Hi, When it comes to gdalwarp I believe that this part of the documentation https://gdal.org/programs/gdalwarp.html is essential
"Starting with GDAL 2.2, if the SRS has an explicit vertical datum that points to a PROJ.4 geoidgrids, and the input dataset is a single band dataset, a vertical correction will be applied to the values of the dataset." Both EPSG:4326 and EPSG:2056 are 2D systems without explicit vertical datum. EPSG:4979 is explicit 3D http://www.epsg-registry.org/export.htm?wkt=urn:ogc:def:crs:EPSG::4979 and the compound crs syntax that you used (-s_srs EPSG:2056+5728) is explicit as well. I do not know how gdaltransform knows to do the conversion in Z coordinate and how to give the -s_srs and -t_srs right for gdalwarp but I would try next with -s_srs EPSG:2056+5728 -t_srs epsg:4979 -Jukka Rahkonen- Pillio Zoltan wrote > Hi, > > I'm new here, and just started using gdal, so maybe I'm misunderstanding > something, but I found that gdalwarp and gdaltransform produces different > results. > > The gdaltransform command is : > echo 2600000 1196000 768 | gdaltransform -t_srs EPSG:4326 -s_srs EPSG:2056 > > and the result is: > 7.43863317174838 46.9151021335816 817.714334204793 > > ,but if I'm converting a geotif with the following command: > gdalwarp -t_srs EPSG:4326 -s_srs EPSG:2056 > SWISSALTI3D_10_TIFF_CHLV95_LN02_2600_1196.tif test.tif > > the height doesn't change. I'm using swisstopo example data from here: > https://cms.geo.admin.ch/Topo/swissalti3d/swissalti3dgeotifflv95.zip > > I did the conversion by myself based on swisstopo documentation (link > above), and the result of gdaltransform is correct, but gdalwarp is wrong. > > Do I misunderstand something, or did I make a mistake? > > I'm using GDAL 2.4.2, released 2019/06/28 > > Thank you in advance for your help. > > Best regards, > Zoltan Pillio > > ps.: > I also found that setting height reference frame has no effect in these > cases: > echo 2600000 1196000 768 | gdaltransform -t_srs EPSG:4326 -s_srs EPSG:2056 > echo 2600000 1196000 768 | gdaltransform -t_srs EPSG:4326 -s_srs > EPSG:2056+5728 > echo 2600000 1196000 768 | gdaltransform -t_srs EPSG:4326 -s_srs > EPSG:2056+5729 > > and the swisstopo documentation for conversion I used: > https://www.swisstopo.admin.ch/content/swisstopo-internet/en/online/calculation-services/_jcr_content/contentPar/tabs/items/documents_publicatio/tabPar/downloadlist/downloadItems/19_1467104393233.download/ch1903wgs84_e.pdf > > _______________________________________________ > gdal-dev mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/gdal-dev -- Sent from: http://osgeo-org.1560.x6.nabble.com/GDAL-Dev-f3742093.html _______________________________________________ gdal-dev mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/gdal-dev
