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Re: [gpsd-dev] PQXFI NMEA, what is it?
From: |
Eric S. Raymond |
Subject: |
Re: [gpsd-dev] PQXFI NMEA, what is it? |
Date: |
Wed, 20 Jul 2016 18:50:24 -0400 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
Gary E. Miller <address@hidden>:
> > First there is time, lat, lon and MSL altitude, then the 3 unknowns.
> > First 2 unknowns vary from about 250 down to about 2, 3rd one varies
> > between about 5 and 0.03. All are bigger when sky is blocked, smaller
> > when view is good. First ones could be uncertainties, in meters, but
> > the 0.03 ?
>
> Yeah, either DOPs or Error Estimates. Have you connected that to gpsd?
>
> gpsd will compute the DOPs and Error Estimates, then you can see
> which match.
They may not match exactly. SiRF does some undocumented jiggery-pokery
to deweight satellites that it thinks are likely to add more noise than
signal. Other vendor firmware might pull similar tricks.
--
<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>
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