Name
ST_Line_Locate_Point — Computes de fraction of a Line from the closest point on the line to the given point.
Synopsis
double ST_Line_Locate_Point(bytea Line, bytea Point);
Description
Computes de fraction of a Line from the closest point on the line to the given point.
The point does not necessarily have to lie precisely on the line. Both geometries must have the same SRID and dimensions.
Coordinate Dimensions
| 2D | 3D | M |
|---|---|---|
 | - | - |
Spatial Standards Support
| OGC SFS for SQL. 1.1 (1999) | OGC SFS for SQL. 1.1.0 (2005) | OGC SFS for SQL. 1.2.0 (2006) | SQL-MM Part 3 |
|---|---|---|---|
| - | - | - | - |
Examples
SELECT ST_Line_Locate_Point(ST_GeomFromEWKT('LINESTRING (29 35, 29 21, 11 21)'),ST_GeomFromEWKT('POINT (20 28)'));
--Result
0.71875
-- Using ST_Line_Interpolate_Point (see graphic below)
SELECT ST_AsText(ST_Line_Interpolate_Point(line,ST_Line_Locate_Point(line,point))) as interpolate
FROM (SELECT ST_GeomFromText('LINESTRING (10 11, 15 26, 29 35)') as line,
ST_GeomFromText('POINT (27 27)') as point)
as foo;
--Result
interpolate
-----------------------------------------------
POINT (23.945848375451263 31.750902527075812)
(1 row)
 |