Mismatch transforming WGS84 to CH1903 using shp2img

[Carsten Dewey]

Dear list,

the transformation from WGS84 to CH1903 Swiss Grid seems not to work
accurately (shp2img).
I have created a map file combining a raster image (Swiss Grid) and a
MapInfo *.tab file (WGS84)
The output projection is set inside the MAP object as follows:
PROJECTION
	"proj=somerc"
   	"ellps=bessel"
   	"lat_0=46.95240555555556"
   	"lon_0=7.439583333333333"
    	"x_0=600000"
   	"y_0=200000"
END
The input projection of the tab file (LAYER object):
PROJECTION	
      #"proj=longlat"
      #"ellps=WGS84"  
END

As you may see looking at the result (attached image) there is a slight
mismatch.

I've tried already to use epsg code ("init=epsg:21781") to specify the
projection, but then I get the following error message using shp2img: 
"msProcessProjection(): Projection library error. lat_0 = 0 or 90 or alpha =
90"
Using "init=world:ch1903" works fine exept from producing still a mismatch.

Using cs2cs with epsg code produces the same error message.
Transforming single points using cs2cs seems to result in mismatches as
well.

My mapserver installation includes gdaldata, gdalplugins and proj.
All relevant paths and variables are set.

Any ideas, suggestions, solutions?
Thanks
carsten


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