## Name

ST_LineLocatePoint — Returns the fractional location of the closest point on a line to a point.

## Synopsis

`float8 ST_LineLocatePoint(`geometry a_linestring, geometry a_point`)`;

`float8 ST_LineLocatePoint(`geography a_linestring, geography a_point, boolean use_spheroid = true`)`;

## Descripción

Devuelve un float entre 0 y 1 que representa la ubicación del punto más cercano en la cadena de línea al punto dado, como una fracción de la longitud total de la 2d line.

Puede utilizar la ubicación devuelta para extraer un punto (ST_LineInterpolatePoint) o una subcadena (ST_LineSubstring).

Esto es útil para aproximar números de direcciones

Modificado: 2.1.0. Hasta 2.0.x esto se llamaba ST_Line_Locate_Point.

## Ejemplos

```--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)

```