Drop M values from MULTIPOLYGON with PostGIS?

Question

The title is self-explanatory. I wonder if there is a simple function like ST_Force2D for the M values?

by "strip out" do you mean extract M values? or drop the M dimension? — Mike T, Oct 3, 2014 at 0:31

Jakub Kania · Accepted Answer · 2014-10-02 23:32:55Z

The function is ST_Force3D if you have XYZM geometry, if it's XYM you should use ST_Force_2D.

From the manual:

ST_Force_2D — Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X and Y coordinates.
ST_Force_3D — Forces the geometries into XYZ mode. This is an alias for ST_Force_3DZ.
ST_Force_3DZ — Forces the geometries into XYZ mode. This is a synonym for ST_Force_3D.
ST_Force_3DM — Forces the geometries into XYM mode.
ST_Force_4D — Forces the geometries into XYZM mode.

WKT · Accepted Answer · 2019-03-28 19:03:31Z

2

From Postgis 2.1.0. Reference

ST_Force2D — Force the geometries into a "2-dimensional mode".
ST_Force3D — Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.
ST_Force3DZ — Force the geometries into XYZ mode.
ST_Force3DM — Force the geometries into XYM mode.
ST_Force4D — Force the geometries into XYZM mode.

answered Mar 28, 2019 at 19:03

WKT

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