Ross Edwards,

Without knowing anything about your axis setup and orientation, my first question would be about your datum plane -A-. I noticed that your first result, gave you a negative value and your second result, gave you a positive number. I have seen in the past that when getting distances from a plane, if the plane is not square to the datum axis, the end result is like taking a measurement of point to point, which would give you erroneous data.

Terry Phillips
terryp@davistl.com