7.45
KM-H has given you all I suspect you need to appreciate how it is done these days.
This may well get moved to the Nostalgia board, but in the old days (early 1970's) the RAF Harriers had an analogue inertial nav system. With this came a portable Ferranti platform on a cart that was put on the deck in front of your jet and you did things with the HUD to align the aircraft and the cart datums so that the cart could tell the aircraft kit how it should align. But it was never really successful in that the quality of alignment was inferior to what you could achieve parked on land.