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Brian Davis Cleveland Clinic Foundation
10-09-1995, 08:04 AM
Dear subscribers

I have been reading the recent comments on Biomch-L regarding the labeling
of x, y and z axes. While Dr. Hatze has identified the differences that
exist between the proposed ISB standards and those he cited, I am still left
with the feeling that there are at least two (not necessarily compatible)
sources that researchers could turn to when justifying their choice of x y
and z directions. These sources do not involve the ISB.

One choice would be to go to the books listed by Dr. Hatze. These are
highly regarded books and give one method for orientating axes. In terms of
kinematics they can be regarded as conforming to one standard. (In other
areas where units of slugs and feet are used, these books would obviously
not be used to set up standards.)

Another choice is (as described in Barbara van Geem's posting) to
go to the American Society of Photogrammetry (ASP). Dr. Hatze gave an
example of where these standards would conflict with those proposed by the
ISB. However, in most settings, the ASP's standards would seem to conflict
those outlined in the books listed by Dr. Hatze. Specifically, in any
situation where a subject's gait is analyzed using cameras on floor-mounted
tripods, the APS would not have the Z axis pointing vertically.

Even before the ISB proposal, a biomechanics researcher could legitimately
have chosen the APS standard or the method described in the books Dr. Hatze
listed, or have chosen his/her own "standard". Since we don't live in
Utopia, finding "the best" standard is unlikely, and what we should hope
for is to reduce the number of possibilities.

Regards, Brian
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Name: Brian L. Davis, PhD
E-mail: davis@bme.ri.ccf.org
Date: 10/09/95
Time: 12:50:04
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Name: Brian L. Davis, PhD
E-mail: davis@bme.ri.ccf.org
Date: 10/09/95
Time: 15:04:57
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