I asked about a similar issue a while back where the answer was on the fly scaling with vrt:// and *type conversion*, and constructing the geolocation array scheme with those, might be helpful : https://github.com/OSGeo/gdal/issues/8404
Cheers, Mike On Sat, Sep 27, 2025 at 12:06 AM Laurențiu Nicola via gdal-dev < [email protected]> wrote: > Hi, > > I have a NetCDF-style product with a separate geolocation dataset I'm > trying to convert to something more easy to work with. Not sure if it > matters, but the geolocation arrays are scaled. I tried to unscale them > first: > > $ cat lat.vrt > <VRTDataset rasterXSize="4865" rasterYSize="4090"> > <VRTRasterBand dataType="Float32" band="1" blockXSize="973" > blockYSize="818"> > <NoDataValue>-2147483648</NoDataValue> > <Scale>1e-06</Scale> > <SimpleSource> > <SourceFilename relativeToVRT="1">NetCDF:geo_coordinates.nc: > latitude</SourceFilename> > <SourceBand>1</SourceBand> > <SourceProperties RasterXSize="4865" RasterYSize="4090" > DataType="Int32" BlockXSize="973" BlockYSize="818" /> > <SrcRect xOff="0" yOff="0" xSize="4865" ySize="4090" /> > <DstRect xOff="0" yOff="0" xSize="4865" ySize="4090" /> > </SimpleSource> > </VRTRasterBand> > </VRTDataset> > > $ gdal_translate -unscale -ot Float32 lat.vrt lat.tif > > # same for lon.{vrt,tif} > > Then I made a VRT for the main dataset: > > <VRTDataset rasterXSize="4865" rasterYSize="4090"> > <Metadata domain="GEOLOCATION"> > <MDI key="X_DATASET">lon.tif</MDI> > <MDI key="X_BAND">1</MDI> > <MDI key="Y_DATASET">lat.tif</MDI> > <MDI key="Y_BAND">1</MDI> > <MDI key="PIXEL_OFFSET">0</MDI> > <MDI key="LINE_OFFSET">0</MDI> > <MDI key="PIXEL_STEP">1</MDI> > <MDI key="LINE_STEP">1</MDI> > </Metadata> > <VRTRasterBand dataType="UInt16" band="1" blockXSize="1217" > blockYSize="1023"> > <NoDataValue>65535</NoDataValue> > <Scale>0.01394645962864161</Scale> > <SimpleSource> > <SourceFilename relativeToVRT="1">Oa01_radiance.nc</SourceFilename> > <SourceBand>1</SourceBand> > <SourceProperties RasterXSize="4865" RasterYSize="4090" > DataType="UInt16" BlockXSize="1217" BlockYSize="1023" /> > <SrcRect xOff="0" yOff="0" xSize="4865" ySize="4090" /> > <DstRect xOff="0" yOff="0" xSize="4865" ySize="4090" /> > </SimpleSource> > </VRTRasterBand> > </VRTDataset> > > The coordinates look fine in the two TIFFs: > > $ gdalinfo -stats lat.tif > Driver: GTiff/GeoTIFF > Files: lat.tif > Size is 4865, 4090 > Image Structure Metadata: > INTERLEAVE=BAND > Corner Coordinates: > Upper Left ( 0.0, 0.0) > Lower Left ( 0.0, 4090.0) > Upper Right ( 4865.0, 0.0) > Lower Right ( 4865.0, 4090.0) > Center ( 2432.5, 2045.0) > Band 1 Block=4865x1 Type=Float32, ColorInterp=Gray > Minimum=39.552, Maximum=52.456, Mean=46.179, StdDev=3.112 > > $ gdalinfo -stats lon.tif > Driver: GTiff/GeoTIFF > Files: lon.tif > Size is 4865, 4090 > Image Structure Metadata: > INTERLEAVE=BAND > Corner Coordinates: > Upper Left ( 0.0, 0.0) > Lower Left ( 0.0, 4090.0) > Upper Right ( 4865.0, 0.0) > Lower Right ( 4865.0, 4090.0) > Center ( 2432.5, 2045.0) > Band 1 Block=4865x1 Type=Float32, ColorInterp=Gray > Minimum=16.249, Maximum=36.250, Mean=25.532, StdDev=4.917 > NoData Value=-2.1474836e+09 > Metadata: > STATISTICS_MINIMUM=16.248615264893 > STATISTICS_MAXIMUM=36.24991607666 > STATISTICS_MEAN=25.532068327481 > STATISTICS_STDDEV=4.9167101776381 > STATISTICS_VALID_PERCENT=100 > > However, this fails with "Warning 1: Too many points (529 out of 529) > failed to transform, unable to compute output bounds.": > > $ gdalwarp -geoloc -t_srs EPSG:4326 Oa01.vrt Oa01.tif > > The files are available at https://nas.dend.ro/browse/datasets/Oa01.zip, > if anyone can to take a look. > > Thanks, > Laurentiu > _______________________________________________ > gdal-dev mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/gdal-dev > -- Michael Sumner Ordinary Member, Streets People Love Hobart Association Research Software Engineer Australian Antarctic Division Hobart, Australia 0438489030 e-mail: [email protected]
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