| | 8 | * [http://postgis.refractions.net/ PostGIS], the [http://www.opengis.org/docs/99-049.pdf OpenGIS SQL Types (pdf)] implementation for Postgresql |
| | 9 | * [http://geos.refractions.net/ GEOS], low-level C++ port of [http://www.jump-project.org/project.php?PID=JTS Jave Topology Suite], used by PostGIS |
| | 10 | * [http://exogen.case.edu/projects/geopy/ Geopy] calcs distances using (very accurate) [http://www.movable-type.co.uk/scripts/LatLongVincenty.html Vincenty], and uses the [http://en.wikipedia.org/wiki/World_Geodetic_System WGS 84] datum. |