Wide Area Augmentation System Wide Area Augmentation System (WAAS)(WAAS)

E. Douglas AguilarE. Douglas Aguilar

CAPT, USAFCAPT, USAF

DevelopmentDevelopment

Joint project betweenJoint project between– Federal Aviation Administration (FAA)Federal Aviation Administration (FAA)– US Department of Transportation (DOT)US Department of Transportation (DOT)

Goal Goal – Provide horizontal and vertical navigation for Provide horizontal and vertical navigation for

precision approaches for everyone everywhere precision approaches for everyone everywhere Continental USContinental US

Error SourcesError Sources

  One Sigma Error (m)

GPS Error Sources Normal C/A Code Dual (P/Y)

Ionosphere 4.00 1.20

Satellite clock 2.10 2.10

Ephemeris data 2.10 2.10

Multipath 1.40 1.40

Troposphere 0.70 0.70

Receiver measurement 0.50 0.50

     

UERE (rms) 5.25 3.60

UERE Filtered (rms) 5.10 3.30 WAAS EGNOS

         

Vertical DOP=2.5 12.75 8.25 3.00 4.00

Horizontal DOP=2.0 10.20 6.60 3.20 2.00

TimelineTimeline

Phase I (1998-2002)Phase I (1998-2002)– 25 reference stations, 2 master stations and 2 25 reference stations, 2 master stations and 2

satellites deployedsatellites deployed– Supports category I precision approach, limited Supports category I precision approach, limited

coverage areacoverage area

TimelineTimeline

Phase II (2003-2007)Phase II (2003-2007)– Full WAAS expected with additional reference and Full WAAS expected with additional reference and

master stationsmaster stations– Airports begin upgrading landing systemsAirports begin upgrading landing systems– 22ndnd and 3 and 3rdrd civil frequencies added to improve civil frequencies added to improve

accuracyaccuracy

TimelineTimeline

Phase III (2008-2015)Phase III (2008-2015)– Full constellation of GPS satellites available for Full constellation of GPS satellites available for

WAASWAAS– Phase out all airport navigational aids and fully Phase out all airport navigational aids and fully

integrate WAAS for commercial aircraftintegrate WAAS for commercial aircraft

WAAS Elements as of Nov 2006 (EGNOS)WAAS Elements as of Nov 2006 (EGNOS)– Only in US (23 countries)Only in US (23 countries)

– 29 Wide-area reference stations (WRS) (34 RIMS)29 Wide-area reference stations (WRS) (34 RIMS)

– 3 Wide-area monitoring stations (WMS) (4MCC)3 Wide-area monitoring stations (WMS) (4MCC)

– 3 Ground earth stations (GES) (6 NLES)3 Ground earth stations (GES) (6 NLES)

– 2 to 4 geosynchronous satellites (3)2 to 4 geosynchronous satellites (3)

WAAS WAAS

Space Based Augmentation Systems

WAAS ComponentsWAAS Components

WAAS FunctionsWAAS Functions

Function 5 - IntegrityFunction 5 - Integrity INPUTSINPUTS

– GPS satellite navigation dataGPS satellite navigation data– GEO satellite navigation dataGEO satellite navigation data– antenna phase center locationsantenna phase center locations– satellite long term error correctionssatellite long term error corrections– IGP locationsIGP locations– IGP vertical ionosopheric delay estimateIGP vertical ionosopheric delay estimate– IPG GIVE dataIPG GIVE data– Satellite User differential range error (UDRE) dataSatellite User differential range error (UDRE) data– message type 10 degradation parametersmessage type 10 degradation parameters– fast correction degradation factorfast correction degradation factor

OUTPUTSOUTPUTS– data to generate “Don’t Use” messagesdata to generate “Don’t Use” messages– data to generate “Not Monitored” messagesdata to generate “Not Monitored” messages– list of satellites that should be in view but whose signals are not being receivedlist of satellites that should be in view but whose signals are not being received

Function 5 shall generate data for a “Don’t Use” message for any satellite Function 5 shall generate data for a “Don’t Use” message for any satellite whose pseudorange errors are not correctable within the limits of the WASS whose pseudorange errors are not correctable within the limits of the WASS message structuremessage structure

ArchitectureArchitecture

Commercial AircraftCommercial Aircraft

BenefitsBenefits

Nav/Landing EquipmentNav/Landing Equipment

http://www.faa.gov/news/press_relhttp://www.faa.gov/news/press_releases/news_story.cfmeases/news_story.cfm

FAA AnnouncementFAA Announcement

FAA Announces Major FAA Announces Major Milestone for Wide Milestone for Wide Area Augmentation Area Augmentation System (WAAS)-System (WAAS)-– FAA Administrator FAA Administrator

Marion C. Blakey. “Less Marion C. Blakey. “Less reliance on a ground-based reliance on a ground-based infrastructure will result in infrastructure will result in improved safety, including improved safety, including enhanced approach and enhanced approach and landing operations in landing operations in marginal weather.”marginal weather.”

LNAV/VNAV 350’

LPV 250’

ILS 200’

3o

March 24, 2006- WAAS use will be March 24, 2006- WAAS use will be extended to 200 feet above an extended to 200 feet above an airport’s surfaceairport’s surface

CoverageCoverage

WAAS SatellitesWAAS Satellites

Original two Inmarsat IIIOriginal two Inmarsat III– PRN#134 Pacific Ocean RegionPRN#134 Pacific Ocean Region– PRN #122 Atlantic Ocean RegionPRN #122 Atlantic Ocean Region

Two additionalTwo additional– PRN #135 Galaxy XV (as of Nov 9PRN #135 Galaxy XV (as of Nov 9thth 2006) 2006)– PRN #138 ANIK F1R (under testing)PRN #138 ANIK F1R (under testing)

IssuesIssues

AccuracyAccuracy– Geo satellites are low on horizon accuracy Geo satellites are low on horizon accuracy

may degrade in Canada-Alaskamay degrade in Canada-Alaska– Correction will decrease in accuracy with Correction will decrease in accuracy with

distance from reference stationdistance from reference station Costly -Costly -

– Update airports and receiversUpdate airports and receivers– Installation of ground stations and satellitesInstallation of ground stations and satellites

Future ImprovementsFuture Improvements

Nine new Wide-area Reference stationsNine new Wide-area Reference stations– Summer 2007Summer 2007

3 Mexico3 Mexico 2 Canada2 Canada

– Fall 2007Fall 2007 2 Mexico2 Mexico 2 Canada2 Canada

SourcesSources Federal Aviation Agency website (Federal Aviation Agency website (http://http://gps.faa.govgps.faa.gov))

– PapersPapers ““Wide-Area Augmentation System Performance Analysis Report” April 2002Wide-Area Augmentation System Performance Analysis Report” April 2002 ““DOD and FAA Specification for the Wide Area Augmentation System” August DOD and FAA Specification for the Wide Area Augmentation System” August

20012001– PresentationsPresentations

““WAAS” Dan Hanlon, Program Manager, April 2003WAAS” Dan Hanlon, Program Manager, April 2003 ““Satellite Navigation Program” August 2000Satellite Navigation Program” August 2000

Free Flight SystemsFree Flight Systems– http://www.freeflightsystems.com/waas.htmhttp://www.freeflightsystems.com/waas.htm

WIKIPEDIAWIKIPEDIA– http://en.wikipedia.org/wiki/WAAS#Operationhttp://en.wikipedia.org/wiki/WAAS#Operation

Research PapersResearch Papers– ““Performance Analysis of GPS Positioning Using WAAS and EGNOS” Dr. Performance Analysis of GPS Positioning Using WAAS and EGNOS” Dr.

Abousalem, Mr. Tubalin; Ashtech Precision Products, May 2000Abousalem, Mr. Tubalin; Ashtech Precision Products, May 2000

Questions?Questions?