Returns true if all exterior rings of a polygon are wound clockwise and all interior rings are wound anticlockwise.
Syntax
boolean ST_IsPolygonCW(geometry geom);Parameters
| Parameter | Description |
|---|---|
geom | The geometry object to check. |
Function properties
Supports 3D geometries and preserves Z coordinates.
Supports M coordinates.
Usage notes
No polygon component
If the input geometry contains no polygon component, the function returns true. A closed LineString is not treated as a polygon.
Same-direction rings
If one or more interior rings are wound in the same direction as an exterior ring, both ST_IsPolygonCW and ST_IsPolygonCCW return false.
Examples
Example 1: Clockwise exterior ring, anticlockwise interior ring (returns true)
SELECT ST_IsPolygonCW('POLYGON((1 0,0 3,3 0,1 0),(1 0,2 0,0 2,1 0))'::geometry);
st_ispolygoncw
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t
(1 row)What's next
ST_IsPolygonCCW — Check whether exterior rings are anticlockwise and interior rings are clockwise.
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