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Re: [gpsd-dev] [gpsd] Altitude in TPV
From: |
Gary E. Miller |
Subject: |
Re: [gpsd-dev] [gpsd] Altitude in TPV |
Date: |
Fri, 2 Nov 2018 14:23:31 -0700 |
Yo Gerry!
On Fri, 2 Nov 2018 15:50:04 -0500
Gerry Creager - NOAA Affiliate <address@hidden> wrote:
> > I'm unfamiliar with 'pseudorange rate'. Is that the same as
> > doppler? RINEX just wants pseudorange, carrierphase and doppler.
> > Doppler is the speed that each satellite is approaching or receding.
> >
>
> PRR is indeed doppler, expressed in m/sec. In the world I grew up in,
> doppler was a frequency rate change in hz/sec... Yes, I'm old.
Not that old. I've been looking at what raw measurements GPS can
output and it was only very recently they seemd to read consensus.
> > Since we can't presently change the GPS receiver firmware, it would
> > have to be done in gpsd, or a gpsd client. Easy to do, if gpsd
> > has the needed data and algorithms.
> >
>
> It's probably marginally do-able in gpsd, but is it worth it? PAGES,
> for example, is stand alone, reads RINEX, and computes the geodetic
> results as an application. Is it useful to overburden gpsd to add the
> functionality?
I'm almost done with a gpsd->RINEX converter. So that would give us
PAGES. RINEX is not well documented and the error messages from
RINEX software are near useless...
> > That is why gpsprof and ntpviz compute skewness, kurtosis, and much
> > more. To clearly show that the data is not even close to a standard
> > distribution. That has been misleading people for decades.
> >
>
> Any idea how long I've been preaching that mantra? My first paper on
> horizontal accuracy and achieving same computed skewness and kurtosis
> and the editors ripped hard-core statistics out as too much
> information/detail.
>
Hehehe...
>
> > > > I guess too much to ask for that code to be put in gpsd?
> > > Depends on how we want to go about it. The decimation approach is
> > > a bit memory expensive but not too bad. Or write it to ramdisk or
> > > a temp file and process from there in a 2-step fashion.
> >
> > Storage is cheap now. I just looked at 512 GB SSD for $80. Run
> > time not an issue since the raw data collection time already many
> > hours long.
>
> Sorta how I'm thinking. That's probably the best first-pass approach,
> is fast-epoch data collection, judicious decimation, and then
> averaging. Two strategies for the averaging are an average of the
> whole decimated dataset, or to process twice, removing, for the
> second and final average, obs where any coordinate is > 2SD out from
> the mean.
gpsprof already does long term basic averaging. Maybe next year worth
revisiting how gpsprof calculates the best guess position.
Before that, I hope to see how post processed RINEX data compares to
the best guess from gpsprof.
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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