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Re: Getting PDOP, VDOP and HDOP in C

From: Gary E. Miller
Subject: Re: Getting PDOP, VDOP and HDOP in C
Date: Tue, 29 Mar 2022 11:30:29 -0700

Yo David!

On Tue, 29 Mar 2022 19:22:50 +0100
David Taylor <> wrote:

> On 29/03/2022 19:03, Gary E. Miller wrote:
> > Yo David!
> > 
> > On Tue, 29 Mar 2022 16:31:42 +0100
> > David Taylor<>  wrote:
> >   
> >> Thanks, Matha.  In this case I'm not (that) interested in how they
> >> are calculated (I have a rough idea), as I've been asked to produce
> >> those figures routinely by a third-party.  
> > I wish u-blox told us how they calculated things, but alas, they do
> > not.  So that text is not what I wish for, but the DOP part is what
> > you need to understand as a user of DOPs.  Unless you just want to
> > push meaningless numbers.
> Thanks, Gary.  In this case, it's the variation of these numbers with
> time, atmospheric conditions etc. which is required.

Another misunderstanding.  DOPs do not vary by atmospheric conditions, etc.
They only vary by time, time being the variatble that tells you where the
sats are at any one time.  Nothing else affects the DOPs, just geometry.

> It's what the
> customer asked for, so!  I'll look at the others, though.

I learned a long time ago that customers often ask for the wrong thing.
If they truly understood the problem, they would not need you.

The trick to to give them what they need.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703  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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