These functions determine spatial relationships between geometries.

# Spatial Relationships

## Topological Relationships

ST_3DIntersects

Returns TRUE if the Geometries "spatially intersect" in 3D - only for points, linestrings, polygons, polyhedral surface (area).

    					boolean ST_3DIntersects

    						geometry
    						geomA

    						geometry
    						geomB

#### Description

Overlaps, Touches, Within all imply spatial intersection. If any of the aforementioned returns true, then the geometries also spatially intersect. Disjoint implies false for spatial intersection.

Changed: 3.0.0 SFCGAL backend removed, GEOS backend supports TINs.

Availability: 2.0.0

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

&Z_support;

&P_support;

&T_support;

&sfcgal_enhanced;

&sqlmm_compliant; SQL-MM 3: ?

#### Geometry Examples

    SELECT ST_3DIntersects(pt, line), ST_Intersects(pt, line)
    	FROM (SELECT 'POINT(0 0 2)'::geometry As pt, 'LINESTRING (0 0 1, 0 2 3)'::geometry As line) As foo;
     st_3dintersects | st_intersects
    -----------------+---------------
     f               | t
    (1 row)

#### TIN Examples

    SELECT ST_3DIntersects('TIN(((0 0 0,1 0 0,0 1 0,0 0 0)))'::geometry, 'POINT(.1 .1 0)'::geometry);
     st_3dintersects
    -----------------
     t

#### See Also

ST_Intersects

ST_Contains

Returns true if and only if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A.

    			boolean ST_Contains

    			geometry
    			geomA

    			geometry
    			geomB

#### Description

Geometry A contains Geometry B if and only if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A. An important subtlety of this definition is that A does not contain its boundary, but A does contain itself. Contrast that to ST_ContainsProperly where geometry A does not Contain Properly itself.

Returns TRUE if geometry B is completely inside geometry A. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID. ST_Contains is the inverse of ST_Within. So ST_Contains(A,B) implies ST_Within(B,A) except in the case of invalid geometries where the result is always false regardless or not defined.

Performed by the GEOS module

Enhanced: 2.3.0 Enhancement to PIP short-circuit extended to support MultiPoints with few points. Prior versions only supported point in polygon.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

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_Contains.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

&sfs_compliant; s2.1.1.2 // s2.1.13.3 - same as within(geometry B, geometry A)

&sqlmm_compliant; SQL-MM 3: 5.1.31

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

The `ST_Contains` predicate returns `TRUE` in all the following illustrations.

`LINESTRING` / `MULTIPOINT` | `POLYGON` / `POINT`
`POLYGON` / `LINESTRING` | `POLYGON` / `POLYGON`

The `ST_Contains` predicate returns `FALSE` in all the following illustrations.

`POLYGON` / `MULTIPOINT` | `POLYGON` / `LINESTRING`

    -- A circle within a circle
    SELECT ST_Contains(smallc, bigc) As smallcontainsbig,
    	   ST_Contains(bigc,smallc) As bigcontainssmall,
    	   ST_Contains(bigc, ST_Union(smallc, bigc)) as bigcontainsunion,
    	   ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
    	   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
      smallcontainsbig | bigcontainssmall | bigcontainsunion | bigisunion | bigcoversexterior | bigcontainsexterior
    ------------------+------------------+------------------+------------+-------------------+---------------------
     f                | t                | t                | t          | t        | f

    -- Example demonstrating difference between contains and contains properly
    SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
       ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
    FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
    			 ( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
    			 ( ST_Point(1,1) )
    	  ) As foo(geomA);

      geomtype    | acontainsa | acontainspropa | acontainsba | acontainspropba
    --------------+------------+----------------+-------------+-----------------
    ST_Polygon    | t          | f              | f           | f
    ST_LineString | t          | f              | f           | f
    ST_Point      | t          | t              | f           | f

#### See Also

ST_Boundary, ST_ContainsProperly, ST_Covers, ST_CoveredBy, ST_Equals, ST_Within

ST_ContainsProperly

Returns true if B intersects the interior of A but not the boundary (or exterior). A does not contain properly itself, but does contain itself.

    			boolean ST_ContainsProperly

    			geometry
    			geomA

    			geometry
    			geomB

#### Description

Returns true if B intersects the interior of A but not the boundary (or exterior).

A does not contain properly itself, but does contain itself.

Every point of the other geometry is a point of this geometry's interior. The DE-9IM Intersection Matrix for the two geometries matches [T**FF*FF*] used in ST_Relate

From JTS docs slightly reworded: The advantage to using this predicate over ST_Contains and ST_Intersects is that it can be computed efficiently, with no need to compute topology at individual points.

An example use case for this predicate is computing the intersections of a set of geometries with a large polygonal geometry. Since intersection is a fairly slow operation, it can be more efficient to use containsProperly to filter out test geometries which lie wholly inside the area. In these cases the intersection is known a priori to be exactly the original test geometry.

Performed by the GEOS module.

Availability: 1.4.0

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

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_ContainsProperly.

#### Examples

    	--a circle within a circle
    	SELECT ST_ContainsProperly(smallc, bigc) As smallcontainspropbig,
    	ST_ContainsProperly(bigc,smallc) As bigcontainspropsmall,
    	ST_ContainsProperly(bigc, ST_Union(smallc, bigc)) as bigcontainspropunion,
    	ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
    	ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
    	ST_ContainsProperly(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
      smallcontainspropbig | bigcontainspropsmall | bigcontainspropunion | bigisunion | bigcoversexterior | bigcontainsexterior
    ------------------+------------------+------------------+------------+-------------------+---------------------
     f                     | t                    | f                    | t          | t                 | f

     --example demonstrating difference between contains and contains properly
     SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
     ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
     FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
    		  ( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
    		  ( ST_Point(1,1) )
    	) As foo(geomA);

      geomtype    | acontainsa | acontainspropa | acontainsba | acontainspropba
    --------------+------------+----------------+-------------+-----------------
    ST_Polygon    | t          | f              | f           | f
    ST_LineString | t          | f              | f           | f
    ST_Point      | t          | t              | f           | f

#### See Also

ST_GeometryType, ST_Boundary, ST_Contains, ST_Covers, ST_CoveredBy, ST_Equals, ST_Relate, ST_Within

ST_Covers

Returns 1 (TRUE) if no point in Geometry B is outside Geometry A

    			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

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

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

#### See Also

ST_Contains, ST_CoveredBy, ST_Within

ST_CoveredBy

Returns 1 (TRUE) if no point in Geometry/Geography A is outside Geometry/Geography B

    			boolean ST_CoveredBy

    			geometry
    			geomA

    			geometry
    			geomB

    			boolean ST_CoveredBy

    			geography
    			geogA

    			geography
    			geogB

#### Description

Returns 1 (TRUE) if no point in Geometry/Geography A is outside Geometry/Geography B

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

Do not use this function with invalid geometries. You will get unexpected results.

Performed by the GEOS module

Availability: 1.2.2

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_CoveredBy.

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

    	--a circle coveredby a circle
    SELECT ST_CoveredBy(smallc,smallc) As smallinsmall,
    	ST_CoveredBy(smallc, bigc) As smallcoveredbybig,
    	ST_CoveredBy(ST_ExteriorRing(bigc), bigc) As exteriorcoveredbybig,
    	ST_Within(ST_ExteriorRing(bigc),bigc) As exeriorwithinbig
    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 | smallcoveredbybig | exteriorcoveredbybig | exeriorwithinbig
    --------------+-------------------+----------------------+------------------
     t            | t                 | t                    | f
    (1 row)

#### See Also

ST_Contains, ST_Covers, ST_ExteriorRing, ST_Within

ST_Crosses

Returns `TRUE` if the supplied geometries have some, but not all, interior points in common.

    		  boolean ST_Crosses

    		  geometry g1

    		  geometry g2

#### Description

`ST_Crosses` takes two geometry objects and returns `TRUE` if their intersection "spatially cross", that is, the geometries have some, but not all interior points in common. The intersection of the interiors of the geometries must not be the empty set and must have a dimensionality less than the maximum dimension of the two input geometries. Additionally, the intersection of the two geometries must not equal either of the source geometries. Otherwise, it returns `FALSE`.

In mathematical terms, this is expressed as:

The DE-9IM Intersection Matrix for the two geometries is:

- `T*T******` (for Point/Line, Point/Area, and Line/Area situations)

- `T*****T**` (for Line/Point, Area/Point, and Area/Line situations)

- `0********` (for Line/Line situations)

For any other combination of dimensions this predicate returns false.

The OpenGIS Simple Features Specification defines this predicate only for Point/Line, Point/Area, Line/Line, and Line/Area situations. JTS / GEOS extends the definition to apply to Line/Point, Area/Point and Area/Line situations as well. This makes the relation symmetric.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

&sfs_compliant; s2.1.13.3

&sqlmm_compliant; SQL-MM 3: 5.1.29

#### Examples

The following illustrations all return `TRUE`.

`MULTIPOINT` / `LINESTRING` | `MULTIPOINT` / `POLYGON`
`LINESTRING` / `POLYGON` | `LINESTRING` / `LINESTRING`

Consider a situation where a user has two tables: a table of roads and a table of highways.

    CREATE TABLE roads (
      id serial NOT NULL,
      the_geom geometry,
      CONSTRAINT roads_pkey PRIMARY KEY (road_id)
    );
    CREATE TABLE highways (
      id serial NOT NULL,
      the_gem geometry,
      CONSTRAINT roads_pkey PRIMARY KEY (road_id)
    );

To determine a list of roads that cross a highway, use a query similiar to:

    SELECT roads.id
    FROM roads, highways
    WHERE ST_Crosses(roads.the_geom, highways.the_geom);

ST_LineCrossingDirection

Given 2 linestrings, returns a number between -3 and 3 denoting what kind of crossing behavior. 0 is no crossing.

    		  integer ST_LineCrossingDirection
    		  geometry  linestringA
    		  geometry  linestringB

#### Description

Given 2 linestrings, returns a number between -3 and 3 denoting what kind of crossing behavior. 0 is no crossing. This is only supported for `LINESTRING`

Definition of integer constants is as follows:

- 0: LINE NO CROSS

- -1: LINE CROSS LEFT

- 1: LINE CROSS RIGHT

- -2: LINE MULTICROSS END LEFT

- 2: LINE MULTICROSS END RIGHT

- -3: LINE MULTICROSS END SAME FIRST LEFT

- 3: LINE MULTICROSS END SAME FIRST RIGHT

Availability: 1.4

#### Examples

Line 1 (green), Line 2 ball is start point, triangle are end points. Query below.
    SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
    	  ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
    FROM (
    SELECT
     ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
     ST_GeomFromText('LINESTRING(171 154,20 140,71 74,161 53)') As line2
    	) As foo;

     l1_cross_l2 | l2_cross_l1
    -------------+-------------
               3 |          -3
| Line 1 (green), Line 2 (blue) ball is start point, triangle are end points. Query below.
    SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
    	  ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
    FROM (
     SELECT
      ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
      ST_GeomFromText('LINESTRING (171 154, 20 140, 71 74, 2.99 90.16)') As line2
    ) As foo;

     l1_cross_l2 | l2_cross_l1
    -------------+-------------
               2 |          -2
Line 1 (green), Line 2 (blue) ball is start point, triangle are end points. Query below.
    SELECT
    	ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
    	ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
    FROM (
     SELECT
      ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
      ST_GeomFromText('LINESTRING (20 140, 71 74, 161 53)') As line2
      ) As foo;

     l1_cross_l2 | l2_cross_l1
    -------------+-------------
              -1 |          1
| Line 1 (green), Line 2 (blue) ball is start point, triangle are end points. Query below.
    SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
    	  ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
    FROM (SELECT
    	ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
    	ST_GeomFromText('LINESTRING(2.99 90.16,71 74,20 140,171 154)') As line2
    	) As foo;

     l1_cross_l2 | l2_cross_l1
    -------------+-------------
              -2 |          2

    SELECT s1.gid, s2.gid, ST_LineCrossingDirection(s1.the_geom, s2.the_geom)
    	FROM streets s1 CROSS JOIN streets s2 ON (s1.gid != s2.gid AND s1.the_geom && s2.the_geom )
    WHERE ST_CrossingDirection(s1.the_geom, s2.the_geom) > 0;

#### See Also

ST_Crosses

ST_Disjoint

Returns TRUE if the Geometries do not "spatially intersect" - if they do not share any space together.

    					boolean ST_Disjoint

    						geometry
    						A

    						geometry
    						B

#### Description

Overlaps, Touches, Within all imply geometries are not spatially disjoint. If any of the aforementioned returns true, then the geometries are not spatially disjoint. Disjoint implies false for spatial intersection.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

Performed by the GEOS module

This function call does not use indexes

NOTE: this is the "allowable" version that returns a boolean, not an integer.

&sfs_compliant; s2.1.1.2 //s2.1.13.3 - a.Relate(b, 'FF*FF****')

&sqlmm_compliant; SQL-MM 3: 5.1.26

#### Examples

    SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
     st_disjoint
    ---------------
     t
    (1 row)
    SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
     st_disjoint
    ---------------
     f
    (1 row)

#### See Also

ST_Intersects

ST_Equals

Returns true if the given geometries represent the same geometry. Directionality is ignored.

    			boolean ST_Equals
    			geometry  A
    			geometry  B

#### Description

Returns TRUE if the given Geometries are "spatially equal". Use this for a 'better' answer than '='. Note by spatially equal we mean ST_Within(A,B) = true and ST_Within(B,A) = true and also mean ordering of points can be different but represent the same geometry structure. To verify the order of points is consistent, use ST_OrderingEquals (it must be noted ST_OrderingEquals is a little more stringent than simply verifying order of points are the same).

This function will return false if either geometry is invalid except in the case where they are binary equal.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

&sfs_compliant; s2.1.1.2

&sqlmm_compliant; SQL-MM 3: 5.1.24

Changed: 2.2.0 Returns true even for invalid geometries if they are binary equal

#### Examples

    SELECT ST_Equals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
    		ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
     st_equals
    -----------
     t
    (1 row)

    SELECT ST_Equals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
    		ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
     st_equals
    -----------
     t
    (1 row)

#### See Also

ST_IsValid, ST_OrderingEquals, ST_Reverse, ST_Within

ST_Intersects

Returns TRUE if the Geometries/Geography "spatially intersect in 2D" - (share any portion of space) and FALSE if they don't (they are Disjoint). For geography tolerance is 0.00001 meters (so any points that close are considered to intersect)

    					boolean ST_Intersects

    						geometry
    						geomA

    						geometry
    						geomB

    					boolean ST_Intersects

    						geography
    						geogA

    						geography
    						geogB

#### Description

If a geometry or geography shares any portion of space then they intersect. For geography -- tolerance is 0.00001 meters (so any points that are close are considered to intersect)

ST_Overlaps, ST_Touches, ST_Within all imply spatial intersection. If any of the aforementioned returns true, then the geometries also spatially intersect. Disjoint implies false for spatial intersection.

Changed: 3.0.0 SFCGAL version removed.

Enhanced: 2.5.0 Supports GEOMETRYCOLLECTION.

Enhanced: 2.3.0 Enhancement to PIP short-circuit extended to support MultiPoints with few points. Prior versions only supported point in polygon.

Performed by the GEOS module (for geometry), geography is native

Availability: 1.5 support for geography was introduced.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

For geography, this function has a distance tolerance of about 0.00001 meters and uses the sphere rather than spheroid calculation.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

&sfs_compliant; s2.1.1.2 //s2.1.13.3 - ST_Intersects(g1, g2 ) --> Not (ST_Disjoint(g1, g2 ))

&sqlmm_compliant; SQL-MM 3: 5.1.27

&sfcgal_enhanced;

#### Geometry Examples

    SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
     st_intersects
    ---------------
     f
    (1 row)
    SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
     st_intersects
    ---------------
     t
    (1 row)

    -- Look up in table. Make sure table has a GiST index on geometry column for faster lookup.
    SELECT id, name FROM cities WHERE ST_Intersects(geom, 'SRID=4326;POLYGON((28 53,27.707 52.293,27 52,26.293 52.293,26 53,26.293 53.707,27 54,27.707 53.707,28 53))');
     id | name
    ----+-------
      2 | Minsk
    (1 row)

#### Geography Examples

    SELECT ST_Intersects(
    		'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456 72.4568)'::geography,
    		'SRID=4326;POINT(-43.23456 72.4567772)'::geography
    		);

     st_intersects
    ---------------
    t

#### See Also

ST_3DIntersects, ST_Disjoint

ST_OrderingEquals

Returns true if the given geometries represent the same geometry and points are in the same directional order.

    			boolean ST_OrderingEquals
    			geometry  A
    			geometry  B

#### Description

ST_OrderingEquals compares two geometries and returns t (TRUE) if the geometries are equal and the coordinates are in the same order; otherwise it returns f (FALSE).

This function is implemented as per the ArcSDE SQL specification rather than SQL-MM. http://edndoc.esri.com/arcsde/9.1/sql_api/sqlapi3.htm#ST_OrderingEquals

&sqlmm_compliant; SQL-MM 3: 5.1.43

#### Examples

    SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
    		ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
     st_orderingequals
    -----------
     f
    (1 row)

    SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
    		ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
     st_orderingequals
    -----------
     t
    (1 row)

    SELECT ST_OrderingEquals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
    		ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
     st_orderingequals
    -----------
     f
    (1 row)

#### See Also

ST_Equals, ST_Reverse

ST_Overlaps

Returns TRUE if the Geometries share space, are of the same dimension, but are not completely contained by each other.

    			boolean ST_Overlaps
    			geometry  A
    			geometry  B

#### Description

Returns TRUE if the Geometries "spatially overlap". By that we mean they intersect, but one does not completely contain another.

Performed by the GEOS module

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

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_Overlaps.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

&sfs_compliant; s2.1.1.2 // s2.1.13.3

&sqlmm_compliant; SQL-MM 3: 5.1.32

#### Examples

The following illustrations all return `TRUE`.

`MULTIPOINT` / `MULTIPOINT` | `LINESTRING` / `LINESTRING` | `POLYGON` / `POLYGON`

    --a point on a line is contained by the line and is of a lower dimension, and therefore does not overlap the line
    			nor crosses

    SELECT ST_Overlaps(a,b) As a_overlap_b,
    	ST_Crosses(a,b) As a_crosses_b,
    		ST_Intersects(a, b) As a_intersects_b, ST_Contains(b,a) As b_contains_a
    FROM (SELECT ST_GeomFromText('POINT(1 0.5)') As a, ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)')  As b)
    	As foo

    a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a
    ------------+-------------+----------------+--------------
    f           | f           | t              | t

    --a line that is partly contained by circle, but not fully is defined as intersecting and crossing,
    -- but since of different dimension it does not overlap
    SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b,
    	ST_Intersects(a, b) As a_intersects_b,
    	ST_Contains(a,b) As a_contains_b
    FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 0.5)'), 3)  As a, ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)')  As b)
    	As foo;

     a_overlap_b | a_crosses_b | a_intersects_b | a_contains_b
    -------------+-------------+----------------+--------------
     f           | t           | t              | f

     -- a 2-dimensional bent hot dog (aka buffered line string) that intersects a circle,
     --	but is not fully contained by the circle is defined as overlapping since they are of the same dimension,
    --	but it does not cross, because the intersection of the 2 is of the same dimension
    --	as the maximum dimension of the 2

    SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b, ST_Intersects(a, b) As a_intersects_b,
    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 dima_intersection_b
    FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 0.5)'), 3)  As a,
    	ST_Buffer(ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)'),0.5)  As b)
    	As foo;

     a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a | dim_a | dim_b | dima_intersection_b
    -------------+-------------+----------------+--------------+-------+-------+---------------------
     t           | f           | t              | f            |     2 |     2 |              2

#### See Also

ST_Contains, ST_Crosses, ST_Dimension, ST_Intersects

ST_PointInsideCircle

Is the point geometry inside the circle defined by center_x, center_y, radius

    			boolean ST_PointInsideCircle
    			geometry  a_point
    			float  center_x
    			float  center_y
    			float  radius

#### Description

The syntax for this functions is ST_PointInsideCircle(<geometry>,<circle_center_x>,<circle_center_y>,<radius>). Returns the true if the geometry is a point and is inside the circle. Returns false otherwise.

This only works for points as the name suggests

Availability: 1.2

Changed: 2.2.0 In prior versions this used to be called ST_Point_Inside_Circle

#### Examples

    SELECT ST_PointInsideCircle(ST_Point(1,2), 0.5, 2, 3);
     st_pointinsidecircle
    ------------------------
     t

#### See Also

ST_DWithin

ST_Relate

Returns true if this Geometry is spatially related to anotherGeometry, by testing for intersections between the Interior, Boundary and Exterior of the two geometries as specified by the values in the intersectionMatrixPattern. If no intersectionMatrixPattern is passed in, then returns the maximum intersectionMatrixPattern that relates the 2 geometries.

    				boolean ST_Relate
    				geometry  geomA
    				geometry  geomB
    				text  intersectionMatrixPattern

    				text ST_Relate
    				geometry  geomA
    				geometry  geomB

    				text ST_Relate
    				geometry  geomA
    				geometry  geomB
    				integer  BoundaryNodeRule

#### Description

Version 1: Takes geomA, geomB, intersectionMatrix and Returns 1 (TRUE) if this Geometry is spatially related to anotherGeometry, by testing for intersections between the Interior, Boundary and Exterior of the two geometries as specified by the values in the DE-9IM matrix pattern.

This is especially useful for testing compound checks of intersection, crosses, etc in one step.

This is the "allowable" version that returns a boolean, not an integer. This is defined in OGC spec

This DOES NOT automagically include an index call. The reason for that is some relationships are anti e.g. Disjoint. If you are using a relationship pattern that requires intersection, then include the && index call.

Version 2: Takes geomA and geomB and returns the DE-9IM

Version 3: same as version 2, but allows to specify a boundary node rule (1:OGC/MOD2, 2:Endpoint, 3:MultivalentEndpoint, 4:MonovalentEndpoint)

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

not in OGC spec, but implied. see s2.1.13.2

&sfs_compliant; s2.1.1.2 // s2.1.13.3

&sqlmm_compliant; SQL-MM 3: 5.1.25

Performed by the GEOS module

Enhanced: 2.0.0 - added support for specifying boundary node rule.

#### Examples

    --Find all compounds that intersect and not touch a poly (interior intersects)
    SELECT l.* , b.name As poly_name
    	FROM polys As b
    INNER JOIN compounds As l
    ON (p.the_geom && b.the_geom
    AND ST_Relate(l.the_geom, b.the_geom,'T********'));

    SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2));
    st_relate
    -----------
    0FFFFF212

    SELECT ST_Relate(ST_GeometryFromText('LINESTRING(1 2, 3 4)'), ST_GeometryFromText('LINESTRING(5 6, 7 8)'));
    st_relate
    -----------
    FF1FF0102

    SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2), '0FFFFF212');
    st_relate
    -----------
    t

    SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2), '*FF*FF212');
    st_relate
    -----------
    t

#### See Also

ST_Crosses, DE-9IM, ST_Disjoint, ST_Intersects, ST_Touches

ST_RelateMatch

Returns true if intersectionMattrixPattern1 implies intersectionMatrixPattern2

    			boolean ST_RelateMatch
    			text  intersectionMatrix
    			text  intersectionMatrixPattern

#### Description

Takes intersectionMatrix and intersectionMatrixPattern and Returns true if the intersectionMatrix satisfies the intersectionMatrixPattern. For more information refer to DE-9IM.

Performed by the GEOS module

Availability: 2.0.0

#### Examples

    SELECT ST_RelateMatch('101202FFF', 'TTTTTTFFF') ;
    -- result --
    t
    --example of common intersection matrix patterns and example matrices
    -- comparing relationships of involving one invalid geometry and ( a line and polygon that intersect at interior and boundary)
    SELECT mat.name, pat.name, ST_RelateMatch(mat.val, pat.val) As satisfied
        FROM
            ( VALUES ('Equality', 'T1FF1FFF1'),
                    ('Overlaps', 'T*T***T**'),
                    ('Within', 'T*F**F***'),
                    ('Disjoint', 'FF*FF****') As pat(name,val)
            CROSS JOIN
                (	VALUES ('Self intersections (invalid)', '111111111'),
                        ('IE2_BI1_BB0_BE1_EI1_EE2', 'FF2101102'),
                        ('IB1_IE1_BB0_BE0_EI2_EI1_EE2', 'F11F00212')
                ) As mat(name,val);

#### See Also

DE-9IM, ST_Relate

ST_Touches

Returns `TRUE` if the geometries have at least one point in common, but their interiors do not intersect.

    			boolean ST_Touches

    			geometry
    			g1

    			geometry
    			g2

#### Description

Returns `TRUE` if the only points in common between `g1` and `g2` lie in the union of the boundaries of `g1` and `g2`. The `ST_Touches` relation applies to all Area/Area, Line/Line, Line/Area, Point/Area and Point/Line pairs of relationships, but not to the Point/Point pair.

In mathematical terms, this predicate is expressed as:

The allowable DE-9IM Intersection Matrices for the two geometries are:

- `FT*******`

- `F**T*****`

- `F***T****`

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

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 using an index, use `_ST_Touches` instead.

&sfs_compliant; s2.1.1.2 // s2.1.13.3

&sqlmm_compliant; SQL-MM 3: 5.1.28

#### Examples

The `ST_Touches` predicate returns `TRUE` in all the following illustrations.

`POLYGON` / `POLYGON` | `POLYGON` / `POLYGON` | `POLYGON` / `LINESTRING`
`LINESTRING` / `LINESTRING` | `LINESTRING` / `LINESTRING` | `POLYGON` / `POINT`

    SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(1 1)'::geometry);
     st_touches
    ------------
     f
    (1 row)

    SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(0 2)'::geometry);
     st_touches
    ------------
     t
    (1 row)

ST_Within

Returns true if the geometry A is completely inside geometry B

    			boolean ST_Within

    			geometry
    			A

    			geometry
    			B

#### Description

Returns TRUE if geometry A is completely inside geometry B. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID. It is a given that if ST_Within(A,B) is true and ST_Within(B,A) is true, then the two geometries are considered spatially equal.

Performed by the GEOS module

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.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

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_Within.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

&sfs_compliant; s2.1.1.2 // s2.1.13.3 - a.Relate(b, 'T*F**F***')

&sqlmm_compliant; SQL-MM 3: 5.1.30

#### Examples

    --a circle within a circle
    SELECT ST_Within(smallc,smallc) As smallinsmall,
    	ST_Within(smallc, bigc) As smallinbig,
    	ST_Within(bigc,smallc) As biginsmall,
    	ST_Within(ST_Union(smallc, bigc), bigc) as unioninbig,
    	ST_Within(bigc, ST_Union(smallc, bigc)) as biginunion,
    	ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion
    FROM
    (
    SELECT ST_Buffer(ST_GeomFromText('POINT(50 50)'), 20) As smallc,
    	ST_Buffer(ST_GeomFromText('POINT(50 50)'), 40) As bigc) As foo;
    --Result
     smallinsmall | smallinbig | biginsmall | unioninbig | biginunion | bigisunion
    --------------+------------+------------+------------+------------+------------
     t            | t          | f          | t          | t          | t
    (1 row)

#### See Also

ST_Contains, ST_Equals, ST_IsValid

## Distance Relationships

ST_3DDWithin

For 3d (z) geometry type Returns true if two geometries 3d distance is within number of units.

    			boolean ST_3DDWithin

    			geometry
    			g1

    			geometry
    			g2

    			double precision
    			distance_of_srid

#### Description

For geometry type returns true if the 3d distance between two objects is within distance_of_srid specified projected units (spatial ref units).

&Z_support;

&P_support;

&sqlmm_compliant; SQL-MM ?

Availability: 2.0.0

#### Examples

    -- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
    -- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
    SELECT ST_3DDWithin(
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
    			126.8
    		) As within_dist_3d,
    ST_DWithin(
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
    			126.8
    		) As within_dist_2d;

     within_dist_3d | within_dist_2d
    ----------------+----------------
     f              | t

#### See Also

ST_3DDistance, ST_Distance, ST_DWithin, ST_3DMaxDistance, ST_Transform

ST_3DDFullyWithin

Returns true if all of the 3D geometries are within the specified distance of one another.

    			boolean ST_3DDFullyWithin

    			geometry
    			g1

    			geometry
    			g2

    			double precision
    			distance

#### Description

Returns true if the 3D geometries are fully within the specified distance of one another. The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

Availability: 2.0.0

&Z_support;

&P_support;

#### Examples

    		-- This compares the difference between fully within and distance within as well
    		-- as the distance fully within for the 2D footprint of the line/point vs. the 3d fully within
    		SELECT ST_3DDFullyWithin(geom_a, geom_b, 10) as D3DFullyWithin10, ST_3DDWithin(geom_a, geom_b, 10) as D3DWithin10,
    	ST_DFullyWithin(geom_a, geom_b, 20) as D2DFullyWithin20,
    	ST_3DDFullyWithin(geom_a, geom_b, 20) as D3DFullyWithin20 from
    		(select ST_GeomFromEWKT('POINT(1 1 2)') as geom_a,
    		ST_GeomFromEWKT('LINESTRING(1 5 2, 2 7 20, 1 9 100, 14 12 3)') as geom_b) t1;
     d3dfullywithin10 | d3dwithin10 | d2dfullywithin20 | d3dfullywithin20
    ------------------+-------------+------------------+------------------
     f                | t           | t                | f

#### See Also

ST_3DMaxDistance, ST_3DDWithin, ST_DWithin, ST_DFullyWithin

ST_DFullyWithin

Returns true if all of the geometries are within the specified distance of one another

    			boolean ST_DFullyWithin

    			geometry
    			g1

    			geometry
    			g2

    			double precision
    			distance

#### Description

Returns true if the geometries is fully within the specified distance of one another. The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

Availability: 1.5.0

#### Examples

    postgis=# SELECT ST_DFullyWithin(geom_a, geom_b, 10) as DFullyWithin10, ST_DWithin(geom_a, geom_b, 10) as DWithin10, ST_DFullyWithin(geom_a, geom_b, 20) as DFullyWithin20 from
    		(select ST_GeomFromText('POINT(1 1)') as geom_a,ST_GeomFromText('LINESTRING(1 5, 2 7, 1 9, 14 12)') as geom_b) t1;

    -----------------
     DFullyWithin10 | DWithin10 | DFullyWithin20 |
    ---------------+----------+---------------+
     f             | t        | t             |

#### See Also

ST_MaxDistance, ST_DWithin

ST_DWithin

Returns true if the geometries are within the specified distance of one another. For geometry units are in those of spatial reference and for geography units are in meters and measurement is defaulted to use_spheroid=true (measure around spheroid), for faster check, use_spheroid=false to measure along sphere.

    				boolean ST_DWithin
    				geometry
    				g1

    				geometry
    				g2

    				double precision
    				distance_of_srid

    				boolean ST_DWithin
    				geography
    				gg1

    				geography
    				gg2

    				double precision
    				distance_meters

    				boolean
    				use_spheroid

#### Description

Returns true if the geometries are within the specified distance of one another.

For `geometry`: The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID.

For `geography` units are in meters and measurement is defaulted to `use_spheroid`=true, for faster check, `use_spheroid`=false to measure along sphere.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries.

Prior to 1.3, ST_Expand was commonly used in conjunction with && and ST_Distance to achieve the same effect and in pre-1.3.4 this function was basically short-hand for that construct. From 1.3.4, ST_DWithin uses a more short-circuit distance function which should make it more efficient than prior versions for larger buffer regions.

Use ST_3DDWithin if you have 3D geometries.

&sfs_compliant;

Availability: 1.5.0 support for geography was introduced

Enhanced: 2.1.0 improved speed for geography. See Making Geography faster for details.

Enhanced: 2.1.0 support for curved geometries was introduced.

#### Examples

    -- Find the nearest hospital to each school
    -- that is within 3000 units of the school.
    --  We do an ST_DWithin search to utilize indexes to limit our search list
    --  that the non-indexable ST_Distance needs to process
    -- If the units of the spatial reference is meters then units would be meters
    SELECT DISTINCT ON (s.gid) s.gid, s.school_name, s.geom, h.hospital_name
    	FROM schools s
    		LEFT JOIN hospitals h ON ST_DWithin(s.the_geom, h.geom, 3000)
    	ORDER BY s.gid, ST_Distance(s.geom, h.geom);

    -- The schools with no close hospitals
    -- Find all schools with no hospital within 3000 units
    -- away from the school.  Units is in units of spatial ref (e.g. meters, feet, degrees)
    SELECT s.gid, s.school_name
    	FROM schools s
    		LEFT JOIN hospitals h ON ST_DWithin(s.geom, h.geom, 3000)
    	WHERE h.gid IS NULL;

    -- Find broadcasting towers that receiver with limited range can receive.
    -- Data is geometry in Spherical Mercator (SRID=3857), ranges are approximate.

    -- Create geometry index that will check proximity limit of user to tower
    CREATE INDEX ON broadcasting_towers using gist (geom);

    -- Create geometry index that will check proximity limit of tower to user
    CREATE INDEX ON broadcasting_towers using gist (ST_Expand(geom, sending_range));

    -- Query towers that 4-kilometer receiver in Minsk Hackerspace can get
    -- Note: two conditions, because shorter LEAST(b.sending_range, 4000) will not use index.
    SELECT b.tower_id, b.geom
      FROM broadcasting_towers b
      WHERE ST_DWithin(b.geom, 'SRID=3857;POINT(3072163.4 7159374.1)', 4000)
    	  AND ST_DWithin(b.geom, 'SRID=3857;POINT(3072163.4 7159374.1)', b.sending_range);

#### See Also

ST_Distance, ST_Expand, ST_3DDWithin