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ST_Covers
source link: http://postgis.net/docs/ST_Covers.html
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Synopsis
boolean ST_Covers(
geometry
geomA, geometry
geomB)
;
boolean ST_Covers(
geography
geogpolyA, geography
geogpointB)
;
Description
Returns 1 (TRUE) if no point in Geometry/Geography B is outside Geometry/Geography A
![[Important]](http://postgis.net/docs/images/important.png)
Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION
![[Important]](http://postgis.net/docs/images/important.png)
Do not use this function with invalid geometries. You will get unexpected results.
This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries. To avoid index use, use the function _ST_Covers.
Performed by the GEOS module
Enhanced: 2.4.0 Support for polygon in polygon and line in polygon added for geography type
Enhanced: 2.3.0 Enhancement to PIP short-circuit for geometry extended to support MultiPoints with few points. Prior versions only supported point in polygon.
Availability: 1.5 - support for geography was introduced.
Availability: 1.2.2
NOTE: this is the "allowable" version that returns a boolean, not an integer.
Not an OGC standard, but Oracle has it too.
There are certain subtleties to ST_Contains and ST_Within that are not intuitively obvious. For details check out Subtleties of OGC Covers, Contains, Within
Examples
Geometry example
--a circle covering a circle SELECT ST_Covers(smallc,smallc) As smallinsmall, ST_Covers(smallc, bigc) As smallcoversbig, ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior, ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc, ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo; --Result smallinsmall | smallcoversbig | bigcoversexterior | bigcontainsexterior --------------+----------------+-------------------+--------------------- t | f | t | f (1 row)
Geeography Example
-- a point with a 300 meter buffer compared to a point, a point and its 10 meter buffer SELECT ST_Covers(geog_poly, geog_pt) As poly_covers_pt, ST_Covers(ST_Buffer(geog_pt,10), geog_pt) As buff_10m_covers_cent FROM (SELECT ST_Buffer(ST_GeogFromText('SRID=4326;POINT(-99.327 31.4821)'), 300) As geog_poly, ST_GeogFromText('SRID=4326;POINT(-99.33 31.483)') As geog_pt ) As foo; poly_covers_pt | buff_10m_covers_cent ----------------+------------------ f | t
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