Presumably when World War 3 kicks off the very first thing each adversary will do is knock out their opponents satellites? These are like flying lightbulbs that shine down usefulness from above, so step one is to cut the lights.

Presumably-squared there is some kind of military backup to survive once the lights (GPS) go dark? Whatever that technology is, why hasn’t it proliferated into civilian life so that we all benefit from a resilient, non-GPS backup?

Perhaps the answer is that every tank has a 10lb inertial navigation gyro or some other thingy in it as a backup, and the platoon around it uses the tank as a moving trig point? In that case I can see it being infeasible to deploy that for civilians.

Perhaps-squared it’s just economics — GPS is cool and cheap now, so why burn profit margin on developing an alternative?