Advanced indoor localization using ultrasonic sensor and digital compass

Several kinds of indoor localization systems have been developed for estimating objects position lately. They are classified according to the environment, the purpose of application, the media type and so on. In this paper, we propose an improved beacon system, having the ultrasonic media type, which can be used for indoor localization; Moreover it can estimate the direction of a mobile object by using a digital compass. However it is very hard for the indoor localization system using ultrasonic sensors to achieve much highly precise localization for mobile objects since the ultrasonic sensor is highly sensitive to noises and external shocks. In order to overcome this problem, we adopt a bandpass-filter to protect ultrasonic sensor from another frequency generated by noise and external shocks. In addition, the multi-modulation of ultrasonic sensors - using two ultrasonic sensors with different frequencies - improves the sampling rate of this system. And we present the application of Unscented Kalman Filter to improve the localization performance of our indoor mobile localization system.