Overlapping cut areas in materials

[WScottAllenPE]

In my cross sections, I have three areas to determine for cut.

1.) Below existing surface and above existing subsurface (where existing pavement needs to be removed in its entirety)
2.) Below existing surface and above proposed subsurface (where existing material needs to be removed to put in new pavement)
3.) Below existing surface and above final grade (to remove overburden to grade to final surface).


Section Material.JPG

I can't do these under one sub-criteria because it will only find areas above BOTH existing and proposed subsurface, but I want to find areas above existing OR proposed (the lower of the two).

The approach I used does find all the areas that I need. However, they overlap. So, when I have a total cut area, it adds the separate parts together, giving me a high quantity.

Overlap Areas.JPG

Any thoughts on how to get the area covered by the unique areas, not the overlapping areas? I can find the area with a fourth criteria of above both, but how would I get C3D to subtract it?

I thought maybe I could combine the subsurfaces to have only one surface to compare, but I can't find out how to build a surface selecting the lower of two surfaces AND KEEP IT DYNAMIC. (You can find where the surface difference contour is zero, use that as boundaries for pasting the surfaces together, etc., but is isn't dynamic, and I know the surfaces will change again. If I had to do this, then it would be just as easy to draw polygons and use fields for their areas.)

[WScottAllenPE]

OK. My brain was working last night. (Have you ever dreamed about C3D? Frightening.) I have figured out how to mostly get what I want. I had to break the criteria into four groups.

1.) Below existing grade, below final grade, above existing subgrade, above proposed subgrade.
2.) Below existing grade, below final grade, above existing subgrade, below proposed subgrade.
3.) Below existing grade, below final grade, below existing subgrade, above proposed subgrade.
4.) Below existing grade, above final grade.

It gets rid of my overlaps.

BUT, it misses some area where the existing and proposed subgrades do not end at the same offset. That is, if the one subgrade is there, but the other subgrade is not, it will not show it, because there is no area here above both or between both, since one surface doesn't exist at all.

Thoughts now?

By the way, this seems to contradict what C3D's help suggests in http://docs.autodesk.com/CIV3D/2014/...=CUGd30e235853.