ST_LineLocatePoint function returns the location of the closest point on a LineString - PolarDB

Returns the fractional location of the closest point on a LineString to a given point.

Syntax

float8 ST_LineLocatePoint(geometry aLinestring, geometry aPoint);
float8 ST_LineLocatePoint(geography aLinestring, geography aPoint);

Parameters

Parameter	Description
`aLinestring`	The LineString object.
`aPoint`	The point object.

Description

ST_LineLocatePoint returns a float8 value between 0 and 1 representing the position of the closest point on a LineString to the given point, expressed as a fraction of the total line length.

This function can be used to estimate the number of addresses.

Examples

geometry

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

Result:

 st_linelocatepoint
--------------------
                0.5
(1 row)

geography

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

Result:

 st_linelocatepoint
--------------------
 0.5000746195163556
(1 row)

The geography result differs slightly from the geometry result because it accounts for Earth's curvature.