PostGIS
Name
ST_Polygonize — Computes a collection of polygons formed from the linework of a set of geometries.
Synopsis
geometry +`*`+ST_Polygonize*(`geometry set `geomfield`)`;
geometry +`*`+ST_Polygonize*(`geometry[] `geom_array`)`;
Description
Creates a GeometryCollection containing the polygons formed by the linework of a set of geometries. If the input linework does not form any polygons, an empty GeometryCollection is returned.
This function creates polygons covering all delimited areas. If the result is intended to form a valid polygonal geometry, use ST_BuildArea to prevent holes being filled.
|
|
Performed by the GEOS module.
Availability: 1.0.0RC1
Examples
Input lines |
Polygonized result |
WITH data(geom) AS (VALUES
('LINESTRING (180 40, 30 20, 20 90)'::geometry)
,('LINESTRING (180 40, 160 160)'::geometry)
,('LINESTRING (80 60, 120 130, 150 80)'::geometry)
,('LINESTRING (80 60, 150 80)'::geometry)
,('LINESTRING (20 90, 70 70, 80 130)'::geometry)
,('LINESTRING (80 130, 160 160)'::geometry)
,('LINESTRING (20 90, 20 160, 70 190)'::geometry)
,('LINESTRING (70 190, 80 130)'::geometry)
,('LINESTRING (70 190, 160 160)'::geometry)
)
SELECT ST_AsText( ST_Polygonize( geom ))
FROM data;
------------------------------------------------------------------------------------------
GEOMETRYCOLLECTION (POLYGON ((180 40, 30 20, 20 90, 70 70, 80 130, 160 160, 180 40), (150 80, 120 130, 80 60, 150 80)),
POLYGON ((20 90, 20 160, 70 190, 80 130, 70 70, 20 90)),
POLYGON ((160 160, 80 130, 70 190, 160 160)),
POLYGON ((80 60, 120 130, 150 80, 80 60)))Polygonizing a table of linestrings:
SELECT ST_AsEWKT(ST_Polygonize(geom_4269)) As geomtextrep
FROM (SELECT geom_4269 FROM ma.suffolk_edges) As foo;
-------------------------------------
SRID=4269;GEOMETRYCOLLECTION(POLYGON((-71.040878 42.285678,-71.040943 42.2856,-71.04096 42.285752,-71.040878 42.285678)),
POLYGON((-71.17166 42.353675,-71.172026 42.354044,-71.17239 42.354358,-71.171794 42.354971,-71.170511 42.354855,
-71.17112 42.354238,-71.17166 42.353675)))
--Use ST_Dump to dump out the polygonize geoms into individual polygons
SELECT ST_AsEWKT((ST_Dump(t.polycoll)).geom) AS geomtextrep
FROM (SELECT ST_Polygonize(geom_4269) AS polycoll
FROM (SELECT geom_4269 FROM ma.suffolk_edges)
As foo) AS t;
------------------------
SRID=4269;POLYGON((-71.040878 42.285678,-71.040943 42.2856,-71.04096 42.285752,
-71.040878 42.285678))
SRID=4269;POLYGON((-71.17166 42.353675,-71.172026 42.354044,-71.17239 42.354358
,-71.171794 42.354971,-71.170511 42.354855,-71.17112 42.354238,-71.17166 42.353675))