transformations

This module contains functions that compute geometric constructions, or alter geometry size or shape.

ST_CENTERMEAN

ST_CENTERMEAN(geom)

Description

Takes a Feature or FeatureCollection and returns the mean center (average of its vertices).

• geom: GEOMETRY for which to compute the mean center.

Return type

GEOMETRY

Example

SELECT carto.ST_CENTERMEAN(ST_GEOMFROMTEXT('POLYGON ((30 10, 40 40, 20 40, 10 20, 30 10))'));
-- POINT (25 27.5)

ST_CENTERMEDIAN

ST_CENTERMEDIAN(geom)

Description

Takes a FeatureCollection of points and computes the median center. The median center is understood as the point that requires the least total travel from all other points.

• geog: GEOMETRY for which to compute the center.

Return type

GEOMETRY

Example

SELECT carto.ST_CENTERMEDIAN(ST_GEOMFROMTEXT('POLYGON ((30 10, 40 40, 20 40, 10 20, 30 10))'));
-- POINT (26.3841869726 19.0088147377)

ST_CENTEROFMASS

ST_CENTEROFMASS(geom)

Description

Takes any Feature or a FeatureCollection and returns its center of mass. It is equivalent to ST_CENTROID.

• geom: GEOMETRY for which to compute the center of mass.

Return type

GEOMETRY

Example

SELECT carto.ST_CENTEROFMASS(ST_GEOMFROMTEXT('POLYGON ((30 10, 40 40, 20 40, 10 20, 30 10))'));
-- POINT (25.4545454545 26.9696969697)

ST_CENTROID

ST_CENTROID(geom)

Description

Takes any Feature or a FeatureCollection as input and returns its centroid. It is equivalent to ST_CENTEROFMASS.

• geom: GEOMETRY for which to compute the centroid.

Return type

GEOMETRY

Example

SELECT carto.ST_CENTROID(ST_GEOMFROMTEXT('POLYGON ((30 10, 40 40, 20 40, 10 20, 30 10))'));
-- POINT (25.4545454545 26.9696969697)

ST_DESTINATION

ST_DESTINATION(geom, distance, bearing, units)

Description

Takes a Point and calculates the location of a destination point given a distance in degrees, radians, miles, or kilometers; and a bearing in degrees. This uses the Haversine formula to account for global curvature.

• geom: GEOMETRY starting point.

• distance: FLOAT8 distance from the origin point in the units specified.

• bearing: FLOAT8 ranging from -180 to 180 (e.g. 0 is North, 90 is East, 180 is South, -90 is West).

• units (optional): VARCHAR(15) units of length. The supported options are: miles, kilometers, degrees or radians. If NULLthe default value kilometers is used.

Return type

GEOMETRY

Examples

SELECT carto.ST_DESTINATION(ST_MakePoint(-3.70325,40.4167), 10, 45);
-- POINT (-3.61964617436 40.4802614598)

SELECT carto.ST_DESTINATION(ST_MakePoint(-3.70325,40.4167), 10, 45, 'miles');
-- POINT (-3.56862505482 40.5189626778)

ST_GREATCIRCLE

ST_GREATCIRCLE(start_point, end_point, n_points)

Description

Calculates a great circle route as a LineString.

• start_point: GEOMETRY source point feature.

• end_point: GEOMETRY destination point feature.

• n_points (optional): INT number of points. Defaults to 100.

Return type

GEOMETRY

Examples

SELECT carto.ST_GREATCIRCLE(ST_MAKEPOINT(-3.70325,40.4167), ST_MAKEPOINT(-73.9385,40.6643));
-- LINESTRING (-3.70325 40.4167, -4.32969777937 40.6355528695, ...

SELECT carto.ST_GREATCIRCLE(ST_MAKEPOINT(-3.70325,40.4167), ST_MAKEPOINT(-73.9385,40.6643), 20);
-- LINESTRING (-3.70325 40.4167, -7.01193184681 41.5188665219, ...