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Federal AviationAdministration
Alternative Positioning, Alternative Positioning, Navigation, and Timing Navigation, and Timing
InitiativeInitiative
Leo Eldredge, Manager GNSSLeo Eldredge, Manager GNSSFAA Navigation ServicesFAA Navigation ServicesStanford University, CaliforniaStanford University, CaliforniaAugust 2010August 2010
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2Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
Federal Airways – CurrentFederal Airways – Current
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3Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
Current Alternative PositioningCurrent 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
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4Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
Navigation Services Evolution
Current
2025NextGen
PrimaryVOR/DMENDB, VORTACTACAN
Q / T Routes Direct TBO Routes RNAV SIDs / STARsRNAV(GPS)RNAV(RNP)
Point-to-PointJet / Victor Routes SIDs / STARs, ILS
GPS, DDIWAAS, LAASOther GNSS ?
DD w/o I ?APNT ?
Alternate/Substitute
GPS, WAAS
PBNTRANSITION
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Navigation (> 99.0% Availability)
Surveillance (>99.9% Availability)
Positioning
Accuracy (95%)
Containment(10-7)
SeparationNACp(95%)
NIC(10-7)
GNSS PNT(99.0 – 99.999%)
En Route
*10 nm 20 nm
5 nm308m
(7)1 nm
(5)GPS*4 nm 8 nm
*2 nm 4 nm
Terminal *1 nm 2 nm3 nm
171m(8)
0.6 nm(6)LNAV *0.3 nm 0.6 nm
RNP (AR) *0.1 nm **0.1 nm2.5 nmDPA
171m(8)
0.2 nm(7)
SBAS
LPV 16m/4m 40m/50m 2.5 nm DPA
171m(8)
0.2 nm(7)LPV-200 16m/4m 40m/35m
GLS Cat-I 16m/4m 40m/10m 2.0 nmIPA
121 m(8)
0.2 nm(7)
GBASGLS Cat-III 16m/2m 40m/10m
GNSS Enables PBN and ADS-BGNSS Enables PBN and ADS-B
Dependent Parallel Approach (DPA)Independent Parallel Approach (IPA)
Surveillance Integrity Level (SIL)Navigation Integrity Category (NIC)
Navigation Accuracy Category for Position (NACp)
* 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.
AP
NT
3 nm171m
(8)0.6 nm
(6)
DMEOnlyGapLNAV *0.3 nm 0.6 nm
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6Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
Alternatives Considered (so far!)Alternatives Considered (so far!)
• Optimized DME Network
• Passive Multi-Lateration
• Pseudolite
• Other?
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7Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
Optimized DME NetworkOptimized DME Network
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8Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
1100 DMEs in Current Nework
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9Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
DME-DME AlternativeDME-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
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10Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
Wide Area Multi-LaterationWide Area Multi-Lateration
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11Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
Passive Wide-Area Multi-Lateration Passive Wide-Area Multi-Lateration (WAM)(WAM)
Combined DME/GBT Network2 - WAM Receives Signal3 - Aircraft Position Determined4 - Aircraft Position Sent to GBT’s
1 –Aircraft Transmits ADS-B Signal6 – Aircraft Uses Own Position for Navigation
5 - TIS-B Sends Position to Aircraft
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12Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
WAM Operational at Steamboat SpringsWAM Operational at Steamboat Springs
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13Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
Approaches HistogramApproaches Histogram NavCanada Independent Verification Of Data NavCanada Independent Verification Of Data
Instrument Procedures
Meters Feet
Average 9.4 30.8
Max 81.3 266.9
Min 0.0 0.0
Median 8.0 26.1
Std. dev 8.0 26.3
Outputs 2378
1-sigma 11.0 36.1
2-sigma 23.0 75.5
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14Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
TIS-B with MLATTIS-B with MLAT
Concept to use TIS-B to provide ADS-B equipped aircraft with backup positioning for navigation using MLAT
Ground BasedTransmitter (GBT)
Control Station FAATIS-B(MLAT)
TIS-B(SSR)
FIS-B
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15Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
656 GBT’s for National Coverage656 GBT’s for National Coverage
Communication Coverage: Not Navigation
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16Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
Combined Network of DMEs and GBTs
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17Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
MLAT AlternativeMLAT 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
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18Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
PseudolitesPseudolites
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19Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
Pseudolite Alternative ConceptPseudolite Alternative Concept
• Combined Network of DME/GBTs etc• GPS-Independent Time Reference• 1 Hz Message ID and Time @ Transmit• PNT Data Broadcast Channel
• Aircraft Calculates Position• RAIM Based Integrity Solution
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20Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
Pseudolite Alternative 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
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21Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
The APNT Initiative within theThe APNT Initiative within theFAA’s Lifecycle Management SystemFAA’s Lifecycle Management System
Research and Systems Analysis
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22Federal AviationAdministration
Alternate Position, Navigation, and Time (APNT)August 2010
QuestionsQuestions