Re: Glitching GPS feed

[Gary E. Miller]

Yo Nick!

On Wed, 18 Oct 2023 09:55:08 +0100
Nick Taylor <nicktaylor@dataskill.uk> wrote:

> - we don't have exact details of how they are doing this behind the 
> scenes but it sounds like there are a couple of devices in between us 
> and the actual GPS receiver.

Yeah, from the gpspipe -r:

"device":"gpsd://10.253.154.161:2947#tcp://10.253.132.170:7000"

Their .170 is sending NMEa to their .161, that you are reading from.
What would possibly go wrong?

As Mike Tubby already pointed out:

$GNTXT,01,01,00,txbuf alloc*61

That means the conenction from the gps receiver is too slow, and data
is being lost.  Nothing you can do about that, they have to fix the
configuration of their receiver.

> We can pickup feed using gpsd:// source, however when using this feed 
> cgps seems to glitch, keeps resetting and never seems to get a fix.

The JSON in the gpspipe -r looks good to me, no idea why cgps would burp.
Snice I can't duplicate, could Iget port 2947 access to your gpsd instance?

> I'm attaching dumps of the received feed (one is gpspipe -r and the 
> other gpspipe -R). These show feed seems to contain multiple GNTXT 
> messages which may or may not be causing the issue.

The gpspipe -R seems to show a good solid 3D fix:

{"class":"TPV","device":"gpsd://10.253.154.161:2947#tcp://10.253.132.170:7000","status":2,"mode":3,"time":"2023-10-17T09:25:06.000Z","ept":0.005,"lat":57.314024000,"lon":-111.763671167,"alt":222.000,"epx":1.928,"epy":1.660,"epv":4.715,"track":128.3500,"speed":15.788,"eps":3.86}

Can't image why that would glitch, except the obious "txbuf alloc" problem
they have.

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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