ST_Touches

Determines if two GEOMETRY objects touch at a single point or along a boundary, but do not have interiors that intersect.

GEOGRAPHY Polygons with a vertex or border on the International Date Line (IDL) or the North or South pole are not supported.

Behavior type

Immutable

Syntax

ST_Touches( g1, g2
                        [USING PARAMETERS spheroid={true | false}] )

Arguments

g1: Spatial object, value of type GEOMETRY
g2: Spatial object, value of type GEOMETRY

Parameters

spheroid = {true | false}

(Optional) BOOLEAN that specifies whether to use a perfect sphere or WGS84.

Default: False

Returns

BOOLEAN

Supported data types

Data Type	GEOMETRY	GEOGRAPHY (WGS84)
Point	Yes	Yes
Multipoint	Yes	No
Linestring	Yes	No
Multilinestring	Yes	No
Polygon	Yes	Yes
Multipolygon	Yes	No
GeometryCollection	Yes	No

Compatible GEOGRAPHY pairs:

Data Type	GEOGRAPHY (WGS84)
Point-Point	No
Linestring-Point	No
Polygon-Point	Yes
Multipolygon-Point	No

Examples

The following examples show how to use ST_Touches.

Two polygons touch at a single point:

=> SELECT ST_Touches(ST_GeomFromText('POLYGON((-1 2,0 3,0 1,-1 2))'),
   ST_GeomFromText('POLYGON((1 3,0 3,1 2,1 3))'));
 ST_Touches
------------
 t
(1 row)

Two polygons touch only along part of the boundary:

=> SELECT ST_Touches(ST_GeomFromText('POLYGON((-1 2,0 3,0 1,-1 2))'),
   ST_GeomFromText('POLYGON((1 2,0 3,0 1,1 2))'));
 ST_Touches
------------
 t
(1 row)

Two polygons do not touch at any point:

=> SELECT ST_Touches(ST_GeomFromText('POLYGON((-1 2,0 3,0 1,-1 2))'),
   ST_GeomFromText('POLYGON((0 2,-1 3,-2 0,0 2))'));
 ST_Touches
------------
 f
(1 row)