[ gpsdrive ] libgps

[Guenther Meyer]

Am Donnerstag 25 Dezember 2008 schrieb Jan-Benedict Glaw:
> On Wed, 2008-12-24 17:43:02 +0100, Guenther Meyer <d.s.e at sordidmusic.com> 
wrote:
> > Am Mittwoch 24 Dezember 2008 schrieb Jan-Benedict Glaw:
> > > > Heading: %.2f\n  Time: %s\n", data->fix.track,utctime);
> > >
> > > This is track direction, not heading.
> >
> > and this is not the same?
>
> Not neccessarily. For a /car/, this is usually the same, because it
> uses a static reference system (earth) for itself. However, the same
> is not true for eg. planes or ships, because wind / water will move,
> too.
>
> Consider a river, flowing from north to south. Think of yourself
> sitting in a very small boat, strictly /heading/ into west direction.
> Your /track/ however is in south-west direction, because the flowing
> water forces you southwards.
>
> With some GPS receivers reporting track (from GPS) as well as heading
> (from eg. a fluxgate compass), you can even have a changing heading
> while staying at the very same position within your track.
>
> So this is a wording issue. "Heading" is where you would go without
> other forces, "track" is where you actually move to (due to outer
> powers applied to you, usually outside of your control).
>
ok. I didn't take this into account...
real heading can't be tracked by most of the gps devices consumers use. as 
this is "track", what we are talking about, maybe we should change the 
displayed description then? but I guess, then some people would ask, what 
that "track" is, and why we don't use "heading"...

or maybe better: we set it depending on the travel mode:
"track" for plane and boat, "heading" for all the others?


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