\subsection{Step- and Turn-Detection}
	
	The smartphone's IMU is used to track the number of steps the pedestrian has made
	(accelerometer) as well as the relative heading change (gyroscope) since the last transition
	\cite{ebner-15}.%
	%
	To avoid potential sample impoverishment, which is induced when using the state transition as proposal distribution,
	we use both values directly within the transition step to constrain the to-be-walked distance and direction for the
	random walk.
	

