Re: DGPS / SBAS

[Nick Taylor]

Thanks Greg

I was thinking that the DGPS fix was somehow cached and not updated 
properly in gpsd - but as you pointed out it's likely a receiver problem.

I restarted gpsd and still see DGPS fix, but if I power cycle the SIM68 
chip then fix reverts to normal 3D FIX so does seem receiver is to blame 
here. Likely we'll have to live with it as don't believe firmware is 
upgradable.

Thanks again

Nick


On 30/11/2023 11:58, Greg Troxel wrote:
> Nick Taylor <nicktaylor@dataskill.uk> writes:
>
> > If the SBAS satellite signal is lost, I would expect fix to revert to
> > basic GPS after the cached DGPS data expires?
> I would expect that too.
>
> > I have run a test where I move antenna so that SBAS signals not seen
> > (with antenna in this location I never get DGPS fix)
> Can you post s summary of statistics for 24h with SBAS and then 24h
> post-move?  Besides the fix indicator, I would more or less expec the
> SBAS statistics to be tighter.
>
> > After several days, cgps is still reporting DGPS fix (see attached
> > screenshot) - you can see that SBAS SNR is zero and it's same for all
> > SBAS satellites that I see shown.
> >
> > We are using the SIM68 chip:
> Obviously you should kill and restart gpsd to make sure that this is a
> case of the GNSS receiver still reporting DGPS when it isn't.
>
> Then, it sounds like you should follow up with your receiver
> manufacturer, starting with reading the documentation and filing a bug
> report about that if it doesn't clearly explain the loss-of-SBAS
> behavior.  Good luck!