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[aprssig] Re: Tracker Smart Pathing: user types, alternatives

scott at opentrac.org scott at opentrac.org
Fri Mar 24 03:21:01 UTC 2006

> I would like to be able to have the tracker transmit when my 
> actual position
> is X number of miles (or whatever measurement) off of where I 
> would be with
> dead-reconing. Along with this, I would also have it transmit 

I thought of this same thing when I first did SmartBeaconing in the
OpenTracker.  I think I probably came to the same conclusion that the
SmartBeaconing creators did, that the calculations were just too much
trouble in an 8-bit micro.

The T2 has a lot more space and I've already got some of the trigonometric
functions loaded, so reusing them doesn't really cost any extra space.  The
Garmin protocol requires it because of the way it uses X/Y/Z velocities
instead of course and speed.  So yeah, maybe now it's a viable alternative.
It does have to do a great circle distance calculation, but it'll probably
need that for other stuff anyway.  Each time it gets a fix, it can figure
its dead reckoned position and do a distance calculation.

Now if only more clients supported dead reconing as well as Xastir does...


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