Summary

Vector operation functions can be used as a rich geoprocessing toolbox, all without leaving the database environment. Using nothing but Spatial SQL, one can split and merge features, reproject them, create buffers and hulls, offset geometries, and much more. And when it comes to querying, PostGIS offers fine-grained spatial relationship functions to pick only specific features. This wouldn't be possible without a rich open source GIS ecosystem; the geoprocessing and spatial relationship functions are available thanks to the GEOS library, and reprojections are done with the help of the PROJ.4 library. Other database vendors often choose to implement spatial functions from scratch, and stick to a moderate set of functions defined in the OGC specification. The geoprocessing toolbox is one of PostGIS's greatest strengths. This toolbox is not limited to vector data manipulation. In the next chapter, we will discuss the functions available for raster data processing.