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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


> 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)?


This gets into basic GNSS theory.  Beyond what gpsd does.

Here is a good text:

> 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

> I stumbled accross this read:
> 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.

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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