GETA sandals: a footstep location tracking system

Abstract

This paper presents the design, implementation, and evaluation of a footstep based indoor location system. The traditional Japanese GETA sandals are equipped with force, ultrasonic, orientation, RFID sensors and an accelerometer to produce a wearable location tracking system that demand little infrastructure in the deployed environment. In its basic form, a user simply puts on GETA sandals to enable tracking of his/her locations relative to a starting point (e.g., a building entrance), making it easy for deployment everywhere. The footstep location system is based on dead-reckoning, which works by measuring and tracking displacement vectors along a trail of footsteps. Each displacement vector is formed by drawing a line between each pair of footsteps, and the position of a user can be calculated by summing up the current and all previous displacement vectors. Unlike most existing indoor location systems, the footstep based method does not suffer from problems with obstacles, multi-path effects, signal noises, signal interferences, and dead spots. There are two technical challenges in the proposed design: (1) location error accumulates over distance traveled, and (2) displacement measurements are sporadic during stair climbing. The first problem is addressed by a light RFID infrastructure, while the second problem is remedied by incorporating an accelerometer into the system. Experiments on GETA prototype are conducted to evaluate the positional accuracy of our system.