Originally Posted by
mm43
. With regard to the southward turn at 1830, I assume that any turn or climb taking place at that time could provide the apparent BFO change.
Yep, the measurement has the problem of all the BFOs: It could be strongly influenced by vertical speed. In this case, if it the low BFO had been caused by vertical speed, it would have been caused by a vertical speed away from the sat, i.e. a descent.
PS: OTOH looking at appendix 1 of the raw data again: The BFO constantly lies between 86 and 90 in the one minute interval between 18:39:55 and 18:40:56. That is indicative of either a constant descent during this minute or a southerly course. To me the latter has higher probability