Official comment
All material above the base plane and inside the polygon is included. The base plane is defined by the lowest point inside the polygon.
Our volume calculations assume a that there is a flat base under the stockpile. If it is even slightly sloped the stockpile's volume will be overstated since it is including a lot of the ground under it.
Here is the text from the calculation popup:
Calculated Volume: 14,191.13 yd³
Void Volume: 25,192.96 yd³
Base Plane: 19.69 ft
Maximum Height: 51.74 ft
Area of Measurement: 3696.47 yd²
Height Samples Used: 298,571
Sample Size: 4 in x 4 in
In this case, the base plane was set at 19.69 ft. This value occurred at one end and the other end is 22.1 ft. Assuming it is a rectangle, which it clearly isn't, and that the slope was consistent from one end to the other, you could multiply the Area of Measurement 3696 yd² by the difference the base heights of .8 yd and divide by 2. This gives a slope contribution to the volume of 1478 yd³.
We will look at accounting for this in the future.
