Hi Steve - I think that will probably need a kind of specialized terrain fitting tool which MoI does not currently have.

Probably the "Patch" command in Rhino is the closest thing I can think of to kind of process something like that more automatically.

One thing you can do in MoI to make some progress is to close each outline with line segments, then you can do some extrusions and booleans to make a solid like this (model attached as contour test2_3dm.zip):




Now with it as a solid shape, there are maybe some other possible steps you could do, like take some lines underneath it and project them up:





That now gives you a set of parallel sections, you can use each one as a guide to snap on to when drawing a smooth curve, and then loft the resulting smooth sections into a surface...

But you'll probably generally have an easier time if you use a tool that has some special things in it for terrain, MoI just does not have anything specialized for that currently.

- Michael