GRASS GIS Geospatial Suite

GRASS GIS (Geographic Resources Analysis Support System) is a free open-source geospatial processing toolkit for data management and analysis, image processing, spatial modeling, and visualization. Originally developed by the US Army CERL starting in 1982, GRASS GIS has been maintained by OSGeo since 2008. Key features: comprehensive raster analysis including map algebra, terrain analysis, hydrological modeling, viewshed analysis, cost surfaces, and interpolation. Topological vector data model supporting point, line, area features with network analysis, buffering, overlay, and spatial queries. Temporal framework (TGRASS) for processing time series of raster and vector maps with temporal algebra. 3D raster (voxel) analysis for volumetric data including 3D interpolation and cross-sections. Satellite and aerial imagery processing including classification, rectification, PCA, and multispectral analysis with Landsat and Sentinel support. Hydrological modeling with watershed delineation, stream extraction, flow accumulation, and flood modeling. GPS and survey data import with coordinate transformation. Publication-quality map composition with legends, scale bars, north arrows via ps.map. Over 400 built-in modules and add-ons. Python scripting via grass.script and PyGRASS. Graphical interface for data management and cartographic display. Over 6,000 coordinate reference systems via PROJ library.