[aprssig] Dumb tracker question

[Robbie, wa9inf]

scott at opentrac.org wrote:

>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 
>
Please explain that statement Scott,  "For APRS purposes, it doesn't 
need to be accurate to more than a degree"! A degree in any purpose 
seems to be far out!! :-)  What were you suggesting?

Robbie

>
>  
>
>>-----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
>>>
>>>      
>>>
>>
>>    
>>
Please explaing that statement Scott,