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Re: [gpsd-users] Strange loss of 3d fix

From: Gary E. Miller
Subject: Re: [gpsd-users] Strange loss of 3d fix
Date: Thu, 15 Aug 2019 12:36:36 -0700

Yo Svenn!

On Thu, 15 Aug 2019 21:28:33 +0200
Svenn Are Bjerkem via gpsd-users <address@hidden> wrote:

> when I mount zed-f9P (with ublox antenna) in the best place I have
> available regarding clear sky, I loose 3d-fix after about one minute.

Not good.  I have not had that problem.

Did you try a ground plane, or choke ring?  Any nearby metal or other
multipath possibilities?

> If I place it in the south-facing window of my office, I have 3D fix
> for thousands of seconds.

What is your lat/lon?  GPS sats do not go above 56 degree latitude.

> Loosing fix means all the calculated
> parameters are lost as if I just plugged in the gps.

Lost me?  If you GPS did not move the data is still valid.

> When observing the gps in my office, I see that there is a "batch" of
> json data being transferred to cgps. This is approximately when the
> "loss" of fix happens in my base station location. I am on laptop
> battery with no wlan at that point.

How about doing a capture, with "gpsipe -w" and "gpspipe -R", and
looking at that.

> I think I need some help to find out which baud rate the autobauding
> is setting

Simple: "stty -F /dev/ttyS0"

> and if the NMEA is turned off when autobauding finds out
> that this is a ublox device.

gpspipe, as above, tells you.  Better yet, ubxtool.

> I am investigating if the massive "good"
> data is causing some lockup in the uart chain.

If can happen.  You should set your receiver to 115200.

> linux, gitlab:master:LATEST zed f9p ver 1.11

What does that mean?

> and I try to reboot the gps by sending a HOTBOOT, but then gpsd stops
> receiving.

Yes, it is rebooting!

> Is there a way to reboot a gps and retain the connection to
> gpsd?

Depends on what interfacce you use.  Not possible with USB as the port
re-enumerates.  Blame u-blox.

> Closing down and pulling the plug is the way I do now.

Pull the plug on what?  Power?  USB?

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  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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