Description

Renvoie un flottant compris entre 0 et 1 représentant l'emplacement du point le plus proche du point donné sur une LineString, en tant que fraction de la ligne 2D longueur.

Vous pouvez utiliser l'emplacement renvoyé pour extraire un point (ST_LineInterpolatePoint) ou une sous-ligne (ST_LineSubstring).

Cette méthode est utile pour calculer approximativement le nombre d'adresses

Disponibilité : 1.1.0

Modifié : 2.1.0. Jusqu'à la version 2.0.x, cette fonction était appelée ST_Line_Locate_Point.

Exemples

--Rough approximation of finding the street number of a point along the street
--Note the whole foo thing is just to generate dummy data that looks
--like house centroids and street
--We use ST_DWithin to exclude
--houses too far away from the street to be considered on the street
SELECT ST_AsText(house_loc) As as_text_house_loc,
        startstreet_num +
                CAST( (endstreet_num - startstreet_num)
                        * ST_LineLocatePoint(street_line, house_loc) As integer) As street_num
FROM
(SELECT ST_GeomFromText('LINESTRING(1 2, 3 4)') As street_line,
        ST_Point(x*1.01,y*1.03) As house_loc, 10 As startstreet_num,
                20 As endstreet_num
FROM generate_series(1,3) x CROSS JOIN generate_series(2,4) As y)
As foo
WHERE ST_DWithin(street_line, house_loc, 0.2);

 as_text_house_loc | street_num
-------------------+------------
 POINT(1.01 2.06)  |         10
 POINT(2.02 3.09)  |         15
 POINT(3.03 4.12)  |         20

 --find closest point on a line to a point or other geometry
 SELECT ST_AsText(ST_LineInterpolatePoint(foo.the_line, ST_LineLocatePoint(foo.the_line, ST_GeomFromText('POINT(4 3)'))))
FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 4 5, 6 7)') As the_line) As foo;
   st_astext
----------------
 POINT(3 4)

Voir aussi

ST_DWithin, ST_Length2D, ST_LineInterpolatePoint, ST_LineSubstring