Thanks Daniel, I tried your variant with the coarser resolution image. The result is not perfect but good enough for my purpose. Regards, Harry -- View this message in context: http://osgeo-org.1560.n6.nabble.com/Remove-red-lines-from-raster-images-tp5000430p5002604.html Sent from the Grass - Users mailing list archive at Nabble.com.