> if the airspeed indicator is accurate, and you know you're heading, all you need is an accurate clock to determine absolute position
Airspeed gives speed relative to the air, not the ground. To compute ground speed, you also need winds aloft, which can be huge if the aircraft is operating in the jet stream.
Getting good data for winds aloft is difficult because there are a relatively small number of actual measurements, and everything else is model output with all the usual caveats.
Airspeed gives speed relative to the air, not the ground. To compute ground speed, you also need winds aloft, which can be huge if the aircraft is operating in the jet stream.
Getting good data for winds aloft is difficult because there are a relatively small number of actual measurements, and everything else is model output with all the usual caveats.
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