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[aprssig] Dead Reckoning in APRS

VE7GDH ve7gdh at rac.ca
Sun Jun 18 02:02:10 UTC 2006

Bob WB4APR wrote...

> Those of us that are used to seeing this multi-dimensional represetation
> of the passage of time, space and distance on each mobile symbol or
> weather object feel very blind when we dont have it.

You must be looking at someone else's APRS client and not one running on 
your own computer! I've never had "dead reckoning" so I have never missed 
it. I do know that if I want to know the time last heard, the bearing and 
distance, status, course and speed, and height if included, I only have to 
hover the cursor over it for a fraction of a second. If I want a graphical 
representation of the direction, I can double-click on it and see the 
station details. I can also look at the variable length vector going out 
from a mobile station to see an approximation of the speed and the 
direction. The faster the station is moving, the longer the red line is. 
You can probably guess which APRS client I'm using. (hint... UI-View32)

> When I see a fixed-color-ICON on a map for a mobile or WX
> object without Dead Reckoning, I always wonder how old that
> posit is a minuite? 30 minutes? a Day?, A week?

>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?

> Though at least most programs fade them to gray after the
> recommended 80 minutes I hope.

The program that I use fades them to grey when the expire time has been 
reached. A minute later, the expired station disappears. If I was tracking 
the station (UI-Route or UIHeightTrack) the track will remain on the screen 
even after the station has expired.

73 es cul - Keith VE7GDH
"I may be lost, but I know exactly where I am!" 

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