create a 3D mesh by terrain data - interpolation error

Hello to Netgen community,
I am newbie so I would like to ask if I could use Netgen and python or other tool to import terrain data (i.e. surface and bottom of a mountain or river)? I would like to create a 3D mesh using netgen for a real topography, but without the creation of 2D footprint mesh and extrusion to 3D.
Also, if I could do that, is any way to calculate the interpolation error for each element? or the total for all elements?
Any advise or help is more than welcome,