adds support for geographic objects to the PostgreSQL object-relational database. In effect, PostGIS "spatially enables" the PostgreSQL server, allowing it to be used as a backend spatial database for geographic information systems (GIS), much like ESRI's SDE or Oracle's Spatial extension.

PostGIS follows the OpenGIS "Simple Features Specification for SQL" and will be submitted for conformance testing at version 1.0.

PostGIS has been developed by Refractions Research Inc as a research project in open source spatial database technology. PostGIS is released under the GNU General Public License. Our list of future projects includes enhanced technology for data loading and dumping, user interface tools for direct data access and manipulation, and support for advanced topologies at the server side, such as coverages, networks, and surfaces.

There are now several open source tools which work with PostGIS. The uDig project is working on a full read amd write desktop environment that can work with PostGIS directly.

For internet mapping, the University of Minnesota Mapserver can use PostGIS as a data source. The GeoTools Java GIS toolkit has PostGIS support, as does the GeoServer Web Feature Server.

GRASS now supports PostGIS as a data source, through the PostGRASS driver. The JUMP Java desktop GIS viewer has a simple plugin for reading PostGIS data, and the QGIS desktop has good PostGIS support.

PostGIS data can be exported to several output GIS formats using the OGR C library and commandline tools (and of cource with the bundled Shape file dumper). And of course any language which can work with PostgreSQL can work with PostGIS -- the list includes Perl, PHP, Python, TCL, C, C , Java, and more.

Installation:

Un-tar the PostGIS tar-ball in the 'contrib' directory of your PostgreSQL source tree. You must untar the PostGIS source there or the Makefile will not work. You must have the PL/pgSQL prodedural language installed before installing PostGIS.

cd contrib
gunzip postgis-0.9.0.tar.gz
tar xvf postgis-0.9.0.tar
cd postgis-0.9.0
make
make install
createlang plpgsql yourtestdatabase
psql -d yourtestdatabase -f postgis.sql
psql -d yourtestdatabase -f spatial_ref_sys.sql

Requirements:

· A complete configured and built PostgreSQL source code tree. PostGIS uses definitions from the PostgreSQL configure/build process to conform to the particular platform you are building on.
· 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.
· (Recommended) Proj4 reprojection library. The Proj4 library is used to provide coordinate reprojection support within PostGIS.
· (Recommended) GEOS geometry library. The GEOS library is used to provide geometry tests (Touches(), Contains(), Intersects()) and operations (Buffer(), GeomUnion(), Difference()) within PostGIS.

What's New in This Release:

· Improvements in the shp2pgsql/pgsql2shp utilities (better Windows support, DBF-only loading support, support for OS X 10.5, and output for Date types in DBF).
· A new function ST_SimplifyPreserveTopology(geometry, float8) to simplify polygons without creating invalid geometry.
· KML support updates and SVG support updates.