Re: DGPS / SBAS

[Nick Taylor]

Yo Gary

Apologies for screenshots - have now managed to freeze cgps so that I 
can cut and paste from it... We don't have xgps on our devices.

Just to clarify, I don't think there's anything wrong with gpsd, but my 
observations just seem strange:

My window is single glazed but old and thick - I found references to old 
glass having metallic traces that obv aren't good for distant radio signals.

With antenna inside the glass GPS works fine but no SBAS satellites - 
and obv reduced signals, if I poke the antenna outside then signals 
increase & I then get SBAS signals so that gps can obtain DGPS fix.

The weirdness is that once I get DGPS - I can move antenna inside and 
the DGPS stays - even for several days. SBAS shows SNR of 0.0 and if I 
power cycle the gps then fix reverts to std 3D GPS and never gets DGPS 
again.

I'm attaching cgps1.txt & cgps2.txt where gps still has DGPS but no SBAS 
seen - and cgps3.txt after power cycle. Along with this gps5.log which 
corresponds with cgps1 & 2.

The only explanations that I can think of are:

1. gps device has a bug

2. There is some low power SBAS signal that's enough to maintain DGPS 
but not enough to initiate it?? (Is this even possible??)

In any case none of this is a deal breaker - just a curiosity...

Many thanks for all your help.

Nick


On 05/12/2023 01:02, Gary E. Miller wrote:
> Yo Nick!
>
> > In the meantime I'll look at the cgps code for DGPS.
> I looked at the code: client/cgps.c, in update_gps_panel().
>
> That is where the current JSON packet is decoded and displayed.
> The status (DGPS, etc.) is decoded just afer CLimb, and just before
> the error guesses.  I don;t see how anything gets cached or delayed.
>
> So, I am back to wanting a screen shot of the gps2.log condition, and
> confirmation that xgps does the same thing.
>
> 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

cgps1.txt
Description: Text document

cgps2.txt
Description: Text document

cgps3.txt
Description: Text document

gps5.log
Description: Text document