Dear Riyad:
Although our lab is called the "SIU Motion Analysis Laboratory", we actually
use a 5 CCD camera VICON system with PC AMASS and Helen Hayes Software (not
Motion Analysis Corp. equipment). Cecilia Concha of Texas Scottish Rite
Hospital recently conducted a survey of clinical gait labs in North America,
the results of which were presented at the 1st North American Clinical Gait
April 94 in Portland. These two labs were listed as having 4 camera Motion
Analysis systems:
- Kluge Children's Rehab Center, Charlottesville, VA
- Orthopaedic Biomech. Lab, Mayo Clinic, Rochester MN (507) 284-4295

or call Motion Analysis (800) 733-6746 or (800) 862-1338 or (707) 579-650

I have learned that successful camera placement can depend on marker
placement on the subject. When we went from the Boston set to the Helen
Hayes marker set (dropping the heel and upper extremity markers), I moved my
two rear corner cameras forward (more like side cameras) and my two front
corner cameras more forward (more like front cameras). Of course, the
success of camera positioning may change if your subject has pronounced
internal or external rotation of the lower limbs. I must say that the 5th
(front) camera really helps too; we used to refer to it as the "catch-all"
camera. Also, some 3D marker trajectory calculation algorithms may get
confused during ray matching if two of your cameras' locations are too close
to mirror images of one another with respect to your calibration volume.
You might also consider marker size and separation, calibration volume,
camera settings, ambient light, and reflective surfaces in camera views when
trying to collect better gait data in 3D.

Good Luck. I hope this was of some help.

Stephen W. Hill, B.Sc.
Kinesiologist/Administrative Director
SIU Motion Analysis Laboratory (1420)
Southern Illinois University School of Medicine
751 North Rutledge Street
Lower Level, Suite 0300
Springfield, IL 62702 USA

phone: (217) 782-6556
fax: (217) 782-7323
Subject: Motion Analysis question
Date: Thursday, February 16, 1995 5:16PM

I am a graduate studend at The university of Toledo, my name is Riyad. I
knew about you from the biome-net. I know that you are the Kinesiologist/
Administrative director, SIU Motion Analysis Labrotory,

At the our university of Toledo, we have a gait lab that uses a the motion
analysis system, I need help on how set up the tracking paramamters when
4 camera, and tracking using expertvision software, by the way tracking in
3-d, I don't seem to have good data that make sense when tracking a walking
person. If you could give me some hints on the camera locations and 3d
parameters like norm of residual and neigborhood segments. or refer me to
someone that could.

Thank you