GEOS provides a spatial object model and fundamental geometric
 functions. It implements the geometry model defined in the
 OpenGIS Consortium Simple Features Specification for SQL.
 Functions provided include:
 .
   * spatial predicates (based on the DE-9IM model),
   * overlay functions (intersection, difference, union,
     symmetric difference),
   * buffer,
   * convex hull,
   * area and distance functions, and
   * topological validity checking
 .
 This package contains the C library.