QGIS (Quantum GIS) is a cross-platform free and open-source desktop geographic information system (GIS) application that supports viewing, editing, and analys…

PostGIS is an open source software program that adds support for geographic objects to the PostgreSQL object-relational database.

GRASS GIS (Geographic Resources Analysis Support System) is a geographic information system (GIS) software suite used for geospatial data management and analy…