Positioning Android Devices in Large Indoor Spaces and Transitioning to Outdoors by Sensor Fusion

Abstract

This work presents an Android application that allows indoor positioning of portable devices, such as mobile phones or tablets, and its smooth transition to outdoors localization. Different technologies and methods have been combined for that purpose: Global Navigation Satellite Systems (GNSS), Ultrasonic Local Positioning Systems (ULPS), measurements of an Inertial Measurement Unit (IMU) carried by the user, and Graph-Matching techniques. The U-LPSs, composed by a set of ultrasonic beacons, are placed in indoor areas where higher precision is required, such as rooms or waypoints. The navigation between different U-LPSs is done through the use of an IMU. The accumulated drift error of the IMU is corrected upon reaching a ULPS; furthermore, graph-matching has also been integrated whether the map of the building is known. Outdoor GNSS signals are used in conjunction with inertial measurements. An Extended Kalman Filter (EKF) has been proposed for the fusion of the ultrasonic signals, the inertial signals from the IMU and the GNSS position provided by the chipset integrated in the portable device. In this way, an Android application installed on the user’s portable device allows to obtain real-time location and displays trajectory indoors, outdoors and in the transition between both.