Federal Aviation Administration Alternative Positioning, Navigation & Timing (APNT) Study Update Leo Eldredge October 14, 2010

Federal AviationAdministration

Alternative Positioning, Alternative Positioning, Navigation & Timing Navigation & Timing

(APNT)(APNT)Study UpdateStudy Update

Leo EldredgeOctober 14, 2010

APNT Study Brief to PNT Advisory Board2Federal Aviation

AdministrationOctober 14, 2010

Why APNT?Why APNT?• The transformation of the National Airspace System (NAS) to the Next

Generation Air Transportation System (NextGen) relies on GPS-Based PNT services and suitable alternate PNT services

– Current ATC system cannot be scaled up to handle 2X traffic

– 2X traffic is more than a controller can handle using radar vectors

– RNAV and RNP procedures for trajectory-based operations (TBO)

– Automation will separate aircraft performing trajectory based operations (TBO)

– Controllers intercede to provide “control by exception”

• TBO Operations may require PNT performance that exceeds DME/DME/IRU

• GPS vulnerability to radio frequency interference (RFI) requires mitigation

– Waiting for the source of the interference to be located and turned off is not an acceptable alternative



•Terminal

•Sector

•D

•Ghost

•Sector

•(not depicted)

•Terminal

•Sector

•A

•En Route

•Sector

•02 (GRUPR)

•En Route

•Sector

•01

• (BAASS)

Baseline Airspace Condition

Enabled by Legacy NAVAIDs

• VOR/DME, VORTAC, NDB

• Point-to-Point Navigation

Enabled by Legacy NAVAIDs

• VOR/DME, VORTAC, NDB

• Point-to-Point Navigation



•Feeder

•Sector - A

• Airport Departure

•Sector - D

•D

•D

•Departure Transition

•Sector

•02 (GRUPR)

•Arrival Transition

Sector

•01

•(BAASS)•Dynamic Airspace

•2

•Dynamic Airspace

•1•Ghost

•SectorBig Airspace Concept

Enabled by PBN

• GPS, WAAS, LAAS, DD, DDI

• Area Navigation (RNAV)

• Required Navigation Performance (RNP)

Enabled by PBN

• GPS, WAAS, LAAS, DD, DDI

• Area Navigation (RNAV)

• Required Navigation Performance (RNP)



TBO 3-Mile Separation with RNP

1 nmOverlap

2 x RNP 0.32 x RNP 0.3

DME / DME / IRUPerformance Limit

RNP-1.0

2 x RNP 1.0

3 Mile Separation

TBO (APNT)Requirement

Primary PNT Service: GPS meets all TBO requirements

Alternate PNT Service: DME/DME/IRU won’t support 3 NM separation

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



PNT Performance ZonesPNT Performance Zones

5 SM of Airport

Zone- 1Enroute High

CONUS

FL-600

FL-180

5000’ AGL

Zone- 2Enroute Low

CONUS Zone-3 TerminalOEPs + Next 100 Busiest Airports

2° Slope from 500’ AGL

27 SM89 SM



Zone 1, 2, and 3 Geographic AreasZone 1, 2, and 3 Geographic Areas



GNSS Challenges: GPS Testing by DODGNSS Challenges: GPS Testing by DOD

•139,795•66,018•455,805

•Geographical Area Impacted

•Maximum•Miles•2

•Minimum

•Miles•2•Average

•Miles•2

139,79566,018455,805

Geographical Area Impacted

MaximumMiles2

Minimum

Miles2Average

Miles2

•782 Hours•90 days

•Cumulative

•Duration•141 •NOTAMs

•Shortest •1.0 hour

•Average •6.63 hours

•Longest •72 hours

782 Hours90 days

Cumulative

9 Month Duration141 NOTAMs

Shortest 1.0 hour

Average 6.63 hours

Longest 72 hours



Commercially Available GPS JammerCommercially Available GPS Jammer(so called “Personal Privacy Device”)(so called “Personal Privacy Device”)



LAAS Antenna Location



Zeta “SnapShot” System Data

•Baseline/Nominal L1 RF•Broadband RFI straddling L1



… … and a few more “Personal Privacy Devices”and a few more “Personal Privacy Devices”

$55 Ebay

$110 Ebay

$335 Ebay$92 Ebay

$152 Ebay$40 GPS&GSM

www.chinavasion.com

$83 GPS&GSM www.Tayx.co.uk



RFI Challenges without APNT

• Transitioning from 3-mile to 5-mile separation en route and on arrivals outside of 40 nm when a GPS RFI event occurs

• Shifting some aircraft to radar vectors – significant implications

• Rerouting aircraft around interference area to reduce demand

• Throttle back demand to compensate for loss of capabilities like parallel runway approaches

• Limit RNAV/RNP arrivals and departures and reduce options to handling arrivals



APNT Alternative 1APNT Alternative 1Optimized DME NetworkOptimized DME Network



1100 DMEs in Current Nework



DME-DME AlternativeDME-DME Alternative

• Strengths– Leverage existing technology and systems– Least Impact on Avionics for Air Carriers

• Weaknesses– General Aviation generally does not equip with DME– DME-DME equipped aircraft without Inertial are not currently

authorized to fly RNAV/RNP routes– DME-DME, even with Inertial, is not authorized for pubic

approach 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



APNT Alternative 2APNT Alternative 2Wide Area Multi-LaterationWide Area Multi-Lateration



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



656 GBT’s for National Coverage656 GBT’s for National Coverage

Communication Coverage: Not Navigation



Combined Network of DMEs and GBTs



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

1-sigma 11.0 36.1

2-sigma 23.0 75.5



MLAT AlternativeMLAT Alternative• Strengths

– Accuracy Demonstrated to be within target levels– Compatible with existing WAM Systems

• Weaknesses– Throughput on 1090ES may limit availability– Minimum of 3 sites required to compute aircraft position– Integrity monitoring and Time to Alert may be challenging– More sites may be needed due to limited signal range– Requires a GPS-Independent common time reference– Significant investment in processing facilities and terrestrial

communications network may be required – Use of MLAT for Navigation will require avionics changes



APNT Alternative 3APNT Alternative 3DME Pseudolites (DMPL)DME Pseudolites (DMPL)



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



Pseudolite Alternative Pseudolite Alternative • Strengths

– Unlimited capacity– Less complexity for ground-based system– Potential for aircraft based integrity solution– Potential to leverage use of existing DMEs and GBTs– Potential to uplink data other navigation data to aircraft

• Weaknesses– Minimum of 3 sites required to compute aircraft position– Significant investment in processing facilities and terrestrial

communications network may be required – Common GPS-independent timing reference needed– Greatest Impact to Aircraft Avionics– Least mature concept, no standards exist



APNT Timing ServiceAPNT Timing Service



DMEs + Planned DMEs + GBTs

Ground-to-Ground Time SynchronizationGround-to-Ground Time Synchronization

30 dB ofprocessing

gain

GEO: WAAS L5

MEO: GNSS

LEO: MSS



WAAS L5 for Ground-to-Ground Synch.WAAS L5 for Ground-to-Ground Synch.

J/S = 45 dB

STAP



Summary

• NextGen Operational Improvements enabled by performance based navigation capabilities increases dependence on GPS and alternate PNT services

• GPS vulnerability to radio frequency interference needs to be addressed for trajectory based operations at some locations

• Alternatives are being studied for further consideration



QuestionsQuestions

Documents

Federal Aviation Administration Alternative Positioning, Navigation & Timing (APNT) Study Update Leo Eldredge October 14, 2010