Hi Frank, thank you for your answer. I have tried gdalwarp -t_srs EPSG:4326 -tr 0.0000031156 0.0000019021 pic_gcp.tif result.tif but neither with QGis nor with SharpMap the map is rendered undistorted. And that although the sizes now have proper values...
Any idea? Best regards, Martin ..\FWTools2.4.2\bin>gdalinfo result.tif Driver: GTiff/GeoTIFF Files: result.tif Size is 15141, 11373 Coordinate System is: GEOGCS["WGS 84", DATUM["WGS_1984", SPHEROID["WGS 84",6378137,298.257223563, AUTHORITY["EPSG","7030"]], AUTHORITY["EPSG","6326"]], PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433], AUTHORITY["EPSG","4326"]] Origin = (13.437037980137905,52.481881537880760) Pixel Size = (0.000003115600000,-0.000001902100000) Metadata: AREA_OR_POINT=Area Image Structure Metadata: INTERLEAVE=BAND Corner Coordinates: Upper Left ( 13.4370380, 52.4818815) ( 13d26'13.34"E, 52d28'54.77"N) Lower Left ( 13.4370380, 52.4602490) ( 13d26'13.34"E, 52d27'36.90"N) Upper Right ( 13.4842113, 52.4818815) ( 13d29'3.16"E, 52d28'54.77"N) Lower Right ( 13.4842113, 52.4602490) ( 13d29'3.16"E, 52d27'36.90"N) Center ( 13.4606246, 52.4710652) ( 13d27'38.25"E, 52d28'15.83"N) Band 1 Block=15141x1 Type=Byte, ColorInterp=Palette Color Table (RGB with 256 entries) 0: 0,0,0,255 1: 1,1,1,255 2: 2,2,2,255 -------- Original-Nachricht -------- > Datum: Fri, 18 Sep 2009 10:39:09 -0400 > Von: Frank Warmerdam <warmer...@pobox.com> > An: Martin Geng <martin.g...@gmx.de> > CC: gdal-dev@lists.osgeo.org > Betreff: Re: [gdal-dev] Cassini_Soldner warping using WGS84 GCPs is distorted > Martin, > > Examining the GCPs in WGS84 space I see: > > >>> (13.4841338099227 - 13.4370322252183) / 15118 > 3.1155962894827404e-06 > >>> "%.10f" % ((13.4841338099227 - 13.4370322252183) / 15118) > '0.0000031156' > >>> "%.10f" % ((52.4818154665202 - 52.4602476117909)/ 11339) > '0.0000019021' > > > Basically, in WGS84 space your source pixels are distinctly > non-square and gdalwarp distorts your image to produce square > pixels in the output projection. If you want to preserve > the original aspect ratio try: > > -tr 0.0000031 0.0000019 > > on the gdalwarp commandline. > > But basically WGS84 and Cassini-Soldner have quite different > characteristics in the area of your image, and WGS84 may not > be a good working coordinate system for the image. > > Best regards, > -- > ---------------------------------------+-------------------------------------- > I set the clouds in motion - turn up | Frank Warmerdam, > warmer...@pobox.com > light and sound - activate the windows | http://pobox.com/~warmerdam > and watch the world go round - Rush | Geospatial Programmer for Rent -- Neu: GMX Doppel-FLAT mit Internet-Flatrate + Telefon-Flatrate für nur 19,99 Euro/mtl.!* http://portal.gmx.net/de/go/dsl02 _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev