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jwalton86
12-21-2001, 03:51 AM
Adam:

Just a suggestion ...

You can probably put two or more markers on FIXED landmarks in
unobtrusive locations on the other side of the room and measure
the vibration being introduced into your video signals. Moreover,
you could quite easily subtract-out the vibration component if it
become a problem. All it would take is a "filter" to extract the
"apparent" 2-D motions of the reference targets before you try to
perform any tracking. Obviously, this is not the "preferred"
solution, but if the vibration appears to be a problem, the extra
effort may be worth the work.

BTW, we use this technique when we have several cameras on a moving
reference frame (a vehicle, for instance) ... it works. Back in
"the old days" :-) we used the same technique to "register" 16-mm
frames that passed through a sloppy film transport.

Jim

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* Fellow, Society of Photo-Optical Instrumentation Engineers *
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-----Original Message-----
From: Biomechanics and Movement Science listserver
[mailto:BIOMCH-L@NIC.SURFNET.NL]On Behalf Of Adam Shortland
Sent: Tuesday, December 18, 2001 2:33 PM
To: BIOMCH-L@NIC.SURFNET.NL
Subject: [BIOMCH-L] BIOMECH-L: Vibrations from the icicle - will they be
important?


Dear members,
On a site less than 10 metres from our clinical gait lab at Guy's Hospital
in London there are plans to construct the tallest building in Europe. The
architectural realisations depict a huge chard of ice pointing towards the
heavens (apologies to humanists/atheists). The building at 62 storeys with a
large radiator on top (the last word in Eco-design) will be twice as tall as
our hospital (the tallest hospital in Europe).
Necessarily, there will be considerable noise, traffic disturbance and dust,
but our main problem will come from the vibrations of the building work. I
understand the concrete pillars that form a part of the base of the building
will be helically-driven to reduce vibration pollution.
I like vibrations as much as the next person except when they interfere with
my equipment! My questions are:
If the magnitude of the vibration at source was known, could we estimate the
level of vibration within our laboratory given some material specifications?
What level of vibration would interfere with the operation of our
cameras/forceplates (some cameras are fixed to plasterboard, others are on
tripods)?
Would long-term vibrations have a deleterious effect on our gait lab
equipment?

We are in the process of making a representation to the local planning
committee and need as much information as possible to construct a case. I
know it's not a Biomechanics question but I'd be grateful for your thoughts.

Adam
Adam Shortland PhD, MIPEM, SRCS
Manager,
One Small Step Gait Laboratory,
Guy's Hospital
LONDON
UK
Tel. +44 20 7955 2339
Fax. +44 20 7955 2340

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