[vtkusers] Smoothing 3D-tracking data

[David Gobbi]

The Polhemus has a built-in smoothing filter that you can turn on and 
off, if I recall.

For averaging 6DOF data, a good method is to express the orientation as 
a quaternion,
convert the quaternion to a versor representation (i.e. a vector where 
the direction of the
vector is the axis of rotation and the magnitude is the angle) and then 
average the versors
together.  There are probably other suitable methods as well.

Any smoothing method will result in a time offset in the data, e.g. if 
you average the previous 5 data
points then the smoothed data will have 2 cycle lag, which is 40 
milliseconds at 50Hz.

 - David

Boettcher, Dr. Peter wrote:

> Using a Polhemus magnetic tracking device I get 6 DOF data at 50 Hz. 
> Is there a good way to smooth the raw-data?
>
>  
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> At this moment I make 5 measurements and compute the mean of each 6 
> DOFs separately.
>
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> I would deeply appreciate any comment ;-)
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>  
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> Regards, Peter.
>
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>  
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