SS4 .904

Question.

When using the analyze volumes tool, the resulting quantity between two terrains should be the same as the quantity as a delta terrain built from the same surfaces and analyze volumes performed against a plane elevation 0.00'.  But, it is not.

We have a project with the following results comparing existing to proposed (analyze volumes).

Cut Factor = 1.0000

Fill Factor = 1.0000

Cut = 6254773.6620 sf3

Fill = 4400699.4384 sf3

Balance = -1854074.2236 sf3 = 68,669.42 cy

We then generated a delta terrain between the same terrains, then used analyze volumes terrain to plane of 0.00 and had the following results.

Cut Factor = 1.0000

Fill Factor = 1.0000

Cut = 6255136.0495 sf3

Fill = 4405001.8043 sf3

Balance = -1850134.2452 sf3

We get the same result regardless of using boundaries.  Could someone try to explain.