[aprssig] Another kind of SmartBeaconing?

Rikard Sohlberg rikard.sohlberg at home.se
Tue Aug 21 16:50:57 CDT 2007

I would like to throw out a question. 

I use APRS for tracking gliders (sailplanes). From humble beginnings here in
Sweden, it has grown into a big success, almost turning a niche sport/event
into a spectator sport. Watching a sport where the track is anywhere from
150 to 500 km (when will you boys go metric
 ;.) used to be a problem. Now
we have some 25 trackers active in Swedish gliders, and everybody loves it.
And, yes, it is perfectly legal, even when there is no ham onboard. Of
course I can’t speak for all jurisdictions, but at least in Sweden, we are


Now to my problem or question. We have tried SmartBeaconing and fixed
interval beacons. Neither one serves a glider particularly well. A glider
(when it leaves to vicinity of the airfield), typically circles in a thermal
to gain altitude and then flies in a straight line to get around the track.
Tests of SmartBeaconing has shown that it is not well suited to this kind of
motion. In fact, it gives the exact opposite of what we want, se below.
Also, to have an exact fix when the glider is 200 km away is not needed.
What is needed, though is fast updating at the end of the track. Incredible
as it may seem, many competitions end up with the gliders chasing each other
within a few meters (ehh
 feet any one
;-) apart in the race to the finish
line. And that is often the case after flying a track of, say 300 km and 3-4
hours. Speeds are typically up to 250 km/h (mph..?) at the race for the
finish line.


So after this wordy preamble
 What I see needed is some kind of
Geofence/box-type beaconing. 

The algorithm being something like:


If (tracker.lat<N60.5 and tracker.lat >59.8 and tracker.long<E16.5 and
tracker.long>15.9) then beacon every 10 secs

If (tracker.distance-to-goal-line < 5 km) beacon every 2 secs


Beacon every 3 minutes


I’m not a programmer (any more), but you are clever guys, you get my idea.
When inside the box (including the starting gate and finish line) beacon
often, outside the box fall back to once every 3 min or so not to clutter up
the QRG. 


Does anyone know of some tracker code/application for this?


Of course, what would also be handy would be a Glider specific mode:


If(course .changes. more than 15 seconds) stop beaconing    ./ When entering
a thermal and starting to circle /.

When (course .eq. last.course(15 sec))) beacon                    ./ When
leaving the thermal and flying in a straight line  /.


Any one out there doing something like this? 


Thanks for any thoughts and ideas.


73 de SM0JWX/Rikard


(Go metric before Burma, please









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