transformations

CORE

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

ST_ANTIMERIDIANSAFEGEOM

ST_ANTIMERIDIANSAFEGEOM(geom)

Description

If geom spans the antimeridian, attempt to convert the Geometry into an equivalent form that is “antimeridian-safe” (i.e. the output Geometry is covered by BOX(-180 -90, 180 90)). In certain circumstances, this method may fail, in which case the input Geometry will be returned and an error will be logged.

geom: Geometry input geom.

Return type

Geometry

Example

WITH t AS (
  SELECT carto.ST_MAKEBBOX(178, 0, 190, 5) AS geom
)
SELECT carto.ST_ASTEXT(carto.ST_ANTIMERIDIANSAFEGEOM(geom)) FROM t;
-- MULTIPOLYGON (((-180 0, -180 5, -170 5, -170 0, -180 0)), ((180 5, 180 0, 178 0, 178 5, 180 5)))

ST_BOUNDARY

ST_BOUNDARY(geom)

Description

Returns the boundary, or an empty Geometry of appropriate dimension, if geom is empty.

geom: Geometry input geom.

Return type

Geometry

Example

WITH t AS (
  SELECT carto.ST_MAKEBBOX(0, 0, 2, 2) AS geom
)
SELECT carto.ST_ASTEXT(carto.ST_BOUNDARY(geom)) FROM t;
-- LINESTRING (0 0, 0 2, 2 2, 2 0, 0 0)

ST_BUFFERPOINT

ST_BUFFERPOINT(point, radius)

Description

Returns a Geometry covering all points within a given radius of Point point, where radius is given in meters.

Returns the boundary, or an empty Geometry of appropriate dimension, if geom is empty.

point: Point Center of the buffer.
buffer: Double radius in meters.

Return type

Geometry

Example

SELECT carto.ST_ASTEXT(carto.ST_BUFFERPOINT(carto.ST_POINT(0, 0), 1));;
-- POLYGON ((0.000009 0, 0.000009 0.0000006, 0.0000089 0.0000011, 0.0000088 0.0000017, ...

ST_CENTROID

ST_CENTROID(geom)

Description

Returns the geometric center of a geometry.

geom: Geometry input geom.

Return type

Point

Example

WITH t AS (
  SELECT carto.ST_MAKEBBOX(0, 0, 2, 2) AS geom
)
SELECT carto.ST_ASTEXT(carto.ST_CENTROID(geom)) FROM t;
-- POINT (1 1)

ST_CLOSESTPOINT

ST_CLOSESTPOINT(geomA, geomB)

Description

Returns the Point on a that is closest to b. This is the first Point of the shortest line.

geomA: Geometry input geom A.
geomB: Geometry input geom B.

Return type

Point

Example

WITH t AS (
  SELECT carto.ST_GEOMFROMWKT("LINESTRING (3 1, 1 3)") AS geomA,
  carto.ST_POINT(0, 0) AS geomb
)
SELECT carto.ST_ASTEXT(carto.ST_CLOSESTPOINT(geomA, geomB)) FROM t;
-- POINT (2 2)

ST_CONVEXHULL

ST_CONVEXHULL(geom)

Description

Aggregate function. The convex hull of a Geometry represents the minimum convex Geometry that encloses all geometries geom in the aggregated rows.

geom: Geometry input geom.

Return type

Geometry

Example

WITH t AS (
  SELECT carto.ST_GEOMFROMWKT(
    'GEOMETRYCOLLECTION(LINESTRING(1 1, 3 5),POLYGON((-1 -1, -1 -5, -5 -5, -5 -1, -1 -1)))'
  ) AS geom
)
SELECT carto.ST_ASTEXT(carto.ST_CONVEXHULL(geom)) FROM t;
-- POLYGON ((-5 -5, -5 -1, 3 5, -1 -5, -5 -5))

ST_DIFFERENCE

ST_DIFFERENCE(geomA, geomB)

Description

Return the part of geomA that does not intersect with geomB.

geomA: Geometry input geom A.
geomB: Geometry input geom B.

Return type

Geometry

Example

WITH t AS (
  SELECT carto.ST_MAKEBBOX(0, 0, 2, 2) AS geomA,
  carto.ST_MAKEBBOX(1, 1, 3, 3) AS geomB
)
SELECT carto.ST_ASTEXT(carto.ST_DIFFERENCE(geomA, geomB)) AS difference FROM t;
-- POLYGON ((0 0, 0 2, 1 2, 1 1, 2 1, 2 0, 0 0))

ST_EXTERIORRING

ST_EXTERIORRING(geom)

Description

Returns a LineString representing the exterior ring of the geometry; returns null if the Geometry is not a Polygon.

geom: Geometry input geom.

Return type

LineString

Example

WITH t AS (
  SELECT carto.ST_MAKEBBOX(0, 0, 1, 1) AS geom
)
SELECT carto.ST_ASTEXT(carto.ST_EXTERIORRING(geom)) FROM t;
-- LINESTRING (0 0, 0 1, 1 1, 1 0, 0 0)

ST_IDLSAFEGEOM

ST_IDLSAFEGEOM(geom)

Description

Alias of st_antimeridianSafeGeom.

geom: Geometry input geom.

Return type

Geometry

Example

WITH t AS (
  SELECT carto.ST_MAKEBBOX(178, 0, 190, 5) AS geom
)
SELECT carto.ST_ASTEXT(carto.ST_IDLSAFEGEOM(geom)) AS geom FROM t;
-- MULTIPOLYGON (((-180 0, -180 5, -170 5, -170 0, -180 0)), ((180 5, 180 0, 178 0, 178 5, 180 5)))

ST_INTERIORRINGN

ST_INTERIORRINGN(geom, n)

Description

Returns a LineString representing the exterior ring of the geometry; returns null if the Geometry is not a Polygon.

geom: Geometry input geom.
n: Int nth ring to take.

Return type

LineString

Example

WITH t AS (
  SELECT carto.ST_GEOMFROMWKT("POLYGON ((10 10, 110 10, 110 110, 10 110, 10 10), (20 20, 20 30, 30 30, 30 20, 20 20), (40 20, 40 30, 50 30, 50 20, 40 20))") AS geom
)
SELECT carto.ST_ASTEXT(carto.ST_INTERIORRINGN(geom, 1)) FROM t;
-- LINESTRING (20 20, 20 30, 30 30, 30 20, 20 20)

ST_INTERSECTION

ST_INTERSECTION(geomA, geomB)

Description

Returns the intersection of the input Geometries.

geomA: Geometry input geom A.
geomB: Geometry input geom B.

Return type

Geometry

Example

WITH t AS (
  SELECT carto.ST_MAKEBBOX(0, 0, 2, 2) AS geomA,
  carto.ST_MAKEBBOX(1, 1, 3, 3) AS geomB
)
SELECT carto.ST_ASTEXT(carto.ST_INTERSECTION(geomA, geomB)) AS intersection FROM t;
-- POLYGON ((1 2, 2 2, 2 1, 1 1, 1 2))

ST_SIMPLIFY

ST_SIMPLIFY(geom, tolerance)

Description

Returns a simplified version of the given Geometry using the Douglas-Peucker algorithm. This function does not preserve topology - e.g. polygons can be split, collapse to lines or disappear holes can be created or disappear, and lines can cross. To simplify geometry while preserving topology use ST_SIMPLIFYPRESERVETOPOLOGY.

geom: Geometry input geom.
tolerance: Double input distance tolerance. double

Return type

Geometry

Example

WITH t AS (
  SELECT carto.ST_BUFFERPOINT(carto.ST_POINT(0, 0), 10) AS geom
)
SELECT
  carto.ST_ASTEXT(carto.ST_SIMPLIFY(geom, 0.00001)) AS simplifiedGeom,
  carto.ST_NUMPOINTS(carto.ST_SIMPLIFY(geom, 0.00001)) AS simplifiedNumpoints,
  carto.ST_NUMPOINTS(geom) AS numPoints
FROM t;
-- POLYGON ((0.0000899 0, 0.0000656 0.0000616, 0 0.0000899, -0.0000616 0.0000656, -0.0000899 0, -0.0000656 -0.0000616, 0 -0.0000899, 0.0000616 -0.0000656, 0.0000899 0)) | 9 | 101

ST_SIMPLIFYPRESERVETOPOLOGY

ST_SIMPLIFYPRESERVETOPOLOGY(geom, tolerance)

Description

Simplifies a Geometry and ensures that the result is a valid geometry having the same dimension and number of components as the input, and with the components having the same topological relationship.

geom: Geometry input geom.
tolerance: Double input distance tolerance. double

Return type

Geometry

Example

WITH t AS (
  SELECT carto.ST_BUFFERPOINT(carto.ST_POINT(0, 0), 10) AS geom
)
SELECT
  carto.ST_ASTEXT(carto.ST_SIMPLIFYPRESERVETOPOLOGY(geom, 1)) AS simplifiedGeom,
  carto.ST_NUMPOINTS(carto.ST_SIMPLIFYPRESERVETOPOLOGY(geom, 1)) AS simplifiedNumpoints,
  carto.ST_NUMPOINTS(geom) AS numPoints
FROM t;
-- POLYGON ((0.0000899 0, 0 0.0000899, -0.0000899 0, 0 -0.0000899, 0.0000899 0)) | 5 | 101

ST_TRANSLATE

ST_TRANSLATE(geom, deltaX, deltaY)

Description

Returns the Geometry produced when geom is translated by deltaX and deltaY.

geom: Geometry input geom.
deltaX: Double distance x to be tralslated.
deltaY: Double distance y to be tralslated.

Return type

Geometry

Example

WITH t AS (
  SELECT carto.ST_POINT(0, 0) AS point
)
SELECT carto.ST_ASTEXT(carto.ST_TRANSLATE(point, 1, 2)) FROM t;
-- POINT (1 2)

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