[time-nuts] Azimuth/elevation dependent satellite masking

Tom Van Baak tvb at LeapSecond.com
Fri Mar 19 20:53:09 UTC 2010


> I played around some with masking sats that were in poor
> signal areas,  but the problem I wound up with is once you
> exclude a sat the Tbolt firmware no longer tracks its position
> so you don't know when its safe to start using it again.    To
> determine that properly you would need to model the sat
> orbits, etc.  It opens up a rather messy can of worms...

Mark,

Have you considered using the individual sat solutions (in
the 8F A7 message), removing one or more of the sat's in
software, and then re-calculating the mean clock bias? This
way you don't stop tracking any SV; you just selectively use
or not use the SV bias data of your choice. This might work
well with your new external software disciplining approach.

Another approach that might be fun is playing with weighting
the SV clock bias contributions rather than the all or nothing
model. You may find that variable weighting by Az or El or
signal level or SVN or time-of-day, etc improves the timing
quality a bit.

If nothing else you could collect a lot of per-SV clock bias
data and then crunch a week's worth of data to look for
correlations. Given that you could then "replay" the timing
solution and see what effect different algorithms would have
had on the timing output.

/tvb





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