[coredog64]

GPS isn’t the only navigation tool. INS is pretty accurate if you zero it correctly, and VOR is good enough to keep to a specific airway.

[glitchc]

All INSes require periodic GPS updates to limit the growth of positional error. Usually it's once per second or once every 10th of a second.

[numpad0]

That sounds way too frequent, isn't typical holdover like 12 hours?