Hi Peter, Viefinder-Panoramas files not only contains voids but some serious errors too, like depressions 1km deep. At least they had some years ago. SRTM data version 3 are mostly void free, but I can see some voids for example in Nepal. Currently you need a login to get SRTM data. I think similar quality could be CGIAR data. There is no SRTM data outside +-60 degree latitude, in these area Viefinder-Panoramas is the best solution. There are other sources of elevation data, for example ASTER DEM or X-SAR DEM, but IMO they contains too many errors, probably still need a lot of processing. EU-DEM seems good. They used to contains voids on country borders, but version 1.1 looks good now. Maybe version 1.0 is usable too, I haven't checked. -- Best regards, Andrzej