Hi,

If you want to create a nurbs surface with your map, I tested a method months ago.

Use Meshlab
- align your ground to be with a top view
- render with shader depthmap to create a heightmap
- scale the rendered image as you want for the precision (warning every pixel will give you a profile curve later)
- use the heightmap plugin in MOI. I think it's a Max plugin
- You will have a X or Y profiles (use only one if possible)
- Now you have curves to do a lofting (perhaps use loose option to smooth).

This lofting is a nurbs surface and you can use it
and delete curves.

A boolean operation can give you a clean surface which could be extrude or could be merged to have a real solid.