Table of Contents
Acknowledgments v Preface vi List of Figures xi List of Tables xii Acronyms and Abbreviations xiv Executive Summary 1 1. Introduction 13 The Task, 13 Joint Study Approach, 14 National Research Council Study Approach, 15 Major Issues and Considerations, 15 Report Organization, 16 GPS Program Overview, 16 GPS Technical Overview, 17 2. GPS Applications and Requirements 19 Introduction, 19 GPS Military Applications, 20 Current and Future Applications and Requirements, 21 Challenges to Full GPS Utilization, 22 Findings, 26 GPS Aviation Applications, 26 Current and Future Applications and Requirements, 27 Challenges to Full Utilization of GPS, 30 Findings, 32 Maritime Use of GPS, 32 Current and Future Applications and Requirements, 33 Challenges to Full Utilization of GPS, 35 Findings, 37 Land Transportation Applications, 38 Current and Future Applications and Requirements, 38 Challenges to Full GPS Utilization, 41 Findings, 42 Mapping, Geodesy, and Surveying Applications, 43 Current and Future Applications and Requirements, 43 Challenges to Full GPS Utilization, 45 Findings, 46 GPS Earth Science Applications, 46 Current and Future Applications and Requirements, 47 Challenges to Full GPS Utilization, 50 Findings, 51 GPS Timing and Telecommunications Applications, 52 Current and Future Applications and Requirements, 52 Challenges to Full GPS Utilization, 55 Findings, 56 Spacecraft Uses of GPS, 56 Current and Future Applications and Requirements, 57 Challenges to Full Utilization, 60 Findings, 61 Summary, 61 3. Performance Improvements to the Existing GPS Configuration 67 Introduction, 67 Current GPS Performance, 68 Accuracy, 68 Integrity and Availability, 70 Selective Availability and Anti-Spoofing, 70 Selective Availability, 71 Findings and Recommendations, 82 Anti-Spoofing, 84 Findings and Recommendations, 85 Signal Structure Modifications to Reduce Atmospheric Delay Error, 86 Guidelines and Technical Considerations, 87 New Signal Structure Options, 88 Improvements Anticipated from Adding L4, 90 Reduction of Receiver Noise and Multipath Errors, 91 Findings and Recommendations, 97 Performance Improvements to the GPS Operational Control Segment and Satellite Constellation, 98 Current Status of the Operational Control Segment and Planned Upgrades, 98 Recommended Upgrades to the Operational Control Segment, 98 Planned Block IIR Operation, 108 Suggested Improvements Using the Autonomous Ranging and Crosslink Communication Capability, 109 Performance Improvements to Enhance the Military Use of GPS, 111 Recommended Technical Improvements to Military User Equipment, 111 Possible Interim Operational Procedures, 116 Improvement Implementation Strategy, 117 4. Technical Enhancements for Future Consideration 123 GPS Improvements to Improve Overall Performance, 123 Use of a 24-Satellite Ensemble Clock, 123 Reduced Satellite Clock Errors Through Use of Improved Clocks, 124 Satellite-Based Integrity Monitoring, 125 Increased L2 Signal Strength, 126 Military Enhancements, 128 Block IIF Signal Structure Military Enhancements, 128 Spot Beams, 132 Enhancements for High-Precision Users, 133 GPS Transmit Antenna Calibration, 133 Knowledge of Spacecraft Characteristics, 134 Improved L1 Signal Reception at Angles Below the Earth's Horizon, 134 Appendix A: Study Participants 135 Appendix B: Abbreviated Committee Biographies 139 Appendix C: Overview of the Global Positioning System and Current or Planned Augmentations 145 Appendix D: Accuracy Definitions and Mathematical Relationships 177 Appendix E: Report From Mr. Michael Dyment, Booz•Allen & Hamilton 179 Appendix F: Report From Dr. Young Lee, The MITRE Corporation 201 Appendix G: Increased Bandwidth Performance Analysis 213 Appendix H: Signal Structure Options 215 Appendix I: Report from Mr. Melvin Barmat, Jansky/Barmat Telecommunications, Inc. 221 Appendix J: Selective Denial of Civilian GPS Signals by the Military 249 Appendix K: Direct Y-Code Acquisition 253 Appendix L: Enhanced Signal Structures for the Military 255 Appendix M: Accuracy of a 14-Satellite Ensemble Versus a 24-Satellite Ensemble 263 List of Figures Figure 1 Current plan for satellite replacement. (Courtesy of the GPS Joint Program Office) Figure 3-1 DGPS coverage provided by commercially available systems, including Skyfix and Sercel. (Courtesy of the National Air Intelligence Center) Figure 3-2 DGPS coverage provided by the planned FAA WAAS (Wide-Area Augmentation System). Source: Innovative Solutions International, Inc. presentation at the National Technical Meeting of the Institute of Navigation Meeting, Anaheim, CA, January 1995. Figure 3-3 Position estimates from GPS and GLONASS obtained from measurement snapshots taken 1 minute apart over an entire day. Position from (a) GPS with SA off, (b) GPS with SA on, (c) GLONASS, and (d) GPS + GLONASS. (Courtesy of MIT Lincoln Laboratory) Figure 3-4 Horizontal scatter plot of 42 meters CEP (100 meters, 2 drms) with SA at its current level and horizontal scatter plot of approximately 10 meters CEP (24 meters, 2 drms) without SA. (Figure Courtesy of Mr. Jules McNeff, Office of the Assistant Secretary of Defense, C3I) Figure 3-5 Approximate stand-alone horizontal SPS accuracy, 2 drms, resulting from recommended improvements and enhancements. Figure 3-6 Current plan for satellite replacement. (Courtesy of the GPS Joint Program Office) Figure 4-1 Wide-band GPS with a 100-watt jammer. Figure 4-2 Wide-band GPS with a 10-kilowatt jammer. List of Tables Table 2-1 Military Aviation and Precision-Guided Munitions Applications and Requirements Table 2-2 Naval Applications and Requirements Table 2-3 Military Land Applications and Requirements Table 2-4 GPS Performance Requirements for Aviation Applications Table 2-5 Requirements for Maritime Applications Table 2-6 Land Transportation Requirements Table 2-7 Current and Future GPS Requirements for GIS, Mapping, Surveying, and Geodesy Table 2-8 GPS Earth Science Requirements Table 2-9 Timing and Telecommunications Requirements Table 2-10 Requirements for GPS Spacecraft Applications Table 2-11 Summary of Military Applications with Accuracy Requirements Unmet by the GPS PPS as Currently Specified Table 2-12 Summary of Civilian Applications with Accuracy Requirements of 100 Meters or Greater (currently achievable with the basic GPS SPS) Table 2-13 Summary of Civilian Accuracy Requirements Between 25 and 100 Meters Table 2-14 Summary of Civilian Accuracy Requirements Between 10 and 25 Meters Table 2-15 Summary of Civilian Accuracy Requirements Between 1 and 10 Meters Table 2-16 Summary of Submeter Civilian Accuracy Requirements Table 3-1 Observed GPS Positioning Errors with Typical SPS and PPS Receivers Table 3-2 SA Errors from DoD/DOT Signal Specification Issues Technical Group Table 3-3 The Effect of Eliminating SA on GPS Stand-Alone Horizontal Accuracy Table 3-4 Effect of SA Removal on RAIM Availability for Aviation Applications Table 3-5 Elimination of Ionospheric Error by the Addition of Another Frequency. Table 3-6 Effect of Reduced Ionospheric Error by the Addition of Another Frequency and Additional Improvements Obtained with Using a More Advanced SPS Receiver Table 3-7 Effect of Using a More Advanced PPS Receiver on Stand-Alone Accuracy Table 3-8 Effect of SA Removal and Dual-Frequency Capability on RAIM Availability for Aviation Applications Table 3-9 Reduction of Combined Clock and Ephemeris Errors Table 3-10 Impact of Reduced Clock and Ephemeris Error on SPS Stand-Alone Accuracy Table 3-11 Impact of Reduced Clock and Ephemeris Error on PPS Stand-Alone Accuracy Table 3-12 Effect of SA Removal, Dual-Frequency Capability and Reduced Clock and Ephemeris Errors on RAIM Availability for Aviation Applications Table 3-13 Space Segment Enhancements Table 3-14 Operational Control Segment Enhancements Table 4-1 GPS Wide-Band Signal Augmentation Performance with a 100-Watt Jammer Table 4-2 GPS Wide-Band Signal Augmentation Performance with a 10-Kilowatt Jammer