There aren't enough of those.
Nanoseconds, if you need GPS clocks.
Both time and frequency on GPS satellites are corrected for the
relativistic effects of their motion and their height in orbit
(gravitational relativistic effects). So GPS _is_ THAT accurate. It
has to be, or it won't work.
There were, but they they didn't achieve the accuracy they manage today.
Sometimes they were off by hundreds of metres.
But it's not possible to shut down GPS for a USER. You either affect
all (non-military) users, or none. Terrorists are not a separately
targetable class of users.
That's when navigation becomes more important than ever.
Nothing surprises me today.
There aren't any other satellite systems that can replace it. GLONASS
comes close, I suppose.
You can't do "contingency planning" unless there are suitable
alternatives. Without electrical power, you can't listen to the radio,
no matter what your plans.
They paid taxes, and that's the same thing.
There's no guarantee that the power will stay on or that the water
supply will be maintained, but both are always present, just the same,
and it's not unreasonable to depend on them.
If you never allow yourself to become dependent on any technology, you
never make any progress.
Which is why nobody will use it.
