my goodness...is there a common consensus on how to calc a GPA?
The DME is based on a nominal 3 degree GPA, then with a myriad of factors, the alt at the rings is provided..
aside from that, the issue remains the same.
With all of your 'calcs' what is the altitude at the DME ring distances?:
1. What is your point of origin?
a. the elevation of the DME (if known)
b. the elevation of the DME plus the accuracy factor.
c. the DME broadcast with slant angle deviation.
d. None of the above (ie read what is on the chart and accept)
Yes DME is the slant range distance...and it is exactly that, distance along a 3 degree GPA..surface distance, irrelevant. That is another issue.