I was watching a letsplay of The Longest Drive and they mentioned GPS: I wonder how long GPS will keep functioning after a civilizational collapse?
Because while yeah, eventually the satellite orbits will decay, but I imagine the lack of updates will kill it faster
because they're regularly updated from ground stations, but I don't know how crucial that is. like, does it just get less accurate over weeks? or does it shut off as soon as it misses the daily clock correction?
@foone Ephemerides get outdated really fast, they're mostly useless in a matter of hours. Some systems do autonomous prediction of ephemerides and may keep functioning for a day or two. There are other sources of navigational data too, but I'm afraid they usually depend on a functioning civilization 😅 Not sure what's the accuracy you can get on almanac alone, perhaps you could get some city- or region-level precision for a few weeks...
@foone Ah, and that would be an accuracy achievable theoretically - most receivers probably won't consider that a valid fix anyway and usually won't report it to the user at all!