PostGIS is a set of extensions for the PostgreSQL database. With PostGIS you can store geospatial data and perform spatial queries on a postgres database.

Unlike the default datatypes on a normal postgres database, spatial data has to be handled differently. The queries you can perform on a spatial database are usually defined by bounding-boxes in 2 or 3 dimensions. To store, index and handle these datatypes postGIS uses a concept called R-Trees, wich is not part of the default postgres-installation.

With a postGIS database, you are able to:

• store spatial data
• perform spatial queries, to retrieve and extract information (points, areas).
• manage spatial information and metadata on tables (like: used coorinate-reference-system).
• convert geometries from one coordinate-system to another
• compare geometries, and extract properties (like: edge-length of a road or building)
• generate new geometries from others.