Geos

GEOS implements all the OpenGIS “Simple Features for SQL”

GEOS Geometry Engine - Open Source is a C++ port of the Java Topology Suite JTS. As such, it aims to contain the complete functionality of JTS in C++. This includes all the OpenGIS “Simple Features for SQL” spatial predicate functions and spatial operators, as well as specific JTS topology functions such as IsValid.

WWW http//trac.osgeo.org/geos/