I found this calculation by a mathemetician named Wright who calculates for woodpiles not stacked by hand with diameters less than 10".
If geometric volume is greater than or equal to 1 m3 or 35.3 ft3:
(6a) Adjusted Pile Volume (m3) = e(0.2106 + 0.7691 × ln(Geometric Volume (m3)))
Interestingly enough, the Geometric Volume is usually the hard number to quantify because it is determined by the overall shape of the pile. DroneDeploy does that for us. "e" is a constant in physics, so the calculation should be easy to quantify with a calculator.