Wide Area Augmentation System (WAAS)

Wide Area Augmentation System (WAAS) E. Douglas Aguilar CAPT, USAF

Development • Joint project between • Federal Aviation Administration (FAA) • US Department of Transportation (DOT) • Goal • Provide horizontal and vertical navigation for precision approaches for everyone everywhere Continental US

Error Sources

Timeline • Phase I (1998-2002) • 25 reference stations, 2 master stations and 2 satellites deployed • Supports category I precision approach, limited coverage area

Timeline • Phase II (2003-2007) • Full WAAS expected with additional reference and master stations • Airports begin upgrading landing systems • 2nd and 3rd civil frequencies added to improve accuracy

Timeline • Phase III (2008-2015) • Full constellation of GPS satellites available for WAAS • Phase out all airport navigational aids and fully integrate WAAS for commercial aircraft

WAAS • WAAS Elements as of Nov 2006 (EGNOS) • Only in US (23 countries) • 29 Wide-area reference stations (WRS) (34 RIMS) • 3 Wide-area monitoring stations (WMS) (4MCC) • 3 Ground earth stations (GES) (6 NLES) • 2 to 4 geosynchronous satellites (3) Space Based Augmentation Systems

WAAS Components

WAAS Functions

Function 5 - Integrity • INPUTS • GPS satellite navigation data • GEO satellite navigation data • antenna phase center locations • satellite long term error corrections • IGP locations • IGP vertical ionosopheric delay estimate • IPG GIVE data • Satellite User differential range error (UDRE) data • message type 10 degradation parameters • fast correction degradation factor • OUTPUTS • data to generate “Don’t Use” messages • data to generate “Not Monitored” messages • list 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 whose pseudorange errors are not correctable within the limits of the WASS message structure

Architecture

Commercial Aircraft

Benefits

Nav/Landing Equipment

LNAV/VNAV 350’ LPV 250’ ILS 200’ 3o FAA Announcement • FAA Announces Major Milestone for Wide Area Augmentation System (WAAS)- • FAA Administrator Marion C. Blakey. “Less reliance on a ground-based infrastructure will result in improved safety, including enhanced approach and landing operations in marginal weather.” March 24, 2006- WAAS use will be extended to 200 feet above an airport’s surface http://www.faa.gov/news/press_releases/news_story.cfm

Coverage

WAAS Satellites • Original two Inmarsat III • PRN#134 Pacific Ocean Region • PRN #122 Atlantic Ocean Region • Two additional • PRN #135 Galaxy XV (as of Nov 9th 2006) • PRN #138 ANIK F1R (under testing)

Issues • Accuracy • Geo satellites are low on horizon accuracy may degrade in Canada-Alaska • Correction will decrease in accuracy with distance from reference station • Costly - • Update airports and receivers • Installation of ground stations and satellites

Future Improvements • Nine new Wide-area Reference stations • Summer 2007 • 3 Mexico • 2 Canada • Fall 2007 • 2 Mexico • 2 Canada

Sources • Federal Aviation Agency website (http://gps.faa.gov) • Papers • “Wide-Area Augmentation System Performance Analysis Report” April 2002 • “DOD and FAA Specification for the Wide Area Augmentation System” August 2001 • Presentations • “WAAS” Dan Hanlon, Program Manager, April 2003 • “Satellite Navigation Program” August 2000 • Free Flight Systems • http://www.freeflightsystems.com/waas.htm • WIKIPEDIA • http://en.wikipedia.org/wiki/WAAS#Operation • Research Papers • “Performance Analysis of GPS Positioning Using WAAS and EGNOS” Dr. Abousalem, Mr. Tubalin; Ashtech Precision Products, May 2000

Questions?

Wide Area Augmentation System (WAAS)