The attached is an alternate method for computing the lower basal wedge volume using the ground perimeter instead of the horizontal offset of high side ground level vs. low side ground level. In some cases the perimeter with a tapeline is easier to obtain. In other cases as with older data, only the perimeter data was taken so this is a way to update old data sets with the improved lower basal wedge model without needing to go back to the tree to get a horizontal offset. The equation gets rather ugly so a numeric solution is needed. See attached write-up and spreadsheet with visual basic to solve the complex equation.
Michael Taylor
WNTS VP