[ gpsdrive ] libgps

[stuart bell]

2008/12/25 Guenther Meyer <d.s.e at sordidmusic.com>:
> 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?

"Track" is where you've been, allowing for leeway, tide etc. " hdg" is
just where you are pointing.
Happy Christmas Everyone.
Stuart
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