At 08:56 AM 9/16/2004, Wouter van Ooijen wrote:

>> I am not sure the conversion helps. If the resulting Cartesian
>coordinates
>> tends to be zero, then the variability of the polar angle increases
>> dramatically.
>
>That is not an artifact of the calculation method, it is inherent in the
>problem statement. What is the average direction of two compass
>readings, one North and one South ?

In my case, I was getting bearings from a doppler DF unit (actually another section of software, and some fun hardware). It would be quite reasonable for me to get bearing data that looks like this:

90,90,87,270,93,91...  Just the nature of the beast. 
The math average is wrong no matter how you do it, because it can't handle the wrap.

What I ended up doing, was five layers of 16 bearings.
When I got the first 16 raw bearings, that made one "level two" bearing.
When I accumulated 16 level two bearings,that made a level three. and so on.
When the signal went away, I would take the best data I had and output it.

In the end, IIRC, I could average up about 4 seconds of 7200 bearings/sec this way, in much less ram than you'd otherwise expect.

With the pol-rect-pol method, I also got the length of the vector, which directly expressed how much "noise" was in the data. A short vector indicates that the bearing is too noisy to use, probably because of multipath reflections.

I never implemented it that way, but I could have tossed the shortest vector in each level before averaging, to clean it up, but I'm not sure that's entirely valid.

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