Le mercredi 21 novembre 2012 18:46:59, Tobias Lohner a écrit : > Hi List, > > I'd like to reproject EUMETSAT EView (geostationary weather satellite) > images to EPSG:3857 (aka web mercator), but I only got jpeg files > without any georeference. > > I tried to add several (up to 16 more or less) equally distributed > ground control points to the image using gdal_transform and warping the > result with gdalwarp: > > # add gcps > gdal_translate -gcp x y lon lat [...] image.jpg output.tiff > # convert the image to EPSG:3857 > gdalwarp -t_srs EPSG:3857 output.tiff output_3857.tiff > > Using third order warping or the thin plate transformer produces a > reprojected image which doesn't fit to the target coordinate system, > especially the corners are off by 0.1 to 0.3 degrees. > > Is it possible to tell gdal that the source images are in geostationary > satellite view (geos projection) for reprojecting them?
You can add -a_srs "+proj=geos [...]" on the gdal_translate command line (or - s_srs on gdalwarp) if the GCP you specify are in coordinates compatible with the geos projection. In your example if you specify lon,lat, you'd likely want to use EPSG:4326. The third order warping is known to suffer from numerical instability. Perhaps try second order with -order 2. The TPS warper should have a perfect fit on the GCPs > > > Tobias Lohner > > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
