I discovered this problem when zooming to the extent of a layer. I got an extent, which was shifted a few hundred meters to the right and top of the display.
I found out that this is because the LatLongBoundingBox in the Capabilities document from GeoServer is in WGS84 geographic coordinates (EPSG:4326) and in uDIG I used EPSG:31256. The extent had only been projected, but without datum transformation. This can be corrected by adding the TOWGS84 parameters to the definition of EPSG:31256 in gt2-epsg.jar like this:
31256=PROJCS["MGI / Austria GK East",GEOGCS["MGI",DATUM["Militar_Geographische_Institute",SPHEROID["Bessel 1841",6377397.155,299.1528128],TOWGS84[577.326,90.129,463.919,5.1365988,1.4742,5.2970436,2.4232]],PRIMEM["Greenwich",0],UNIT["Decimal Degree",0.01745329251994328]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",16.33333333333333],PARAMETER["scale_factor",1],PARAMETER["false_easting",0],PARAMETER["false_northing",-5000000],UNIT["metre",1],AUTHORITY["EPSG","31256"]]
It would be preferable to include these parameters in future versions of GeoTools. I don't know how this can be done in the new format of GeoTools 2.5.
This should be done for all EPSG codes for Austria, which use the MGI datum:
The correct values for Austria are
I would be grateful for any hint, how this can be done for GeoServer 1.7, which already uses the new format (GeoTools 2.5). So I could change it at least for our installation.