[mapserver-users] Different projections with MapServer and PostGIS

[Paul Ramsey]

In Mapserver, add a PROJECTION block to the LAYER:

PROJECTION
  "init=epsg:26913"
END

And also a projection block to the MAP:

PROJECTION
  "init=epsg:4326"
END

And then alter the DATA block to declare your data SRID.

DATA "the_geom FROM listing USING UNIQUE listing_id USING srid= 26913"

Now everything will work. Your requests to mapserver will get
transformed (by mapserver) into the correct projection for your
postgis data. All the reprojection will happen inside mapserver,
postgis will be blissfully ignorant of transforms.

P.


On Wed, Dec 2, 2009 at 12:34 PM, Timbonicus Hansen
<timbonicus at realgo.com> wrote:
> Hi all,
>
> I'm using MapServer to connect to PostGIS and not getting the any
> results since the MapServer query and the data in postgresql are
> different projections. The 'USING srid' option in the mapfile DATA
> field only controls the GeomFromText call that MapServer generates
> rather than enforcing a ST_Transform on the database column to match
> the projection. Is there any way to make this work?
>
> Here is the PostGIS section from the mapfile I am using:
>    CONNECTIONTYPE POSTGIS
>    CONNECTION "user=postgres dbname=lqms_prod"
>    DATA "the_geom FROM listing USING UNIQUE listing_id USING srid=4326"
>
> Which MapServer munges into this SQL:
>    select status,encode(AsBinary(force_collection(force_2d("the_geom")),'NDR'),'base64')
> as geom,listing_id from listing where the_geom &&
> GeomFromText('POLYGON((-105.074620715937
> 39.804844079017,-105.074620715937 39.869217095375,-104.927912119243
> 39.869217095375,-104.927912119243 39.804844079017,-105.074620715937
> 39.804844079017))',4326);
>
> Unfortunately, the_geom in my database is in EPSG:26913 and the WKT is
> in EPSG:4326. It seems the overlap operator (&&) is not smart enough
> to pick up on this and convert one or the other - surprisingly,
> neither is ST_Overlap. If I modify the query to ST_Transform(the_geom,
> 4326) && ... results come back as expected (or
> ST_Transform(GeomFromText..., 26913)).
>
> The options I see are:
> - Change the database column the_geom to use EPSG:4326
> - Create a view on the database that translates to EPSG:4326. Does
> anyone know if this is feasible or the performance impact?
> - Change the passed-in geometry to be EPSG:26913
>
> Is there another option with MapServer? Is there a bug/feature request
> to make "USING srid" do a transform on the DB column to match the WKT
> conversion?
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