Estimating Step Distance Using Simple Harmonic Motion

Some prior studies proposed the use of Pedestrian Dead Reckoning (PDR) for indoor localization. The PDR system does not require a beacon-based infrastructure, in which a small number of sensors are put on the pedestrian. These sensors (such as G-sensor and Gyro) are used to estimate the distance and direction that the user traveled. The PDR approach can be generally categorized into two types: foot-mounted and waist-mounted. In general, the foot-mounted system can get accurate step length, but perform poorly in estimated heading direction. On the other hand, the waist-mounted system can estimate direction with high accuracy, but is hard to measure the step length. In this work, we proposed a waist-mounted based PDR to estimate step length using one 3-axis accelerometer. We utilize vertical acceleration to implement double integral for measuring the user´s instant height change and use some physical features of vertical acceleration during the walking to calibrate the measurement. Based on the Pythagoras´ Theorem, we can then estimate each step length based on the user´s height change during his/her walking.