PostGIS

ST_3DClosestPoint
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ST_3DClosestPoint

8.12. Measurement Functions

Name

ST_3DClosestPoint — Returns the 3D point on g1 that is closest to g2. This is the first point of the 3D shortest line.

Synopsis

geometry +`*`+ST_3DClosestPoint*(`geometry `g1, geometry g2`)`;

Description

Returns the 3-dimensional point on g1 that is closest to g2. This is the first point of the 3D shortest line. The 3D length of the 3D shortest line is the 3D distance.

check This function supports 3d and will not drop the z-index.

check This function supports Polyhedral surfaces.

Availability: 2.0.0

Changed: 2.2.0 - if 2 2D geometries are input, a 2D point is returned (instead of old behavior assuming 0 for missing Z). In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z.

Examples

linestring and point — both 3d and 2d closest point

SELECT ST_AsEWKT(ST_3DClosestPoint(line,pt)) AS cp3d_line_pt,
        ST_AsEWKT(ST_ClosestPoint(line,pt)) As cp2d_line_pt
    FROM (SELECT 'POINT(100 100 30)'::geometry As pt,
            'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)'::geometry As line
        ) As foo;


 cp3d_line_pt

cp2d_line_pt -----------------------------------------------------------+------------------------------------------ POINT(54.6993798867619 128.935022917228 11.5475869506606)

POINT(73.0769230769231 115.384615384615)

----

linestring and multipoint — both 3d and 2d closest point

SELECT ST_AsEWKT(ST_3DClosestPoint(line,pt)) AS cp3d_line_pt,
        ST_AsEWKT(ST_ClosestPoint(line,pt)) As cp2d_line_pt
    FROM (SELECT 'MULTIPOINT(100 100 30, 50 74 1000)'::geometry As pt,
            'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)'::geometry As line
        ) As foo;


                       cp3d_line_pt

cp2d_line_pt -----------------------------------------------------------+-------------- POINT(54.6993798867619 128.935022917228 11.5475869506606)

POINT(50 75)

----

Multilinestring and polygon both 3d and 2d closest point

SELECT ST_AsEWKT(ST_3DClosestPoint(poly, mline)) As cp3d,
    ST_AsEWKT(ST_ClosestPoint(poly, mline)) As cp2d
        FROM (SELECT  ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
                ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
                (1 10 2, 5 20 1))') As mline ) As foo;
                   cp3d

cp2d -------------------------------------------+-------------- POINT(39.993580415989 54.1889925532825 5)

POINT(20 40)

----

PostGIS

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