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Re: [gpsd-users] gpsd with ntrip

From: Gary E. Miller
Subject: Re: [gpsd-users] gpsd with ntrip
Date: Thu, 17 Jan 2019 11:07:13 -0800

Yo Ralph!

On Thu, 17 Jan 2019 12:54:22 +0100
Ralph Nemitz <address@hidden> wrote:

> Now I found out, that "status" in the struct gps_data_t tells me
> whether the DGPS data were taken into account:

Sometimes.  Many (most?) GPS do not report that.  Many (most?) of the
gpsd drivers do not report that.  Most new GPS that report DGPS will set
that if SBAS is in use.

So it is not a reliable indication of anything.  Maybe you can count on
it in a few very specific cases.  But you have given me no specifics.

And it does not really tell you anything.  What you really care about
is the error estimates.  Is it improving your error estimates, or not?

> so far so good but status is always 2 independet from the gpsd call,

From what GPS?  In binary or NMEA?  With SBAS?  With ntrip?

Most modern GPS will have that bit on, unless you disable SBAS.  And most
ntrip no use when you have SBAS, so not a problem either.

> whithout ntrip:
> gpsd -D 4 -n -N /dev/ttyO3 /dev/pps0
> gpsd:CLIENT: => client(0): 
> {"class":"TPV","device":"/dev/ttyO3","status":2,"mode":3,"time":"2019-01-17T11:41:20.000Z",
> "ept":0.005,"lat":53.601633333,"lon":11.418965000,"alt":45.700,"epx":4.788,"epy":3.248,"epv":10.580,"track":268.9100,
> "speed":0.000,"climb":0.000,"eps":9.58,"epc":21.16}\x0d\x0a

Very odd.  Missing a LOT of output.  I assume you just overly trimmed it.
> or with ntrip:

What is your GPS model?  Can it use the ntrip?  Is the ntrip short baseline?

> gpsd -D 4 -n -N /dev/ttyO3 /dev/pps0 -G 
> ntrip://user:address@hidden:2101/VRS_3_2G_SN

Clearly you are getting RTCM3 reports.  But not much useful in them, not
enough precision.  I see no indication the GPS is using them.  They are
probably no help to the GPS anyway.

Since you sent no TPV records, no way to tell much.

> I thought that with "ntrip://...." in the gpsd call the "status"
> would become "2" but it's also "2" whithout "ntrip://..." in the call.

As thought, but exactly as I would expect.  ntrip pretty useless, exccept
in very special cases.

> Can you that explain to me?

Dunno, maybe after you answer my questions and I see exactly what you

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  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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