View Full Version : Re: coordinate standards.

Steve Hughes
10-02-1995, 09:26 PM
>Hi Edward.
I note your reply to my - deliberately challenging - statements about the
battle over what to call "up". The intensity of the discussions has an
absurd element about it - matched by Swift's debate over which end to open
an egg from, (in Gulliver's Travels).

My point was and remains that it matters less what the axes are called but
much much more that the data is presented with unambiguous descriptors of
the orientation in which is was taken.
If we were all to ASSUME that the new (or any other convention) has been
used then errors can occur if the convention was in fact not used. It
follows that in any data description it will still be important to state
which (or that) the convention has been used. Thus if the presentation of
data anyway needs that qualifying statementfor total certainty, the
imagined benefits of a standard name for axes sets becomes less valuable.
If it is less valuable then why let it become a major concern. By setting
standards instead which define what information MUST be given when data
are presented the ambiguity is reduced as are the possibilties of error.

It has been our experience with surgeons and physiotherapists that verbal
descriptors of direction are must more acceptable than algebraic ones. And
I have yet to meet a patient who would prefer algebra to clear simple
words!!! For the medical professional there have been standard
descriptors available for many years describing body orientation - the
anatomists were there first!1

I agree with you that most engineers are well able to make any minor
transpositions in their equations so long as they are given definitions of
how the data were collected, -- so I remain unclear as to who really
benefits from setting a standard which already has inherent conflicts with
long established practices and which has no real purpose. - Perhaps the
standards meetings are fun!!
Steve Hughes
Director of BioMedical Engineering
University of Surrey,
Guildford. UK. GU2 5XH