PostGIS

PostGIS is an open source software that adds support for geographic objects to the PostgreSQL object-relational database system. It is an extension to the PostgreSQL which allows GIS (Geographic Information Systems) objects to be stored in the database. In effect, PostGIS "spatially enables" the PostgreSQL server, allowing it to be used as a backend spatial database for GIS. The database can then be used to store and query spatial data (points, lines and polygons).

PostGIS follows the OpenGIS "Simple Features Specification for SQL" and has been certified as compliant with the "Types and Functions" profile. PostGIS includes support for GiST-based R-Tree spatial indexes, and functions for analysis and processing of GIS objects.

PostGIS does for PostgreSQL what Oracle Spatial does for Oracle, ArcSDE does for Microsoft SQL Server/Oracle.

Main features of PostGIS

• High performance, robust spatial database built on PostgreSQL;
• Simple Features for SQL (SFSQL) compliance;
• Proven reliability and transactional integrity (ACID compliance);
• Provides spatial representations of geometry types (points, lines, polygons);
• Support for common and advanced spatial operations such as geometry creation and conversion, reprojection, buffer, convex hull, generalization, union, and more;
• Geodetic support for measurements across the globe/dateline;
• Command-line and graphical tools for flexible management;
• PostGIS is widely supported as a spatial database back-end to client and server software, including:
  • Open Source Server: GeoServer, Mapserver, Mapnik, DeeGree, SharpMap;
  • Open Source Desktop: GRASS, QGIS, uDig, gvSIG;
  • Proprietary Server: ArcServer, Ionic Enterprise, MapDotNet Server;
  • Proprietary Desktop: ArcGIS, Manifold, Safe FME, CadCorp SIS, MapInfo Professional.

More about PostGIS:
http://www.postgis.org/