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ST_Tessellate

Signature

GEOMETRY ST_Tessellate(GEOMETRY geom)

Description

Return the tessellation of a geometry with adaptive triangles.

Remark

Input geometry (geom) can only be a POLYGON or a MULTIPOLYGON.

Examples

Case with POLYGON
SELECT ST_Tessellate('POLYGON ((1 1, 1 5, 3 5, 3 4, 2 4, 
				2 3, 4 3, 4 2, 1 1))');

-- Answer: 
MULTIPOLYGON (((1 5, 2 4, 3 5, 1 5)), ((2 4, 3 4, 3 5, 2 4)), 
	      ((2 4, 1 5, 2 3, 2 4)), ((1 5, 1 1, 2 3, 1 5)), 
	      ((2 3, 1 1, 4 2, 2 3)), ((2 3, 4 2, 4 3, 2 3)))

Case with MULTIPOLYGON
SELECT ST_Tessellate('MULTIPOLYGON (
			((1 1, 1 3, 2 4, 3 3, 3 2, 2 2, 1 1)), 
  			((3 5, 4 3, 4 2, 3 1, 5 1, 5 4, 3 5)))');

-- Answer: 
MULTIPOLYGON (((2 4, 1 3, 3 3, 2 4)), ((1 3, 2 2, 3 3, 1 3)), 
	      ((2 2, 3 2, 3 3, 2 2)), ((1 3, 1 1, 2 2, 1 3)), 
	      ((3 5, 4 3, 5 4, 3 5)), ((4 3, 5 1, 5 4, 4 3)), 
	      ((4 3, 4 2, 5 1, 4 3)), ((4 2, 3 1, 5 1, 4 2)))

Application with real data

The tessellation is made on a set of urban plots (in grey) (stored in a layer called “PLOTS”)

SELECT ST_Tessellate(THE_GEOM) as THE_GEOM FROM PLOTS;

The resulting triangles are displayed in pink.

See also