I can confirm also that it works when I set a target srs. But must admit that the current behaviour was confusing. I knew how to interpret the input data - under the assumption that a geotransform is not changed when I do no transformations or interpolations: If I know that my data are "points" rather than "pixels" - the first "point" is lying half a cellsize downwards and rightwards from the upper left corner that GDAL reports. That's what I always assume - not relying on other metadata items than the GeoTransform.
So I agree that it might be worth a ticket. Cheers, Simon On Thu, Nov 19, 2015 at 10:29 AM, Ari Jolma <ari.jo...@gmail.com> wrote: > > On 19.11.2015 11:26, Even Rouault wrote: > >> >> >> GDAL version: >> GDAL 1.11.2, released 2015/02/10 >> Simon, >> >> Regarding the fact that the geotiff file looses the half-pixel shift, it >> seems >> to be due to the absence of a SRS. If I do "gdal_translate test.asc >> test.tif - >> a_srs EPSG:32630" for example, then the geotransform I get back is >> correct. >> This is a defect of the GeoTIFF writer that writes the GeoTIFF Tiepoints >> with >> the PixelIsPoint convention (since your original data is flagged as >> such), but >> fails to write GTRasterTypeGeoKey=RasterPixelIsPoint as a geotiff key when >> there's no SRS. Could be worth a ticket. >> > > My conclusion is the same. I think the key should be set regardless of the > existence of a SRS. > > Ari > > >> Some background: >> https://trac.osgeo.org/gdal/wiki/rfc33_gtiff_pixelispoint >> >> A workaround : >> gdal_translate test.asc test.tif -mo AREA_OR_POINT=AREA >> >> This will force the geotiff writer to use the default convention, and thus >> avoiding going back to the centerofpixel convention when writing the >> GeoTIFF >> tiepoints. >> >> Even >> >> > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev >
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