To determine lower landmark, the subject's PSISs were palpated and a line connecting both PSIS represents the level of S2.
As a result, especially for the lower legs, landmark configurations during locomotion substantially differ from the mean landmark configuration, i.e., the motions are non-stationary [31, 32].
Besides the non-stationary motion, another major problem is the non-discriminative texture information of the lower leg landmarks (cf. landmarks 12 to 15 and 19 to 22 in Figure 1b), which additionally complicates the fitting process of AAMs.
Only very specific anatomical landmark subsets can be tracked, e.g., the torso landmarks [17, 30] or the lower leg landmarks [16].
However, all previously published works in this field suffer from at least one of the following shortcomings, which is a major drawback for the usage of these methods for actual zoological and biomechanical studies: Only very specific anatomical landmark subsets can be tracked, e.g., the torso landmarks [17, 30] or the lower leg landmarks [16].
In addition, certain landmarks exist which are covered by neither of the current approaches, e.g., the lower leg landmarks of the top camera view (cf. landmarks 12 to 15 and 19 to 22 in Figure 1b).
On the other hand, not all landmarks would be covered by these methods, as for instance the lower leg landmarks in the top view (cf. Figure 1b).
However, the holistic approach has the essential advantage that it also can reliably and consistently track landmarks which are covered by neither of the non-holistic approaches, as for instance the lower leg landmarks of the top camera view (cf. Figure 5).
We include the tracking results for the lower leg landmarks as additional constraints π local into the augmented AAM.
