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This review provides an overview of the U.S. GPS system, its applications, and the ongoing modernization program to improve accuracy and reliability.
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U.S. Space-Based Positioning, Navigation and Timing: A Policy and Program Review 25 February 2008 Polytechnic University of Turin Michael Shaw, Director U.S. National Coordination Office for Space-Based Positioning, Navigation, and Timing (PNT)
Introduction • Like the Internet, GPS is a critical component of the global information infrastructure • Scalable applications enabling broad new capabilities • Facilitating innovations in efficiency, safety, environmental, public security and science • In the past decade, GPS has grown into a global utility providing space-based positioning, navigation and timing (PNT) • Consistent, predictable, dependable policy and performance • Augmentations improve performance
GPS as a Global “Public Service” • Owned and operated by the U.S. Government • Paid for by U.S. taxpayers • Managed at a national level as multi-use asset • Acquired and operated by the U.S. Air Force on behalf of the U.S. Government • GPS service is a one-way broadcast, like FM radio • Unlimited number of users • Access to civilian GPS signals is free of direct user charges • Public domain documentation • Available on an equal basis to users and industry • Anyone in the world can develop GPS user equipment
Overview Systems Applications Policy International Cooperation
The Global Positioning System • Baseline 24 satellite constellation in medium earth orbit • Global coverage, 24 hours a day, all weather conditions • Satellites broadcast precise time and orbit information on L-band radio frequencies • Two types of signals: • Standard (free of direct user fees) • Precise (U.S. and Allied military) • Three segments: • Space • Ground control • User equipment
Current Constellation 30 GPS SatellitesSet Healthy (as of 14 Feb 08) (Baseline Constellation: 24) • 13 Block IIA satellites operational • 12 Block IIR satellites operational • 5 Block IIR-M satellite operational • Transmitting new second civil signal (L2C) • Continuously assessing constellation health to determine launch need • Next launch: March 2008 • Global GPS civil service performance commitment has been met continuously since December 1993
GPS Modernization Program Increasing System Capabilities w Increasing Defense / Civil Benefit Block IIA/IIR Block III Block IIR-M • Basic GPS • Standard Service • Single frequency (L1) • Coarse acquisition (C/A) code navigation • Precise Service • Y-Code (L1Y and L2Y) • Y-Code navigation • IIR-M: IIA/IIR capabilities plus • 2nd civil signal (L2C) • M-Code (L1M and L2M) • Currently being launched • IIF: IIR-M capability plus • 3rd civil signal (L5) • Begin launch 2009 • Backward compatibility • 4th civil signal (L1C) • Increased accuracy • Assured availability • Increased security • System survivability • Begin launch ~2014 Block, IIF
Modernized GPS – Civil Signals • Second civil signal (“L2C”) • Designed to meet commercial needs • Higher accuracy through ionospheric correction • Higher effective power and improved data structure reduce interference, speed up signal acquisition, enable miniaturization of receivers, may enable indoor use • Began with GPS Block IIR-M in Sep 2005; 24 satellites: ~2014 • Third civil signal (“L5”) • Designed to meet demanding requirements for transportation safety (safety-of-life) • Uses highly protected Aeronautical Radio Navigation Service (ARNS) band • Begins with GPS Block IIF • First launch: ~2008 (GPS IIR-M Demo); ~2009 (GPS IIF); 24 satellites: ~2016 • Fourth civil signal (“L1C”) • Designed with international partners to enable GNSS interoperability • Begins with GPS Block III • First launch: ~2014; 24 satellites: ~2021
Benefits of GPS Modernization • System-wide improvements in accuracy, availability, integrity, and reliability for all users • Higher standalone accuracy • Augmentations likely will still remain • More robust against interference • Operational capability for second (L2C) and third (L5) civil signals • In combination with GPS IIR-M and IIF satellites • Delivers L1C for interoperability with Galileo and other GNSS • Improved indoor, mobile, and urban use
GPS Program Update • New GPS Operational Control Segment -- September 2007 • Upgrading GPS ground segment – OCX – 2012 - 2016 • Will implement full functionality for L2C and L5 • Contract awarded – January 2008 • Acquiring next generation of GPS satellites – GPS IIIA • In source selection - anticipate contract award – early 2008 • GPS SPS Performance Standard update in progress – Apr 08
Continuous Performance Improvement Key measures of Effectiveness to evaluate GPS services • Accuracy • Bounded inaccuracy • Assured Availability • Integrity • Resistance to RF Interference/Jamming Accuracy Performance Standard Decreasing range error Year
. Augmentation Systems Improves basic GPS performance (e.g. accuracy, integrity, etc) • Sub-centimeter accuracy for geodesy, geology, etc. • 2-5 cm accuracy for real-time positioning, surveying, etc. • <3 m vertical accuracy with 6 second time to alarm for aviation SBAS GBAS
Global Differential GPS System International GNSS Service Augmentations Satellite-Based Augmentations Ground-Based Augmentations (NDGPS, CORS, LAAS, etc.)
Satellite-Based Augmentations • Geostationary satellites provide regional coverage • GPS-like signals enable simplified receivers • International Partner Service Providers • US (WAAS), Europe (EGNOS), Japan (MTSAT), and India (GAGAN) • WAAS operational – Jul 03; Expanding capability with L5 • GPS-based EGNOS leading way for Galileo • Independent signal monitoring supports the interests of each individual State • International assured aviation integrity standard
U.S. GPS Augmentation Update • Wide Area Augmentation System commissioned in 2003 • Two GEO satellites launched in 2005 (Galaxy XV & Anik F1R) • Provides dual satellite coverage over the U.S. • Service expanded into Canada and Mexico – operational Sep 07 • New reference stations (5 Mexico and 4 Canada) • Nationwide DGPS System (NDGPS) • Maritime, rail, survey, precision agriculture, weather forecasting, and resource management • International standard in over 50 countries • DOT completing assessment for inland component • Maritime NDGPS component remain operational
Overview Systems Applications Policy International Cooperation
Commercial GNSS Applications Span A Wide Range of Economic Activities Satellite Operations Power Grid Management Personal Navigation Surveying & Mapping Trucking & Shipping Aviation Communications Network Synchronization Recreation Railroads Fishing & Boating Offshore Drilling 16
Civil GNSS Applications • Enabling technology • New applications emerging every day • $68 Billion industry worldwide by year 2010 • Wide use in transportation safety • Aviation, maritime, railroad, highway, etc. • Potential to reduce land-based navigation systems • Centerpiece of future transportation infrastructure • Wide range of civil uses • Telecommunications, surveying, law enforcement, emergency response, agriculture, mining, etc. • Used in conjunction with remote sensing
Aviation • Reliable and accurate positioning worldwide • Reduced delays • More fuel-efficient routes • Increased system capacity with enhanced safety Maritime
Maritime • Large ships, fishing & recreation boats • Harbor entrance and approach • Regardless of visibility • Hydrographic Survey • Buoy Positioning, etc.
Railroads • Enhances safety • Reduces accidents • Increases capacity and efficiency • Closer train spacing reduces investments • Reduces fuel consumption • Rapid rail structure and condition mapping • Improves maintenance capability • Increased efficiency and capacity through positive train control • Tracking location of vehicles/containers • Rapid rail structure and conditioning mapping
GNSS Applications –Improving Highway Operations Vehicle Infrastructure Integration (VII) • Improving safety and reducing congestion will require more efficient management of the roadway system • Vehicle-highway information exchange is key to improved management and operation of the transportation network • Provide information on traffic conditions, crashes, adverse weather and road conditions, etc.
GNSS Applications – Automatic Vehicle Location • Cargo Fleet Tracking • Improves safety and security • Fleet Control/Dispatch • Increases fuel savings • Improves asset management • Emergency Operations • Reduces response times • Reduces injury and property loss • Road Maintenance • In Vehicle Navigation • Determines accurate position • Reduces air pollution
Surveying/Mapping/GIS • Sub-centimeter accuracy • 100%-300% savings in time, cost, labor • Most major development projects require surveying • Rural electrification • Telecom tower placement • Pipeline installation • Dam construction • Port dredging operations • Oil, gas, and mineral exploration • Flood plain mapping
Precision Agriculture • Maximize use of resources • Optimize plowing of crop rows • Tailor applications of seeds, fertilizer, water, pesticides • Improve management of land, machinery, personnel, time • Greater crop yields • Net benefit: $5-14 per acre • Minimize environmental impacts • Localize identification and treatment of distressed crops that reduces chemical use • Precisely level fields to prevent fluid runoff
Environmental Protection • Forest protection • Logging enforcement (e.g., Mato Grosso) • Firefighting • IBAMA: 230 GPS units • Fishing boundary enforcement • Endangered species and habitat preservation • Natural resource management • Hazardous cleanup • Oil spills, toxic waste • Atmospheric modeling
Scientific Research • Monitoring geological change • Glaciers, tectonic plates, earthquakes, volcanoes • Wildlife behavior • Atmospheric modeling • Water vapor content • Oceanic studies • Tidal patterns • Surface mapping • Time transfer • Space Exploration
Timing • GPS offers an inexpensive alternative to costly, high maintenance timing equipment • Telecommunications network synchronization & management • Phones, pagers, wireless systems • LANs, WANs, Internet • Financial transactions, e-commerce • Electrical power grid management & fault location
New Applications Emerging Every Day • Wireless/mobile applications • Child/pet tracking • Spacecraft control • Power grid management • Open pit mining • Automatic snowplow guidance
Overview Systems Applications Policy International Cooperation
U.S. Policy History • 1978: First GPS satellite launched • 1983: U.S. President offers free civilian access to GPS • 1996: First U.S. GPS Policy. Established GPS a dual-use system under joint civil/military management • 1997: U.S. Congress passes law requiring civil GPS to be provided free of direct user fees • 2000: U.S. President set Selective Availability to “Zero” • 2004: U.S. President issued U.S. Policy on Space-Based PNT • 2007: U.S. President announces Selective Availability will no longer be built into modernized GPS III satellites
National Space-Based PNTOrganization Structure WHITE HOUSE Defense Transportation NATIONALEXECUTIVE COMMITTEEFOR SPACE-BASED PNT Executive Steering Group Co-Chairs: Defense, Transportation State ADVISORY BOARD Sponsor: NASA Agriculture Commerce Homeland Security NATIONAL COORDINATION OFFICE Host: Commerce Interior Joint Chiefs of Staff NASA GPS International Working Group Chair: State Engineering Forum Co-Chairs: Defense, Transportation Ad HocWorking Groups
National Space-Based PNT Executive Committee • National Space-Based PNT Executive Committee established in 2004 U.S. Policy • Chaired by Deputy Secretaries of Defense and Transportation • Membership includes: State, Agriculture, Interior, Commerce, Homeland Security, JCS and NASA • Supported by a new National Coordination Office • National Coordination Office (NCO) was established with staff from each member agency • Director, Deputy Director, and 6 staff
National Coordination Office • Facilitates information sharing, coordination, and issue resolution regarding space-based PNT programs, requirements, budgets, and policies across all U.S. Agencies • Facilitates coordination among Agencies regarding plans to modernize U.S. space-based PNT infrastructure • Conducts or oversees space-based PNT studies, analyses and projects with a U.S. National benefit • Informs state, local and international GNSS users and participants of National Executive Committee activities
Advisory Board • Conducts assessments; makes recommendations to the Executive Committee in support of national policy goals and objectives for space-based PNT • Twenty-four members; 6 international members • Met twice in 2007 • Next meeting: 27-28 March 2008
Program Oversight Five-Year National Plan National PNT Architecture GPS Modernization Civil GPS Funding GPS Augmentations Nationwide Differential GPS Distress Alerting Satellite System (DASS) International Engagement Bilateral Multilateral Spectrum Management Interference Detection and Mitigation Plan Spectrum Protection Plan Outreach Publications, websites, exhibits Conferences and other venues Coordination of U.S. message EXCOM Activities
Selective Availability • Selective Availability (SA) feature was used in the past to intentionally degrade civilian GPS service • First fully implemented in 1995 • Discontinued (set zero) by the President in May 2000 • Has not been used since then • USG made decision that the next generation of GPS satellites (GPS III) will be built without the Selective Availability feature • Secretary of Transportation Peters announced decision at ICAO General Assembly on 18 September 2007
2004 U.S. Policy • Demonstrates U.S. Government commitment to space-based PNT for all stakeholders • Provides framework for public/private decision makers • Improves ability to coordinate efforts across the various agencies of the U.S. Government • Creates basis for meaningful dialogue between service providers and end users • Promotes common standards for worldwide interoperability
Overview Systems Applications Policy International Cooperation
Active Diplomacy • Results of over a decade of bilateral/multilateral diplomatic efforts are beginning to be seen: • New satellite constellations and regional augmentation systems, while independently owned and operated, are being designed to be compatible and interoperable • Coordination mechanisms are being created to promote interoperability, promote GNSS use, and ensure a level playing field in the global marketplace
Compatibility - Interoperability • “Compatible” –ability of U.S. and non-U.S. space based PNT services to be used separately or together without interfering with each individual service or signal • Compatibility should also involve spectral separation between each system’s authorized service signals and other systems’ signals • “Interoperable” – ability of civil U.S. and non-U.S. space-based PNT services to be used together to provide the user better capabilities than would be achieved by relying solely on one service or signal Interoperable = Better Together than Separate
Provide civil GPS and augmentations free of direct user fees on a continuous, worldwide basis Provide open, free access to information needed to develop equipment Improve performance of civil GPS and augmentations to meet or exceed that of international systems Encourage international development of PNT systems based on GPS Seek to ensure international systems are interoperable with civil GPS and augmentations Address mutual security concerns with international providers to prevent hostile use U.S. Policy Principles Outlined in 2004 Presidential Policy on Space-Based Positioning, Navigation, and Timing (PNT)
GPS-Galileo Cooperation • 2004 US-EU agreement provides a solid foundation for cooperation • Action now divided among four working groups set up by the agreement: • Technical, trade, and security issues working groups have already met • Improved new civil signal (MBOC) adopted in July 2007 June 26, 2004, press conference at U.S.-EU Summit in Ireland (U.S. Sec. of State Colin Powell, Irish Foreign Minister Brian Cowen, EU Vice-President Loyola De Palacio)
GPS-GLONASS Cooperation • U.S.- Russia Joint Statement issued in Dec 2004 • Several productive technical working group meetings have been held: • Russia WG-1 chair proposed adopting two new civil CDMA signals at L1, L5 which will be interoperable with GPS • Negotiations for a U.S.-Russia agreement on satellite navigation cooperation have been underway since late 2005: • Next meeting will be held in early 2008
U.S. – Japan Cooperation • Japan’s status as a world leader in GPS applications and user equipment makes it an important partner • Regular policy consultations and technical meetings on GPS cooperation have been held since 1996 and led to the 1998 Clinton-Obuchi Joint Statement • Both countries have benefited from the close relationship: • QZSS is designed to be compatible and interoperable with GPS • U.S. working with Japan to set up QZSS monitoring stations in Hawaii and Guam
U.S.-India Cooperation • Policy and technical consultations on GPS cooperation underway since 2005 • One aim is to ensure interoperability between GPS augmentation system WAAS and India’s planned GAGAN augmentation system based on GPS • Another important topic is ionospheric distortion and solutions • U.S.-India Joint Statement on GNSS Cooperation • Issued in Feb 2007 in Washington • Bi-lateral meeting held in Bangalore in Sep 2007
U.S.-Australia Cooperation • Long history of GPS cooperation between U.S. and Australia • U.S.-Australia Joint Delegation Statement on Cooperation in the Civil Use of GPS signed Apr 19 • Cooperation expands upon existing efforts to ensure interoperability between GPS and Australia's Ground-based Regional Augmentation System (GRAS) and Ground Based Augmentation System (GBAS) • U.S. Coast Guard NAVCEN posts a daily Position Dilution of Precision (PDOP) report in response to Australia’s concerns over planned GPS outages
International Committee on Global Navigation Satellite Systems (ICG) • Emerged from 3rd UN Conference on the Exploration and Peaceful Uses of Outer Space Jul 1999 • Promote the use of GNSS and its integration into infrastructures, particularly in developing countries • Encourage compatibility and interoperability among global and regional systems • Members include: GNSS providers (U.S., EU, Russia, China, India, Japan), international organizations, and international associations