ST_LineLocatePoint¶

Returns the location of the closest point on a LineString as a fraction of its total length.

Usage¶

double ST_LineLocatePoint(geomA: geometry, geomB: geometry)
double ST_LineLocatePoint(geogA: geography, geogB: geography)

Arguments¶

geogA (geography): Input geography
geogB (geography): Input geography
geomA (geometry): Input geometry
geomB (geometry): Input geometry

Description¶

Returns a double between 0 and 1, representing the location of the closest point on the LineString as a fraction of its total 2D length. The first argument must be a LineString. For geometry, the fraction is computed using 2D Cartesian distance. For geography, the fraction is computed based on spherical interpolation between vertices.

Examples¶

SELECT ST_LineLocatePoint(
    ST_GeomFromText('LINESTRING (0 0, 0 1)'),
    ST_GeomFromText('POINT (0 0.5)')
);

┌──────────────────────────────────────────────────────────────────────────────┐
│ st_linelocatepoint(st_geomfromtext(Utf8("LINESTRING (0 0, 0 1)")),st_geomfro │
│                        mtext(Utf8("POINT (0 0.5)")))…                        │
╞══════════════════════════════════════════════════════════════════════════════╡
│                                                                          0.5 │
└──────────────────────────────────────────────────────────────────────────────┘

SELECT ST_LineLocatePoint(
    ST_GeogFromWKT('LINESTRING (0 0, 1 1, 2 2)'),
    ST_GeogFromWKT('POINT (1 1)')
);

┌──────────────────────────────────────────────────────────────────────────────┐
│ st_linelocatepoint(st_geogfromwkt(Utf8("LINESTRING (0 0, 1 1, 2 2)")),st_geo │
│                        gfromwkt(Utf8("POINT (1 1)")))…                       │
╞══════════════════════════════════════════════════════════════════════════════╡
│                                                           0.5000380781430777 │
└──────────────────────────────────────────────────────────────────────────────┘