Gravity Direction Estimation and Heading Determination for Pedestrian Navigation

One of the common ways to perform indoor localization for pedestrians is to employ the smartphone's inertial sensors, in a process known as pedestrian dead reckoning (PDR). Estimation of the pedestrian's heading is a crucial step in PDR algorithms, since it is a key factor in the positioning accuracy. In this paper, rather than assuming the smartphone to be fixed in a certain orientation on the pedestrian, we focus on estimating the vertical direction within the sensor frame of an unconstrained device. To that end, we establish a framework for gravity direction estimation and highlight the important role it has for solving the heading in the horizontal plane. By employing only accelerometers and gyroscopes, we derive, present and compare different approaches both for estimating the gravity direction and for computing the heading angle. The results are demonstrated and analyzed using data recorded from field experiments.