[postgis-users] 'Measure' 3D points on Polygons?

[David William Bitner]

Use AsEWKT(), astext() only supports 2D

On Feb 12, 2008 5:17 PM, <cgnicholas at alamedanet.net> wrote:

> Hmmm - this is interesting for providing one's own data directly in the
> query, but I'm still unclear how to actually get the Z value from a table.
>
> For example, I  am trying:
>
> create table ingest.sfterrain (gid serial PRIMARY KEY);
>
> select AddGeometryColumn('ingest', 'sfterrain', 'the_geom',
> '32610','POLYGONM', 3);
>
> insert into ingest.sfterrain (the_geom) values
> (GeometryFromText('POLYGONM((552161.99 4181849.92 7.31689,552174.81
> 4181862.97 7.31689,552149.81 4181887.53 7.31689,552161.99 4181849.92
> 7.31689))',32610));
>
>
> but when I select the row, I just get 2D points back, without the 'z':
>
> p9test3=# SELECT AsText(the_geom), GeometryType(the_geom),
> NDims(the_geom), ZMFlag(the_geom) FROM ingest.sfterrain limit 1;
>
>                                             astext
>                     |
> geometrytype | ndims | zmflag
>
> ------------------------------------------------------------------------------------------------+--------------+-------+--------
>  POLYGON((552161.99 4181849.92,552174.81 4181862.97,552149.81
> 4181887.53,552161.99 4181849.92)) | POLYGONM     |     3 |      1
>
>
> Am I inserting or selecting them incorrectly ?
>
> thanks in advance!
> Chris
>
> > Yes, it's supported.
> >
> > test=# SELECT GeometryType(geom), NDims(geom), ZMFlag(geom) FROM
> >          (SELECT 'POLYGON((0 0 10 1, 0 1 10 2, 1 1 10 3, 1 0 10 4, 0 0
> > 10 1))'::geometry AS geom) AS foo;
> >           summary          | ndims | zmflag
> > ---------------------------+-------+--------
> >                            |     4 |      3
> >  Polygon[ZMB] with 1 rings
> >     ring 0 has 5 points
> >
> > (1 row)
> >
> > How are you retrieving the vertex data?
> > -- Kevin
> >
> >
> > cgnicholas at alamedanet.net wrote:
> >> greetings - I'm wondering if the 'Measure' stuff works at all for
> >> Polygons.  I'm trying to associate a Z value with each vertex of a
> >> polygon
> >> (restricted to triangles for the moment.
> >>
> >> I AddGeometryColumn with a dimension of '3', etc, and am able to insert
> >> points that indeed have a Z. Things are GiST indexed properly, etc.
> >>
> >> But I don't seem to be able to retrieve the vertex data with the Z
> >> value...is this supported for polygons?  I'm trying to cast things to
> >> 'PolygonM', etc; still no luck...
> >>
> >> thanks!
> >> Chris
> >>
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> >>
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>
>
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-- 
************************************
David William Bitner
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