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The Wide Area Augmentation System (WAAS) is an GPS Augmentation system developed by the [http://www.faa.gov Federal Aviation Administration (FAA)], with the goal of improving its accuracy, integrity, and availability. Essentially, WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including precision approaches to any airport within its coverage area.


WAAS uses a network of ground-based reference stations, in North America and Hawaii, to measure small variations in the GPS satellites' signals in the western hemisphere. Measurements from the reference stations are routed to master stations, which queue the received Deviation Correction (DC) and send the correction messages to geostationary WAAS satellites in a timely manner (every 5 seconds or better). Those satellites broadcast the correction messages back to Earth, where WAAS-enabled GPS receivers use the corrections while computing their positions to improve accuracy.<ref>[http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System WAAS in Wikipedia]</ref>
The Wide Area Augmentation System (WAAS) is the United States [[SBAS General Introduction|Satellite Based Augmentation System]]. The programme, started in 1992, is being carried out by the [http://www.faa.gov/ Federal Aviation Agency (FAA)]<ref name="FAA_NAV_HISTORY">[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/history/satnav/index.cfm Navigation Services - History - Satellite Navigation,] [http://www.faa.gov/ FAA.]</ref> and is specially developed for the civil aviation community.<ref name="FAA_WAAS">[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/waas/ Navigation Services - Wide Area Augmentation System (WAAS)], [http://www.faa.gov/ FAA.]</ref> The system, which was declared operational in late 2003,<ref name="STANFORD_WAAS">[http://waas.stanford.edu/research/waas.htm Wide Area Differential GPS (WADGPS), Stanford University]</ref> currently supports thousands of aircraft instrument approaches in more than one thousand airports in USA and Canada.<ref>[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/approaches/index.cfm GNSS - GPS/WAAS Approaches,] [http://www.faa.gov/ Federal Aviation Agency (FAA).]</ref> WAAS service area includes CONUS, Alaska, Canada and Mexico.<ref>[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/waas/news/ WAAS Service Expanded into Canada and Mexico, September 28, 2007,] [http://www.faa.gov/ Federal Aviation Agency (FAA).]</ref> The WAAS programme is continuously in evolution; two development phases have been already covered, a third is in progress, and there are plans to improve the capability of the system in parallel with the evolution of the SBAS standards towards a dual-frequency augmentation service.<ref>[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/library/satnav/media/SatNav_March08.pdf SatNav News, Vol. 33, March 2008,] [http://www.faa.gov/ Federal Aviation Agency (FAA).]</ref>


==WAAS Space Segment==
==WAAS Space Segment==

Revision as of 10:38, 26 July 2011


WAASWAAS
Title WAAS Space Segment
Author(s) GMV.
Level Basic
Year of Publication 2011
Logo GMV.png


The Wide Area Augmentation System (WAAS) is the United States Satellite Based Augmentation System. The programme, started in 1992, is being carried out by the Federal Aviation Agency (FAA)[1] and is specially developed for the civil aviation community.[2] The system, which was declared operational in late 2003,[3] currently supports thousands of aircraft instrument approaches in more than one thousand airports in USA and Canada.[4] WAAS service area includes CONUS, Alaska, Canada and Mexico.[5] The WAAS programme is continuously in evolution; two development phases have been already covered, a third is in progress, and there are plans to improve the capability of the system in parallel with the evolution of the SBAS standards towards a dual-frequency augmentation service.[6]

WAAS Space Segment

Broadcast footprints of the WAAS GEOs in December 2010

The WAAS Space Segment consists of multiple geosynchronous communication satellites (GEO) which broadcast the correction messages generated by the Wide-area Master Stations for reception by the User segment. The satellites also broadcast the same type of range information as normal GPS satellites, effectively increasing the number of satellites available for a position fix. As of January 2011, the Space segment consists of two commercial satellites, Inmarsat-4 F3 and Telesat's Anik F1R, and also Intelsat's Galaxy 15, that has resumed service in March, 2011.[7]

The original two WAAS satellites, named Pacific Ocean Region (POR) and Atlantic Ocean Region-West (AOR-W), were leased space on Inmarsat III satellites. These satellites ceased WAAS transmissions on July 31, 2007. With the end of the Inmarsat lease approaching, two new satellites (Galaxy 15 and Anik F1R) were launched in late 2005. Galaxy 15 is a PanAmSat, and Anik F1R is a Telesat. As with the previous satellites, these are leased services under the FAA's Geostationary Satellite Communications Control Segment contract with Lockheed Martin for WAAS geostationary satellite leased services, who is contracted to provide up to three satellites through the year 2016. Since September 23, 2008, the ranging data that Galaxy 15 and Anik F1R transmit have been flagged as "Precision Approach". The Galaxy 15 satellite ceased responding to control commands between April 5, 2010, when solar activity damaged the spacecraft’s communication package, and December 23, 2010, when its battery drained and the Baseband Equipment command unit reset. During this time, the satellite drifted from its original location of 133 degrees west to 93 degrees west, but the WAAS signal continued to be broadcast until December 16, 2010. Intelsat has been able to return the satellite to its original location in March, 2011, back into operational mode, thereby restoring WAAS service to a large area in northwest Alaska.[7]

The list of GEO satellites used in WAAS are in the following table:

Satellite Name & Details NMEA / PRN Location
Inmarsat 4F3 NMEA #46 / PRN #133 98°W
Galaxy 15 NMEA #48 / PRN #135 133°W
Anik F1R NMEA #51 / PRN #138 107.3°W
Pacific Ocean Region (POR)
Ceased WAAS transmissions 		NMEA #47 / PRN #134 178°E
Atlantic Ocean Region-West
Ceased WAAS transmissions 		NMEA #35 / PRN #122 142°W

Notes

References

  1. ^ Navigation Services - History - Satellite Navigation, FAA.
  2. ^ Navigation Services - Wide Area Augmentation System (WAAS), FAA.
  3. ^ Wide Area Differential GPS (WADGPS), Stanford University
  4. ^ GNSS - GPS/WAAS Approaches, Federal Aviation Agency (FAA).
  5. ^ WAAS Service Expanded into Canada and Mexico, September 28, 2007, Federal Aviation Agency (FAA).
  6. ^ SatNav News, Vol. 33, March 2008, Federal Aviation Agency (FAA).
  7. ^ a b FAA WAAS News
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