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

Immutable

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

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

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)