This topic describes the ST_ConvexHull function, which obtains the minimum convex geometry that encloses all geometries within a raster.

Syntax

geometry ST_ConvexHull(raster source);
geometry ST_ConvexHull(raster source, 
                       integer pyramid);

Parameters

Parameter Description
source The raster whose minimum convex geometry you want to obtain.
pyramid The pyramid level at which the raster resides. Valid values start from 0. Default value: 0.

Description

This function obtains the minimum convex geometry that encloses all geometries within a raster.

Minimum convex geometry

Example

SELECT st_astext(st_convexhull(rast_object))
FROM raster_table;

----------------------------------------------------
 POLYGON((-180 90,180 90,180 -90,-180 -90,-180 90))

--Specify the pyramid level at which the raster resides.                 
SELECT st_astext(st_convexhull(rast_object,  1))
FROM raster_table;

----------------------------------------------------
 POLYGON((-180 90,180 90,180 -90,-180 -90,-180 90))