[gdal-dev] Re: coordinate transformation problem in python

[WolfgangZ]

WolfgangZ schrieb:
> Hi all,
> 
> I was trying to program a short script in python to do coordinate 
> transformation from latlong/WGS84 to GaussKrüger Zone 4. An example how 
> to do that is on the gdal web page. To keep it simple I used the EPSG 
> codes. Here my code (ps I know that it should be "from osgeo import ogr" 
> but I run my code on the recent version of FWTools 2.2.2):
> 
> import ogr
> 
> #original SRS
> oSRS=ogr.osr.SpatialReference()
> oSRS.ImportFromEPSG(4326)
> 
> #target SRS
> tSRS=ogr.osr.SpatialReference()
> tSRS.ImportFromEPSG(31468)
> 
> poCT=ogr.osr.CoordinateTransformation(oSRS,tSRS)
> 
> x=12.074760
> y=47.893320
> res=poCT.TransformPoint(x,y,0.)
> print 'x= %10.2f , y= %10.2f' % (res[0],res[1])
> 
> 
> The result is
> x= 4505693.98 , y= 5306127.81
> 
> I checked against another software and got a different result:
> 4505697, 5306126
> 
> Then I tried it with cs2cs.exe ad the result from there is:
> cs2cs.exe +proj=latlong +datum=WGS84 +to +proj=tmerc +lat_0=0 +lon_0=12 
> k=1.000000 +x_0=4500000 +y_0=0 +ellps=bessel 
> +towgs84=591.28,81.35,396.39,1.477,-0.0736,-1.458,9.82 +units=m +no_defs
> 12.074760 47.893320
> 4505696.75      5306125.78 -52.43
> 
> I suppose the my python code is ignoring the different ellipsoid. Is 
> that behaviour desired? What about other gdal software like gdalwarp?
> 
> Thanks for any clarification.
> Wolfgang

to extent the example, cs2cs gives the same result when using the EPSG 
codes:

cs2cs.exe +init=EPSG:4326 +to +init=EPSG:31468
12.074760 47.893320
4505693.98      5306127.81 -3.67

Regards
Wolfgang