PostGIS "Lightweight Geometry" library

 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".
 .
 This library is the generic geometry handling section of PostGIS. The
 geometry objects, constructors, destructors, and a set of spatial
 processing functions, are implemented here.