measurements

CORE

This module contains functions that compute measurements of distance, area and angles. There are also functions to compute geometry values determined by measurements.

ST_AREA

ST_AREA(geom)

Description

If Geometry g is areal, returns the area of its surface in square units of the coordinate reference system (for example, degrees^2 for EPSG:4326). Returns 0.0 for non-areal geometries (e.g. Points, non-closed LineStrings, etc.).

• geom: Geometry input geom.

Return type

Double

Example

SELECT carto.ST_AREA(carto.ST_MAKEBBOX(0, 0, 2, 2));
-- 4

ST_DISTANCE

ST_DISTANCE(geomA, geomB)

Description

Returns the 2D Cartesian distance between the two geometries in units of the coordinate reference system (e.g. degrees for EPSG:4236).

• geomA: Geometry input geom A.

• geomB: Geometry input geom B.

Return type

Double

Example

SELECT carto.ST_DISTANCE(carto.ST_POINT(0, 0), carto.ST_POINT(0, 5));
-- 5

ST_DISTANCESPHERE

ST_DISTANCESPHERE(geomA, geomB)

Description

Approximates the minimum distance (in meters) between two longitude/latitude geometries assuming a spherical earth.

• geomA: Geometry input geom A.

• geomB: Geometry input geom B.

Return type

Double

Example

SELECT carto.ST_DISTANCESPHERE(carto.ST_POINT(0, 0), carto.ST_POINT(0, 5)) / 1000;
-- 555.9753986718438 (distance in km)

ST_LENGTH

ST_LENGTH(line)

Description

Returns the 2D path length of linear geometries, or perimeter of areal geometries, in units of the the coordinate reference system (e.g. degrees for EPSG:4236). Returns 0.0 for other geometry types (e.g. Point).

• line: LineString input line.

Return type

Double

Example

SELECT carto.ST_LENGTH(carto.ST_GEOMFROMWKT('LINESTRING(0 0, 0 3, 5 3)'));
-- 8

ST_LENGTHSPHERE

ST_LENGTHSPHERE(line)

Description

Approximates the 2D path length of a LineString geometry using a spherical earth model. The returned length is in units of meters. The approximation is within 0.3% of st_lengthSpheroid and is computationally more efficient.

• line: LineString input line.

Return type

Double

Example

SELECT carto.ST_LENGTHSPHERE(carto.ST_GEOMFROMWKT('LINESTRING(0 0, 0 3, 5 3)')) / 1000;
-- 888.7982099954688 (distance in km)