On Calibrating the Sensor Errors of a PDR-Based Indoor Localization System

Kun-Chan Lan,Wen-Yuah Shih

doi:10.3390/s130404781

Abstract

Many studies utilize the signal strength of short-range radio systems (such as WiFi, ultrasound and infrared) to build a radio map for indoor localization, by deploying a large number of beacon nodes within a building. The drawback of such an infrastructure-based approach is that the deployment and calibration of the system are costly and labor-intensive. Some prior studies proposed the use of Pedestrian Dead Reckoning (PDR) for indoor localization, which does not require the deployment of beacon nodes. In a PDR system, a small number of sensors are put on the pedestrian. These sensors (such as a G-sensor and gyroscope) are used to estimate the distance and direction that a user travels. The effectiveness of a PDR system lies in its success in accurately estimating the user's moving distance and direction. In this work, we propose a novel waist-mounted based PDR that can measure the user's step lengths with a high accuracy. We utilize vertical acceleration of the body to calculate the user's change in height during walking. Based on the Pythagorean Theorem, we can then estimate each step length using this data. Furthermore, we design a map matching algorithm to calibrate the direction errors from the gyro using building floor plans. The results of our experiment show that we can achieve about 98.26% accuracy in estimating the user's walking distance, with an overall location error of about 0.48 m.

Highlights

The accurate localization of objects and people in an environment has long been considered an important component of ubiquitous networking
We propose a zero velocity update method to calibrate the sensor data based on the concept of Simple Harmonic Motion (SHM) [57]
We first discuss the results of our step length estimation method, and show the performance of the above-mentioned map matching algorithm

Summary

Introduction

The accurate localization of objects and people in an environment has long been considered an important component of ubiquitous networking. A personal dead reckoning or pedestrian dead reckoning (PDR) system is a self-contained technique for indoor localization This technique only requires a couple of sensors to be put on the user, so that it can be used in any building without pre-installing beacon nodes or prebuilding RF maps/propagation models based on surveys of the environment. Most PDR systems use inertial sensors (such as an accelerometer, gyroscope, or digital compass) to measure step length and heading direction. The foot-mounted method [17,18,19,20,21,22,23,24,25,26,27] uses a double integral on horizontal acceleration to estimate distance, and a gyroscope or compass to measure the heading direction. A waist-mounted method is generally more feasible to be implemented on a hand-held device, its accuracy in estimating the step length is typically worse than that of a foot-mounted method which, on the other hand, performs poorly with regard to obtaining an accurate orientation [33]

Methods

Results

Conclusion