[postgis-users] Projection problem

[Jaime Fiers]

Hi Ralf.

You gave me the correct way.  Thanks a lot.

Finally, I used a similar SQL, with the double transformation you said, and
result is good:


CREATE OR REPLACE VIEW vista_23030 AS
 SELECT "GID", transform_geometry(transform( geom, 4326), '+proj=longlat
+ellps=WGS84 +datum=WGS84 +no_defs '::text, '+proj=utm +ellps=intl +zone=30
+units=m +towgs84=-131,-100.3,-163.4,-1.244,-0.02,-1.14 +no_defs'::text,
23030)
 AS geom
   FROM capa_25830;

Regards
Jaime

2010/7/23 Ralf Suhr <Ralf.Suhr at itc-halle.de>

> Hi Jaime,
>
> to get transformation with towgs84 parameter working you have to use wgs84
> ellipsoid. Transform from ETRS89 to wgs84 and second from wgs84 to ED50.
>
> ST_Transform(ST_Transform( 25830_geom, 4326), 23030)
>
> Gr
> Ralf
>
> Am Freitag 23 Juli 2010, 08:42:39 schrieb Jaime Fiers:
> > Hello guys
> >
> > I hava a "little" problem with Postgis projection.
> >
> > I need get a reprojected view.  Original data layer is in SRS=25830
> (ETRS89
> > UTM30) and view in SRS=23030 (ED50 UTM30)
> >
> > I try this:
> >
> > CREATE OR REPLACE VIEW vista_23030 AS
> >  SELECT id, transform_geometry("GEOMETRY", '+proj=utm +zone=30
> +ellps=GRS80
> > +units=m +no_defs
> >
> +towgs84=131.0,100.3,163.4,1.2439999999999989,0.01999999999999998,1.1439999
> > 999999988,-9.39 '::text,
> >  '+proj=utm +zone=30 +ellps=intl +units=m +nadgrids +no_defs'::text,
> 23030)
> > AS "GEOMETRY"
> >    FROM capa_25830;
> >
> > (If we do not include "+nadgrids" we don't get anything, but that is not
> a
> > problem).
> > I always get a +-90 meter error.
> >
> > Can anybody help me.
> >
> > Thanks in advance
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