The breathe of spatial functions that PostGIS provides is too large to be covered completely in any book. We invite you to explore the rich PostGIS manual to learn about all the functions. In this chapter we cover the main relationship and relationship output functions you will commonly find in PostGIS for the core spatial types geometry,geography, raster, and topogeoms. Many of these functions you will also find in other spatial databases such as Oracle Spatial/Locator, SQL Server 2008, IBM DB2 Spatial Datablade, and SQLite SpatiaLite.
We describe the fundamental OGC spatial concepts that many of these functions are founded on. Some of the functions such as ST_DWithin are particular to PostGIS, but have parallels in Oracle Locator/Spatial SDO.Within_Distance, SQL Server 2008 , and IBM DB2.
We describe DE9IM intersection matrix model that many spatial relationships are founded and are fairly standard across all spatial databases. We demonstrate an example that exercises the confusing corner cases of this model. In the hopefully entertaining example of The house with a courtyard, a walkway, the front door and courtyard greeters we explore how we can determine the orientation of these objects relative to each other by using these functions.
Stay tuned for our next book pgRouting: A Practical Guide with LocatePress due out late 2015.
© Leo Hsu and Regina Obe 2014