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.