I have a LiDAR data tile (raster file in GeoTIFF format) that is currently in WGS 84 (lat/long) geographic coordinate system. However, the data was collected in New Arc 1950 / UTM Zone 36 South projection / Clarke 1880 spheroid. This system does not exist in QGIS, but I tried adding it as a custom CRS in QGIS 3.0.0 using the proj4 reference:

+proj=utm +zone=36 +south +a=6378249.145 +b=6356514.966398753 +towgs84=-143,-90,-294,0,0,0,0 +units=m +no_defs. 

I found the proj4 reference here: https://epsg.io/20936

When I then use the 'Assign Projection' tool, setting the desired CRS as the custom one I just created, I get the following error: Failed to process SRS definition: USER:100026

The full log message is:

Processing algorithm… AlgorithmDialog Input parameters: { 'INPUT' : 'C:/Users/hp/Desktop/COOPI/GIS_Data/REFINED_DATABASE/Elevation/Lower_Shire_LiDAR/DTM Data Sample Tile/731500_8170000_class_DTM/731500_8170000_class_DTM.tif', 'CRS' : 'USER:100026' }

GDAL command: cmd.exe /C gdal_edit.bat -a_srs USER:100026 "C:/Users/hp/Desktop/COOPI/GIS_Data/REFINED_DATABASE/Elevation/Lower_Shire_LiDAR/DTM Data Sample Tile/731500_8170000_class_DTM/731500_8170000_class_DTM.tif" GDAL command output: Failed to process SRS definition: USER:100026 Execution completed in 0.37 seconds Results: {'OUTPUT': 'C:/Users/hp/Desktop/COOPI/GIS_Data/REFINED_DATABASE/Elevation/Lower_Shire_LiDAR/DTM ' 'Data Sample ' 'Tile/731500_8170000_class_DTM/731500_8170000_class_DTM.tif'}

Loading resulting layers Algorithm 'Assign projection' finished

  • Until the bug is fixed, you could try gdal_translate -a_srs inside the OSGEO4W shell. BTW the EPSG code does exists in QGS 2.18.
    – AndreJ
    Commented May 11, 2018 at 5:29

1 Answer 1


It's a bug in QGIS 3.0, which will be fixed in 3.2/3.0.3

See https://github.com/qgis/QGIS/pull/6969

  • I think a workaround in QGIS 3.02 is to change the coordinate reference system in the raster properties. Is it ok? It seems to work for me.
    – Ernesto561
    Commented May 21, 2018 at 7:00

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