Originally Posted by
slats11
It's not an easy task. Trying to determine ground speed and heading over many hours from a handful of values for velocity away from a satellite.
Agree that vertical velocity will influence velocity relative to satellite. But not sufficient to produce a false (of to conceal a real) major heading change.
According to ATSB, aircraft systems don't compensate for vertical velocity at all. (Unlike horizontal velocity, which is compensated for, but with assumptions about stationary satellite.) Uncompensated velocity of 3000 fpm is equal to Doppler shift of 84 Hz at 1.645 GHz.
The difference between BFOs at 18:28 and 18:40 (and the difference between heading northwest and heading south) is around 55 Hz.