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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

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Presentation on theme: "GPS and GNSS Research at Stanford University Sam Pullen, Per Enge, Todd Walter, Sherman Lo, Jason Rife, and Brad Parkinson Stanford University"— Presentation transcript:

1 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

2 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 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 GPS People at Stanford

3 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)

4 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

5 GPS Overview  24+ Satellites  12 Hour Orbits  6 Orbital Planes  1 Way Ranging  Atomic Clocks  Spread Spectrum  Global 3D Positioning   100 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

6 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 > 10 m  Availability and Continuity Must Meet Requirements

7 Aircraft Guidance Goals  Key Elements:  Accuracy  Availability  Integrity  Continuity Integrity: Accuracy < Protection Limit Courtesy: Rich Fuller

8 LAAS Components Courtesy: FAA

9 Geostationary Satellites GEO Uplink Stations Network of Reference Stations Master Stations WAAS Components Courtesy: FAA

10 WAAS

11 WAAS and LAAS extend GPS Navigation Capabilities CAT I 200 ft DH L-NAV V-NAV 350 ft DH NPA CAT II 100 ft DH CAT III 0-50 ft DH GLS 250 ft DH DH = Decision Height Requirement: Better Accuracy, Tighter Bounds Benefit: Lower DH Courtesy: Sherman Lo WAAS Today WAAS Future LAAS Near-Future LAAS End-State

12 GPS Research Timeline at Stanford 1990 Development of LAAS carrier- smoothed code architecture 199520002004 Flight testing of early IBLS and WAAS prototypes 737 IBLS-guided autolands in Central CA WAAS flight- test validation (Lake Tahoe) RAIM, IBLS, WAAS concept development Completion of example LAAS ground system design Development and validation of WAAS integrity equation Beginning of JPALS and LORAN research WAAS NSTB prototype development and testing LAAS IMT prototype development and testing FAA LAAS Integrity Panel (LIP) formed FAA WAAS Integrity and Performance Panel (WIPP) formed FAA WAAS Certification (July 2003) FAA Awards CAT I LAAS Ground System Contract GPS/UWB RFI Testing Alaska and Moffett Field Flight Tests

13 NSTB (FAATC/SU WAAS Prototype)

14 NSTB Accuracy Comparison (Center of Country)

15 NSTB Performance at Cold Bay, Alaska

16 NSTB Performance at Cold Bay, Alaska (2)

17 Queen Air Flight Test Aircraft

18 Final approach pathway Flight path vector Ground- speed Distance to touchdown Heading Vertical deviation Horizon line Horizontal deviation Bank angle Tunnel Display Courtesy: Keith Alter

19 Localizer Approaches at Moffett Field Courtesy: Sharon Houck

20 Integrity Beacon Landing System (IBLS)

21 United/Boeing 737 Autoland Results 110 Automatic Landings of Boeing 737-300 (Crows Landing, CA) 

22 LAAS Architecture Overview Corrected carrier-smoothed -code processing  VPL, LPL calculation airport boundary Cat I Airport Pseudolites (optional) LGF Ref/Mon Rcvrs. and Processing VHF Data Broadcast GPS Antennas Cat I/II/III VHF Antennas

23 IMT Functional Flow Diagram

24 “Evil Waveform” Failure Mode Example Comparison of Ideal and “Evil Waveform” Signals for Threat Model C C/A PRN Codes Chips Volts Correlation Peaks Code Offset (chips) Normalized Amplitude   1/f d Threat Model A: Digital Failure Mode (Lead/Lad Only:  ) Threat Model B: Analog Failure Mode (“Ringing” Only: f d  ) Note:

25 “  -Tests” (C EARLY -C LATE ) “Ratio Tests” (C LATE / C PROMPT ) C EARLY C LATE C PROMPT Code Offset (chips) Normalized Amplitude Multicorrelator EWF Monitor

26 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…” 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…” INITIAL CLIMB OCEANIC / EN ROUTE TERMINAL NON- PRECISION APPROACH ARRIVALDEPARTURE TAKE OFF TAXI CAT ICAT IICAT IIIA 200 0 100 MISSED APPROACH Category (CAT) I - 200 FT DH and 1/2 Mile Vis CAT II - 100 FT DH and 1/4 Mile Vis CAT IIIA - 0 FT DH and 700 FT Vis ENROUTE

27 JPALS Operational Environments Shipboard Tactical Fixed Base Special Missions

28 Aircraft Carrier Landing Targeted Hook Touch Down Point Between 2 & 3 Wires Hook engages 3 wire 1 Wire 2 Wire 3 Wire 4 Wire

29 SRGPS “At Sea” Challenge Yardarm (Port) Antenna Yardarm (Starboard) Antenna Yardarm Antennas

30 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)


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