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Re: ntrip and sending position

From: Gary E. Miller
Subject: Re: ntrip and sending position
Date: Tue, 17 Dec 2019 13:39:28 -0800

Yo Greg!

On Tue, 17 Dec 2019 16:21:30 -0500
Greg Troxel <address@hidden> wrote:

> "Gary E. Miller" <address@hidden> writes:
> > Yo Greg!
> >
> > On Tue, 17 Dec 2019 13:11:48 -0500
> > Greg Troxel <address@hidden> wrote:
> >  
> >> > That URL is just used verbatim.  So whatever your NTRIP server
> >> > wants is what you put there.    
> >> 
> >> The parsing code uses strchr to look for '@', so I would expect a
> >> username that's an email address to fail.  Probably that should be
> >> strrchr.  (I have an account without an @, so I'm avoiding this.)  
> >
> > No point "fixing" it until it is a problem.  
> It is a problem.  Anyone who has a username with an @ -- which is
> normal these days to use an email address as a username -- will lose,
> and the docs don't explain this.

I've never heard of an NTRIP passworkd being an email address.

Can't fix w/o doc.

> > But not well enough to code from.  I see ORGN also does MAX, iMAX
> > and CMR+, whatever they are...  
> MAX apparently sends multiple station info to the rover which is
> supposed to interpolate, and iMax the server interpolates.  It may be
> that iMax and "virtual reference station" are two words for the same
> thing.

Not much we can do w/o doc.

> CMR is a proprietary version of RTK info, and apparently not used so
> much these days.

ORGN is big on CMR+

> >>   gpsd:PROG: RTCM3: unknown type 1230, length 12  
> >
> > RTCM 1230: GLONASS L1 and L2 code-phase biases.
> >
> > u-blox does it.  Not sure how to decode it.  I'm not spending $275
> > for the doc...  
> Thanks; that's helpful.  I'm trying to do regular differential, not
> RTK.

You keep thinking they are different.  They are not.

> > Those are one and the same thing.  
> I don't think they are.  RTK is concerned with carrier phase and
> pseudoranges are not carrier phase.

I think you over specify RTK.  RTK, depending on the implementation,
will take what you can give it.

Psuedoranges are computed from carrier phases plus the ephemeris.

The end result is the same.

> I am not sure that RTK users look
> at pseudorange corrections at all.

u-blox rovers do.

> But maybe that's part of
> bootstrapping to fix the integer ambiguities.

More a matter of how much processing to do in the bas and how
much in the rover.  Just an engineering choice.

> I am still unclear on if my corrections are being applied and helping
> (vs SBAS corrections).

Depending on your GNSS receiver, gpsd will decode the stream and set
the proper codes.  My u-blox NEO-M8T goes from #D FIX to 3D DGPS FIX.

Some older receivers will report 3D DGPS FIX when they have the RTCM2
data from WAAS.

> Definitely when I walk in the woods the
> accuracy is not good enough with just SBAS for pleasing trail mapping.

Which is why some GNSS receivers can use NTRIP from the netvia your
phone.  Or post process the data.

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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