The Global Positioning System and Other Global Navigation Satellite Systems

1
The Global Positioning System and Other Global
Navigation Satellite Systems

• July 19, 2006

Jason Y. Kim, Senior Advisor National Space-Based
Positioning, Navigation, and Timing (PNT)
Coordination Office Washington, D.C., USA
2
Overview

• Introduction
• GPS Performance
• Next-Generation GPS
• Cooperation with Galileo
• Cooperation with GLONASS
• Other Systems

3
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

4
U.S. Augmentations
5
International Augmentations
6
GPS is a Global Public Service

• Free access to civilian signals
• One-way broadcast, like FM radio
• Public domain documentation
• Anyone can develop user equipment
• Worldwide utility providing consistent,
  predictable, dependable performance
• Critical component of global information
  infrastructure
• Owned and operated by the U.S. Government
• Paid for by U.S. taxpayers
• Guided at a national level as multi-use asset
• Acquired and operated by Air Force on behalf of
  USG

Available NowEmpowering the Future
7
Organizational Structure
WHITE HOUSE
Defense
Transportation
NATIONALSPACE-BASED PNT EXECUTIVE
COMMITTEE Co-Chairs Defense, Transportation
State
ADVISORYBOARD Sponsor NASA
Commerce
Homeland Security
NASA
COORDINATIONOFFICE Host Commerce
Joint Chiefs of Staff
8
International Growth in Global Navigation
Satellite Systems (GNSS)

• Europe Galileo, EGNOS
• Russia GLONASS
• Japan MSAS, QZSS
• India GAGAN, IRNS
• Australia GRAS
• China Beidou, Compass
• Canada CWAAS
• Mexico WAAS

• Multilateral International GNSS Service
• Most major nations Differential GPS, geodetic
  reference networks
• Galileo partners China, India, Canada, Mexico,
  Ukraine, Israel, Morocco, South Korea
  discussions ongoing with Brazil, others

9
U.S. Cooperation Strategy
Outlined in Presidential policy on space-based
positioning, navigation, and timing (PNT)

• 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
• Or at a minimum, are compatible
• Address mutual security concerns with
  international providers to prevent hostile use

10
Overview

• Introduction
• GPS Performance
• Next-Generation GPS
• Cooperation with Galileo
• Cooperation with GLONASS
• Other Systems

11
Constellation Status
29 Operational Satellites (Baseline
Constellation 24)

• 16 Block II/IIA satellites
• 12 Block IIR satellites
• Modernizing 8 remaining Block IIR satellites
• 1 Block IIR-M satellite
• Transmitting new L2C signal
• Continuously assessing constellation health to
  determine launch need
• Next launch September 2006
• All future satellites will feature L2C

12
Civil GPS Performance Standards

• U.S. commitments to civil GPS performance are
  documented in the GPS Standard Positioning
  Service Performance Standard (2001)
• In support of the service availability standard,
  24 operational satellites must be available on
  orbit with 0.95 probability (averaged over any
  day). At least 21 satellites in the 24 nominal
  plane/slot positions must be set healthy and
  transmitting a navigation signal with 0.98
  probability (yearly averaged).

13
GPS Signal in Space Performance
Performance Standard
Decreasing range error
Signal in Space RMS URE Root Mean Square User
Range Error
System accuracy far exceeds current standard
14
Ground Segment Expansion for Improved GPS
Accuracy

• Tripling the amount of GPS monitor data to
  improve accuracy and integrity of existing system
• 10-15 improvement in accuracy of GPS data
  broadcast

Schriever AFB


VandenbergAFB
Master Control Station (MCS)
Alternate MCS




15
Improving GPS Performance with Augmentations

• Augmentations enhance GPS accuracy, monitor
  integrity
• Sub-centimeter accuracy for geodesy, geology,
  etc.
• 2-5 cm accuracy for real-time positioning,
  surveying, etc.
• lt3 m vertical accuracy with 6 second time to
  alarm for aviation

16
GPS Performance with WAAS

• U.S. Federal Aviation Administration developed
  the Wide Area Augmentation System (WAAS) to
  provide the necessary accuracy, integrity, and
  availability to support flight operations during
  all phases of flight
• Based on observations from January to March 2006.
  Results are valid when the Localizer Approach
  with Vertical Guidance (LPV) service is
  available. During this time frame, LPV was
  available 98 to 99 of the time.

17
GPS Performance with CORS
Post-Mission Positioning Accuracy
Based on dual-frequency GPS carrier-phase
observations
18
Overview

• Introduction
• GPS Performance
• Next-Generation GPS
• Cooperation with Galileo
• Cooperation with GLONASS
• Other Systems

19
Benefits of Next-Generation GPS

• For civil users
• Higher standalone accuracy
• Robustness against interference
• Improved indoor, mobile, and urban use
• Interoperability with other GNSS constellations
• For military Enhances navigation warfare
• For all users
• System-wide improvements in accuracy,
  availability, integrity, and reliability
• Backward compatibility
• Maintains international competitiveness

20
GPS Modernization Program
Increasing System Capabilities w Increasing
Defense / Civil Benefit
Block IIA/IIR
Block III
Block IIR-M, IIF

• Backward compatibility
• 4th civil signal (L1C)
• Increased accuracy
• Increased anti-jam power
• Assured availability
• Navigation surety
• Controlled integrity
• Increased security
• System survivability

• IIR-M IIA/IIR capabilities plus
• 2nd civil signal (L2C)
• M-Code (L1M L2M)
• IIF IIR-M capability plus
• 3rd civil signal (L5)
• Anti-jam flex power

• Basic GPS
• Standard Service
• Single frequency (L1)
• Coarse acquisition (C/A) code navigation
• Precise Service
• Y-Code (L1Y L2Y)
• Y-Code navigation

21
Second Civil Signal (L2C)

• Freely available since December 2005
• Currently on 1 satellite
• Will be on all future satellites
• Designed to meet commercial needs
• Higher accuracy through ionospheric correction
• Benefits thousands of existing high-end receivers
  using L2 frequency
• Higher effective power and improved data
  structure reduce interference, speed up signal
  acquisition, enable miniaturization of receivers,
  may enable indoor use
• Expected to create over 5 billion in user
  productivity benefits
• Full benefits will arrive after more satellites
  are launched and ground control system is upgraded

1227 MHz (L2) Begins with GPS Block
IIR-M First launch 2005 24 satellites
2014 Signal defined in IS-GPS-200
22
Third Civil Signal (L5)

• Designed to meet demanding requirements for
  transportation safety
• Higher power than other GPS civil signals
• Wider bandwidth improves resistance to
  interference
• Uses highly protected Aeronautical Radio
  Navigation Service (ARNS) band
• New signal structure for enhanced performance
• May also enable global, centimeter-level accuracy
  via multi-signal techniques
• Interoperable with Galileos E5a signal

1176 MHz (L5) Begins with GPS Block
IIF First launch 2007 24 satellites
2016 Signal defined in IS-GPS-705
Currently Reassessing Date
23
Fourth Civil Signal (L1C)

• Designed with international partners to enable
  GNSS interoperability
• Galileo Open Service
• Japans Quasi-Zenith Satellite System
• Possibility for GLONASS?
• Modernized civil signal at L1 frequency
• Aeronautical Radio Navigation Service Band
• Improved code and carrier tracking
• New message structure
• L1 C/A will be retained for backwards
  compatibility

1575 MHz (L1) Begins with GPS Block
III First launch 2013 Signal defined in
IS-GPS-800 (draft)
24
GPS III

• Next-generation satellite bus needed to
  accommodate increasing power requirements
• Revised acquisition strategy
• Spiral development approach to reduce risk,
  increase flexibility
• Separate contracts for space and ground segments
  to ensure best of breed technology
• Civil benefits
• Provides operational capability for L2C and L5
• In combination with GPS IIR-M and IIF satellites
• Delivers L1C for interoperability with Galileo,
  QZSS
• Significant increase in system accuracy
• Improved availability of accuracy with integrity

25
GPS III Proposed Accuracy

• Draft System Specifications
• Includes the effects of receivers
• Threshold low-cost/low-performance receiver
• Objective high-cost/high-performance receiver

ACCURACY (95) THRESHOLD OBJECTIVE
Horizontal 2.5 m 0.5 m
Vertical 4.5 m 1.1 m
Timing 5.7 ns 1.3 ns
26
Overview

• Introduction
• GPS Performance
• Next-Generation GPS
• Cooperation with Galileo
• Cooperation with GLONASS
• Other Systems

27
U.S. GPS Cooperation

• U.S. Government has pursued formal cooperative
  arrangements with Europe, Japan, Russia since
  1996
• To ensure compatibility (non-interference) and
  interoperability with foreign systems
• To protect national security
• To maintain level playing field in the global
  market
• Additional efforts under way with Australia,
  India, Brazil
• Multilateral cooperation established through U.N.
  International Committee on GNSS
• As well as ICAO, IMO, NATO

28
GPS-Galileo Agreement

• In 2004, United States and European Community
  signed historic agreement on GPS-Galileo
  cooperation, recognizing importance of
  compatibility and interoperability for all
  parties
• Agreed to spectrally separate signals for
  military, civilian, and public regulated services
• Agreed to implement a common, open, civil signal
  on both Galileo and GPS III, free of direct user
  fees
• Working groups establishedto continue dialogue
• Compatibility Interoperability
• Trade Commercial Applications
• Next-Generation GNSS
• Security Issues

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)
29
Working Group ACompatibility Interoperability

• Common civil signal for GPS and Galileo (L1C/L1F)
• Centered on L1 frequency used by GPS today
• Agreement includes baseline modulation scheme but
  allows for optimization
• Working Group A spent 21 months collaborating
  towards optimized signal design
• Optimized design (MBOC) achieved in March 2006
• Satisfies all compatibility requirements
• Still awaiting formal acceptance at political
  level
• Time and geodesy
• GPS and Galileo are based on different time
  standards and geodetic reference frames
• Broadcasting GPS-Galileo Time Offset will solve
  time problem
• Geodesy offset considered insignificant (lt5 cm)

30
Improving GNSS Interoperability

• Characteristic
• Common time and reference frames, or broadcast
  offsets
• Common carrier frequencies
• Similar spreadingmodulation spectra
• Common spreading code lengths and common code
  family
• Common data message structure and encoding

• Interoperability Benefit
• Navigation solutions can blend measurements from
  different systems
• Common antenna and receiver front endlower power
  and cost common carrier tracking for higher
  accuracy
• Common-mode dispersive errors removed in
  navigation solution for higher accuracy
• Lower cross-correlation sidelobes for better
  weak-signal reception common receiver processing
  for acquisition and tracking
• Common receiver processing for data message
  decoding and processing

31
Working Group BTrade Commercial Applications

• Agreement includes provisions to maintain level
  playing field in GNSS market
• Recognizes obligations under World Trade
  Organization
• Affirms nondiscriminatory approach to trade in
  GNSS goods/services
• Requires equal access to open signals and
  technical information needed for receiver
  development
• Requires consultations on proposed measures
  affecting GNSS use
• U.S. remains guarded about Galileo business plan
• Not fully revealed due to concessionaire process
• Licensing, royalties on chipsets not well
  understood
• Fee structure for subscription services unknown
• Interface Control Document for Galileo signals
  released in 2006
• Positive step towards providing access to
  technical information
• However, questions remain
• U.S. intends to convene Working Group B in fall
  time frame

32
Other Working Groups

• Working Group C Development of Next Generation
  Civil GNSS
• Harmonization of GPS L2C, L5, and L1C with
  Galileo E5 safety-of-life and commercial services
• Joint monitoring of GPS/Galileo civil signals
• Joint coordination on system maintenance,
  satellite tracking, and back-up capabilities for
  civil applications
• Next-generation augmentation techniques
• Coordination of multilateral efforts to protect
  civil GNSS spectrum through non-ITU bodies (ICAO,
  IMO, etc.)

• Working Group D Security Issues
• Preventing technology transfer to third parties
• Protection of Galileo Public Regulated Service

33
Overview

• Introduction
• GPS Performance
• Next-Generation GPS
• Cooperation with Galileo
• Cooperation with GLONASS
• Other Systems

34
Russia

• United States and Russian Federation issued Joint
  Statement establishing cooperation in 2004
• Continue to provide GPS and GLONASS civil signals
  on a continuous, worldwide basis, free of direct
  user fees
• Cooperate on matters of mutual interest related
  to GNSS in relevant international organizations
  and fora
• Maintain radio frequency compatibility between
  systems
• Promote civil interoperability between systems
• Annual consultations and workinggroups
  established
• Currently pursuing formal cooperation agreement

GLONASS satellite
35
Working Group Meetings

• Working Group 1 GPS-GLONASS Compatibility and
  Interoperability
• October 2005, Moscow
• June 2006, Cocoa Beach
• Pursuing increased GPS-GLONASS radio frequency
  compatibility and user equipment interoperability

• Working Group 2COSPAS/SARSAT (Search and Rescue
  Capability)
• June 2005, London
• March 2006, Moscow
• September 2006, Las Vegas
• Significant progress being made toward technical
  coordination of search and rescue capabilities on
  future satellites

36
Overview

• Introduction
• GPS Performance
• Next-Generation GPS
• Cooperation with Galileo
• Cooperation with GLONASS
• Other Systems

37
Japan

• Worlds largest consumer of GPS technology
• U.S.-Japan cooperation began in 1998
• Initially focused on interoperability with MSAS,
  Japans GEO-based augmentation system
• Promotes common principles such as free market
  access
• Annual plenary meetings, technical working groups
• Current focus is on Quasi-Zenith Satellite System
  (QZSS)
• Regional system to complement, augment GPS over
  Japan
• Will improve performance in urban canyons and
  mountains
• Will freely broadcast GPS L1C, L2C, L5 signals
• GPS-QZSS interoperability achieved

MT-SAT used for MSAS
38
Current View of GNSS Interoperability

• Characteristic
• Common time and reference frames, or broadcast
  offsets
• Common carrier frequencies
• Similar spreadingmodulation spectra
• Common spreading code lengths and common code
  family
• Common data message structure and encoding

• Interoperability Benefit
• Navigation solutions can blend measurements from
  different systems
• Common antenna and receiver front endlower power
  and cost common carrier tracking for higher
  accuracy
• Common-mode dispersive errors removed in
  navigation solution for higher accuracy
• Lower cross-correlation sidelobes for better
  weak-signal reception common receiver processing
  for acquisition and tracking
• Common receiver processing for data message
  decoding and processing

39
International Committee on GNSS

• Multilateral group chartered through United
  Nations
• First meeting December 2005

• Purpose Promote use of GNSS to improve
  efficiency and security of transport, search
  rescue, geodesy, etc., particularly in developing
  countries
• Coordination among providers to improve
  compatibility and interoperability
• Assistance to developing countries in integration
  of PNT services
• Focal point for international information
  exchange
• Forum for addressing future user needs

40
Summary

• U.S. policy encourages worldwide use of civil GPS
  and augmentations
• GPS performance is better than ever and will
  continue to improve
• Augmentations enable high performance today
• New GPS signal now available
• Many additional upgrades scheduled
• International cooperation is a priority
• Compatibility and interoperability are critical

41
Muito Obrigado!
PNT.GOV

• National Space-Based PNT Coordination Office6822
  Herbert C. Hoover Building Washington, D.C.
  20230USA
• pnt.office_at_pnt.gov1 [phone]