gpsd-dev
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: how to forward RTCM data to gpsd?


From: Gary E. Miller
Subject: Re: how to forward RTCM data to gpsd?
Date: Sat, 12 Dec 2020 08:54:17 -0800

Yo Greg!

On Sat, 12 Dec 2020 08:24:48 -0500
Greg Troxel <gdt@lexort.com> wrote:

> "Gary E. Miller" <gem@rellim.com> writes:
> 
> > Yo Greg!
> >
> > On Fri, 11 Dec 2020 20:19:44 -0500
> > Greg Troxel <gdt@lexort.com> wrote:
> >  
> >> I wonder why you are only getting GPS from the local station, but
> >> presumabbly it's old and not sending Galileo and GLONASS
> >> corrections.  
> >
> > RTCM 3 is GPS and GLONASS only.  

Yes.  My mistake, I meant RTCM 2.
 
> Perhaps in some trivial spec sense, but my local reference network is
> sending MSM4 format for other constellations.  An update read:
> 
> 7/10/19-     RTCM 3.x (MSM4) single site products introduced.  All
> RTCM MSM (Multi Signal Messages) now include GPS with L5, Glonass,
> Galileo and BeiDou.

Yes, a big part of RTCM 3, over 2, was the additional constellations.

> >> Repeating something I said earlier my local RTCM3 provider is now
> >> sending data on all 4 constellations.  
> >
> > Not all 6?  
> 
> Which do you mean beyond GPS, GLONASS, Galileo and Beidou?

As defined by BNEA 4,11, from gps.h

     *  1 = GPS       1-32
     *  1 = SBAS      33-64, 152-158
     *  1 = QZSS      193-197  Undocumetned u-blox goes to 199
     *  2 = GLONASS   1-32, nul
     *  3 = Galileo   1-36
     *  4 - BeiDou    1-37
     *  x = IMES                Not defined by NMEA
     *  6 = NavIC (IRNSS)               NMEA 4.11+

So NavIC, and QZSS.

> If you mean IRNSS and QZSS, those are regional, not global, and I do
> not hear of anyone receiving them in CONUS

I get QZSS in Oregon.  gpsd has usrs that get NavIC.

> > I have run tests with GPS+SBAS and GPS only.  Both using SBAS
> > correction. Adding SBAS to the fix decreases the fix quality.
> > YMMMV.  
> 
> I gather you mean "adding the SBAS pseudoranges".

Of course.

>  I was talking about
> uncorrected pseudoranges from a bunch of satellites vs those same
> satellites

Never heard of that.  Got a reference?

> and also using corrections that arrived via SBAS.

Which are just RTCM2.

> The onlu psue  My
> impression, not rigorously confirmed, is that using the corrections
> helps.

My tests on u-blox 9 show otherwise.  Feel free to send us your test
results.

> > Some do.  Depending on your u-blox model ubxtool will tell your the
> > difference. Plain "used" means the ranges were used.  The DGPS flag
> > is set if SBAS or RTCM corrections applies.  So if you have no
> > local RTCM, the DGPS flag tells you if the SBAS corrections were
> > used. Indepene nt of the "used" flag.  
> 
> Make sense; perhpas it's not as confusing as I thought.

Of course.  "Everything in math is either trivial, or false".  :-)

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

Attachment: pgpYkVrkHcF2m.pgp
Description: OpenPGP digital signature


reply via email to

[Prev in Thread] Current Thread [Next in Thread]