ST_ConvexHull

Calculates the smallest convex GEOMETRY object that contains a GEOMETRY object.

Behavior type

Syntax

ST_ConvexHull( g )

Arguments

g: Spatial object for which you want the convex hull, type GEOMETRY

Returns

GEOMETRY

Supported data types

Data Type: GEOMETRY
Point: Yes
Multipoint: Yes
Linestring: Yes
Multilinestring: Yes
Polygon: Yes
Multipolygon: Yes
GeometryCollection: Yes

Examples

The following examples show how to use ST_ConvexHull.

For a pair of points in a geometry collection:

=> SELECT ST_AsText(ST_ConvexHull(ST_GeomFromText('GEOMETRYCOLLECTION(
   POINT(1 1),POINT(0 0))')));
       ST_AsText
-----------------------
 LINESTRING (1 1, 0 0)
(1 row)

For a geometry collection:

=> SELECT ST_AsText(ST_ConvexHull(ST_GeomFromText('GEOMETRYCOLLECTION(
   LINESTRING(2.5 3,-2 1.5), POLYGON((0 1,1 3,1 -2,0 1)))')));
                  ST_AsText
---------------------------------------------
 POLYGON ((1 -2, -2 1.5, 1 3, 2.5 3, 1 -2))
(1 row)

The solid lines represent the original geometry collection and the dashed lines represent the convex hull.