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Application and Importance of L2C

Tom StansellStansell Consulting

Tom@Stansell.com

CGSIC, 10 March 2004

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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 2nd 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

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S/A Off Encourage Civil GPSTHE 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.

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Promise of a Second Civil Signal

THE WHITE HOUSE

Office of the Vice President_____________________________________________________________________________________________For Immediate Release March 30, 1998

VICE PRESIDENT GORE ANNOUNCESENHANCEMENTS 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.

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L2C Expected in 2003THE WHITE HOUSE

Office of the Vice President

For Immediate ReleaseJanuary 25, 1999

VICE PRESIDENT GORE ANNOUNCES NEW GLOBAL POSITIONING SYSTEM MODERNIZATION INITIATIVE

Initiative Would Make Global Positioning SystemMore 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 1227.60 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.

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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

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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

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Estimated L2C and L5 Availability

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250 Year Record of Sunspot Activity

Not very severe

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Next Solar Peak Could Be Worse

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Tracking Advantage of L2C

-20

-10

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30 35 40 45 50

Input Signal C/No (dB)

Ava

ilab

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(d

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Coherent

Code Aided

Full Bandwidth

L2C

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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

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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?

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New Trimble Product with L2C Now

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Another Trimble Product with L2C

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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.

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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 SnowDirector of Sales and Marketing, NCSA Land SurveyThales Navigation

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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

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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

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100%

100% 100% 10.58%

97.58% 58.45% 49.25%

L1+L2+L5

L1+L2 L1+L5 L2+L5

L1 L2 L5

Potential WAAS Availability of 99.9% APV 1.5 Coverage

Shau-Shiun Jan, Department of Aeronautics and Astronautics, Stanford University

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L1 Only vs. Dual Frequency WAAS

97.58% in CONUS 100% in CONUS

The key differences are accuracy, availability,continuity, and coverage beyond CONUS!

Shau-Shiun Jan, Department of Aeronautics and Astronautics, Stanford University

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WAAS Availability with L1 Only

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Dual-Frequency WAAS Availability

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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

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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