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Re: Recommend a USB gps for Rpi

From: Gary E. Miller
Subject: Re: Recommend a USB gps for Rpi
Date: Sat, 10 Oct 2020 17:56:09 -0700

Yo TarotApprentice!

On Sun, 11 Oct 2020 00:28:58 +0000 (UTC)
TarotApprentice <> wrote:

> I have the following in ntp.conf for the the gps:

Looks good to me.

> Cgps says "seen 30/used 18" which if I am not mistaken means it can
> see 30 satellites and is using 18 for its 3D fix. 

Looks good to me.

> If I do ntpq -p with a 16 second loop I get the following, that is
> the offset column is 24.526 at one point, drops to 15.025 and then
> back to 26 and 27.

Ignore the SHM(0) column, that is mostly telling you how long your
receiver takes to sent the NMEA to gpsd over USB.

You SHM(1) is solid around 0.1.  That is about as well as you can get
over USB.

> to use for tuning (the how-to guide recommends averaging over 4
> hours) and admittedly I haven't fine tuned the time1 parameter above.

Don't bother over USB.

> Is it normal to see it see it drop and then come back like this?

Looks solid to me.  Ignore SHM(0) and all your SHM(1) have an

> *SHM(1) [...] 0.135

Pretty good over USB.  Be happy.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703  Tel:+1 541 382 8588

            Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin

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