Re: Invalid position given by Telit HE910-EUG

[Gary E. Miller]

Yo Titouan!

On Sat, 4 Apr 2020 12:37:12 +0200
Titouan Christophe <address@hidden> wrote:

> > Ouch.  And you are sure it is plain NMEA0183?  
> 
> As far as I can tell, yes.

Not totally convincing.

> > How did you ruin gpspipe?  With "-R", "-r", or "-w"?  
> 
> Some more context:

I usually prefer my simple questions are answered before further
elaboration.  So the answer is??

> we're remotely operating a fleet of embedded
> devices that are installed into rail vehicles.

Not sure why that matters to this issue.

> The device on which
> the error happened is running gpsd 3.18.

3.18 is old.  Can you duplicate on 3.20 or from the git head code?

> Our end user applications
> use the gpsd C client, and makes use of
> gpsdata->fix.latitude/longitude (amongst others).

In that case, what I sent you proves thatt git head does the right thing.

> This is how we
> connect to gpsd and read TPV data:
> 
> gps_stream(&gps_data, WATCH_ENABLE | WATCH_JSON | WATCH_NMEA, NULL);
> while (running) {
>      if (gps_waiting(&gps_data, 2000000)) {
>          r = gps_read(&gps_data, NULL, 0);
>          if (r > 0){
>              // do something with gps_data
>          }
>      }
> }

Of course the issue you report is in the "do something" part.  So that
snippet not useful.


> Because we have had a lot of trouble with these Telit HE910-EUG
> chips,

Yeah, they are junk.

> we also run a daemon that continuously dump the NMEA stream
> into a weekly rotated log, as to make post-mortem analysis of GPS
> failures.

Fair enough.

> We invoke gpspipe like this:
> gpspipe -r -T %s -n $LINES -o $FILENAME

So dumping the raw NMEA.  Why not -R?  There may be stuff other than
NMEA in there.


> >> As you can see, this GPS has also rolled over in year 2000, but
> >> this is a different subject.  
> > 
> > gpsd in git head can often handle GPS week roll over (WKRO) problems
> > now.  
> 
> This Telit chip has a pretty bad behaviour (see 
> https://rutronik-tec.com/wp-content/uploads/2019/02/Telit_Cellular_WeekRollover_Application_Note_r0.pdf),
>  

All you had to say was "Telit'>

> and there was no WKRO patch available for 3.18 at that time (it was 
> maybe even 3.17 back then), so we maintain a patch out of the gpsd
> tree for that matter; see http://paste.awesom.eu/QGyb

Fixed in git head, so old news to this project.  My previous message
showed you it works.

So, back to your original issue.  The current gpsd code works for me.
We agree the NMEA 0183 in is bad.  I showed you that current gpsd
does the right thing with your data.  You have not shown that the
gpsd 3.18 is sending bad data.

Simple solution, update your gpsd version.

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

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    "If you can't measure it, you can't improve it." - Lord Kelvin

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