On Thu, 16 Sep 2004 13:14:20 +0200 (CEST), dr. Imre Bartfai wrote:

> Hi,
> 
> 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.

But surely the points you are converting would be on the circumference of an imaginary circle, so only one of 
the coordinates of any point could be 0.  Since we're dealing with an angle, and the circle doesn't really 
exist, the diameter of the circle can be anything convenient - say 100, so the four cardinal points would be 
100,0 0,100 -100,0 and 0,-100.

If this doesn't give sufficient accuracy, use a larger circle!  It's really just moving the decimal point in 
the calculations, but that may make things easier.
 
> I would suggest the following process:
> 
> 1. add a huge constant to each number before averaging
> 2. calculate the average
> 3. subtract the said constant from the result
> 
> Actually the user moves the point in a secure distance from the origo.

I don't quite follow what you mean here - adding a constant to the original value (say in degrees) wouldn't 
help, because the average of 10000359 and 10000001 is 10000180, minus 10000000 still gives 180 the same as 
averaging 359 and 1, when it should be zero.  If you mean adding it to the cartesian coordinates, then I don't 
see that gets anything that "using a large circle" doesn't.

Cheers,


Howard Winter
St.Albans, England


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