In this chapter, you will work with a set of PostGIS functions and vector datasets. You will first take a look at how to use PostGIS with GPS data—you will import such datasets using ogr2ogr and then compose polylines from point geometries using the ST_MakeLine function.
Then, you will see how PostGIS helps you find and fix invalid geometries with functions such as ST_MakeValid, ST_IsValid, ST_IsValidReason, and ST_IsValidDetails.
You will then learn about one of the most powerful elements of a spatial database, spatial joins. PostGIS provides you with a rich set of operators, such as ST_Intersects, ST_Contains, ST_Covers, ST_Crosses, and ST_DWithin, for this purpose.
After that, you will use the ST_Simplify and ST_SimplifyPreverveTopology functions to simplify (generalize) geometries when you don't need too many details. While this function works well...
