Ok, so it sounds like you have a terrain model for the surface and you have a terrain model (or almost so) for a subsurface feature.
If this is true, have a look at Create Delta Terrain Model. That might get you closer to where you need to be.
If this is not true, could you explain more where this 0,60 and 0,75 and 1,00 come from? How did you decide on them?
If this is true, have a look at Create Delta Terrain Model. That might get you closer to where you need to be.
If this is not true, could you explain more where this 0,60 and 0,75 and 1,00 come from? How did you decide on them?