The Global Positioning System (GPS) is a satellite-based navigation system that was originally designed for the U.S. military. However, the number of civilian GPS users now exceeds the military users, and many commercial markets have emerged. This book identifies technical improvements that would enhance military, civilian, and commercial use of the GPS. Several technical improvements are recommended that could be made to enhance the overall system performance. Table of Contents Front Matter Executive Summary TASK 1 Recommendations that Enhance GPS Performance for Civil and Commercial Users Recommendations that Enhance GPS Performance for All Users (Civil, Commercial, and Military) Improvement Implementation Strategy TASK 3 THE TASK JOINT STUDY APPROACH MAJOR ISSUES AND CONSIDERATIONS GPS PROGRAM OVERVIEW GPS TECHNICAL OVERVIEW INTRODUCTION GPS MILITARY APPLICATIONS Current and Future Applications and Requirements Accuracy and Integrity Anti-Jam and Anti-Spoof Capability GPS AVIATION APPLICATIONS Current and Future Applications and Requirements Resistance to Radio Frequency Interference Operational Procedures MARITIME USE OF GPS Current and Future Applications and Requirements Associated Technologies Selective Availability Findings Current and Future Applications and Requirements Accuracy Versus Other Requirements Findings Current and Future Applications and Requirements Challenges to Full GPS Utilization GPS EARTH SCIENCE APPLICATIONS Oceanography Airborne Geophysics Accuracy Requirements Oceanography Findings Current and Future Applications and Requirements Time Synchronization SPACECRAFT USES OF GPS Orbit Determination Launch and Re-entry Vehicle Guidance Signal Visibility SUMMARY INTRODUCTION Accuracy SELECTIVE AVAILABILITY AND ANTI-SPOOFING Selective Availability Military Utility of SA Impact of SA on GPS User Equipment Manufacturers and U.S. Competitiveness Impact of SA on Civil Users Findings and Recommendations Impact of A-S on Military Users Findings and Recommendations SIGNAL STRUCTURE MODIFICATIONS TO REDUCE ATMOSPHERIC DELAY ERROR Guidelines and Technical Considerations New Signal Structure Options Option 2: Narrow-Band L4 Signal Increased Accuracy Reduction of Receiver Noise and Multipath Errors Findings and Recommendations Recommended Upgrades to the Operational Control Segment Accuracy Improvements Overall System Improvements Planned Block IIR Operation Accuracy Improvements by Incorporating Satellite Ranging Data into Ground Solution Ground-Based Integrity Improvements Rapid, Direct Y-Code Acquisition Inertial Aiding Improvements Signal Processing Improvements Improved L2 Ionospheric Correction Possible Interim Operational Procedures IMPROVEMENT IMPLEMENTATION STRATEGY Use of a 24-Satellite Ensemble Clock Reduced Satellite Clock Errors Through Use of Improved Clocks Satellite-Based Integrity Monitoring Cross-Correlation Type Y-Codeless Receivers Y-Code Tracking PPS Receivers Wide-Band Signals at High Frequency Spot Beams GPS Transmit Antenna Calibration Improved L1 Signal Reception at Angles Below the Earth's Horizon Appendix B Abbreviated Committee Biographies ORIGINS AND DEVELOPMENT OF THE NAVSTAR GPS PROGRAM Department of Defense Department of Transportation The Federal Radionavigation Plan GPS TECHNICAL OVERVIEW Space Segment Operational Control Segment User Equipment GPS Signal Characteristics and Operational Concepts Selective Availability and Other Positioning Errors Atmospheric Error Receiver Errors Availability Resistance to RF Interference Differential GPS Carrier Phase (Interferometric) GPS Receiver Autonomous Integrity Monitoring (RAIM) Combined Use of GPS and GLONASS GPS and Loran-C PERMANENT DIFFERENTIAL GPS AUGMENTATIONS FAA Wide-Area and Local-Area DGPS Concepts NOAA Continuously Operated Reference Stations Maritime DGPS Services Inmarsat Racal Survey ACCQPOINT Differential Corrections Inc. Appendix D Accuracy Definitions And Mathematical Relationships Appendix E Report From Mr. Michael Dyment, Booz Allen & Hamilton Appendix F Report From Dr. Young Lee, The MITRE Corporation EFFECT OF ELIMINATING SELECTIVE AVAILABILITY (SA): IMPACT ON RAIM Appendix G Increased Bandwidth Performance Analysis Appendix H Signal Structure Options OPTION 6 OPTION 9 Appendix I Report From Mr. Melvin Barmat, Jansky/Barmat Telecommunications, Inc. Appendix J Selective Denial of Civilian GPS Signals by the Military OLD TECHNOLOGY (100,000 GATE ASIC) DISCUSSION Appendix L Enhanced Signal Structures for the Military SCENARIO 1: UNAIDED Y-CODE BANDWIDTH SIGNAL WITH A STANDARD ANTENNA SCENARIO 5: AIDED WIDE BANDWIDTH STANDARD ANTENNA SCENARIO 7: AIDED WIDE BANDWIDTH WITH NULLING AND BEAM-FORMING ANTENNA Analysis Analysis

Table of Contents:
1 Front Matter; 2 Executive Summary; 3 1 Introduction; 4 2 GPS Applications and Requirements; 5 3 Performance Improvements to the Existing GPS Configuration; 6 4 Technical Enhancements for Future Consideration; 7 Appendix A: Study Participants; 8 Appendix B: Abbreviated Committee Biographies; 9 Appendix C: Overview of the Global Positioning System ..; 10 Appendix D: Accuracy Definitions and Mathematical Relationships; 11 Appendix E: Report From Mr. Michael Dyment, Booz, Allen & Hamilton; 12 Appendix F: Report From Dr. Young Lee, The MITRE Corporation; 13 Appendix G: Increased Bandwidth Performance Analysis; 14 Appendix H: Signal Structure Options; 15 Appendix I: Report from Mr. Melvin Barmat, Jansky/Barmat..; 16 Appendix J: Selective Denial of Civilian GPS Signals by the Military; 17 Appendix K: Direct Y-Code Acquisition; 18 Appendix L: Enhanced Signal Structures for the Military; 19 Appendix M: Accuracy of a 14-Satellite Ensemble Versu a 24-Satellite Ensemble