VOLUME CALCULATION

[vagk_18]

Hi Lars,
My worry is this:
Is there a way to calculate the volume of an excavation, by comparing two surfaces (3d faces triangles) and choose a closed boundary to
determine where should be the excavation limits?
For example, a dwg containing three layers (one layer for the 1st surface, one layer for the second surface and one layer for the closed boundary).
If you have any suggestions, please inform me.
I'm attaching a sample for you.

[Lars]

Hi!

If you don't have the saved surface files you can import triangles to surface files.

• Turn all layer off except the existing ground
• Open Edit/View Surface, menu Import Surface, select all by crossing, save as "Existing Ground"
• Turn all layers off except the Design Surface
• Once again use menu Import Surface, select all by crossing, save as "Design"
• Open Command "Surface Volume"
• Select Existing surface and Design Surface and calculate volumes

With your surfaces I get a warning about mismatching area. If you open a report you'll see a difference of 4 in the area. You can verify the area of your design surface by open it in "View Surface" and use the tab with properties. There you'll see the true surface area, compare it with the area in the report, there you see that the area difference of 4. Probably there is a minor problem in the volume calculation while projecting triangles onto the Existing Surface, probably nothing to pay any attention to.

[vagk_18]

I'm familiar with the procedure to calculate the volume. My consern is that i must use the excavation limit boundary, as it is, to calculate the volume.
How can i use this boundary after I have chosen the two surfaces for comparison?
Thanks in advance.

[Lars]

I'm not sure but you want to limit the volume calculation by a perimeter?

If so you need to drape the perimeter onto the Design Surface and then select the draped perimeter and all triangles and then triangulate (As breaklines). Plot the triangles and use the draped perimeter to delete all triangles inside the perimeter. There is a tool for that Booth in Edit/View Triangles and triangulate.

The drape and triangle procedure results in triangles inside and outside the perimeter without crossing the perimeter.

It's a bit tricky, hope it helps!

/Lars