Changes between Version 2 and Version 3 of UsersWikiSplitPolygonWithLineString

Timestamp:

Apr 6, 2015, 2:52:13 PM (9 years ago)

Author:

Mike Taves

Comment:

Mention ST_Split at top, add 'ST_SplitPolygon' function

UsersWikiSplitPolygonWithLineString

@@ +1 @@
+'''Note:''' As of PostGIS 2.0, [http://postgis.net/docs/ST_Split.html ST_Split] returns a collection of geometries resulting by splitting a geometry.
+
 = Split Polygon With Line String =
 
@@ -145 +147 @@
 
 Yo!Zik
+
+== Function: ST_SplitPolygon ==
+For versions of PostGIS before 2.0, a custom function can be used to split polygons using a linestring.
+{{{
+CREATE OR REPLACE FUNCTION ST_SplitPolygon(poly geometry, blade geometry)
+  RETURNS geometry AS
+'SELECT ST_Polygonize(ST_Union(ST_Boundary($1), $2))' LANGUAGE sql IMMUTABLE STRICT COST 100;
+}}}
+For example:
+{{{
+SELECT ST_AsText(ST_SplitPolygon(circle, line)) result
+FROM (SELECT 
+    ST_MakeLine(ST_MakePoint(10, 10),ST_MakePoint(190, 190)) line,
+    ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50) circle) f;
+
+           result
+-----------------------------------------
+GEOMETRYCOLLECTION(
+  POLYGON((150 90,...,150 90)),
+  POLYGON((60.1371179574584 60.1371179574584,...,60.1371179574584 60.1371179574584)))
+}}}