On 2021-10-16 08:51, David Lesher wrote:
> It occurs to me that one of the systems could have put some/all
> of its birds in polar orbits. With such added to the mix,
> there's be no high-latitude shortcomings.
> Higher launch costs, however.
> Pondering if generic receivers could cope with them, or they'd
> fall over.
There are no significant high latitude shortcomings for basic GPS
service. At the north pole you have a ton of satellites in view.
If you had 6 polar orbit satellites, then there would no coverage
directly over the pole most of the time v. the existing constellation.
I suppose you could low orbit these for more coverage some of the time,
with more sats, or have more sats in the very expensive 12 hour orbit as
well to improve things. But they're "good enough" as is.
What you don't have is SBAS because those sats are geosynchronous
meaning you need a really good "view" close to the horizon (in the icy
wastes probably not a difficult thing...). IAC, the correction data is
not done for extreme high latitudes.
Generic receivers will receive any signal for which a PRN code is known
to exist. Indeed SBAS satellites (WAAS, EGNOS, etc.) "emulate" the
military C/A signal to transmit data to the receiver (this includes
positioning data (WAAS) as well as correction data. Of course they use
a PRN that is different from the US Air Force "set".