I don't think a GPS is an appropriate speed guage, and I think if more accurate measurement was used, he would be off by some 50 MPH.
and
.........and a cheap/small GPS that accurate over such short distances, which also does not take into account the vertical plane - I don't think so!
Knocking GPS as a speed measurement is laughable. GPS measures speed at 1 Hz, and since it measures in relation to previous position - not absolute position - it is not subject to the position errors. It just measures current position minus previous position and clculates speed. You don't need a "high-grade" GPS as it's a simple measurement and calc. Yet 1 Hz is long enough time that it won't react to vibration and give spurious spikes. Over small (few meters) relative distances it is MORE accurate than say over some kilometers. Even with Selective Availablity ( signal degradation by the US Dod) any GPS doing 1Hz updates will be accurate within 0.6 mph. They work up to 999 mph. There's your reality check.
Looks to me like ET and Mr. Mike are just reaching for things to try to discredit Vmax with. Join the modern world fellas. Unless you want to accuse Vmax of lying, there is no 50 mph error here.
I'll give him the 350 mph ( groundspeed
) badge.