PostGIS Cookbook - Second Edition

How to do it...

With preparations in place, now we are ready to create the Voronoi diagram. First, we will create the table that will contain the MultiPolygon:

DROP TABLE IF EXISTS chp04.voronoi_diagram; 
CREATE TABLE chp04.voronoi_diagram( 
  gid serial PRIMARY KEY, 
  the_geom geometry(MultiPolygon, 3734) 
);

Now, to calculate the Voronoi diagram, we use ST_Collect in order to provide a MultiPoint object for the ST_VoronoiPolygons function. The output of this alone would be a GeometryCollection; however, we are interested in getting a MultiPolygon instead, so we need to use the ST_CollectionExtract function, which when given the number 3 as the second parameter, extracts all polygons from a GeometryCollection:

INSERT INTO chp04.voronoi_diagram(the_geom)( ...