ST_3DLength
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## Name

ST_3DLength — Returns the 3D length of a linear geometry.

## Synopsis

`float ST_3DLength(`geometry a_3dlinestring`)`;

## Description

Returns the 3-dimensional or 2-dimensional length of the geometry if it is a LineString or MultiLineString. For 2-d lines it will just return the 2-d length (same as ST_Length and ST_Length2D)

This function supports 3d and will not drop the z-index.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 7.1, 10.3

Changed: 2.0.0 In prior versions this used to be called ST_Length3D

## Examples

Return length in feet for a 3D cable. Note this is in feet because EPSG:2249 is Massachusetts State Plane Feet

    SELECT ST_3DLength(ST_GeomFromText('LINESTRING(743238 2967416 1,743238 2967450 1,743265 2967450 3,
    743265.625 2967416 3,743238 2967416 3)',2249));
    ST_3DLength
    -----------
    122.704716741457

## See Also

ST_Length, ST_Length2D

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