Dear list, while translating or warping rasterdata with gdal_translate or gdalwarp I experienced a difference in the origin of an image in the tags of the GeoTiff-header and the tfw-file. The header of my original image looks as follows:
Driver: GTiff/GeoTIFF Files: C:\test\in.tif Size is 10000, 10000 Coordinate System is: PROJCS["DHDN / 3-degree Gauss-Kruger zone 3", GEOGCS["DHDN", DATUM["Deutsches_Hauptdreiecksnetz", SPHEROID["Bessel 1841",6377397.155,299.1528128000009, AUTHORITY["EPSG","7004"]], AUTHORITY["EPSG","6314"]], PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433], AUTHORITY["EPSG","4314"]], PROJECTION["Transverse_Mercator"], PARAMETER["latitude_of_origin",0], PARAMETER["central_meridian",9], PARAMETER["scale_factor",1], PARAMETER["false_easting",3500000], PARAMETER["false_northing",0], UNIT["metre",1, AUTHORITY["EPSG","9001"]], AUTHORITY["EPSG","31467"]]Origin = (3406000.000000000000000,5703000.000000000000000) Pixel Size = (0.100000000000000,-0.100000000000000) [ ... ] Corner Coordinates: Upper Left ( 3406000.000, 5703000.000) ( 7d38'50.85"E, 51d27'18.40"N) Lower Left ( 3406000.000, 5702000.000) ( 7d38'51.81"E, 51d26'46.05"N) Upper Right ( 3407000.000, 5703000.000) ( 7d39'42.63"E, 51d27'19.00"N) Lower Right ( 3407000.000, 5702000.000) ( 7d39'43.58"E, 51d26'46.64"N) Center ( 3406500.000, 5702500.000) ( 7d39'17.22"E, 51d27'2.52"N) The tfw-file coming out using the creation option -co TFW=YES (gdal_translate -co TFW=YES C:\test\in.tif C:\test\out.tif) looks like this: 0.1000000000 0.0000000000 0.0000000000 -0.1000000000 3406000.0499999998 5702999.9500000002 The GeoTiff-tags in this image (out.tif) is still the same as above. But amazingly there is a slight difference in x and y coordinate of approximately 5 cm between tfw and GeoTiff. This difference does occur the other way around too. For example creating a GeoTiff from a png image with a tfw-file I get the difference in the new GeoTiff-tags as well. I start with those values in the tfw-file ... 0.0846596700 0.0000000000 0.0000000000 -0.0846596700 392000.0000000000 5733000.0000000000 ... and get these in the GeoTiff: Origin = (391999.957670164990000,5733000.042329834800000) Pixel Size = (0.084659670000000,-0.084659670000000) As mentioned above, the coordinates for the origin are not the same, but the image didn't change. Does anybody know about this behavior? I would be glad to hear from you. Thanks so far and best regards Andreas Im Auftrag Andreas Fischer Kreis Unna - Der Landrat Zentrale Datenverarbeitung Friedrich-Ebert-Straße 17 59425 Unna Fon 02303 27-4416 Fax 02303 27-2896 Diese E-Mail wurde beim Ausgang auf Viren geprueft. Wegen der potentiellen Gefahr auf den Uebertragungswegen wird zu einer Vireneingangskontrolle geraten. Eine Haftung für Virenfreiheit wird ausgeschlossen.
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