In this example file the subject is walking in the anterior direction in one walking trial and walking in the posterior direction of the laboratory coordinate system (LAB) in the other trial. If the pelvis angle is defined as the pelvis with respect to the laboratory, the data are rotated 180 degrees from the desired angle for one of the trials (see Pelvis Angle wrt Lab in Example3.cmo file).

To create a pelvis angle that makes intuitive sense (e.g. in the direction of walking), a virtual lab segment was created. The pelvis angle can then be defined with respect to the virtual lab (see Pelvis Angle wrt Virtual Lab in Example3.cmo file). In Example 2 (see Example2.cmo file), the virtual laboratory was defined statically. In Example 3, the Virtual lab is defined relative to the lateral direction of the pelvis segment; the lateral direction is forced to lie along one of the principal axes rather than to float with the pelvis.

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For more information please view the Virtual Lab Tutorial.