Use this tag for PostGIS, which is a spatial database extension for PostgreSQL. Before using this tag, please consider whether your question might be a better fit for the Geographic Information Systems Stack Exchange site (e.g. if it's more about configuration or geodetic principles than about actual programming).
PostGIS is an open source extension for PostgreSQL that adds support for geographic objects. In effect, PostGIS "spatially enables" the PostgreSQL server, allowing it to be used 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 has been certified as compliant with the "Types and Functions" profile.
PostGIS questions also on-topic for the Geographic Information Systems Stack Exchange site.
PostGIS has been developed by Refractions Research as a project in open source spatial database technology and is released under the GNU General Public License.
Features
- Geometry types for points, linestrings, polygons, multipoints, multilinestrings, multipolygons and geometrycollections.
- Spatial predicates for determining the interactions of geometries using the 3x3 Egenhofer matrix (provided by the GEOS software library).
- Spatial operators for determining geospatial measurements like area, distance, length and perimeter.
- Spatial operators for determining geospatial set operations, like union, difference, symmetric difference and buffers (provided by GEOS).
- R-tree-over-GiST (Generalised Search Tree) spatial indexes for high speed spatial querying.
- Index selectivity support, to provide high performance query plans for mixed spatial/non-spatial queries.
Tutorials:
