Ok, time for an aviation experience here...
I used my eTrex 20 on a flight to Townsville to see whether the street navigation would work at 900 KPH! Yes, cruel I know, but me has got's ta know this!
On the trip back the pilot announced that we were going to be late and that there was turbulence ahead. The eTrex 20 showed that we were well below max altitude and 200 kph off the top speed from the trip up and so I called the stewardess and asked:
"why are we going so slow?"
Dumbfounded she said "are you a pilot"?
I said "no but my GPS says that we are going much slower and lower than usual"
She said she'd check with the pilot and I asked "would the pilot consider going to max altitude to miss the turbulence, get up to the 900kph normal speed and get us home on time."
Ok, here am I expecting to get hot coffee into my lap with my outrageous request but she went and had a chat with the pilot!
Meanwhile the passenger next to me was thinking "yeah right!"
As I got off the plane and passed the stewardess to say goodbye, she grinned and said "did you notice the increase in speed and altitude!"
I said "yes I did" grinning back at her.