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[aprssig] Dumb tracker question

scott at opentrac.org scott at opentrac.org
Sat Sep 30 19:25:49 UTC 2006


Could be.  I was running in Garmin mode, and there may be a glitch in the
calculation.  It comes from the GPS receiver in meters/second North and East
- takes a bit of math to get it to degrees and knots.  The arctangent
function takes a lot of processor time and stack space, so it's a prime
candidate for weird glitches.  I'll probably replace it with an
approximation when I get a chance.  For APRS purposes, it doesn't need to be
accurate to more than a degree or so.

Scott
N1VG 

> -----Original Message-----
> From: aprssig-bounces at lists.tapr.org 
> [mailto:aprssig-bounces at lists.tapr.org] On Behalf Of Tyson S.
> Sent: Saturday, September 30, 2006 11:59 AM
> To: TAPR APRS Mailing List
> Subject: Re: [aprssig] Dumb tracker question
> 
> I was watching Scott drive North on highway 101 when he was 
> testing the
> new T2-135 and his heading was wrong most of the time. I don't know if
> that is because of the tracker, or APRS-IS. When his heading should
> have been something like 20-30 (NNE) is was something like 180 or 270
> or some other weird direction.
> 
> --- Earl Needham <needhame1 at plateautel.net> wrote:
> 
> > 
> > A friend of mine runs a tracker as W5ROY-15, and when I see 
> him on my
> > HamHUD, his heading is usually incorrect, sometimes by as 
> much as 180
> > degrees.
> > 
> > Am I remembering correctly that some TNC's do something odd like
> > that? Or
> > could it be something else that's causing this?
> > 
> > Thanks,
> > Earl
> > 
> > 
> > Earl Needham, KD5XB, Clovis, New Mexico DM84jk
> > 
> > 
> > 
> > _______________________________________________
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> > aprssig at lists.tapr.org
> > https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig
> > 
> 
> 
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