I wonder if it would be possible today to bring back old school navigation techniques (sun, clock, stars, inertia) with the kind of precision we're used to with gps.
I'm going to wager the answer is, no. By and large, the main advantage of GPS is it is now extremely compact and relatively low power. My gut feel: To do the same with the sun and stars, you need very finely calibrated optical instruments, probably on a motion compensated surface to get maybe 1/10th of the precision. Also a precise timesource would need to be thermally compensated etc. That's not portable or low power and I don't really see how portable that can be made. The inertia + gyros thing is already used by GPS systems as a backup when traveling in tunnels.
If we spent some time I bet we could come up with a laser gyros small and affordable enough for phones or at least small navigation units. The bad part would be having to align your INS every day or two. Or if it restarts...
Oh you bet. Inertial navigation (INS) is found in most large planes and fighter jets as a backup for GPS. In addition some spy planes used to use star positions, sun position, and timers to determine global position. In addition there are ILS, VOR, and ADF radio beacons for most civilian traffic.
It was the SR-71 that used star positions I guess.