Salute!
Nope, Ivor.
Firstly, GPS doesn't give a rats about where you are on the Earth or at a fairly high altitude.
And secondly, The nav computer will use the lat/long from the GPS and then start looking at sensed accelerations and rates. [EDIT: Using a Kalman filter or other algorithm, the nav system "corrects" the inertial until its output is what the theoretical values are for your position in space. The really old systems used a technique called gyrocompassing, and those usually "pointed" north once aligned. Most also used accelerometers fixed on a gyro-stabilzed platform. Computer and sensor technology got much better, and nowadays strapdown systems literally bolted on the airframe are as good as or better than the best systems we had in the 70's, 80's and early 90's. ] You can speed things up a lot by providing rough attitude relative to the Earth, but even without that a good system will get your "platform" aligned. And BTW, since the late 70's, inertials didn't have to "point" to true north all t he time. See "wander angle" and such. Hell, they don't even have to be "stabilized" in space either.
Gums sends...
Last edited by gums; 13th Apr 2020 at 01:18.
Reason: added gyrocompassing