Hi Michael ...

I do think that is what I was running into. I was trying to find a way to set the snap to surface in the plan view. After I reset the snaps back to default and worked in the 3d view MoI performed just fine. I was laying out paths on a multi building site and wanted to be on the land surface and still layout a combination of 2d dimensionable lines and arcs.

I finally used 2d for layout and then adjusted individual points vertically. This is still in the preliminary layout stages illustrated in a 3d model form so I am finding it a bit of a challenge.
Learning a lot and finding most 'terrain' programs (including Rhino 'patch') to be pretty inaccurate in interpreting contours. I mostly use contour lines at correct vertical intervals and then 'sweep' along them with MoI ... the results are usually pretty good.

cheers,
eric