Application and Importance of L2C Tom Stansell Stansell Consulting CGSIC, 10 March 2004

The L2C Initiative  1996 – Presidential Decision Directive  "encourage acceptance and integration of GPS into peaceful civil, commercial and scientific applications worldwide; and to encourage private sector investment in and use of U.S. GPS technologies and services."  “committed the U.S. to discontinuing the use of SA by 2006 with an annual assessment”  With S/A off, ionospheric error becomes significant  1998 – V.P. Gore announced L2 as 2 nd civil signal  1999 – V.P. Gore “for launch beginning in 2003”  2001 – L2C was defined & presented to the public  Two public meetings, ION paper, GPS World article, ICD-GPS-200 update, NAVCEN WEB posting

S/A Off  Encourage Civil GPS THE WHITE HOUSE Office of the Press Secretary For Immediate Release May 1, 2000 STATEMENT BY THE PRESIDENT REGARDING THE UNITED STATES' DECISION TO STOP DEGRADING GLOBAL POSITIONING SYSTEM ACCURACY Today, I am pleased to announce that the United States will stop the intentional degradation of the Global Positioning System (GPS) signals available to the public beginning at midnight tonight. We call this degradation feature Selective Availability (SA). This will mean that civilian users of GPS will be able to pinpoint locations up to ten times more accurately than they do now. GPS is a dual-use, satellite-based system that provides accurate location and timing data to users worldwide. My March 1996 Presidential Decision Directive included in the goals for GPS to: "encourage acceptance and integration of GPS into peaceful civil, commercial and scientific applications worldwide; and to encourage private sector investment in and use of U.S. GPS technologies and services." To meet these goals, I committed the U.S. to discontinuing the use of SA by 2006 with an annual assessment of its continued use beginning this year. The decision to discontinue SA is the latest measure in an on-going effort to make GPS more responsive to civil and commercial users worldwide. Last year, Vice President Gore announced our plans to modernize GPS by adding two new civilian signals to enhance the civil and commercial service. This initiative is on-track and the budget further advances modernization by incorporating some of the new features on up to 18 additional satellites that are already awaiting launch or are in production. We will continue to provide all of these capabilities to worldwide users free of charge.

Promise of a Second Civil Signal THE WHITE HOUSE Office of the Vice President _____________________________________________________________________________________________ For Immediate Release March 30, 1998 VICE PRESIDENT GORE ANNOUNCES ENHANCEMENTS TO THE GLOBAL POSITIONING SYSTEM THAT WILL BENEFIT CIVILIAN USERS WORLDWIDE Washington DC -- Vice President Gore today announced that a second civilian signal will be provided by the U.S. Global Positioning System. "This new civilian signal will mean significant improvements in navigation, positioning and timing services to millions of users worldwide -- from backpackers and fishermen to farmers, airline pilots, and scientists," the Vice President said. The addition of a second civil signal represents a strong commitment by the United States to civil GPS users worldwide and is a major step in the evolution of GPS as a global information utility. Much like the Internet, GPS is becoming increasingly indispensable for navigation, positioning, and timing by users around the world. Also like the Internet, GPS has become an engine of economic growth and efficiency as businesses and consumers continue to develop new and creative applications of this technology.

L2C Expected in 2003 THE WHITE HOUSE Office of the Vice President For Immediate Release January 25, 1999 VICE PRESIDENT GORE ANNOUNCES NEW GLOBAL POSITIONING SYSTEM MODERNIZATION INITIATIVE Initiative Would Make Global Positioning System More Accessible to Civilian Users Washington, DC -- Vice President Gore announced today a $400 million new initiative in the President's balanced budget that will modernize the Global Positioning System (GPS) and will add two new civil signals to future GPS satellites, significantly enhancing the service provided to civil, commercial, and scientific users worldwide. "The United States is proud to be a leader in the development of the Global Positioning System -- a wonderful example of how technology is benefiting our citizens and people around the world," Vice President Gore said. "This initiative represents a major milestone in the evolution of GPS as a global information utility, and will help us realize the full benefits of this technology in the next millennium." This initiative is only the most recent step in an ongoing public-private effort to make GPS more responsive to the needs of civilian users worldwide. National and regional GPS-based networks are now being created by governments and industry around the world to help guide everything from planes, trains, ships, and cars to tractors, snowplows, earthmovers, and mining equipment. As announced by Vice President Gore last March, the second civil signal will be located at MHZ along with the current military signal, and will be available for general use in non-safety-critical applications. The President's Budget supports implementing this new signal on the satellites scheduled for launch beginning in 2003.

L2C Availability and Impact  ~18 L2C signals should be available before 2011  In time for the next solar maximum  L2C availability will precede L5 by almost 3 years  By 2011 to 2013 there will be enough L2C signals for new commercial and consumer applications  2013 to 2015 for L5  But, current survey and scientific users can benefit immediately, one satellite launch at a time  L2 access today is costly, can’t track high ionospheric rates, and is 10 to 30 dB weaker than with L2C  Some manufacturers already are making receivers with L2C capability

Why L2C Gives Immediate Benefits  Whereas a new signal frequency must be available from 18 to 24 satellites before it is of much value  All dual-frequency receivers today track L2  The first IIR-M satellite will provide a stronger and better L2 signal, which can be used immediately  Thus, the transition to L2C can begin now, one launch at a time  Pilot signal code and carrier measurements are the main benefits for these applications  Message data is of secondary importance at most  Message uncertainty will not delay applications

Estimated L2C and L5 Availability

250 Year Record of Sunspot Activity Not very severe

Next Solar Peak Could Be Worse

Tracking Advantage of L2C L2C

Survey and Scientific Applications  Estimated 100,000 high precision receivers  Prices range from $6K for decimeter to $15K for cm  Rapid growth of centimeter & decimeter applications:  Survey and agriculture  Real time machine control  Infrastructure monitoring (bridges, dams, skyscrapers)  Many thousands of scientific receivers  Geodesy (coordinate system, continental drift, etc.)  Earthquake and volcano research and monitoring  Weather research and prediction  All require L1 and L2 signals

L2C Marketing Strategy (1 of 2)  Based on expected L2C availability in 2004, each company has developed an L2C strategy, e.g.,  Trimble  NovAtel  Thales  What is the winning strategy?

New Trimble Product with L2C Now

Another Trimble Product with L2C

NovAtel L2C Recommendation Establishing the new signals in space ASAP, even as “test signals”, is the best thing for our industry. This encourages innovation and new product development. Pat _____________________________ Patrick Fenton P.Eng. CTO NovAtel Inc.

Cautious Thales L2C Position We have therefore chosen to introduce L2C capability when we believe that our customers could experience a clear operational advantage out of this enhancement, which is not the case to date. Our focus is on providing customers the solutions they need - not selling them more technology than what really benefits them. Best Regards, Robert Dr. Robert Snow Director of Sales and Marketing, NCSA Land Survey Thales Navigation

L2C Marketing Strategy (2 of 2)  Prediction: actual and perceived benefits and competition will drive all manufacturers of precision GPS receivers to use L2C sooner rather than later  Researchers also look forward to having three frequencies, L1, L2, and L5

Aviation Use of L2C ?  Aviation authorities currently don’t support L2C  It is not in an ARNS band  Waiting for L5 which is an ARNS frequency  However, some practical interest is developing  Earlier availability of dual-frequency advantages  Redundant navigation signal  Unlikely to be accepted

100% 10.58% 97.58%58.45% 49.25% L 1 +L 2 +L 5 L 1 +L 2 L 1 +L 5 L 2 +L 5 L1L1 L2L2 L5L5 Potential WAAS Availability of 99.9% APV 1.5 Coverage Shau-Shiun Jan, Department of Aeronautics and Astronautics, Stanford University

L1 Only vs. Dual Frequency WAAS 97.58% in CONUS100% in CONUS The key differences are accuracy, availability, continuity, and coverage beyond CONUS! Shau-Shiun Jan, Department of Aeronautics and Astronautics, Stanford University

WAAS Availability with L1 Only

Dual-Frequency WAAS Availability

Other Dual & Single Frequency Uses  Examples  Car navigation  Marine  Handheld  E-911  L2C long-term future depends on Galileo schedule and signal choices  Will Galileo signals precede full L2C availability?  Build receivers for signals from only half the satellites?  Galileo schedule and signal choices may cause most long-term future dual frequency receivers to be L1/L5  L2C use may be limited to multi-frequency receivers

Summary  L2C is useful immediately for dual frequency high precision survey and scientific applications  Much more robust signal, better ionosphere tracking  Preserves the legacy of L1/L2 antenna designs and millions of archived measurements  Value increases over the next 7 to 10 years  Meets Presidential Decision Directive  Long term future depends on Galileo  Manufacturers will favor receivers for common signals  Because of ionosphere and Galileo commonality, L1 will remain the preferred single frequency signal