ORIGINAL: cavandish
gps records the whole flight,and gives a top speed, but I have always assumed that it was 'one dimentional', Ie records speed parralel to the ground, negating the higher speed achieved during a dive.
I would guess that somewhere between a 30 and 45 degree dive, the ground speed would start to diminish. But I feel certain a shallow dive would increase the ground speed. Add a little tail wind and you could get 148.