> >So which formula would you use to calculate the average? 
> >Simple sum(Xi)/N does not work: take 170 and -170, sum = 0, 
> >average would be 0, correct answer is 180.
> 
> Actually, 180 is one correct answer, 0 is the other.  Given 
> two arbitrary
> points to average between and no other inforamtion, you do 
> not know how the
> heading is varying between samples.  One would naturaly 
> assume that it would
> be the smaller angle, but there are no guarantees.

I don't understand that. Your encoding uses -180 ... + 180 for the full
circle, so 170 and -170 are pretty close, just 20 degrees apart, so
there is only one average (south, if 0 is north).

Wouter van Ooijen

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