Le jeudi 19 novembre 2015 10:47:50, Simon Lyngby Kokkendorff a écrit : > 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.
Please file one. > > 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 -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
