Amritsar Jan Seva Express: हम मजदूर है साहब! - Piyush Singh

again not true
gps stands for global position satellite
its basically a satellite receving and sending datas to give us exact location
it will be more accurate at higher altitude rather than on ground bcoz on ground we have so many distrubances like wall,building,roof etc so it solves the purpose,but not very accurate on ground for speed measurements
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height of 10km{or 35000ft} there are no obstructions apart from aircraft shell itself,so its more accurate than on ground
i wont say my data was 100% accurate, but as announced in flight that we were flying at mach0.85 at 38000ft, so it was above 1000kmph for sure