[postgis-users] st_union drops M values

[Paul Ramsey]

It's a "known issue". The GEOS library that is doing the Union
operation only supports x/y/z, there is no room in its model for an m
ordinate. Only idea would be a re-working of GEOS to support m, which
is probably already ticketed, but unfunded.

P.

On Mon, Nov 21, 2011 at 2:53 AM, Lauri Kajan <lauri.kajan at gmail.com> wrote:
> Hi all,
>
> I aked this before but no answers. Does anybody have any ideas?
>
> I'm trying to make a union of geometries with M-values.
> But ST_Union seems to drop all the M-values.
>
> Or am I doing something wrong?
> Here is a sample query:
>  select st_asewkt(st_union('LINESTRINGM(0 0 0, 1 1
> 1)'::geometry,'LINESTRINGM(1 1 1, 2 2 2)'::geometry));
> Output of this is
> "MULTILINESTRING((0 0,1 1),(1 1,2 2))"
>
> Same happens with 4D LINESTRING geometries. Output is only XYZ.
>
> Is there a other way to accomplish what I want or is this a bug?
>
>
>
> Thanks
>
> -Lauri
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