[Meet the New Boss]

Presumably there is also a relativity effect when measuring tiny differences in elapsed time at 22,000 miles above the earth compared to an aircraft flying 7 miles above the earth. I don’t know whether it is big enough to be relevant, but if they are taking into account these tiny variations in the satellite orbit, these must be very small calculations they are making.

[steve86]

Presumably there is also a relativity effect when measuring tiny differences in elapsed time at 22,000 miles above the earth compared to an aircraft flying 7 miles above the earth. I don’t know whether it is big enough to be relevant

It is definitely significant enough to be included in hand held GPS units -- error would increase significantly if it weren't.