PostGIS

ST_MakeLine
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ST_MakeLine

7.3. Geometry Constructors

Name

ST_MakeLine — Creates a LineString from Point, MultiPoint, or LineString geometries.

Synopsis

+geometry +ST_MakeLine(+`geometry `+geom1, geometry geom2`)`;

+geometry +ST_MakeLine(+`geometry[] `+geoms_array`)`;

+geometry +ST_MakeLine(+`geometry set `+geoms`)`;

Description

Creates a LineString containing the points of Point, MultiPoint, or LineString geometries. Other geometry types cause an error.

Variant 1: accepts two input geometries

Variant 2: accepts an array of geometries

Variant 3: aggregate function accepting a rowset of geometries. To ensure the order of the input geometries use ORDER BY in the function call, or a subquery with an ORDER BY clause.

Repeated nodes at the beginning of input LineStrings are collapsed to a single point. Repeated points in Point and MultiPoint inputs are not collapsed. ST_RemoveRepeatedPoints can be used to collapse repeated points from the output LineString.

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

Availability: 2.3.0 - Support for MultiPoint input elements was introduced

Availability: 2.0.0 - Support for LineString input elements was introduced

Availability: 1.4.0 - ST_MakeLine(geomarray) was introduced. ST_MakeLine aggregate functions was enhanced to handle more points faster.

Examples: Two-input variant

Create a line composed of two points.

SELECT ST_AsText( ST_MakeLine(ST_Point(1,2), ST_Point(3,4)) );

      st_astext
---------------------
 LINESTRING(1 2,3 4)

Create a 3D line from two 3D points.

SELECT ST_AsEWKT( ST_MakeLine(ST_MakePoint(1,2,3), ST_MakePoint(3,4,5) ));

        st_asewkt
-------------------------
 LINESTRING(1 2 3,3 4 5)

Create a line from two disjoint LineStrings.

 select ST_AsText( ST_MakeLine( 'LINESTRING(0 0, 1 1)', 'LINESTRING(2 2, 3 3)' ) );

          st_astext
-----------------------------
 LINESTRING(0 0,1 1,2 2,3 3)

Examples: Array variant

Create a line from an array formed by a subquery with ordering.

SELECT ST_MakeLine( ARRAY( SELECT ST_Centroid(geom) FROM visit_locations ORDER BY visit_time) );

Create a 3D line from an array of 3D points

SELECT ST_AsEWKT( ST_MakeLine(
          ARRAY[ ST_MakePoint(1,2,3), ST_MakePoint(3,4,5), ST_MakePoint(6,6,6) ]  ));

        st_asewkt
-------------------------
LINESTRING(1 2 3,3 4 5,6 6 6)

Examples: Aggregate variant

This example queries time-based sequences of GPS points from a set of tracks and creates one record for each track. The result geometries are LineStrings composed of the GPS track points in the order of travel.

Using aggregate ORDER BY provides a correctly-ordered LineString.

SELECT gps.track_id, ST_MakeLine(gps.geom ORDER BY gps_time) As geom
    FROM gps_points As gps
    GROUP BY track_id;

Prior to PostgreSQL 9, ordering in a subquery can be used. However, sometimes the query plan may not respect the order of the subquery.

SELECT gps.track_id, ST_MakeLine(gps.geom) As geom
    FROM ( SELECT track_id, gps_time, geom
            FROM gps_points ORDER BY track_id, gps_time ) As gps
    GROUP BY track_id;