Even, what suprises me is that the following workaround shows not artefacts:
1) gdalwarp a larger part of the desired bouding box (keep SRS) 2) gdalwarp to the target srs 3) gdalwarp for cutting to desired bounding box with -tr and -te option. 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'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 <[email protected]> wrote: > Le vendredi 04 septembre 2015 21:29:02, vous avez écrit : >> Hi >> >> On Thu, Sep 3, 2015 at 10:58 AM, Even Rouault >> >> <[email protected]> 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 _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
