Re: GPSd/NTPd timesync issue in JSON mode

[Gary E. Miller]

Yo Jürgen!

On Mon, 5 Sep 2022 21:04:45 +0200
Jürgen Hausladen <hausladen.j@gmail.com> wrote:

> > > Not a surprise.  Tey gpsd in the standard configuration.  If that
> > > fails then we could work on some patches.  
> 
> I started using the JSON mode with NTPd due to an issue we had back a
> couple of years ago, where it happened, that the system time
> (sometimes after days or even a week) suddenly started drifting away
> in shared memory mode even in the range of seconds.

That can happen when you forget the "preferred" keyword in ntp.conf and
the PPS gets outvoted.

> > > 10Hz mode is a lie anyway, little
> > > need to use it.  
> 
> I actually don't need the 10Hz update rate for the time sync, but when
> using the device also for location based event triggering in a
> vehicle.  What do you actually mean by 10Hz mode is a lie anyway?

Almost no receiver calculates fixes faster than 1Hz.  In almost all
cases, sub second PVT is Dead Reckoning (DR).  Which can be very
misleading.

> The
> GPS module I am using is at least from its specs capable of running
> with 10Hz.

"Running", yes.  But complete fixes?  Very unlikely.

The only way to get good sub-Hz fixes is with a wheel tick sensor.

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

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