[time-nuts] GPSDO+PC as a NTP server

[Bob kb8tq]

Hi

The “ideal” solution (at least to me) would be a setup that let you estimate the time based
on each system independently. Even things like survey locations vary a bit system to system. 
Give each one the “fix” that it thinks is best and go from there. Then report the output PPS time 
offset for each of them. Let “higher authority” decide what to make of the results.

Taking this a step further, correction information is available real time for various systems. The
quality (and availability) of these streams is not 100%. The same “give it to me both ways”
approach likely makes sense there as well. 

Redundancy is fine when you actually have independent outputs. Getting it all mashed together 
in some unknown / hidden fashion …. yikes ….

Bob

> On Oct 24, 2019, at 2:30 AM, David J Taylor via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> From: Fiorenzo Cattaneo
> []
> GPS and GLONASS are the best GNSS around, they are operated by the
> military as a military operation and have the best reliability record.
> Beidu is fairly new, and Galileo is operated by civlian agencies.
> They've had major operational issues. So this leaves GPS and GLONASS.
> GLONASS tends to have better coverage on the polar regions, but
> otherwise I think GPS is better, and GPS has better time and space
> accuracy. Although I'm not that with the accuracy of RS232 interrupt
> handling it would be possible to even tell the time differenbce.
> between UTS(GPS) and UTC(GLONASS).
> 
> I'm not even sure than running GLONASS and GPS together will give you
> a better time solution, although it will definitely improve
> availability.
> =======================================
> 
> GPS, GLONASS and Galileo have /all/ had operational difficulties, and possibly BeiDou too.  For precision timekeeping Galileo has the best on-board sources, but using GPS and Galileo is perhaps the best combination of accuracy and reliability.  The offset between GPS time and UTC, and Galileo time and UTC is regularly reported (possibly in the satellite feed itself).  It's nanoseconds, and very unlikely to affect a system using a PPS signal from a typical amateur cost source.
> 
> I think you underrate Galileo, certainly in suggesting GLONASS above Galileo.
> 
> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6308660/
> https://www.itnews.com.au/news/satellite-failure-caused-global-gps-timing-anomaly-414237
> https://www.theverge.com/2019/7/15/20694395/europe-galileo-satellite-navigation-system-offline-outage-technical-incident
> 
> 
> Cheers,
> David
> -- 
> SatSignal Software - Quality software for you
> Web: http://www.satsignal.eu
> Email: david-taylor at blueyonder.co.uk
> Twitter: @gm8arv 
> 
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