University of Calgary PRISM: University of Calgary's Digital Repository Graduate Studies The Vault: Electronic Theses and Dissertations 2013-12-13 Four-constellation GNSS Reliability and the Estimation of Inter-system Time-offsets for Improved Performance in Challenging Signal Environments Winit, Rasika Winit, R. (2013). Four-constellation GNSS Reliability and the Estimation of Inter-system Time-offsets for Improved Performance in Challenging Signal Environments (Unpublished master's thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/26219 http://hdl.handle.net/11023/1194 master thesis University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission. Downloaded from PRISM: https://prism.ucalgary.ca UNIVERSITY OF CALGARY Four-constellation GNSS Reliability and the Estimation of Inter-system Time-offsets for Improved Performance in Challenging Signal Environments By Rasika Winit A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE DEPARTMENT OF GEOMATICS ENGINEERING CALGARY, ALBERTA December 2013 © Rasika Winit 2013 ABSTRACT The new GNSS constellations such as Galileo and BeiDou being planned and launched will result in a greatly increased number of available ranging sources, hence, improvement in constellation geometry and coverage. When using signals from multiple constellations, however, the challenges are not only to maximize the benefit from the additional ranging observations but also to deal with the differences among satellite systems such as the time-offset between the constellations. Also, challenges exist when using the ranging signal in GNSS degraded environments where GNSS users potentially see a limited number of satellites from multiple GNSS constellations. This work investigates the accuracy and reliably of position solutions when using ranging signals from combined GPS, GLONASS, BeiDou and Galileo constellations in urban environments. Furthermore, this study assesses the benefits of using a priori inter-system clock-offset information. The positioning performance of multiple GNSS constellations has been examined through covariance simulation and with live data. The benefit of using a priori clock-offset constraints has been demonstrated. It has been found that the benefits of using a priori clock-offset constraints to help enhance the availability of position solutions and fault detection and exclusion capabilities are particularly significant when the receiver is located in areas where limited GNSS signals are available such as in the urban-canyon environment. ii ACKNOWLEDGEMENTS I would like to express my deepest appreciation to my supervisor, Dr. Kyle O’Keefe, for his gracious support, guidance and continuous encouragement during my studies. I would like to thank him for providing me with this opportunity to learn and explore my interests in the field of satellite navigation. I would like to express my gratitude to Dr. Mark Petovello for his vast knowledge and his kind support in software development for this research. I would also like to thank my colleagues in Position Location And Navigation (PLAN) Group for their instructive discussions and for providing an enjoyable and cooperative work environment. Special thanks to Srinivas Bhaskar, Anup Dhital, G.S. Naveen, Vimal Bhandari, Bernhard Aumayer and Vijay Bellad. Finally, I am most grateful to my parents for their boundless love, support and encouragement. What I have achieved would not have been possible without them. iii To my parents, If I am an eagle, you are my wings iv TABLE OF CONTENTS Abstract ........................................................................................................................................... ii Acknowledgements ........................................................................................................................ iii Table of Contents .............................................................................................................................v list of tables ................................................................................................................................... vii List of Figures and Illustrations ................................................................................................... viii list of symbols ............................................................................................................................... xii list of Abbreviations ..................................................................................................................... xvi CHAPTER ONE: BACKGROUND AND INTRODUCTION .......................................................1 1.1 Multi-constellation GNSS and GNSS Modernization ............................................................2 1.2 GNSS Constellations ..............................................................................................................3 1.2.1 GPS ................................................................................................................................3 1.2.2 GLONASS .....................................................................................................................5 1.2.3 Galileo ............................................................................................................................6 1.2.4 BeiDou ...........................................................................................................................7 1.3 Universal Time Standard and GNSS Time .............................................................................8 1.3.1 GPS Time .....................................................................................................................11 1.3.2 GLONASS Time ..........................................................................................................11 1.3.3 Galileo Time ................................................................................................................12 1.3.4 BeiDou Time ................................................................................................................12 1.4 Inter-system Time-offset Issue .............................................................................................14 1.5 Integrity Parameters and Reliability Requirements ..............................................................15 1.5.1 Threat Space and Types of Ranging Signal Errors ......................................................15 1.5.2 Integrity Requirements and Protection Levels .............................................................17 1.6 Use of Satellite-based Augmentation System (SBAS) .........................................................19 1.7 Overview of Receiver Autonomous Integrity Monitoring (RAIM) .....................................20 1.8 Limitation of Previous Works ...............................................................................................23 1.9 Objectives and Contributions ................................................................................................29 1.10 Author’s Contribution ...........................................................................................................30 1.11 Thesis Outline .......................................................................................................................30 CHAPTER TWO: ESTIMATION ALGORITHM AND RELIABILITY PARAMETERS .........33 2.1 Receiver-satellite Geometry and Design Matrix ...................................................................33 2.2 Least-squares Estimation ......................................................................................................35 2.3 Dilution of Precision .............................................................................................................38 2.4 Blunder Detection .................................................................................................................40 2.5 Internal and External Reliability ...........................................................................................42 2.5.1 Internal Reliability .......................................................................................................42 2.5.2 External Reliability ......................................................................................................43 v 2.6 Design Matrix Using Multiple GNSS constellations ............................................................44 2.7 Number of Satellites Requirements ......................................................................................52 CHAPTER THREE: SIMULATION DESCRIPTION AND RESULTS .....................................54 3.1 Simulation Description .........................................................................................................55 3.2 User Equivalent Range Error Model.....................................................................................57 3.3 Positioning Reliability When Using GPS and GLONASS with SBAS Corrections ............63 3.4 Performance of GPS, GLONASS, BeiDou and Galileo Constellations ...............................68 3.5 Availability and Reliability Performance of Multiple GNSS Constellations with a Priori Inter-system