AW: [gdal-dev] An issue about using GDALWARP to do theNTv2transformation

[Schmitz, Uwe]

Heng,
> 
> 
> http://osgeo-org.1803224.n2.nabble.com/file/n5848200/gdalwarp_
> problem1.doc
> gdalwarp_problem1.doc 
> Hi Uwe,
> 
> I have tried your suggestion on the same raster file with a modified
> "+x_0=500000" parameter in the command line (as seen in the 
> attached doc). I
> could see the major difference:there is still one error 
> message left. When I
> tried on another raster file with the same modified 
> parameter, I have got
> much less error messages than before. However, is it still 
> possible that my
> raster data are outside the area of the grid shift file? All 
> the raster data
> I was trying to transform are GK (DHDN) zone 4, which false 
> easting value is
> 4500000. This was why I used "+x_0=4500000" instead of 
> "+x_0=500000" in the
> command line. As I am getting to know all these georeference 
> settings at the
> moment, can you tell me why you suggested the modified 
> parameter and what
> you meant about "raster data lacks the Gauss-Krueger meridian prefix"?
> 
that was just a guess, because your coordinates lie far in the
west of DHDN/GK zone 4.
Normally DHDN/GK coordinates are noted as e.g.:
4500000.0 Rechts 5500000.0 Hoch

Omitting the Gauss-Krueger meridian prefix you have:
 500000.0 Rechts 5500000.0 Hoch
(Note: Rechts coordinate has only six digits) an thats 
far in the west of the real position. It's very simple and
therefore you may give it a try. 

If it's not the case, may be you can post the output of:
gdalinfo l0.tif

That would help to see, if the file is correctly georeferenced.

Regards
Uwe