delays with a Polhemus Fastrak

[Andrew Karduna]

Here is a problem for those of you who are familiar with the Polhemus
Fastrak magnetic tracking device. As opposed to the Ascension system,
the Polhemus unit multiplexes between receivers so that data are not
collected at the same exact moment in time – I believe that there is a
delay of about 8 ms between each receiver. This is not a problem under
static conditions or for slow motions, but can result in high errors for

faster motions in which the relative motion between two receivers is
needed.

This is not the same latency that is described in the manual, which
focuses on the absolute delay. I am only interested in the relative
delay
between receivers.

I have had some modest success in interpolating the data to obtain
position and orientation estimates of all receivers at the same instant
in
time. I'd be interested in finding out if anyone has tried this or any
other
approaches to this problem.

Thanks,

- Andy Karduna

--
__________________________________________________ _______________

Andrew Karduna, Ph.D.
Associate Professor, Department of Rehabilitation Sciences
Director, Biomechanics Laboratory
219 N Broad St, 8th Floor fax: (215) 762-6076
MCP Hahnemann University phone: (215) 762-5057
Philadelphia, PA 19107 email: karduna@drexel.edu
__________________________________________________ _______________

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