Originally Posted by
A Squared
Well, yeah, what else are you going to measure ground speed relative to? Again, groundspeed is inherently relative to (in the frame of reference of) the ground.
You can't make any meaningful analysis when the axes of your reference system move whenever a person looks in a different direction.
Sure you can. If your last sentence is true, then it is not a meaningful analysis that in Scenario A the Cessna went from 90 to 110 groundspeed when turning East to West. Did you look at scenario A? Do you think that's meaningful or meaningless?