APPLICATION OF AIRBORNE LASER SCANNER - AERIAL NAVIGATION A dissertation presented to the faculty of the Russ College of Engineering and Technology of Ohio University In partial fulfillment of the requirements for the degree Doctor of Philosophy Jacob L. Campbell June 2006 This dissertation entitled APPLICATION OF AIRBORNE LASER SCANNER- AERIAL NAVIGATION by JACOB L. CAMPBELL has been approved for the School of Electrical Engineering and Computer Science and the Russ College of Engineering and Technology by Maarten Uijt de Haag Associate Professor of Electrical Engineering and Computer Science Frank van Graas Fritz J. and Dolores H. Russ Professor of Electrical Engineering Dennis Irwin Dean, College of Engineering Abstract CAMPBELL, JACOB L., Ph.D., June 2006. Electrical Engineering APPLICATION OF AIRBORNE LASER SCANNER- AERIAL NAVIGATION (134 pp.) Directors of Dissertation: Maarten Uijt de Haag and Frank van Graas This dissertation explores the use of an Airborne Laser Scanner (ALS) for use in aircraft Terrain- Referenced Navigation (TRN). Position estimation techniques developed in this dissertation enable the use of large sets of high accuracy ALS measurements to solve for position in real-time. The explored techniques were then used to design, implement, and - for the first time ever - fly a real-time ALS-based TERRain Aided Inertial Navigator (TERRAIN) precision approach system. During the flight tests, the system provided meter-level horizontal and vertical positioning accuracies in real-time. The ALS-based TRN techniques discussed in the dissertation are constrained to the information found in the terrain shape domain. The data acquisition, pre-processing, and position estimation techniques of ALS TRN vary significantly from traditional radar altimeter-based TRN primarily due to differences in the measurement mechanism used in both TRN systems. First, traditional radar altimeter-based TRN senses the terrain contours traversed in the along-track direction, whereas ALS-based TRN makes measurements in the along-track and in the cross-track directions. The second difference is that the ALS laser’s milli-radian beamwidth has sufficient resolution to identify not only the ground, but also objects on the ground such as buildings. A radar altimeter with a beamwidth of several degrees can not observe the same level of detail. These differences increase the spectral content of the ground measurement data in the ALS-based system thus permitting high-accuracy position estimates. The described ALS TRN navigation techniques include methods to estimate the position based on the best match between ALS data and a high resolution/accuracy terrain database. Finally, the dissertation explores the certification path for an ALS-based landing system. Approved by: Maarten Uijt de Haag Associate Professor of Electrical Engineering and Computer Science Frank van Graas Fritz J. and Dolores H. Russ Professor of Electrical Engineering To my parents - for their examples of integrity and a positive outlook. Acknowledgements This dissertation would not have been possible without the help of many fellow co- workers/students (which I prefer to call friends given all the good times we have had together performing this research). I can honestly say that the experiences I have been part of and the people I have met in the course of this research will be close to me for the rest of my life. First, I thank my fellow office mates, Jeff Dickman, Lukas Marti, Andrey Soloviev, and Ananth Vadlamani, for providing an excellent source of ideas during the countless discussions on the research. I also thank them for helping with the development of equipment and flight tests. For research support from NASA Langley I thank Steve Young, Rob Kudlinski, and Dan Baize who made the LIDAR data collection effort in Reno, NV possible. For the Reno, NV DC-8 flight test I thank the US Army for use of their LIDAR equipment, as well as the support staff from Optech for their expertise on the installation and help in the LIDAR data processing. I also thank the NASA DC-8 flying laboratory crew and support staff for their flexibility and help collecting the data and NOAA for the use of a LIDAR generated terrain map of the Reno area. With respect to the successful creation and testing of a proof-of-concept real-time laser scanner based approach system I thank Dr. van Graas and Dr. Uijt de Haag for help with the development and funding. I thank Jay Clark and his team at the Ohio University Airport for the customized installation of the equipment in the DC-3 aircraft, and thank the DC-3 pilots, Dr. McFarland and Bryan Branham, for their part in the successful flight tests at Braxton County Airport (K48I). I thank Delft University of Technology for the use of their Synthetic Vision / Flight Director display, and I thank the Canaan Valley Institute, specifically Sandra Frank, for providing the LIDAR data for K48I. I also thank my Dad, Steve Campbell, for help with the survey of K48I. I thank my Ph.D. committee members, Dr. Chris Bartone, Dr. Martin Molenkamp, and Dr. Jim Rankin, for their ideas and guidance from the topic proposal through their reviewing of this dissertation. And, I thank Dr. Mikel Miller for his support in editing my dissertation. Also, and most importantly, I thank my Co-Advisors, Dr. Maarten Uijt de Haag and Dr. Frank van Graas for the countless hours spent discussing the research in this dissertation, reviewing papers, and for their examples not only as great advisors, but also as great people. Finally I thank my wife, Nikki, for her support and love throughout my work on this dissertation, and most importantly I thank God for giving me the strength to complete my Ph.D. 6 Table of Contents Abstract............................................................................................................................................3 Acknowledgements..........................................................................................................................5 Acronyms / Abbreviations .............................................................................................................11 1. Introduction............................................................................................................................15 2. Background............................................................................................................................18 2.1. Terrain-Referenced Navigation History .......................................................................19 2.1.1. The Early Years, Analog Systems............................................................................19 2.1.2. Digital Age of Terrain Navigation ...........................................................................21 2.1.3. Bayesian Approaches to Terrain-Referenced Navigation Research ........................23 2.1.4. Beyond ‘Traditional’ Radar Altimeter Terrain-Referenced Navigation ..................23 2.2. Survey of Terrain-Based Navigation Systems..............................................................26 2.2.1. ATRAN – Automatic Terrain Recognition And Navigation ...................................26 2.2.2. TERCOM – TERrain COntour Matching ................................................................27 2.2.3. SITAN – Sandia Inertial Terrain-Aided Navigation ................................................29 2.2.4. SPARTAN – StockPot Algorithm Robust Terrain-Aided Navigation.....................30 2.2.5. TERPROM® – TERrain PROfile Matching.............................................................31 2.2.6. APALS® - Autonomous Precision Approach and Landing System.........................32 2.2.7. PTAN® - Precision Terrain Aided Navigation.........................................................33 2.3. Summary of Survey of Terrain-Based Navigation Systems.........................................34 2.4. System Characteristics: GPS, WAAS, INS, GPS-Aided INS, Coasting INS...............35 2.4.1. GPS ..........................................................................................................................35 2.4.2. WAAS......................................................................................................................36 2.4.3. Inertial Navigation ...................................................................................................36 2.4.4. GPS-Aided Inertial Calibration................................................................................37 3. Airborne Laser Scanner & LIght Detection And Ranging (LIDAR) Mapping Systems .......41 3.1. ALS Characteristics and Operation ..............................................................................41 3.1.1. ALS Laser Rangers ..................................................................................................41 3.1.2. ALS Scanning Mechanisms .....................................................................................43 3.1.3. ALS Pointing Accuracy Characteristics...................................................................47 3.2. ALS in a LIDAR Mapping System ..............................................................................49 3.2.1. Laser Scanner Sensor Errors ....................................................................................49 3.2.2. Kinematic GPS Sensor Errors..................................................................................50 3.2.3. GPS/IMU Orientation Sensor Errors........................................................................51 3.2.4. Total LIDAR