GPS and GNSS Research at Stanford University

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GPS and GNSS Research at Stanford University

• Sam Pullen, Per Enge, Todd Walter, Sherman Lo,
  Jason Rife,
• and Brad Parkinson
• Stanford University
• http//scpnt.stanford.edu

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GPS People at Stanford
Aero/Astro Faculty Per Enge, Brad Parkinson, Bob
Twiggs, Dave Powell Senior Research Engineers
Todd Walter, Sam Pullen Research Associates Eric
Phelts, Sherman Lo, Jason Rife Research
Engineers Ming Luo, Juan Blanch, Godwin Zhang,
Doug Archdeacon Postgraduate Researcher Jiyun
Lee Consultant A.J. Van Dierendonck PhD
Students Lee Boyce, Ung-Suok Kim, Michael
Koenig, Seebany Datta- Barua, Tsung-Yu Chiou,
Dave DeLorenzo, Ju-Yong Do, Hiroyuki Konno,
Alexandru Ene, Di Qiu, Alex Chen, Grace Gao,
Eui-Ho Kim, Nikolai Alexeev, Mohamad
Charafeddine Support Tom Langenstein (SCPNT),
Sherann Ellsworth, Dana Parga Allied Efforts (not
including those within SCPNT) ARL Profs. Steve
Rock and Bob Cannon Hybrid Systems Lab Prof.
Claire Tomlin Mechanical Engineering Prof.
Chris Gerdes Geophysics Prof. Paul
Segal University of Colorado Prof. Dennis
Akos Illinois Institute of Technology Prof.
Boris Pervan University of Minnesota Prof.
Demoz Gebre-Egziabher MIT Prof. Jonathan How
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NASA and FAA-Funded GPS Ph.D. Graduates
Penny Axelrad Faculty of University of
Colorado Changdon Kee Faculty of Seoul National
University Boris Pervan Faculty of Illinois
Inst. of Technology Glenn Lightsey Faculty of UT
Austin Demoz Gebre-Egziabher Faculty of Univ. of
Minn. Gabe Elkaim Faculty of UC Santa Cruz
Shau-Shiun Jan Faculty in Taiwan The following
founded IntegriNautics, a company specializing in
high integrity positioning Clark Cohen
President and founder Stewart Cobb
co-founder Dave Lawrence co-founder Paul
Montgomery Integrinautics Mike O'Connor
Integrinautics Tom Bell Integrinautics (now at
LM) The following founded Traxsis, a
company specializing in internet based
positioning Roger Hayward President and
founder Jock Christie Traxsis co-founder Rich
Fuller Traxsis The following founded Nav3D, a
company specializing in 3-D perspective
displays Andy Barrows President and
founder Keith Alter Nav3D co-founder Awele
Ndili Cofounder of M Shift
Sam Pullen Senior Research Engineer leading
the LAAS effort at Stanford. Matt Rabinowitz
Co-Founder of Rossum Ping-Ya Ko Engineer in
Taiwan Y.C. Chao Co-Founder of
Televigation Yeou-Jyh Tsai Engineer at ITRI in
Taiwan Ran Gazit Engineer at Rafael in
Israel Jaewoo Jung Trimble Navigation Andy
Rekow Engineer at John Deere Eric Phelts
Research Associate WAAS LAAS Harris Teague
Seagull Technology Inc. Eric Abbott Engineer
with L3 Communications Hiro Uematsu Engineer
with NASDA Donghai Dai Engineer with
Televigation Sharon Houck Engineer at Seagull
Technology Andrew Hansen Engineer at
Meta-VR Konstantin Gromov Engineer at JPL Eric
Olsen Engineer at Johns Hopkins APL Gang Xie
Engineer at Motorola Sherman Lo Research
Associate (LORAN) Jenny Gautier Research
Associate (JPALS)
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Projects at Stanford

• FAA
• Wide Area Augmentation System
• Local Area Augmentation System
• LORAN Datalink and GPS Backup
• DoD
• JPALS (land and sea-based versions)
• DoT
• UWB Analysis and Testing of Interference to GPS
• Office of Technology and Licensing
• Atlantis
• John Deere
• Autonomous Tractor

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GPS Overview

• 24 Satellites
• 12 Hour Orbits
• 6 Orbital Planes
• 1 Way Ranging
• Atomic Clocks
• Spread Spectrum
• Global 3D Positioning
• lt100 m Horiz.

• Requires at Least 4 Satellites in View
• Declared Fully Operational in July 1995
• Operated by U.S. Air Force in Colorado Springs, CO

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Why Augmentation?

• Current GPS and GLONASS Constellations Cannot
  Support Requirements For All Phases of Flight
• Integrity is Not Guaranteed
• All satellites are not monitored at all times
• Time-to-alarm is from minutes to hours
• No indication of quality of service
• Accuracy is Not Sufficient
• Even with SA off, vertical accuracy gt 10 m
• Availability and Continuity Must Meet Requirements

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Aircraft Guidance Goals

• Key Elements
• Accuracy
• Availability
• Integrity
• Continuity

Courtesy Rich Fuller
Integrity Accuracy lt Protection Limit
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LAAS Components
Courtesy FAA
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WAAS Components
Courtesy FAA

• Geostationary Satellites
• GEO Uplink Stations

• Network of Reference Stations
• Master Stations

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WAAS
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WAAS and LAAS extend GPS Navigation Capabilities
WAAS Today
NPA
WAAS Future
L-NAV V-NAV 350 ft DH
LAAS Near-Future
Benefit Lower DH
GLS 250 ft DH
CAT I 200 ft DH
LAAS End-State
CAT II 100 ft DH
CAT III 0-50 ft DH
Courtesy Sherman Lo
Requirement Better Accuracy, Tighter Bounds
DH Decision Height
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GPS Research Timeline at Stanford
Development and validation of WAAS integrity
equation
Beginning of JPALS and LORAN research
FAA LAAS Integrity Panel (LIP) formed
Development of LAAS carrier-smoothed code
architecture
Completion of example LAAS ground system design
FAA WAAS Integrity and Performance Panel (WIPP)
formed
RAIM, IBLS, WAAS concept development
1990
1995
2000
2004
WAAS NSTB prototype development and testing
Flight testing of early IBLS and WAAS prototypes
FAA WAAS Certification (July 2003)
GPS/UWB RFI Testing
WAAS flight-test validation (Lake Tahoe)
LAAS IMT prototype development and testing
FAA Awards CAT I LAAS Ground System Contract
737 IBLS-guided autolands in Central CA
Alaska and Moffett Field Flight Tests
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NSTB (FAATC/SU WAAS Prototype)
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NSTB Accuracy Comparison (Center of Country)
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NSTB Performance at Cold Bay, Alaska
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NSTB Performance at Cold Bay, Alaska (2)
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Queen Air Flight Test Aircraft
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Tunnel Display
Bank angle
Final approach pathway
Flight path vector
Vertical deviation
Horizon line
Ground- speed
Heading
Courtesy Keith Alter
Distance to touchdown
Horizontal deviation
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Localizer Approaches at Moffett Field
Courtesy Sharon Houck
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Integrity Beacon Landing System (IBLS)
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United/Boeing 737 Autoland Results
110 Automatic Landings of Boeing 737-300 (Crows
Landing, CA)
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LAAS Architecture Overview
airport boundary
Corrected carrier-smoothed -code processing -
VPL, LPL calculation
Cat I/II/III
Cat I
GPS Antennas
VHF Antennas
Airport Pseudolites (optional)
LGF Ref/Mon Rcvrs. and Processing
VHF Data Broadcast
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IMT Functional Flow Diagram
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Evil Waveform Failure Mode Example
Comparison of Ideal and Evil Waveform Signals
for Threat Model C
C/A PRN Codes
Volts
Chips
Note
Threat Model A Digital Failure Mode (Lead/Lad
Only ?)
Threat Model B Analog Failure Mode (Ringing
Only fd?)
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Multicorrelator EWF Monitor
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JPALS Mission Need Statement
JROC validated Mission Need Statement, August
95 a rapidly deployable, adverse weather,
adverse terrain, survivable, maintainable, and
interoperable precision approach and landing
system (on land and at sea) that supports the
warfighter when ceiling and visibility are
limiting factors
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JPALS Operational Environments
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Aircraft Carrier Landing
Targeted Hook Touch Down Point Between 2 3
Wires
1 Wire
2 Wire
3 Wire
Hook engages 3 wire
4 Wire
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SRGPS At Sea Challenge
Yardarm Antennas
Yardarm (Starboard) Antenna
Yardarm (Port) Antenna
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Technical Challenges and Opportunities

• Ionosphere Spatial Decorrelation
• Rare ionosphere storms can create regions of
  unusual spatial decorrelation
• Mitigated by WAAS and LAAS monitoring, but
  observability cannot be guaranteed
• JPALS mitigates with dual-frequency removal of
  ionosphere measurement effects
• Rare-Event Error Bounding
• Tails of GNSS error distributions are fatter
  than predicted by Gaussian
• Insufficient data exists to ID tail
  distributions
• Exploiting GPS and GNSS Modernization
• Signal and integrity enhancements in GPS III
• Galileo ranging satellite constellation
• 2nd civil frequency (GPS L5 / Galileo E5)