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Re: GPS/PPM very large offset

From: Gary E. Miller
Subject: Re: GPS/PPM very large offset
Date: Fri, 6 Nov 2020 16:42:06 -0800

Yo Mike!

On Fri, 6 Nov 2020 23:51:38 +0000
Mike Simpson <> wrote:

> Big. Sometimes 3s, sometimes 4s. B&A complaining of 5s. 


> On my Pi when it was happening I noticed that the time offset field
> of cgps would jump about rapidly from 0.2s-0.4s to 3.something and
> ntpsec would state that both pps and gps were 3 seconds off. 

Apples and Oranges.  The "Time Offset" in cgps is the delay of the
NMEA/binary data from the receiver to gpsd.  Unrelated to PPS, and
why you want SHM) set to ignore.

> Removing GLONASS kept the cgps time offset at 0.something and
> corrected the time seen by ntpsec. 


> Second time this has come up on the list with the ublox8. 

GLONASS is known to be not good for timekeeping, but not that

Depending on  your receiver model you may be able to store the
GLONASS disable.  For absolutly best timekeeping you want only
GPS, not even SBAS.

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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