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Alternative Positioning, Navigation, and Timing Initiative

Alternative Positioning, Navigation, and Timing Initiative. Leo Eldredge, Manager GNSS FAA Navigation Services Stanford University, California August 2010. Federal Airways – Current. Current Alternative Positioning. ADS-B Surveillance Uses GNSS for primary positioning

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Alternative Positioning, Navigation, and Timing Initiative

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  1. Alternative Positioning, Navigation, and Timing Initiative Leo Eldredge, Manager GNSS FAA Navigation Services Stanford University, California August 2010

  2. Federal Airways – Current

  3. Current Alternative Positioning • ADS-B Surveillance • Uses GNSS for primary positioning • Secondary Surveillance Radar (SSR) Backup • Only a subset of existing SSRs will be retained over the longer term • Multi-Lateration Used to Validate GPS Position • Performance Based Navigation (PBN) Backup • Transport Category Aircraft rely on DME/DME/INS + ILS • Optimized DME retained to support enroute and terminal PBN • ILS retained for final approach guidance • General Aviation aircraft rely on VORs, (not DME equipped) • VOR not an optimum solution for PBN • Continuation of Current State Requires Recapitalization of VORs - ~$1.0B Investment

  4. Navigation Services Evolution Point-to-Point Jet / Victor Routes SIDs / STARs, ILS Primary VOR/DME NDB, VORTAC TACAN Alternate/ Substitute GPS, WAAS Current PBN TRANSITION Q / T Routes Direct TBO Routes RNAV SIDs / STARs RNAV(GPS) RNAV(RNP) GPS, DDI WAAS, LAAS Other GNSS ? DD w/o I ? APNT ? 2025 NextGen

  5. GNSS Enables PBN and ADS-B APNT * Operational requirements are defined for total system accuracy, which is dominated by fight technical error. Position accuracy for these operations is negligible. ** Containment for RNP AR is specified as a total system requirement; value representative of current approvals. Dependent Parallel Approach (DPA) Independent Parallel Approach (IPA) Surveillance Integrity Level (SIL) Navigation Integrity Category (NIC) Navigation Accuracy Category for Position (NACp)

  6. Alternatives Considered (so far!) • Optimized DME Network • Passive Multi-Lateration • Pseudolite • Other?

  7. Optimized DME Network

  8. 1100 DMEs in Current Nework

  9. DME-DME Alternative • Strengths • Leverage existing technology and systems • Least Impact on Avionics for Air Carriers • Weaknesses • Significant Impact on Avionics for General Aviation • General Aviation avionics are unavailable • DME-DME equipped aircraft without Inertial are not currently authorized to fly RNAV/RNP routes • DME-DME, even with Inertial, is not authorized for operations less than RNAV/RNP-1.0 • DME-DME interrogations saturate in very high traffic environments • Will require retention and capitalization of nearly half the VORs unless GA equipped with DME/DME inertial

  10. Wide Area Multi-Lateration

  11. Passive Wide-Area Multi-Lateration (WAM) 1 –Aircraft Transmits ADS-B Signal 6 – Aircraft Uses Own Position for Navigation 5 - TIS-B Sends Position to Aircraft Combined DME/GBT Network 2 - WAM Receives Signal 3 - Aircraft Position Determined 4 - Aircraft Position Sent to GBT’s

  12. WAM Operational at Steamboat Springs

  13. Approaches Histogram NavCanada Independent Verification Of Data

  14. Ground Based Transmitter (GBT) TIS-B (SSR) Control Station FAA TIS-B (MLAT) FIS-B TIS-B with MLAT Concept to use TIS-B to provide ADS-B equipped aircraft with backup positioning for navigation using MLAT

  15. 656 GBT’s for National Coverage Communication Coverage: Not Navigation

  16. Combined Network of DMEs and GBTs

  17. MLAT Alternative • Strengths • Minimal impact on existing avionics for surveillance • Accuracy demonstrated to be within target levels • Compatible with existing WAM systems • Creates additional benefits for users who equip with ADS-B In • Weaknesses • Frequency congestion on 1090ES may limit availability • Integrity monitoring and time to alert necessary to meet navigation requirements may be very challenging • More sites to meet requirements due to limited signal range • Capacity limited in high density traffic environments • Requires a GPS-independent common time reference • Significant investment in processing facilities and terrestrial communications network may be required • Use of MLAT for navigation requires avionics changes

  18. Pseudolites

  19. Pseudolite Alternative Concept • Aircraft Calculates Position • RAIM Based Integrity Solution • Combined Network of DME/GBTs etc • GPS-Independent Time Reference • 1 Hz Message ID and Time @ Transmit • PNT Data Broadcast Channel

  20. Pseudolite Alternative • Strengths • Unlimited capacity • Aircraft based position and integrity solution • Potential to leverage use of existing DMEs and GBTs • Modified to transmit the PL signal • Potential to use a variety of FAA transmitters to increase coverage. • Weaknesses • Minimum of 3 sites required to compute aircraft position • Common GPS-independent timing reference needed • Greatest impact to aircraft avionics • Least mature concept, no avionics in development and no standards • Will require retention and capitalization of nearly half the VORs unless GA equipped with pseudolite avionics

  21. The APNT Initiative within theFAA’s Lifecycle Management System Research and Systems Analysis You Are Here

  22. Questions

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