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.