[mapserver-users] PostGIS data in EPSG:31300 using for Google Maps overlay

[Steven De Vriendt]

Brent,

Maybe quite a basic question, but I'm not used to define my data
syntax as the one you propose.
Can you help me out with the <gid> declaration.
I'm quite confused what to fill in for gid

Do I leave it like it is and just write gid or doi I have
or do I have to define my primary key column (f.i.: tbl_b_cabu_pkey).

For both I get an error message, saying either column OID does not
exist or column tbl_b_cabu_pkey does not exist.
However there are both there...

DATA "new_geom from (select gid, transform(the_geom,4326) as new_geom from
  table) as mytable using unique gid using srid=4326"

Thanks for helping out !

On Tue, Apr 8, 2008 at 8:25 PM, Steven De Vriendt <gisaalter at gmail.com> wrote:
> Brent,
>
>  Very, very usefull info. Thanks.  I was just about to reprojecting my data :-)
>  I thought the SRID table was "constrained" to the geometry and you couldn't
>  change it. Seems like that's why the 'virtual' table is there for. Ok,
>  well, I'll give
>  it a try. Thanks for your input !
>
>  Regards,
>  Steven
>
>
>
>  On Tue, Apr 8, 2008 at 7:58 PM, Brent Wood <pcreso at pcreso.com> wrote:
>  >
>  >  --- Steven De Vriendt <gisaalter at gmail.com> wrote:
>  >
>  >  > Hi list,
>  >  >
>  >  > I have some data in PostGIS I wish to overlay in Google Maps using WMS
>  >  > I'm using the same data in a mapserver application, where EPSG code
>  >  > 31300 is used.
>  >  > Now for overlay in Google Maps, 4326 is required.
>  >  > I have made a copy of my map-file and specified 4326 as projection
>  >  > system.Yet, non of my data is showing up.
>  >  >
>  >  > Do I need to reproject my data for this use ? I thought PostGIS was
>  >  > capable of doing reprojection on the fly ?
>  >
>  >  Hi Steven,
>  >
>  >  Both mapserver & POstGIS can reproject the data on the fly, but they need to be
>  >  told the input & output projections.
>  >
>  >  As your data is all displayed via mapserver, the instructions either way will
>  >  be in your mapfile.
>  >
>  >  To reproject using PostGIS, edit the SQL command in your data statement which
>  >  retrieves the PostGIS data. You need to tell PostGIS to return a virtual table
>  >  to mapserver, and transform the data to the required projection in this. Edit
>  >  the data line in the layer something like this:
>  >
>  >  DATA "new_geom from (select gid, transform(the_geom,4326) as new_geom from
>  >  table) as mytable using unique gid using srid=4326"
>  >
>  >
>  >  To reproject in mapserver, you need to set the main mapfile projection to
>  >  EPSG:4326, using, in the global header part of the mapfile:
>  >
>  >  UNITS DD
>  >  PROJECTION
>  >   "init=epsg:4326"
>  >  END
>  >
>  >  In the METADATA section, you'll need to set the output projection for WMS, eg:
>  >  METADATA
>  >   "wms_title" "My WMS Server"
>  >   "wms_srs"   "EPSG:4326"
>  >  END
>  >
>  >  Then in the layer definition, you specify the layer's native projection, so
>  >  mapserver can reproject from one to the other:
>  >
>  >  LAYER
>  >   ...
>  >   PROJECTION
>  >     "init=epsg:31300"
>  >   END
>  >   ...
>  >  END
>  >
>  >  Note that to reproject in PostGIS, Proj.4 support must be compiled into
>  >  PostGIS, and similarly for mapserver if you do the reprojection there. If you
>  >  compiled these from source, this is not done by default, & you'll need to run
>  >  configure with the appropriate flag. If you installed from a package, or on
>  >  Windows, proj support is generally built in.
>  >
>  >
>  >  HTH,
>  >
>  >   Brent Wood
>  >
>