STV_DWithin

Determines if the shortest distance from the boundary of one spatial object to the boundary of another object is within a specified distance.

Parameters g1 and g2 must be both GEOMETRY objects or both GEOGRAPHY objects.

Behavior type

Syntax

STV_DWithin( g1, g2, d )

Arguments

g1

Spatial object of type GEOMETRY or GEOGRAPHY

g2

Spatial object of type GEOMETRY or GEOGRAPHY

d

Value of type FLOAT indicating a distance. For GEOMETRY objects, the distance is measured in Cartesian coordinate units. For GEOGRAPHY objects, the distance is measured in meters.

Returns

BOOLEAN

Supported data types

Compatible GEOGRAPHY pairs:

Data Type

GEOGRAPHY (Perfect Sphere)

Point-Point

Yes

Point-Linestring

Yes

Point-Polygon

Yes

Point-Multilinestring

Yes

Point-Multipolygon

Yes

Examples

The following examples show how to use STV_DWithin.

Two geometries are one Cartesian coordinate unit from each other at their closest points:

=> SELECT STV_DWithin(ST_GeomFromText('POLYGON((-1 -1,2 2,0 1,-1 -1))'),
   ST_GeomFromText('POLYGON((4 3,2 3,4 5,4 3))'),1);
 STV_DWithin
-------------
 t
(1 row)

If you reduce the distance to 0.99 units:

=> SELECT STV_DWithin(ST_GeomFromText('POLYGON((-1 -1,2 2,0 1,-1 -1))'),
   ST_GeomFromText('POLYGON((4 3,2 3,4 5,4 3))'),0.99);
 STV_DWithin
-------------
 f
(1 row)

The first polygon touches the second polygon:

=> SELECT STV_DWithin(ST_GeomFromText('POLYGON((-1 -1,2 2,0 1,-1 -1))'),
   ST_GeomFromText('POLYGON((1 1,2 3,4 5,1 1))'),0.00001);
 STV_DWithin
-------------
 t
(1 row)

The first polygon is not within 1000 meters from the second polygon:

=> SELECT STV_DWithin(ST_GeomFromText('POLYGON((45.2 40,50.65 51.29,
   55.67 47.6,50 47.6,45.2 40))'),ST_GeomFromText('POLYGON((25 25,25 30,
   30 30,30 25,25 25))'), 1000);
 STV_DWithin
--------------
 t
(1 row)