Projection trouble

[Arnulf Christl]

Hi,
sorry I postet a wrong link. The problem can be seen here:
http://www.mapbender.org/testbed.html
I just added a box where the projection can be changed on the fly. Zoom
in to below 1:50000 and switch to WGS84 and everything looks fine, the
geometries from both servers overlap perfectly. Switch to GK3
(EPSG:31467) and there is that offset.

Arnulf.

Arnulf Christl wrote:
> Hi,
> we experience a strange offset when overlaying the same data as WMS maps
> with MapServer versions 4.0.1 and 4.4.1.
>
> *4.0.1 server*
> Windows 2000: SP4
> IIS: 5
> proj: came with 4.0.1
> gd: came with 4.0.1
> gdal: came with 4.0.1
> Cap URL:
> http://wms.ccgis.de/umn/bin/mapserv.exe?map=d:/umn/germany.map&SERVICE=WMS&REQUEST=GetCapabilities&VERSION=1.1.0
>
> Data: local shape files in EPSG:4326 projected to EPSG:31467
>
> *4.4.1 server*
> FreeBSD: 4.10
> Apache: 1.3.33
> proj: 4.4.9
> gd: 2.0.33
> gdal: 1.2.1
> Cap URL:
> http://wms1.ccgis.de/cgi-bin/mapserv?map=/data/umn/germany_demo/germany_demo.map&VERSION=1.1.1&REQUEST=GetCapabilities&SERVICE=WMS
>
> Data: the same shape files as above (WGS84) but dumped to
> PostgreSQL/PostGIS (and also projected to EPSG:31467).
>
> The problem does not seem to result from MapServer but from proj?
>
> You can have a look at the problem here:
> http://www.mapbender.org/demoserver.html
>
> Zoom in to a scale of 1:100,000 or less to see the post code areas. They
> overlap with an x-offset (north):
> in northern Germany 190m
> in central Germany 145m
> in southern Germany 100m
>
> The y-offset (east) is:
> in western Germany 45m
> in eastern Germany 125m
>
> That resembles a lot to a datum shift which we stumbled accross (years
> ago) when reading GPS EPSG:4326 WGS84 data directly into the database
> and overlaying it with Gauss-Kruger EPSG:31467 (Bessel projection).
>
> What has been changed and what impact does it have on projects which
> overlay other data?
>
> Best regards, Arnulf.
>