.Salute!
It may surprise you, Flash, but a year or two before you were born we could do an airborne alignment in our SLUF.
Crude level for the "platform" like most AHRS did those days, then use a rough present position to start the alignment ( that provided theoretical Earth rotation data) and then use velocity inputs from our doppler. Find a good reference for a position update 15 or 20 minuites later and walla!
As you assert, technology has progressed, and further and faster than most of us ever imagined.
Gums sends...