(/post'-jis/) is an open source
Geographic Information System software program that adds support for geographic objects to the
PostgreSQL object-relational database. PostGIS follows the
Simple Features for SQL specification from the
Open Geospatial Consortium . As such, PostGIS includes:
- Geometry types for points, linestrings, polygons, multipoints, multilinestrings, multipolygons and geometrycollections.
- Spatial predicates for determining the interactions of geometries using the 3x3 Egenhofer Matrix .
- Spatial operators for determining geospatial measurements like area, distance, length and perimeter.
- Spatial operators for determining geospatial set operations, like union, difference, symetric difference and buffers.
- R-tree spatial indexes for high speed spatial querying.
- Index selectivity support, to provide high performance query plans for mixed spatial/non-spatial queries.
The PostGIS implementation is based on "light-weight" geometries and indexes optimized to reduce disk and memory footprint. Using light-weight geometries helps servers increase the amount of data migrated up from physical disk storage into RAM, improving query performance substantially.
The first version was released in 2001 by Refractions Research under the
GNU General Public License , and development has continued since then actively. In 2006, PostGIS was certified as a compliant Simple Features for SQL database by the Open Geospatial Consortium.
There are a large number of software products than can use PostGIS as a database backend, including:
