ST_VoronoiPolygons
Name
ST_VoronoiPolygons — Returns the cells of the Voronoi diagram of the vertices of a geometry.
Synopsis
geometry
ST_VoronoiPolygons
(
geometry
geom
,
float8
tolerance = 0.0
,
geometry
extend_to = NULL
)
;
Description
Computes a two-dimensional
Voronoi diagram
from the vertices of
the supplied geometry.
The result is a GEOMETRYCOLLECTION of POLYGONs that covers an envelope larger than the extent of the input vertices.
Returns null if input geometry is null. Returns an empty geometry collection if the input geometry contains only one vertex.
Returns an empty geometry collection if the
extend_to
envelope has zero area.
Optional parameters:
-
tolerance: The distance within which vertices will be considered equivalent. Robustness of the algorithm can be improved by supplying a nonzero tolerance distance. (default = 0.0) -
extend_to: If present, the diagram is extended to cover the envelope of the supplied geometry, unless smaller than the default envelope (default = NULL, default envelope is the bounding box of the input expanded by about 50%).
Performed by the GEOS module.
Availability: 2.3.0
Examples
Points overlaid on top of Voronoi diagram
SELECT ST_VoronoiPolygons(
'MULTIPOINT (50 30, 60 30, 100 100,10 150, 110 120)'::geometry
) AS geom;
ST_AsText output
GEOMETRYCOLLECTION(POLYGON((-110 43.3333333333333,-110 270,100.5 270,59.3478260869565 132.826086956522,36.8181818181818 92.2727272727273,-110 43.3333333333333)),
POLYGON((55 -90,-110 -90,-110 43.3333333333333,36.8181818181818 92.2727272727273,55 79.2857142857143,55 -90)),
POLYGON((230 47.5,230 -20.7142857142857,55 79.2857142857143,36.8181818181818 92.2727272727273,59.3478260869565 132.826086956522,230 47.5)),POLYGON((230 -20.7142857142857,230 -90,55 -90,55 79.2857142857143,230 -20.7142857142857)),
POLYGON((100.5 270,230 270,230 47.5,59.3478260869565 132.826086956522,100.5 270)))
Voronoi diagram, with tolerance of 30 units
SELECT ST_VoronoiPolygons(
'MULTIPOINT (50 30, 60 30, 100 100,10 150, 110 120)'::geometry,
30) AS geom;
ST_AsText output
GEOMETRYCOLLECTION(POLYGON((-110 43.3333333333333,-110 270,100.5 270,59.3478260869565 132.826086956522,36.8181818181818 92.2727272727273,-110 43.3333333333333)),
POLYGON((230 47.5,230 -45.7142857142858,36.8181818181818 92.2727272727273,59.3478260869565 132.826086956522,230 47.5)),POLYGON((230 -45.7142857142858,230 -90,-110 -90,-110 43.3333333333333,36.8181818181818 92.2727272727273,230 -45.7142857142858)),
POLYGON((100.5 270,230 270,230 47.5,59.3478260869565 132.826086956522,100.5 270)))