The Global Positioning System: A Shared National Asset -- Copyright -- Acknowledgements -- Preface -- Contents -- Acronyms and Abbreviations -- Executive Summary -- TASK 1 -- TASK 2 -- Recommendations that Enhance GPS Performance for Civil and Commercial Users -- Recommendations that Enhance GPS Performance for Military Users -- Recommendations that Enhance GPS Performance for All Users (Civil, Commercial, and Military) -- Improvement Implementation Strategy -- TASK 3 -- 1 Introduction -- THE TASK -- JOINT STUDY APPROACH -- National Research Council Study Approach -- MAJOR ISSUES AND CONSIDERATIONS -- REPORT ORGANIZATION -- GPS PROGRAM OVERVIEW -- GPS TECHNICAL OVERVIEW -- 2 GPS Applications and Requirements -- INTRODUCTION -- GPS MILITARY APPLICATIONS -- Current and Future Applications and Requirements -- Challenges to Full GPS Utilization -- Accuracy and Integrity -- Anti-Jam and Anti-Spoof Capability -- Findings -- GPS AVIATION APPLICATIONS -- Current and Future Applications and Requirements -- Challenges to Full Utilization of GPS -- Selective Availability and Anti-Spoofing -- Resistance to Radio Frequency Interference -- Operational Procedures -- Findings -- MARITIME USE OF GPS -- Current and Future Applications and Requirements -- Challenges to Full Utilization of GPS -- Associated Technologies -- Selective Availability -- Integrity -- Availability and Radio Frequency Interference -- Findings -- LAND TRANSPORTATION APPLICATIONS -- Current and Future Applications and Requirements -- Challenges to Full GPS Utilization -- Accuracy Versus Other Requirements -- The Cost of Integrated Systems -- Findings -- MAPPING, GEODESY, AND SURVEYING APPLICATIONS -- Current and Future Applications and Requirements -- Challenges to Full GPS Utilization -- Findings -- GPS EARTH SCIENCE APPLICATIONS -- Current and Future Applications and Requirements.

Meteorology -- Oceanography -- Geodynamics -- Airborne Geophysics -- Accuracy Requirements -- Challenges to Full GPS Utilization -- Meteorology -- Oceanography -- Geodynamics -- Airborne Geophysics -- Findings -- GPS TIMING AND TELECOMMUNICATIONS APPLICATIONS -- Current and Future Applications and Requirements -- Challenges to Full GPS Utilization -- Time Transfer -- Time Synchronization -- Findings -- SPACECRAFT USES OF GPS -- Current and Future Applications and Requirements -- Orbit Determination -- Attitude Determination -- Launch and Re-entry Vehicle Guidance -- Challenges to Full GPS Utilization -- Orbit Determination and Orbital Positioning -- Attitude Determination -- Signal Visibility -- Findings -- SUMMARY -- 3 Performance Improvements to the Existing GPS Configuration -- INTRODUCTION -- CURRENT GPS PERFORMANCE -- Accuracy -- Integrity and Availability -- 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 -- Anti-Spoofing -- Impact of A-S on Military Users -- Impact of A-S on Civil Users -- Findings and Recommendations -- SIGNAL STRUCTURE MODIFICATIONS TO REDUCE ATMOSPHERIC DELAY ERROR -- Guidelines and Technical Considerations -- New Signal Structure Options -- Option 1: Wide-Band L4 Signal -- Option 2: Narrow-Band L4 Signal -- Additional Considerations -- Improvements Anticipated from Adding L4 -- Increased Accuracy -- Additional Benefits of L4 -- Reduction of Receiver Noise and Multipath Errors -- Findings and Recommendations -- PERFORMANCE IMPROVEMENTS TO THE GPS OPERATIONAL CONTROL SEGMENT AND SATELLITE CONSTELLATION -- Current Status of the Operational Control Segment and Planned Upgrades -- Recommended Upgrades to the Operational Control Segment.

Accuracy Improvements -- Overall System Improvements -- Planned Block IIR Operation -- Suggested Improvements Using the Autonomous Ranging and Crosslink Communication Capability -- Accuracy Improvements by Incorporating Satellite Ranging Data into Ground Solution -- Satellite Health Monitoring to Improve System Reliability and Availability -- Ground-Based Integrity Improvements -- PERFORMANCE IMPROVEMENTS TO ENHANCE THE MILITARY USE OF GPS -- Recommended Technical Improvements to Military User Equipment -- Rapid, Direct Y-Code Acquisition -- Antenna Subsystem Improvements -- Inertial Aiding Improvements -- Signal Processing Improvements -- Improved L2 Ionospheric Correction -- Possible Interim Operational Procedures -- IMPROVEMENT IMPLEMENTATION STRATEGY -- 4 Technical Enhancements for Future Consideration -- GPS IMPROVEMENTS TO IMPROVE OVERALL PERFORMANCE -- Use of a 24-Satellite Ensemble Clock -- Reduced Satellite Clock Errors Through Use of Improved Clocks -- Satellite-Based Integrity Monitoring -- Increased L2 Signal Strength -- Cross-Correlation Type Y-Codeless Receivers -- L2 Squaring Y-Codeless Receivers -- Y-Code Tracking PPS Receivers -- MILITARY ENHANCEMENTS -- Block IIF Signal Structure Military Enhancements -- Wide-Band Signals at High Frequency -- Spot Beams -- ENHANCEMENTS FOR HIGH-PRECISION USERS -- GPS Transmit Antenna Calibration -- Knowledge of Spacecraft Characteristics -- Improved L1 Signal Reception at Angles Below the Earth's Horizon -- Appendix A Study Participants -- Appendix B Abbreviated Committee Biographies -- Appendix C Overview Of The Global Positioning System And Current Or Planned Augmentations -- ORIGINS AND DEVELOPMENT OF THE NAVSTAR GPS PROGRAM -- GPS POLICY, MANAGEMENT, AND OPERATIONS -- 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 -- Clock and Ephemeris Error -- Multipath Errors -- Receiver Errors -- Dilution of Precision -- IMPROVING THE CAPABILITIES OF GPS -- Integrity -- Availability -- Continuity of Service -- Resistance to RF Interference -- Augmentations and Enhancements -- Differential GPS -- Carrier Phase (Interferometric) GPS -- Pseudolites -- Receiver Autonomous Integrity Monitoring (RAIM) -- Combined Use of GPS and GLONASS -- GPS/Inertial Navigation System (INS) Integration -- GPS and Loran-C -- PERMANENT DIFFERENTIAL GPS AUGMENTATIONS -- U.S. Government-Supported Differential GPS -- FAA Wide-Area and Local-Area DGPS Concepts -- U.S. Coast Guard DGPS Service -- NOAA Continuously Operated Reference Stations -- State and Local Government DGPS -- Differential Systems Supported by Foreign Governments and International Organizations -- Maritime DGPS Services -- International Participation in the FAA's WAAS -- Inmarsat -- The International GPS Service for Geodynamics -- Racal Survey -- John E. Chance & Associates, Inc. (A member of the Fugro Group of Companies) -- 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 -- OPTIONS 1 AND 2 -- OPTIONS 3 AND 4 -- OPTION 5 -- OPTION 6 -- OPTION 7 -- OPTION 8 -- OPTION 9 -- Appendix I Report From Mr. Melvin Barmat, Jansky/Barmat Telecommunications, Inc.

Appendix J Selective Denial of Civilian GPS Signals by the Military -- Appendix K Direct Y-Code Acquisition -- OLD TECHNOLOGY (100,000 GATE ASIC) -- CURRENT TECHNOLOGY (500,000 GATE ASIC) -- DISCUSSION -- Appendix L Enhanced Signal Structures for the Military -- SCENARIO 1: UNAIDED Y-CODE BANDWIDTH SIGNAL WITH A STANDARD ANTENNA -- SCENARIO 2: AIDED Y-CODE BANDWIDTH WITH A STANDARD ANTENNA -- SCENARIO 3: AIDED Y-CODE BANDWIDTH WITH NULLING ANTENNA -- SCENARIO 4: UNAIDED WIDE BANDWIDTH WITH STANDARD ANTENNA -- SCENARIO 5: AIDED WIDE BANDWIDTH STANDARD ANTENNA -- SCENARIO 6: AIDED WIDE BANDWIDTH WITH MINIATURIZED NULLING ANTENNA -- SCENARIO 7: AIDED WIDE BANDWIDTH WITH NULLING AND BEAM-FORMING ANTENNA -- Appendix M Accuracy of a 14-Satellite Ensemble Versus a 24-Satellite Ensemble -- CASE A -- Analysis -- CASE B -- Analysis.