Re: satellites used - NMEA feed

[Frank Nicholas]

Hello Gary,

Here’s an OCR of the picture (verified visually).  Hope this helps:

Dec 13, 2022
libgps/libgps_json.c: restore init of satellites_used.                          
fef7dae4
Gary E. Miller authored 1 year ago

Dec 10, 2022
libgps/libgps_json.c: Read uSat from SKY.                                       
        fd33a59d
Gary E. Miller authored 1 year ago

Thanks,
Frank


> On May 10, 2024, at 3:40 PM, Gary E. Miller <gem@rellim.com> wrote:
> 
> Yo Nick!
> 
> On Fri, 10 May 2024 13:14:48 +0100
> Nick Taylor <nicktaylor@dataskill.uk> wrote:
> 
>> Could you cast your memory back to Dec 2022 - we found that using
>> NMEA feed we weren't getting satellite data although there was used
>> satellite count available...
> 
> Yeah, Sats Seen and  Sats Used just gets worse and worse.
> 
>> You kindly made a patch to pick this up as used satellite count if
>> the satellite data wasn't available (see screenshot attached)
> 
> I can'read read your screenshot, my eyes are going bad and that is way
> to grainy for me to read.  And I certianly can't cut/paste the
> commit number from a course image.
> 
>> On recently upgrading to latest gpsd release it seems that something
>> has changed that makes used satellite count disappear again - we pick
>> this up from gpslib variable gps_data_t.satellites_used
> 
> And it is only going to get worse.  Newer receivers can never seem to
> report sat counts consistently.  I have one receiver here that reports 4
> different sat counts in the same epoch.  Which is correct?
> 
> This gets more complicated when the receiver can pick up 3 signals (L1,
> L2 and L5) from the same sat.  Should that be reportd as 1 sat, or 3?
> For now, gpsd leans to reporting 3, except that not all new multi-frequency
> receivers report enough data to know which is which.
> 
>> I'm also attaching output from gpspipe -R
> 
> That looks good.  I'll play with that today.
> 
> RGDS
> GARY
> ---------------------------------------------------------------------------
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>       gem@rellim.com  Tel:+1 541 382 8588
> 
>           Veritas liberabit vos. -- Quid est veritas?
>    "If you can't measure it, you can't improve it." - Lord Kelvin