Originally Posted by
hoss183
I'm not talking about the align accuracy or time, that is clearly effected by the magnetic / true variation.
Genuine question - Is that actually the case? As far as I'm aware (emphasis on that!!) that certainly wasn't the situation with the old steam driven INSs.
The old systems levelled the platform to local horizontal and then ( and I'm very very much simplifying here) "found" and torqued the platform to align to True North by sensing the effect of the Earth's rotation on the platform.. mag var didn't come into the align process, am I wrong?/is it done differently now?
(Very belated edit to add that I'm assuming strap down systems must align in a different manner to that used in gimballed platforms - but the underlying question still stands - do they use variation in their alignment process?)