ST_BuildArea
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Name

ST_BuildArea — Creates a polygonal geometry formed by the linework of a geometry.

Synopsis

geometry ST_BuildArea(geometry geom);

Description

Creates an areal geometry formed by the constituent linework of the input geometry. The input can be LINESTRINGS, MULTILINESTRINGS, POLYGONS, MULTIPOLYGONS, and GeometryCollections. The result is a Polygon or MultiPolygon, depending on input. If the input linework does not form polygons, NULL is returned.

This function assumes all inner geometries represent holes

[Note]

Input linework must be correctly noded for this function to work properly

Availability: 1.1.0

Examples

These will create a donut

--using polygons
SELECT ST_BuildArea(ST_Collect(smallc,bigc))
FROM (SELECT
    ST_Buffer(
      ST_GeomFromText('POINT(100 90)'), 25) As smallc,
    ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50) As bigc) As foo;
                

--using linestrings
SELECT ST_BuildArea(ST_Collect(smallc,bigc))
FROM (SELECT
    ST_ExteriorRing(ST_Buffer(
      ST_GeomFromText('POINT(100 90)'), 25)) As smallc,
    ST_ExteriorRing(ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50)) As bigc) As foo;

See Also

ST_Node, ST_MakePolygon, ST_MakeValid, ST_BdPolyFromText, ST_BdMPolyFromText (wrappers to this function with standard OGC interface)

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