Fig. 5

Graphical representation of the mean values of the distribution of position errors a and b and angle errors (c and d) of each of the FHA with respect to the mean FHA for each of the positions of the stool in the horizontal grid. The mean errors of the Elite system for both variables are shown on panels a and c, while panels b and d show the same results for the three sensors of the Polhemus system. Values are expressed in mm and degrees respectively. Areas with no differences between each polhemus sensor with respect to the Elite are indicated by stars