User's Manual

Document MV0319P.N

MVN User Manual

109

Global reference frame:

X positive when pointing to the local magnetic North (red).

Y according to right handed co-ordinates (West) (green).

Z positive when pointing up (blue).

Local coordinate frame:

Body: segments in anatomical pose:

 Origin: center of rotation (proximal)

 X forward.

 Y up, from joint to joint.

 Z pointing right.

This difference in coordinate systems will not affect results.

After the calibration procedure, the right heel of the character is set at the origin (0,0,0). This is the begin

point of the red arrow in the 3D viewport (pointing in the positive X-direction).

The orientation output is represented using quaternions. The definition of the segment co-ordinate

system can be found in Section 19.6. Joint origins are determined by the anatomical frame and are

defined in the center of the functional axes with the directions of the X, Y and Z being related to functional

movements. For example, flexion/extension of the knee is described by the rotation about the

Z-axis of

the lower leg with respect to the upper leg; abduction/adduction is the rotation about the

X-axis; and

endo/exo rotation is about the

Y-axis. Note that in some studies, different anatomical and reference

frames definitions are used; to compare results proper co-ordinate frame transformations must be

performed.