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Re: Precise point positioning
From: |
Gary E. Miller |
Subject: |
Re: Precise point positioning |
Date: |
Tue, 26 May 2020 13:25:03 -0700 |
Yo Jeroen!
On Tue, 26 May 2020 21:37:08 +0200
Jeroen Balduyck <address@hidden> wrote:
> > Using this new ephemeris data, when it becomes available, combined
> > with
> the receiver’s raw data, better fixes can be computed. This is the
> basis of PPP.
> I think I understand basic PPP it's better clock- and orbit data
> combined with the raw measurements and this is fed to the PPP
> algorithm.
The basis, not the entirety. Optional adjustments to clock errors,
ocean tides, etc. also help.
> But what is this RAW data? Are these carrier phase
> measurements
yes.
> or pseudo range
Sort of. You need to know your position to know your psuedo ranges,
But you compute your fix from your psuedo ranges. So it is an
iterrative process.
> (or both)?
No.
This gets into basic GNSS theory. Beyond what gpsd does.
Here is a good text:
http://www.nbmg.unr.edu/staff/pdfs/Blewitt%20Basics%20of%20gps.pdf
> Does the post processing
> solve the ' the *carrier phase integer* ambiguity problem'
Nope. carrier phase is something you measure.
> What has improved in the
> u-blox ZED-F9P and ZED-F9T chips making this new level of accuracy
> possible.
L2 was added.
> I still find it strange there is not talk of PPP in their
> spec's though.
Because they do not do it, they don't talk about it. The user does
that.
> I stumbled accross this read:
> https://www.gpsworld.com/innovation-instantaneous-centimeter-level-multi-frequency-precise-point-positioning/
> showing that there is something quasi real time too as long as you
> can get PPP to converge.
"converge" and "real time" don't mix.
gpsworld is marketing blather, often technical hand waving.
> But a word on real time PPP would be cool.
"real time" and PPP do not mix.
RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
address@hidden Tel:+1 541 382 8588
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