[time-nuts] How long to monitor GPS? (was: Re: Rapco 1804M - serial problems?)
David J Taylor
david-taylor at blueyonder.co.uk
Fri Oct 21 16:50:35 UTC 2011
>>> I've now written a small plotting program to show the PDOP, satellite
>>> signal strength, inactive/coarse/fine lock mode etc. This ideally
>>> needs to
>>> run for several days with the box connected to each puck in turn, but
>>> preliminary results show that the unit achieved "fine" lock several
>>> times
>>> with the new antenna, but never with the old.
> 24 hours should in theory be enough but 2 is not a statistically valid
> sample size. you need more samples before you can say anything about
> the probability of locking. How many depends on the size of the error
> bars you can live with.
>
> Chris Albertson
Thanks, Chris. I just ran the GPS visibility part of my orbit prediction
program (WXtrack), and it seems to show a very similar pattern from
day-to-day, albeit with a slight time drift as the days progress. So it
looks as if the very first time I plugged the new puck antenna in we were
just going into a maximum number of satellites visible phase.
Looking further it's about 4 minutes a day, so making me wonder whether
the satellites are locked to a "sidereal" orbit (I expect that's not the
right term!).
Cheers,
David
--
SatSignal software - quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk
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