Actually I recently flew to Dallas and was able to get a gps fix by holding the N810 to the window of the plane. Clocked the speed @ 484MPH @ 27000Ft before losing satellite fix. I believe the difficulty in maintaining a fix was due to the aluminum skin of the plane rather than hardware limitations. The unit seemed to be confused as to exactly "where" I was but my guess is this is due to the difference in time dilation between 484MPH & 30,000Ft and sea level (give or take a few thousand feet) and traveling 70MPH on the ground GPS systems have to take into account that clocks on GPS satellites run a bit slower than clocks on Earth in order to get an accurate location fix. So you are most likely correct in that you may mot get accurate data unless you could figure out how to modify the gps software.