[time-nuts] Can eloran Backup GPS?

[jimlux]

On 9/8/18 4:52 PM, paul swed wrote:
> Hello to the group I won't quote figures here but did indeed help UrsaNav
> do testing. Hey 90 days with a HP 5071 that was a sweet deal at the cost of
> some power.
> They do send corrective data in the signal from reference sites and that
> helps propagation corrections in the receive software.
> It was impressive and even in buildings no less. Its been a while so thats
> why I don't want to quote figures.
> I sort of thought all of this would have been resolved by now. But nope not
> until the S.. hits the fan and finger pointing starts.
> I do know the other satellite system lightspeed? is trying to become an
> alternate.
> Regards
> Paul
> WB8TSL
> 



But here's the problem - if "the network" is wiped out, how do you send 
the correction information?

I suppose you could have a low rate network (i.e. not "the internet") 
and for the most part, the propagation corrections (whether using 60kHz, 
Loran, Omega, or GPS) can be done with "climatology" - time of day and 
time of year.

BUT - if we're talking about a Carrington event or similar, a series of 
high altitude nuclear bursts - the propagation is going to be totally 
anomalous anyway.

If we're talking about a evil-doer taking down GPS AND "the network" 
together, but not perturbing the ionosphere, there may be other things 
to worry about - the network carrying "time" is also carrying all those 
high value transactions, phone calls, etc. and that's probably a bigger 
business disruption than losing network sync.

So I think GPS actually works pretty well - it will provide good sync 
for any non-global disaster.  Likewise, a "campus" network will be able 
to stay synchronized, because they've got wired connections.

In a local disaster (hurricane, earthquake) it's likely that business 
has been disrupted by the disaster sufficiently that time sync is less 
important.