ST_Length
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Name

ST_Length — Returns the 2D length of a linear geometry.

Synopsis

float ST_Length(geometry a_2dlinestring);

float ST_Length(geography geog, boolean use_spheroid = true);

Description

For geometry types: returns the 2D Cartesian length of the geometry if it is a LineString, MultiLineString, ST_Curve, ST_MultiCurve. For areal geometries 0 is returned; use ST_Perimeter instead. The units of length is determined by the spatial reference system of the geometry.

For geography types: computation is performed using the inverse geodesic calculation. Units of length are in meters. The spheroid is specified by the SRID; when no SRID is provided, WGS84 is used. If use_spheroid = false, then the calculation is based on a sphere instead of a spheroid.

Currently for geometry this is an alias for ST_Length2D, but this may change to support higher dimensions.

[Warning]

Changed: 2.0.0 Breaking change -- in prior versions applying this to a MULTI/POLYGON of type geography would give you the perimeter of the POLYGON/MULTIPOLYGON. In 2.0.0 this was changed to return 0 to be in line with geometry behavior. Please use ST_Perimeter if you want the perimeter of a polygon
[Note]

For geography the calculation defaults to using a spheroidal model. To use the faster but less accurate spherical calculation use ST_Length(gg,false);

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 7.1.2, 9.3.4

Availability: 1.5.0 geography support was introduced in 1.5.

Geometry Examples

Return length in feet for line string. Note this is in feet because EPSG:2249 is Massachusetts State Plane Feet

SELECT ST_Length(ST_GeomFromText(
'LINESTRING(743238 2967416,743238 2967450,743265 2967450,
743265.625 2967416,743238 2967416)',
2249));
122.63074400009504

This example transforms a WGS 84 LineString to Massachusetts State Plane meters.

SELECT ST_Length(ST_Transform(
		ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45, -72.1240 42.45666, -72.123 42.1546)'),
			26986
	)
);
34309.4563576191

Geography Examples

Return length of WGS 84 geography line

This example uses the default spheroid calculation.

SELECT ST_Length(the_geog) As length_spheroid,  ST_Length(the_geog,false) As length_sphere
FROM (SELECT ST_GeographyFromText('SRID=4326;LINESTRING(-72.1260 42.45, -72.1240 42.45666, -72.123 42.1546)') As the_geog)
 As foo;
 length_spheroid  |  length_sphere
------------------+------------------
34310.5703627284 | 34346.20609607416