Figure 1.

Example of sensor displacement introduced during the user self-placement of a sensor (a), and its effect at the feature level (b). In this particular example, the displacement with respect to the predefined deployment in the self-placement case applies to the right calf (RC), while the placement remains approximately similar for the sensor attached to the left calf (LC). In (b), the mean and standard deviation computed from the sensor acceleration signals is represented for various instances of a given activity. Confidence ellipses are plotted to represent the feature distribution for each case.