Figure 2.

Decision tree describing the threshold-based activity recognition using the smartphone’s barometer and accelerometer measurements. The respective thresholds are given by $t_{\mathrm{acc}}$ and $t_{\mathrm{baro}}$. For each sensor the sigma of the arithmetic mean $\Delta \overline{\omega }={\overline{\omega }}_{\mathrm{l}}-{\overline{\omega }}_{\mathrm{s}}$ of two different fix-sized windows ${\mathit{\omega }}_{\mathrm{s}}$ (short) and ${\mathit{\omega }}_{\mathrm{l}}$ (long), holding a set of the most current sensor measurements, is calculated. The process updates with every incoming barometer reading.