Craig Sawyers <c.sawyers@...>
Yeah, I read that story when I googled "time-nuts". Cool stuff. It got me to wondering: If (as heGPS has to be corrected for both special and general relativity. Special because the satellites are
not geosynchronous, and are moving relative to a ground observer, and general because of the gravity
well. On the one hand this is deterministic, and on the other hand there needs to be constant
tweaking because tides and weather and so forth needs to be taken account of.
Without such correction, your position would drift by 10km per day and render GPS useless.
The Allen deviation of GPS time derived clocks has to be measured with respect to a ground reference
as you say, which itself has an Allen deviation less than that of GPS itself.