Benedikt Hallinger said: " the last problem now is, that the surface lox is in a different coordinate system than the caves (EPSG:31468 vs. lat-long) :/ I hoped loch would recognize this and recalculate as appropriate, but that was not the case. Is there some option to convert conveniently?" I have never used Lat/Long but I do have a quite extensive data set that uses two different EPSG numbers, one UTM - and I think there's an IOS or two in there somewhere but cannot find them quickly - and this has generated a lox file that seems to have put everything in the right places. I have only ever seen "computer says no" messages when there have been sections where the co-ordinate system had not been specified at all. I'd be wary about stating the cs in your thconfig file as that will clash if a different cs has been used elsewhere in the data set, I think. Graham