A suite of opensource GIS tools provided by Frank Warmerdam. Very useful utilities such as GDAL and OGR2OGR which allows translating between various popular GIS formats such as MapInfo Tab, ESRI Shape, PostGIS, GML, KML, MrSID to name a few. The newest version also supports Oracle Spatial and Arc SDE Raster (note for these proprietary ones, external libraries may be needed and you may need to compile yourself).

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