Indoor Navigation System for Handheld Devices A Major Qualifying Project Report Submitted to the faculty of the Worcester Polytechnic Institute Worcester, Massachusetts, USA In partial fulfillment of the requirements of the Degree of Bachelor of Science on this day of October 22, 2009 by __________________________ Manh Hung V. Le __________________________ Dimitris Saragas __________________________ Nathan Webb Advisor __________________________ Advisor __________________________ Professor Alexander Wyglinski Professor Richard Vaz Abstract This report details the development of an indoor navigation system on a web-enabled smartphone. Research of previous work in the field preceded the development of a new approach that uses data from the device’s wireless adapter, accelerometer, and compass to determine user position. A routing algorithm calculates the optimal path from user position to destination. Testing verified that two meter accuracy, sufficient for navigation, was achieved. This technique shows promise for future handheld indoor navigation systems that can be used in malls, museums, hospitals, and college campuses. i Acknowledgements We would like to sincerely thank the individuals who guided us through our Major Qualifying Project and who made our experience a memorable one. We would like to thank our project sponsors, Dr. Sean Mcgrath and Dr. Michael Barry, for providing us with the necessary information and resources to complete our project. We would also like to thank our advisors, Professor Richard Vaz and Professor Alexander Wyglinski for their continuous help and support throughout the project. ii Executive Summary Dashboard mounted GPS receivers and online mapping services have replaced paper maps and atlases in modern society. Contrasting these advances in automobile navigation, wall mounted maps and signs continue to be the primary reference for indoor navigation in hospitals, universities, shopping malls, and other large structures. In this project the development, implementation, and testing of a smartphone- based indoor navigation system are described. The HTC Hero was selected as the development platform for this project. Reasons for its selection include the open-source nature of the Google Android operating system, the large number of sensors built in to the phone, and the high computational power of the device. Apple iPhone OS was also considered. Three primary objectives were identified that summarize the challenges faced in this project. First, the device must be capable of determining its location in the building. Second, it must be capable of determining the optimal route to a destination. Third, an intuitive user interface must provide the user with access to these features. Numerous candidate positioning techniques and technologies were considered for meeting the first objective. The decision was made to implement an integrated positioning system making use of multiple sources of information common to modern smartphones. Signal strength measurements from the device’s wireless adapter are used to estimate position based on the known locations of wireless access points. The method used is similar to the calibration-heavy technique of location fingerprinting, but a pre-generated wireless propagation model is used to alleviate the calibration requirement. Measurements of acceleration and orientation from the device’s accelerometer and magnetic compass are used to repeatedly approximate the device’s motion. These sources of information are combined with information from past sample periods to continually estimate the user location. To overcome the challenge of determining an optimal path to the user’s destination, the rooms and hallways of the building were represented as graphical nodes and branches. Many common routing algorithms were considered for use in determining the best path to the user’s destination in the defined graph. Dijkstra’s algorithm was chosen for its low computational complexity, its guarantee of determining the optimal path, and its potential for efficient handling of sparse graphs. iii The user interface was developed using the Google Android software development kit and provides the user with the ability to determine their location, select a destination from a database of people and places, and follow the route that the phone determines. Device testing showed that the three primary objectives were accomplished. The integrated positioning techniques achieved an average deviation between estimated positions and the user’s path of less than two meters. Matching these position estimates to known paths and locations in the building further increased the accuracy. Additionally, the location database and routing algorithm accomplished the objective of optimal routing. A user interface was constructed that allowed access to these functions. Contributions made through the completion of this project include the use of an integrated propagation model to simulate wireless propagation and hence negate the need for data collection in a WiFi- fingerprinting like system. Also, a statistical method was developed for estimating position based on successive, unreliable, measurements from WiFi positioning and inertial navigation sensors. The development of these techniques made possible an innovative approach to the challenge of indoor positioning and navigation that is less difficult to implement and is compatible with existing handheld devices. Future directions for research in this area were identified. These include development of an application that automates conversion of map images into wireless propagation information, incorporation of a more robust propagation model, and automated accessing of map files hosted on local or remote servers. Progress in these three areas is deemed necessary for a handheld device application to greatly improve upon current techniques for indoor navigation. iv Table of Contents Abstract ................................................................................................................................................... i Acknowledgements ................................................................................................................................ ii Executive Summary ............................................................................................................................... iii Table of Contents.................................................................................................................................... v Table of Figures...................................................................................................................................... ix Table of Tables ....................................................................................................................................... xi 1 Introduction .................................................................................................................................... 1 2 Background Research ...................................................................................................................... 4 2.1 Potential Technologies ................................................................................................................ 4 2.1.1 Satellites............................................................................................................................. 4 2.1.2 Cellular Communication Network ....................................................................................... 5 2.1.3 WiFi .................................................................................................................................... 5 2.1.4 Bluetooth ........................................................................................................................... 6 2.1.5 Infrared .............................................................................................................................. 7 2.1.6 Ultra Wide Band ................................................................................................................. 7 2.1.7 Potential Technology Summary .......................................................................................... 9 2.2 Positioning Techniques ............................................................................................................. 10 2.2.1 Cell of Origin ..................................................................................................................... 10 2.2.2 Angle of Arrival ................................................................................................................. 10 2.2.3 Angle Difference of Arrival ................................................................................................ 11 2.2.4 Time of Arrival .................................................................................................................. 12 2.2.5 Time Difference of Arrival ................................................................................................. 13 2.2.6 Triangulation .................................................................................................................... 14 2.2.7 Location Fingerprinting ..................................................................................................... 14 2.2.8 Positioning Technique Summary ....................................................................................... 15 2.3 Indoor Propagation Models .....................................................................................................