View Full Version : Re: Quaternions vs. Euler angles (How much does it matter)

Hamid Rassoulian
04-24-2001, 06:57 PM
Dear Colleagues,

A very interesting discussion, and certainly one that is useful to us here, as we have recently acquired a "Polaris" system which actually outputs the marker positions in.....guess what,....... Quaternions!! So we do have a vested interest to fully understand this concept.

However, I would like to raise a very important and related issue, i.e. the practical (clinical) utilisation of gait/motion data. This I think should be considered as a basis for all such discussions.
Does it matter which angular representation is used?
Under many clinical circumstances, gait/ motion information is nearly unhelpful, and such mathematical delicacies are ignored completely.

I don't dispute the academic validity of this type of argument, and perhaps its mathematical fascination. Detailed discussion of these concepts would be important for the purposes of computer simulations and calculations of movements, say in VR applications or other computerised processes, where dealing with the errors is not only a calculation but a mathematical flirtation. However, when trying to understand the gait recovery of a 57 year old stroke patient and decide where to focus the physiotherapy efforts, all these seem like "star trek".

I would like to encourage contributions from all colleagues who have the pleasure of having to deal with the pragmatic world of health care. At least from a clinical point of view, it is important to stimulate discussions about gait data analysis that aims to enhance patient care, or at least make it clear that how the discussion could be potentially relevant to "shop floor".

Dr. H Rassoulian BSc, MSc, PhD, MIPEM, SRCS
Head of Clinical Bioengineering Group
Dept. Medical Physics & Bioengineering
Southampton University Hospitals NHS Trust
Southampton SO16 6YD
United Kingdom
Tel: 023 80796945
Fax: 023 80794117
email1: Hamid.Rassoulian@suht.swest.nhs.uk
email2: hamidR@soton.ac.uk

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