I have a crater-like area on my property that was at one point an in-ground pool installed by the previous owner. He then removed the pool and filled it in, but over the years the fill must have settled, and I’m left with a circular crater, about 15’ in diameter. At its lowest point, it’s about 2’ below grade.

I’d like to fill it in and am puzzling over how to determine the volume of the crater, so I know how much fill to have delivered. I can find formulas for determining the volume of a sphere and hemisphere, but not this- I’m not even sure if this shape has a name.

If it were a circle I’d be talking about the chord *BX*(http://en.wikipedia.org/wiki/Image:Chord_in_mathematics.svg), but as a sphere I don’t know what it is, or how to determine the volume.

Any ideas?