Re: RTK Fix woes again

[Gary E. Miller]

Yo pisymbol!

On Tue, 24 Mar 2020 07:16:19 -0400
"pisymbol ." <address@hidden> wrote:

> > > But we need cm accuracy.  
> > Then your base stations had better be really close to the rover.
> It's more complicated than that:
> https://positioningservices.trimble.com/services/vrs/vrs-now/

Nothing new there.  Trimble has no secret sauce that invalidates physics.

> > > Trimble says we have RTK fix and have sub-10cm accuracy but gpsd
> > > says we are DGPS.  
> >
> > Rememeber how old the Trimble TSIP language is.  Before the year
> > 2000, when RTCM 2.0 was starting to be broadcast by the SBAS birds,
> > that RTK and DGPS and WAAS were exactly the same thing.  The TSIP
> > language is from that era.
> >  
> 
> I don't know TSIP but this is coming out of the RMC/GGA strings from
> NMEA. For my "edjumication", where is TSIP involved here?

The Trimble binary protocol is called TSIP.  NMEA is even worse.
As bad as TSIP is, you should use that in preference to NMEA.

> > The perfect time to do it is when your stuff is sitting in your
> > office and you are at home.
> >  
> 
> The device is in a remote location in Chile. Things take time.

No problem at the speed of light.  ssh is your friend.

> > I have been working on the FAA status flag.  The changes are
> > extensive, so it will be one big patch.  The gpsd handling will be
> > improved. 
> 
> Great! I'm more than happy to facilitate any data or patches that you
> want. I think my initial claim about having kind of heuristic instead
> of a simple setter for fix quality applies.

gpsd is one giant hairball of heuristics.  All based on a lot of
regressions gathered over two decades.  If you see an oddity, grab the
raw data and we can adjust.

> I have another unit at home and I will run gpsprof on it shortly as a
> data point.

Assuming the setup (antenna, cabling, temps, etc.) are similar, then you
should get similar results.  The only variables you are stuch with are
differing skyviews, absolute value of latittude, and base station
proximity.

The base station proximity overwhelms all else.

Also maybe no WAAS corrections, the SBAS birds send North American
corrections, but nothing for further south.  That should not matter with
RTK.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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    "If you can't measure it, you can't improve it." - Lord Kelvin

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