Any modern positioning system needs an accurate clock. Leap seconds aren’t completely predictable, so you can’t deploy something like a GPS unit with future leap seconds encoded. These computers are often spread across vast distances, so it’s the most difficult thing to possibly update.
Wouldn't a positioning system just need accurate time differences and synchronization between transmitters?
E.g., suppose you made a system where each satellite transmits messages of the form "Here comes beep #N. At the time of beep #N this satellite is at this position: <X>, <Y>, <Z>. Here is beep <N>: BEEP!".
The satellites are synced so that beep <N> occurs at the same time on all of them.
By looking at the time difference between the arrival of beep <N> from several satellites a receiver could tell the differences between its distances from those satellites. Combined with the position information for those satellites at the time they beeped the receiver would be able to tell its location.
If the satellite broadcasts use a high enough frequency and that frequency is known and very stable the receiver would not even need an accurate stand alone timer. It could sync a counter to the frequency of the satellite radio.
