[postgis-users] Calculate z value based on attribute field

[Stephen Woodbridge]

Right, that make perfect sense. You created a geometry column of tile 
MULTIPOLYGON and you are trying to add a POINT to it!

What is your original geometry type?

if it is a POINT then do

select 
addgeometrycolumn('public','allhousefinal','the_geom3d',4326,'POINT',3);

if it is a MULTIPOLYGON then you need to change the way you are adding 
the z to it and do something like:

update allhousefinal set the_geom3d = 
st_translate(st_force_3d(the_geom), 0, 0, result_hig*3);

I have not tested this so you might have to play with it a little.

-Steve W

On 4/21/2011 11:32 AM, Gis Mage wrote:
> Hello again!
>
> Doing as proposed I get an error.
>
> wizbase=# select
> addgeometrycolumn('public','allhousefinal','the_geom3d',4326,'MULTIPOLYGON',3);
>                            addgeometrycolumn
> ---------------------------------------------------------------------
>   public.allhousefinal.the_geom3d SRID:4326 TYPE:MULTIPOLYGON DIMS:3
> (1 row)
>
> wizbase=# update allhousefinal set the_geom3d = st_union(the_geom,
> st_setsrid(st_makepoint(st_x(st_pointonsurface(the_geom)),st_y(st_pointonsurface(the_geom)),
> result_hig*3),st_srid(the_geom)));
> ERROR:  new row for relation "allhousefinal" violates check constraint
> "enforce_geotype_the_geom3d"
>
> As you can see the geometry type is MULTIPOLYGON, so I think the problem
> is somewhere around st_makepoint.
> Can you please help me out?
>
> Nikolai
>
> Re: [postgis-users] Calculate z value based on attribute
> field
> To: PostGIS Users Discussion <postgis-users at postgis.refractions.net
> <mailto:postgis-users at postgis.refractions.net>>
> Message-ID: <20110419175447.GG13611 at keybit.net
> <mailto:20110419175447.GG13611 at keybit.net>>
> Content-Type: text/plain; charset=us-ascii
>
> On Tue, Apr 19, 2011 at 01:45:48PM -0400, Stephen Woodbridge wrote:
>  > On 4/19/2011 8:52 AM, Gis Mage wrote:
>  > >Hello list!
>  > >
>  > >I've got a table in PostGIS with the_geom field with 2 dimensions.
>  > >I wonder how can I add a z dimension and fill it up with values from
>  > >attribute field elev (its type is integer) ?
>  >
>  > One way would be to add a new geometry column and then populate it,
>  > maybe something like (untested):
>  >
>  > select addgeomtrycolumn('myschema', 'mytable', 'geom3d', 4326,
> 'POINT', 3);
>  >
>  > update mytable set geom3d=setsrid(makepoint(st_x(
> the_geom),
>  > st_y(the_geom), z_column::double percision), 4326);
>
> A geometry type agnostic way would be to union whatever you have
> with a 3d point known to be contained in it. GEOS would then use
> the only Z value to fill up an elevation grid used to elevate
> the resulting geometry:
>
>   -- untested query
>   update mytable set geom3d = st_union(the_geom,
>         st_setsrid(st_makepoint(
>                 st_x(st_pointonsurface(the_geom)),
>                 st_y(st_pointonsurface(the_geom)),
>                 z_column), st_srid(the_geom)));
>
> --strk;
>
>   ()   Free GIS & Flash consultant/developer
>   /\ http://strk.keybit.net/services.html
>
>
>
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