PostGIS
Name
ST_Overlaps — Tests if two geometries intersect and have the same dimension, but are not completely contained by each other.
Description
Returns TRUE if geometry A and B "spatially overlap". Two geometries overlap if they have the same dimension, each has at least one point not shared by the other (or equivalently neither covers the other), and the intersection of their interiors has the same dimension. The overlaps relationship is symmetrical.
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Performed by the GEOS module
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| this is the "allowable" version that returns a boolean, not an integer. |
This method
implements the OGC Simple
Features Implementation Specification for SQL 1.1. s2.1.1.2 //
s2.1.13.3
This method
implements the SQL/MM specification. SQL-MM 3: 5.1.32
Examples
ST_Overlaps returns TRUE in the following situations:
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A Point on a LineString is contained, but since it has lower dimension it does not overlap or cross.
SELECT ST_Overlaps(a,b) AS overlaps, ST_Crosses(a,b) AS crosses,
ST_Intersects(a, b) AS intersects, ST_Contains(b,a) AS b_contains_a
FROM (SELECT ST_GeomFromText('POINT (100 100)') As a,
ST_GeomFromText('LINESTRING (30 50, 40 160, 160 40, 180 160)') AS b) AS t
overlaps | crosses | intersects | b_contains_a
---------+----------------------+--------------
f | f | t | t
A LineString that partly covers a Polygon intersects and crosses, but does not overlap since it has different dimension.
SELECT ST_Overlaps(a,b) AS overlaps, ST_Crosses(a,b) AS crosses,
ST_Intersects(a, b) AS intersects, ST_Contains(a,b) AS contains
FROM (SELECT ST_GeomFromText('POLYGON ((40 170, 90 30, 180 100, 40 170))') AS a,
ST_GeomFromText('LINESTRING(10 10, 190 190)') AS b) AS t;
overlap | crosses | intersects | contains
---------+---------+------------+--------------
f | t | t | f
Two Polygons that intersect but with neither contained by the other overlap, but do not cross because their intersection has the same dimension.
SELECT ST_Overlaps(a,b) AS overlaps, ST_Crosses(a,b) AS crosses,
ST_Intersects(a, b) AS intersects, ST_Contains(b, a) AS b_contains_a,
ST_Dimension(a) AS dim_a, ST_Dimension(b) AS dim_b,
ST_Dimension(ST_Intersection(a,b)) AS dim_int
FROM (SELECT ST_GeomFromText('POLYGON ((40 170, 90 30, 180 100, 40 170))') AS a,
ST_GeomFromText('POLYGON ((110 180, 20 60, 130 90, 110 180))') AS b) As t;
overlaps | crosses | intersects | b_contains_a | dim_a | dim_b | dim_int
----------+---------+------------+--------------+-------+-------+-----------
t | f | t | f | 2 | 2 | 2