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Originally Posted by
pineteam
I don’t see how an airplane can do a full alignement in the air like some guys are mentioning here. You can have basic mode like attitude and heading but how the IRS will sense the earth rotation during flight???
if the aircraft maintains a constant heading in level flight for some minimum time and the IRS system is fed ground velocity (Doppler or GPS info) then it can recalculate, from the expected apparent wander, and determine the direction of True North again.
For some mind boggling feats of navigation, see
https://web.mit.edu/digitalapollo/Do...progreport.pdf
Apparently one crew managed to input “on launch pad at Cape Canaveral” in mid flight. They realigned the IMU (Inertial measurement unit) using star shots.