[OSM-dev] Garmin GPX madness

[Oliver Eichler]

Nick,

if a building, rock or similar is shading half of the sky you can record the same trail at 30 diferent times and together with the DOP you know which recording is useless and which has a chance to be accurate. Togeteher with the velocity and heading you have a chance to narrow the corridor of likelyhood. With a Garmin track you just stick with the result Garmin thinks that it will be good enought for you. 

A Garmin track for normal rural areas is nice. For most streets you just need 2 waypoints anyway. For medieval towns or hicking trails in the mountains track recording can go quite beserk. And with a Garmin you have no chance to process the result. 

And for the brainwash :) As I assume that most of you have a scientific background you all should know that any data processing needs an equidistant sample base. This is defined by the Nyquist theorems. Thus stating that Garmin tracks are real good to derive data for further processing is somehow against any scientific carefulness. And, in this case, discussing agressively pro Garmin is a rather disconcerting attempt. Don't you think so?

IMHO Stefan's statement is true. Garmin devices are not really made for serious tracking. Data loggers like the i-Blue 747 et al. provide a better database.

The funny part is that the PVT protocol of the bigger Garmins coughs out all that information every second. However that part of the protocol is not documented. And there is no way to record it internally to SD ram. I can't see any glory here at all. 

Oliver





-------- Original-Nachricht --------
> Datum: Mon, 22 Sep 2008 11:36:30 +0100
> Von: "Nick Black" <nickblack1 at gmail.com>
> An: "Stefan de Konink" <skinkie at xs4all.nl>
> CC: dev at openstreetmap.org
> Betreff: Re: [OSM-dev] Garmin GPX madness

> If you had 30 traces down a road and no dop information and you
> derived a centre line, using only the lat lons of the 30 different
> traces, how much less precise would the result be than taking 30
> traces with dop info and figuring out a centre line?
> 
> Stefan and Oliver - if you really believe that the community have been
> brainwashed by Garmin, what's your plan of action to reverse the
> brainwashing and liberate our minds?
> 
> 
> 
> 
> 
> On Sun, Sep 21, 2008 at 10:54 PM, Stefan de Konink <skinkie at xs4all.nl>
> wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA512
> >
> > Richard Fairhurst schreef:
> >> When people learn to draw decent curves with polylines, _then_ we'll
> >> start worrying about GPS accuracy.
> >
> > Since we are already in serious preparations to go and support NURBS...
> > polylines even will get irrelevant too, less nodes, more accuracy and
> > better data representation :)
> >
> > Oh I love those mapping parties that end up in devtalk ;)
> >
> > Stefan
> > -----BEGIN PGP SIGNATURE-----
> > Version: GnuPG v2.0.9 (GNU/Linux)
> > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
> >
> > iEYEAREKAAYFAkjWwp4ACgkQYH1+F2Rqwn0JcgCglEHr59MvWqJNEMfVW8hjkSOo
> > egwAn0GPRg/ExStV4ndQTx3EDxKrVm9k
> > =31HK
> > -----END PGP SIGNATURE-----
> >
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> >
> 
> 
> 
> -- 
> Nick Black
> --------------------------------
> http://www.blacksworld.net
> 
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