Le samedi 05 septembre 2015 22:59:00, Stefan Ziegler a écrit : > Even, > > what suprises me is that the following workaround shows not artefacts: > > 1) gdalwarp a larger part of the desired bouding box (keep SRS)
If no reprojection is involved and no resizing is involved, then gdalwarp basically does what gdal_translate does, so it is expected that there's no artifacts > 2) gdalwarp to the target srs If you don't constraint the result, the automatically selected bounds might limit the artifacts, without guarantee... > 3) gdalwarp for cutting to desired bounding box with -tr and -te option. Your descripton of 3) looks very much like your not_working.sh, so... > > All gdalwarp commands with nearest neighbor. Sounds this > comprehensible for you? Or is it just by accident (and/or I did not > found an existing breaking edge)? I'd say accident. For high quality result, nearest neighbour isn't advised. > > I'm gonna try the original command with the different resampling > options as you proposed. > > regards > Stefan > > On Fri, Sep 4, 2015 at 11:26 PM, Even Rouault > > <even.roua...@spatialys.com> wrote: > > Le vendredi 04 septembre 2015 21:29:02, vous avez écrit : > >> Hi > >> > >> On Thu, Sep 3, 2015 at 10:58 AM, Even Rouault > >> > >> <even.roua...@spatialys.com> wrote: > >> > This occurs in the middle of a source tile, or at the boundary between > >> > 2 tiles ? > >> > >> In the middle of a source file. > >> > >> > Just to be sure: you mean you are using the above -s_srs and -t_srs on > >> > one of the tile that makes the ortho2014.vrt ? > >> > >> Yes. > >> > >> > And what if you make a VRT with just that source image ? > >> > >> I think it has nothing to do with the VRT. Using the gdalwarp command > >> on a single tif file it has the same breaking edge when using the -te > >> option. I did try the -et 0 option. Same error but not at the same > >> place (but only few pixels to the left) and much slower. > >> > >> gdalwarp -overwrite -s_srs "+proj=somerc +lat_0=46.952405555555555 > >> +lon_0=7.439583333333333 +ellps=bessel +x_0=600000 +y_0=200000 > >> +units=m +k_0=1 +nadgrids=./chenyx06a.gsb" -t_srs "+proj=somerc > >> +lat_0=46.952405555555555 +lon_0=7.439583333333333 +ellps=bessel > >> +x_0=2600000 +y_0=1200000 +units=m +k_0=1 +nadgrids=@null" -tr 0.125 > >> 0.125 -te 2611000 1233000 2612000 1234000 -co 'TILED=YES' > >> 611233_12_5cm.tif 2611_1233_12_5cm.tif > > > > Stefan, > > > > as you work with sub-meter accuracy, forcing the bounds to nearest meter, > > while using the default resampling (nearest neighbour) is the likely > > cause. The issue seems to be a pixel shift in the vertical direction, > > likely due to a pixel coordinate expressed as a floating point value > > being rounded suddenly from the floor integer to the the ceiling > > integer. > > > > I've quickly tried with cubic resampling (-r cubic) and the result seems > > to be much better/smoother. Bilinar could probably work as well. > > > > Even > > > > -- > > Spatialys - Geospatial professional services > > http://www.spatialys.com -- 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