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Re: [gpsd-dev] Another query on terminology


From: Eric S. Raymond
Subject: Re: [gpsd-dev] Another query on terminology
Date: Tue, 14 Apr 2015 09:09:46 -0400
User-agent: Mutt/1.5.23 (2014-03-12)

Sanjeev Gupta <address@hidden>:
> On Tue, Apr 14, 2015 at 7:54 PM, Eric S. Raymond <address@hidden> wrote:
> 
> > Sanjeev Gupta <address@hidden>:
> > > Suddenly, PRN 129 and 137 (both MSAS) are reported as in use by gpsd.
> > >
> > > Is there anyway to dig deeper into whether they are being used as GPS or
> > > SBAS?  I am outside the area MSAS has corrections for, for SBAS.
> >
> > Depends.  What's your device type?
> >
> 
> In this case, the GR-601W.  Connected over USB to a Raspberry Pi, running
> release-3.14-410-g0532106 (git HEAD)
> 
> I can give you (and anyone else) root access.

Not needed. Looking at the driver source, I can see that the driver does
not add an SBAS bird to the skyview unless the chip tells us that SBAS is
in use (the original driver was by ckuethe, but I think I wrote that 
particular code).  The PRN of the last SBAS bird seen is kept around
specifically so it can be added to the skyview on the following cycle.

So the fact that you see those means you're getting SBAS corrections from 
one of them, but the driver doesn't pass out the information about which
one.

Bot the fact that I see *two* diamonds on the screenshot actually
worries me a little.  The UBX chip and driver only retain coverage info
for one SBAS sat at a time, which implies that one of those two is
being seen as a conventional GPS sat despite the high PRN.  I don't
know if this is expected or a bug.
-- 
                <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>



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