H2GIS

Fork me on GitHub

ST_MaxDistance

Signature

DOUBLE ST_MaxDistance(GEOMETRY geomA, GEOMETRY geomB);

Description

Returns the 2-dimensional longest distance between the points of two geometries (geomA and geomB).

If geomA and geomB are the same, the function will return the longest distance between the two farthest vertices in this geometry.

Distance is measured in the units of the spatial reference system.

Remark

To return the geometry (LINESTRING) that correspond to the longest distance, the user may use ST_LongestLine.

Examples

Cases where geomA and geomB are different
SELECT ST_MaxDistance('POLYGON ((0 1, 1 1, 1 0, 0 0, 0 1))', 
                      'POLYGON ((2 3, 2 2, 3 2, 4 3, 2 3))');
-- Answer: 5

SELECT ST_MaxDistance('POLYGON ((0 1, 1 1, 1 0, 0 0, 0 1))', 
		      'LINESTRING (1 3, 4 3)');
-- Answer: 5

SELECT ST_MaxDistance('POLYGON ((0 1, 1 1, 1 0, 0 0, 0 1))', 
		      'POINT (3 2)');
-- Answer: 3,605551275463989 

SELECT ST_MaxDistance('MULTIPOLYGON (((0 1, 1 1, 1 0, 0 0, 0 1)),
				    ((2 3, 2 2, 3 3, 2 3)))', 
		      'POINT (3 2)');
-- Answer: 3,605551275463989

Case where geomA is equal to geomB
SELECT ST_MaxDistance('POLYGON ((1 3, 0 0, 3 2, 1 3))', 
		      'POLYGON ((1 3, 0 0, 3 2, 1 3))');
-- Answer: 3,605551275463989

See also