Originally Posted by
Capt Pit Bull
This, and everything else resting upon it, is total bollocks.
Groundspeed is a Scalar. An objects ground vector is comprised of its ground speed and its track.
When an aircraft is heading directly into a wind that exceeds the TAS then it's track is the reciprocal of the heading.
If you try and call that a negative ground speed you are taking account of the same thing twice.
...is just another way of saying its GS has become negative.