## Name

ST_3DDWithin — Tests if two 3D geometries are within a given 3D distance

## Synopsis

`boolean ST_3DDWithin(`geometry g1, geometry g2, double precision distance_of_srid`)`;

## Descrizione

Returns true if the 3D distance between two geometry values is no larger than distance `distance_of_srid`. 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 be in the same coordinate system (have the same SRID).

 Questa funzione incorpora l'uso di una comparazione tra i bounding box in modo da usare qualunque indice spaziale disponibile sulle geometrie.

Questa funzione supporta il 3d e non distrugge gli z-index.

Questa funzione supporta le Polyhedral Surface.

Questo metodo implementa la specifica SQL/MM. SQL-MM ?

Disponibilità: 2.0.0

## Esempi

```-- 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
```