GPS groundspeed
Interesting problem here somebody might be able to help me with.
Flew two sorties on the same day, using two different GPS sets (one a Garmin panelmount, not quite sure the other but it was a handheld) to generate groundspeed as reference data.
It appears that the two sets gave markedly different (16%) groundspeed values under what seem to be identical circumstances. Now some of this is inevitably repeatability error - but not that much.
The first thing that springs to mind is that possibly there are more than one method - for example differentiation versus some kind of doppler measurement, used in determining speed in a GPS set and that this has led to different GS indications.
I may yet simply go and do a cross-calibration of the two sets against each other, which will give some clue, but has anybody else any experience to lend to the problem?
G