The three-dimensional coordinates of the following
points in the absolute reference system are used
to calculate the embedded coordinate systems: sacral
wand tip, right and left ASIS markers, hip center,
knee center, ankle center, thigh-wand tip, shankwand
tip, and foot marker. The embedded coordinates
are represented by three orthogonal unit vectors
I, J, and K along the embedded X, Y, and Z
axes, respectively. For the pelvic coordinates, J is
the unit vector along the line from the right ASIS to
the left ASIS marker. The unit vector I is perpendicular
to J, pointing forward, and is in the plane
defined by both ASIS and sacral markers. The third
unit vector K is perpendicular to both I and J, defining
a right-handed Cartesian coordinate system.