ST_LocateAlong

Description

Return a derived geometry collection value with elements that match the specified measure. Polygonal elements are not supported.

If an offset is provided, the resultant will be offset to the left or right of the input line by the specified number of units. A positive offset will be to the left, and a negative one to the right.

Semantic is specified by: ISO/IEC CD 13249-3:200x(E) - Text for Continuation CD Editing Meeting

Availability: 1.1.0 by old name ST_Locate_Along_Measure.

Changed: 2.0.0 in prior versions this used to be called ST_Locate_Along_Measure.

	Use this function only for geometries with an M component

This function supports M coordinates.

Examples

SELECT ST_AsText(the_geom)
		FROM
		(SELECT ST_LocateAlong(
			ST_GeomFromText('MULTILINESTRINGM((1 2 3, 3 4 2, 9 4 3),
		(1 2 3, 5 4 5))'),3) As the_geom) As foo;

						 st_asewkt
-----------------------------------------------------------
 MULTIPOINT M (1 2 3)

--Geometry collections are difficult animals so dump them
--to make them more digestable
SELECT ST_AsText((ST_Dump(the_geom)).geom)
	FROM
	(SELECT ST_LocateAlong(
			ST_GeomFromText('MULTILINESTRINGM((1 2 3, 3 4 2, 9 4 3),
	(1 2 3, 5 4 5))'),3) As the_geom) As foo;

   st_asewkt
---------------
 POINTM(1 2 3)
 POINTM(9 4 3)
 POINTM(1 2 3)
	

See Also

ST_Dump , ST_LocateBetween , ST_LocateBetweenElevations