Does anyone know for sure what the AC uses to determine it's altitude? I assume it's possible a number of different ways and it would seem to make sense to use different methods depending on circumstances/environment.
I suppose the possibilities are:
GPS: My guess is this is unlikely as GPS sample rates would be low and accuracy is probably not the greatest as it's based of geoid approximation of the earth.
Dead Reckoning: Doubtful. Obvious issues with accuracy based on imperfect conditions &/or calibration.
Vision Sensors: I can't imagine these would be accurate beyond more than a few feet AGL & would likely require a good deal of CPU cycles.
Ultrasound: Probably relatively reliable up to 30-40ft AGL. To me, I could imagine it making sense to use this method at altitudes where the sensors are in range to detect the ground. Only caveat would be unusual surfaces that could mess things up like water.
Barometer: I'm guessing this is what's used. Good refresh rate, accurate, not really susceptible to a weather related drop/rise given the flight time of the AC. So they just zero/tare the reading at takeoff as 0 AGL?
So is it 1 or combination of these? Or something else entirely I'm not thinking of?
I suppose the possibilities are:
GPS: My guess is this is unlikely as GPS sample rates would be low and accuracy is probably not the greatest as it's based of geoid approximation of the earth.
Dead Reckoning: Doubtful. Obvious issues with accuracy based on imperfect conditions &/or calibration.
Vision Sensors: I can't imagine these would be accurate beyond more than a few feet AGL & would likely require a good deal of CPU cycles.
Ultrasound: Probably relatively reliable up to 30-40ft AGL. To me, I could imagine it making sense to use this method at altitudes where the sensors are in range to detect the ground. Only caveat would be unusual surfaces that could mess things up like water.
Barometer: I'm guessing this is what's used. Good refresh rate, accurate, not really susceptible to a weather related drop/rise given the flight time of the AC. So they just zero/tare the reading at takeoff as 0 AGL?
So is it 1 or combination of these? Or something else entirely I'm not thinking of?
