Calibration Wires

They consist of very thin metal cables with magnetic attachments at the top, small weights to maintain tautness at the bottom, and reflective markers placed at known distances along their lengths.

The magnets are attached to a large metal overhead ceiling frame in the center of the lab and positioned so the strings hang at each of the four corners defining a volume within the lab space. This volume is determined by estimating the amount of space the subject's motions will require.

For example, a study recording a subject bending his or her knees while standing in-place would most likely require a much smaller volume (defined by the strings) than a study recording a subject sprinting across the lab.

By knowing the precise location of each of the reflective markers on each of the strings, the Data Collection Computer can then be configured and checked for accuracy prior to collecting true motion data.

After the computer and cameras are checked and calibrated, the strings are then removed from the test area, and the subject can be brought in.