ST_LineLocatePoint
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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

Disponibilidad: 1.1.0

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

Ejemplos

This example approximates the street number of a house by locating the closest point on a street line. The subquery generates sample house and street data, and ST_DWithin excludes houses that are too far from 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

This example finds the 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;
POINT(3 4)