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Re: Repeated tpv values
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From: |
Gary E. Miller |
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Subject: |
Re: Repeated tpv values |
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Date: |
Fri, 8 Oct 2021 11:07:56 -0700 |
Yo Marcin!
On Fri, 8 Oct 2021 09:34:19 +0200
Marcin Bułka <marcin.bulka@jrdltd.co.uk> wrote:
> Hi all,
>
> I'm using gpsd 3.23.1 and I saw that I have most values repeated in
> different tpv objects. For example I have tpv objects with values
> like this:
>
> timestamp: 1633008508200, eps: 0.16, lat: 45.11, lon: -0.85
> timestamp: 1633008508200, eps: 86, lat: 45.11, lon: -0.85
> timestamp: 1633008508300, eps: 0.16, lat: 45.12, lon: -0.86
> timestamp: 1633008508400, eps: 0.16, lat: 45.13, lon: -0.87
> timestamp: 1633008508400, eps: 180, lat: 45.13, lon: -0.87
That is normal.
> So in most cases (not always) for given tpv object there is another
> tpv object with all values the same except for eps (one is always
> small like 0.15 and second is much bigger like 80). Is this normal?
That is normal.
> And how should I interpret it, which eps value is correct for given
> timestamp and localization?
They can all be correct at the same time. There is no standard or
definition for how error probablilites are calculated. They
may be a 50%, 66%, 95, 99% or whatever.
An ep(50%) of 3m may be the same as an ep(99%) of 10m.
gpsd calculates missing numbers, then as the receiver eventually sends it
numbers, those over-write the gpsd calcualted ones.
They should only be used as relative goodness indicators.
> In a previous version 3.20 I had similar problem but for the same
> timestamps I didn't have different eps but localizations, for example:
>
> timestamp: 1633008508200, eps: 0.16, lat: 45.11, lon: -0.85
> timestamp: 1633008508200, eps: 0.16, lat: 45.12, lon: -0.86
> timestamp: 1633008508300, eps: 0.15, lat: 45.12, lon: -0.86
> timestamp: 1633008508300, eps: 0.15, lat: 45.13, lon: -0.87
>
> And here I don't know which localization is correct for a given
> timestamp.
They all are.
RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com 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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