It's deeply embarrassing to be disagreeing with somebody who obviously knows more about GPS and aircraft than I do, especially as we seem to be totally at cross purposes.
cribbagepeg
read message 4463 - what you're talking about is phase tracking...
In 4463 you said ...
The phase-tracking used in attitude detection is a different animal. The wavelength at GPS frequencies is roughly (very) 25cm, so the theory predicts that one receiver moving vertically (e.g.) relative to a second one, toward or away from the satellite(s), would experience a detectable phase difference in the order of centimeters. Needs superfast processor and GPS chips, but it works....
I'm talking about taking the difference in readings between two bog-standard GPS receivers at the wing-tips. Bog-standard, without superfast processor and GPS chips. So how can I be talking about the phase tracking you refer to?
I was trying to make a simple observation. Which I still feel is correct, and is supported by the maths at the end of message 4472 ...
If you take the
difference of the positions reported by two bog-standard GPS receivers on your plane, then the accuracy you achieve is the same as you would have achieved using two civilian differential-GPS receivers [and a nearby base station].
If you have an argument directed against this observation, I'm really interested. Perhaps offline as we're taking bandwidth.
Regards, Peter