In the meantime I found a workaround method. I export the 3D model from Csurvey. Then open it in Meshlab and run a Screened Poisson surface reconstruction on the imported mesh. This results in a much better 3d model then the one directly from CS, but the resulting model preserves only the georeferenced Z coordinates while X and Y are lost. Meshlab also has a function to transform coordinates to their georeferenced equivalent, but it does not seem to work as intended, so the model needs to be exported as dxf, imported to Qgis, converted to 3d polylines and then translated back to original georeferenced position. And voila, you get a georeferenced dxf polyline 3d model of a cave. Not great, not terrible.
