. Author manuscript; available in PMC: 2012 Dec 1.

Published in final edited form as: Pervasive Mob Comput. 2011 Dec;7(6):746–760. doi: 10.1016/j.pmcj.2011.09.002

Table 3.

The intuition behind the six major extracted features. Letters in parenthesis represent the features in Figure 2

Activity	Feature	Characteristic
Walking	Max energy in power spectrum (D)	Impact of strides on acceleration
Walking	Sum of energy in power spectrum (F)	Impact of strides on acceleration
Walking	Maximum of Max amplitudes for all axes (A > B, A > C)	Motion range
Walking	Ratio of amplitude in different axes $(\frac{A}{C}, \frac{A}{B})$	Degree of freedom in movement
Non-walk	Number of orientation variations	Degree of freedom in movement