Figure 3:

Measurement of human stride parameters during walking. (A.) Data from an inertial measurement unit on each shoe were processed to estimate the position and orientation of the foot. Individual strides were demarcated within a locally defined walking reference frame and aligned to begin at the origin, so that the endpoints represented the stride variations. (B.) Stride variability for a representative subject is shown as viewed from above, including foot placements (and their covariance ellipse, solid line) and external rotation. External foot rotation or heading is represented by lines for each footfall, colored from blue (pointing to the left) to red (pointing to the right).