[aprssig] Dead Reckoning in APRS

[Wes Johnston,AI4PX]

I really like the implementation in xastir... it shows the icon's last 
position and "ghosts" a version of the icon at the dead reconed position. It 
also (very nice!) draws an uncertainty arc that shows you a semicircle of 
where the station might be.   I'm not sure how it decides what portion of an 
arc to draw but it seems to vary with the speed of the object and the length 
of time since last heard.  This method of projection works on curvey roads.

Wes


----- Original Message ----- 
From: "VE7GDH" <ve7gdh at rac.ca>
To: <aprssig at lists.tapr.org>
Sent: Saturday, June 17, 2006 10:02 PM
Subject: Re: [aprssig] Dead Reckoning in APRS

>>From your earlier description of dead reckoning in APRSdos, it sounds like
> it is well implemented. Dead reckoning must work well IF the road is 
> straight and there aren't any intersections. Again, I only have to hover 
> over a station to see when last heard. I know I have the expire time set 
> for 60 minutes (at least on the machine I'm on right now) so I know that 
> no station is older than that. I have on occasion set it to for a longer 
> period, but a week??? When was the last time you saw someone set their 
> expire time for a week?