Re: Precise point positioning

[Gary E. Miller]

Yo Jeroen!

On Mon, 25 May 2020 16:04:17 +0200
Jeroen Balduyck <address@hidden> wrote:


> I had an interesting conversation with Gary on PPP after reading his great
> tutorial here https://gpsd.gitlab.io/gpsd/ppp-howto.html

I added a new section, Background, based on our discussion.  Please
read and comment.

> However, previous U-Blox chips (like the NEO-7P here
> https://www.u-blox.com/sites/default/files/products/documents/NEO-7P_ProductSummary_%28UBX-13003350%29.pdf)
> had PPP-processing onboard, combining it with SBAS (EGNOS, WAAS, ...)
> SAT-data.

Marketing speek.  PPP is post processing.  So can not be done in the
receiver.  Typical of the slime in marketing to take a perfectly good
term, like LTE, 5G, and PPP, and twist it into something their part does
to trikc (lie) to the customer.

All they are doing is taking the RTCM2 that SBAS sends and using it to
improve the basic fix.  That is NOT the PPP we are talking about, that
is marketing puke.

> Furthermore, it seems the low cost receivers seem to move away from
> 'internally processed' PPP in favour of RTK whilst PPP can be so
> useful at remote locations.

RTK needs a local base station, something else again.

> As far as I can tell PPP (in dual frequency GNSS receivers where it
> corrects for ionospheric errors) is almost as good as RTK apart from
> PPP

For some definition of "almost as good".  YMMV, so do your own tests.
Compare you PPP (real PPP) with gpsprof.

> not being able to correct tropospheric for errors (or it can, but
> not as good as RTK can?)

Ocean Tidal Loading, etc.

Do not compare RTK and PPP.  RTK is for relative fixes of
base to rover.   PPP is for absolute fixes.  If you base has been
surveyed in, somehow, then the relative rover fix to base can be almost
an absolute fix.

RGDS
GARY
---------------------------------------------------------------------------
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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