[NorthMountain]

And from that distance you actually have to account for the curvature of the Earth.

Hmmm ...

That means:

1) If you assume a flat Earth, and Earth is in fact spheroidal ... you'll miss.

2) If you assume a spheroidal Earth, and Earth is in fact flat ... you'll miss.

Very Interesting.

[Reily]

I always first assume a spherical cow expressed in toroidal coordinates.