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When are GPS Airspeed meters and Altimeters going to be introduced if they not already in use? Are they more accurate than systems in use now and? How much would it cost to install them to older aircraft?

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In general, even very low cost GPS units can provide very very accurate velocity vectors.

Altimetry is not quite as good, and is different in that it is referenced to a geoid, rather than a barometric pressure.

Similarly, airspeed is referenced to the ambient air, and while a GPS is a very accurate velocity vector source, there is no easy way to know the ambient air velocity.

So in short, by necessity to maintain safe flight, airspeed utilizes relative wind on an aircraft, and there is not an easy way to determine that with GPS alone. And altimeter settings by convention, are based upon ambient air. However, by utilizing a geoid model reasonably accurate absolute altitudes or MSL altitudes could be determined. Cost? As much as an old cellphone and some software. Pretty cheap.

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  • $\begingroup$ Except that if using GPS for these types of instrumentation, the costs aren't going to be cheap. The system will still have to be certified in the aircraft, and an old cell phone and some software isn't going to cut it. $\endgroup$ Aug 3 '17 at 17:56
  • $\begingroup$ Geoid, in the sense that the altitude information for aircraft is conventionally referenced to MSL. If functioning as an analog to a radar altimeter then the answer is different. With respect to costs, I did not speculate on the certification costs, and the avionics manufacturing costs, as that would obscure the fundamental low cost of the underlying device. $\endgroup$
    – mongo
    Aug 3 '17 at 18:14
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    $\begingroup$ Based on my experience with using GPS to estimate altitude in cycling, the pilot who relies on such a device will soon be a dead pilot. $\endgroup$ Aug 3 '17 at 18:14
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    $\begingroup$ I take it your cycle GPS is not WAAS enabled (grin). $\endgroup$
    – mongo
    Aug 3 '17 at 18:18

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