Re: satellites used - NMEA feed

[Gary E. Miller]

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

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