> appears that "altitute" is not a valid option for line of type survey. No it is not. It is just working for walls. > Where do I add that Z coordinate ? :-) In your layout. Example layout x grid-origin 0 0 1230 m endlayout or directly in the export map command export map -layout-grid-origin 0 0 1230 m assuming entrance altitude is 1230 m. Regards, S.