[gps-talkusers] Re: GPS mathematics
- From: "Chip Orange" <Corange@xxxxxxxxxxxxxxx>
- To: <gps-talkusers@xxxxxxxxxxxxx>
- Date: Thu, 20 May 2004 12:36:38 -0400
Matthias,
I'm a gps developer, although not much these days, and don't get to read
this list all that often either (darn day job!!!).
Anyway, you can, for rather short distances (say a few miles) just use
the lat/lon degrees (in decimal form) and your standard high-school trig
to determine distances and angles. The distances will also be degrees,
and you can estimate that 1 degree equals one nautical mile, or about
6076 feet.
For larger distances, it becomes quite a bit more complex. Check out an
aviation navigation site at:
http://williams.best.vwh.net/
For some very helpful formulas, but be sure to read all the text info
about implementation details, intro, etc. Especially note that for the
convenience of north american users, he has reversed the sign of the
common usage of latitude in his formulas (it's normally represented in
north america as a negative number), so you'll need to compensate for
that.
Also, note that there are different formulas for a rhumline verses a
great circle route, and the ones for a rhumline are probably what you
want, but since pilots use great circle routes more often, those are the
ones featured.
Hth,
Chip
=20
> -----Original Message-----
> From: gps-talkusers-bounce@xxxxxxxxxxxxx=20
> [mailto:gps-talkusers-bounce@xxxxxxxxxxxxx] On Behalf Of=20
> Matthias Weingart
> Sent: Thursday, May 20, 2004 10:47 AM
> To: gps-talkusers@xxxxxxxxxxxxx
> Subject: [gps-talkusers] GPS mathematics
>=20
> Hi,
>=20
> maybe I am asking in the wrong group (this is a group for GPS=20
> users, and not developers?), but I would like to know=20
> something of the GPS basics.
> In fact I would like to calculate the distance and angle=20
> between 2 GPS coordinates (or position in a x-y diagram,=20
> where one coordinate is (0,0)).
> (starting from the NMEA-string, result should be meters).
>=20
> I would be very happy, if somebody here could point me to=20
> some good ressources.
>=20
> Matthias
>=20
>=20
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