Re: [gpsd-dev] [PATCH 1/3] TSIP: improve comments

[Gary E. Miller]

Yo Nuno!

On Tue, 21 Jun 2016 19:11:53 +0100
Nuno Gonçalves <address@hidden> wrote:

> On Tue, Jun 21, 2016 at 6:53 PM, Gary E. Miller <address@hidden>
> wrote:
> > I don't have the NMEA doc, but one reference says only 12 PRNs are
> > allowed in that sentence.  Another says 14.  We'll need to check
> > that. Also, will there be GLONASS, BeiDou or other sats in there?
> > Then maybe it should be a GNGSA.  
> 
> Yes, probably all L1 services (GPS, QZSS, SBASs, and Galileo) and
> GLONASS.
> 
> I have to look where is the NMEA being created. This will probably
> take a while.

If we can resolve the max count in the GPGSA I could live with that.
There seems to be no consistency about usage of the xxGSA's.  So a bigger
problem than just TSIP.

Here is how Skytraq does it, others are wiildly different:

        "Used to represent the ID’s of satellites which are 
        used for position fix. When both GPS and Beidou 
        satellites are used in position solution, a $GNGSA 
        sentence is used for GPS satellites and another 
        $GNGSA sentence is used for Beidou satellites. When
        only GPS satellites are used for position fix, a 
        single $GPGSA sentence is output. When only Beidou 
        satellites are used, a single $BDGSA sentence is 
        output. "

> > So what is the delay you see?  Can you identify your model and put
> > in the fudge you see automagically?  If not can you add in your
> > observed fudge as a comment?  
> 
> I see delays from 0.028 to 0.5s, depending on device, as specified in
> the comments, depending on device, number of visible SV, and probably
> firmware versions.
> 
> I don't think it is reliable to assume any value, so 0 looks the
> neutral assumption.

A minimum value would be nice, but if we cant solve it, ttthen documenting
is a start.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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