Application and Importance of L2C

1
Application and Importance of L2C

• Tom Stansell
• Stansell Consulting
• Tom_at_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

3
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.
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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
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.
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L2C Expected in 2003
THE WHITE HOUSEOffice 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, cant 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
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 Snow Director of
Sales and Marketing, NCSA Land Survey Thales
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 dont 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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Potential WAAS Availability of 99.9 APV 1.5
Coverage
100
L1L2L5
100
100
10.58
L1L2
L1L5
L2L5
97.58
58.45
49.25
L1
L2
L5
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
23
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