Figure 4.

Illustration of uniform sampling simulation. N sample points were pseudo-randomly picked from 10 landmark subsets (indicated with different color dots) of the UI10/5 system (Jurcak et al., 2007). Each subset mainly covers one specific part of the head with roughly equal superficial area. Thus, a roughly uniform sampling can be drawn by the following: 1. All points are picked from the candidate sets; 2. All points are unique; 3. At least one point is picked from each subset; 4. The maximal difference in the number of points picked between any two subsets is not more than one.