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{{Article Infobox2
|Category=WAAS
|Category=WAAS
|Title={{PAGENAME}}
|Editors=GMV  
|Authors=GMV.
|Level=Basic
|Level=Basic
|YearOfPublication=2011
|YearOfPublication=2011
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The Wide Area Augmentation System ([[WAAS General Introduction|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 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">[https://gps.stanford.edu/research/currentcontinuing-research/waas-sbas 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 name="APPROACHES">[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 name="WAASExpanded">[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; three development phases have been already covered, and there are on-going plans to improve the capability of the system in parallel with the evolution of the SBAS standards towards a dual-frequency augmentation service.<ref name="EXTENSION">[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>


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 User Segment==


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 WAAS user segment consists in the GNSS receivers that combine GPS information with the SBAS signal-in-space broadcast by the [[WAAS Space Segment|WAAS GEO satellites]]. As such, the user segment is not under the control of the WAAS service provider, FAA, and it is driven by the GNSS application market. Although the prime target of WAAS is the civil aviation user community, most of GPS receivers nowadays can be configured to receive and process WAAS signal-in-space (SIS), so they can benefit from the enhanced accuracy and/or integrity offered by WAAS.<ref name="SBAS RECEIVERS">[http://www.egnos-pro.esa.int/SBAS_receivers.pdf List of available SBAS receivers, ESA, March 2006.]</ref>


==WAAS User Segment==
WAAS users include any aircraft with approved SBAS avionics using a SBAS-enabled GPS receiver. The WAAS user equipment shall be compliant (certified) against several standards, i.e. RTCA MOPS DO 229  (see article [[SBAS Standards]]). The civil aviation certified equipment is in the highest rank with respect its cost. There exist a large number of certified receivers manufacturers worldwide, including:<ref name="WAAS STATUS">[http://www.afceaboston.com WAAS Program Update, 2011, FAA]</ref>
[[File:FAA WAAS System Overview.jpg|WAAS System|300px|thumb]]
* [http://www.garmin.com/garmin/cms/site/us GARMIN]
* [http://honeywell.com/Pages/Home.aspx Honeywell]
* [http://www.rockwellcollins.com/ Rockwell Collins]
* [http://www.uasc.com Universal Avionics]
* [http://www.cmcelectronics.ca CMC Electronics]
* [http://www.avidyne.com/ Avidyne]
 
[http://www.faa.gov/aircraft/air_cert/design_approvals/stc/ Aircraft Supplemental Type Certificates (STC)] have been issued by the FAA for an important number of aircraft models equipping WAAS-compliant avionics, including, among others, aircraft from Boeing, Bombardier, Cessna, Embraer, Falcon, Hawker...<ref name="WAAS STATUS"/> Other certificates are in progress including airplanes from other companies such as Airbus or Lockheed Martin.<ref name="WAAS STATUS"/>


The WAAS User Segment is the GPS and [[Work in Progress:WAAS Receivers|WAAS receiver]], which uses the information broadcast from each GPS satellite to determine its location and the current time, and receives the WAAS corrections from the Space segment.
Aircraft equipped with WAAS compliant avionics may take benefit from the more than 2000 LPV/LP approaches approved in USA and Canada airports <ref name="APPROACHES"/> (see the article [[WAAS Services]]).


The WAAS User segment is not under the control of the WAAS service provider, FAA, as it is driven by the WAAS application market.  In general, the WAAS service operator provides different services aiming at different market sectors, namely an Open Service, a Safety of Life service (SoL) and even a Commercial Service. For the Safety-of-Life (SoL) service, the WAAS user equipment shall be compliant (certified) against several standards, i.e. RTCA MOPS DO 229  (see article [[SBAS Standards]]). The SoL civil aviation certified equipment is in the highest rank with respect its cost. There exist a large number of certified receivers manufacturers worldwide, in the US: GARMIN, Honeywell, Rockwell Collins, General Avionics, etc. The Open Service (OS) targets low cost, general purpose GPS equipment that uses the WAAS Signal-In-Space (SIS) to provide the user with an enhanced accuracy performance in comparison with the one provided by a standalone GPS device. In comparison with the certification requirements of the SoL user equipment, user equipment is not necessarily compliant with the RTCA MOPS DO 229 processing rules, but might only make use of the processing algorithms that render the accuracy corrections provided by the SBAS SIS.


In the WAAS receiver, the two types of [[WAAS Messages|WAAS correction messages]] received (fast and slow) are used in different ways. The GPS receiver can immediately apply the fast type of correction data, which includes the corrected satellite position and clock data, and determines its current location using normal GPS calculations. Once an approximate position fix is obtained the receiver begins to use the slow corrections to improve its accuracy. Among the slow correction data is the ionospheric delay. As the GPS signal travels from the satellite to the receiver, it passes through the ionosphere. The receiver calculates the location where the signal pierced the ionosphere and, if it has received an ionospheric delay value for that location, corrects for the error the ionosphere created. While the slow data can be updated every minute if necessary, ephemeris errors and ionosphere errors do not change this frequently, so they are only updated every two minutes and are considered valid for up to six minutes.
The non-safety-of-life devices comprise low cost, general purpose GPS equipment that uses the WAAS signal-in-space (SIS) to provide the user with an enhanced accuracy performance in comparison with the one provided by a standalone GPS device. In comparison with the certification requirements of the safety-of-life user equipment, the general-purpose equipment is not necessarily compliant with the RTCA MOPS DO 229 processing rules, but might only make use of the processing algorithms that render the accuracy corrections provided by the SBAS SIS.


==Notes==
==Notes==

Latest revision as of 08:55, 16 February 2021


WAASWAAS
Title WAAS User Segment
Edited by 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; three development phases have been already covered, and there are on-going 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 User Segment

The WAAS user segment consists in the GNSS receivers that combine GPS information with the SBAS signal-in-space broadcast by the WAAS GEO satellites. As such, the user segment is not under the control of the WAAS service provider, FAA, and it is driven by the GNSS application market. Although the prime target of WAAS is the civil aviation user community, most of GPS receivers nowadays can be configured to receive and process WAAS signal-in-space (SIS), so they can benefit from the enhanced accuracy and/or integrity offered by WAAS.[7]

WAAS users include any aircraft with approved SBAS avionics using a SBAS-enabled GPS receiver. The WAAS user equipment shall be compliant (certified) against several standards, i.e. RTCA MOPS DO 229 (see article SBAS Standards). The civil aviation certified equipment is in the highest rank with respect its cost. There exist a large number of certified receivers manufacturers worldwide, including:[8]

Aircraft Supplemental Type Certificates (STC) have been issued by the FAA for an important number of aircraft models equipping WAAS-compliant avionics, including, among others, aircraft from Boeing, Bombardier, Cessna, Embraer, Falcon, Hawker...[8] Other certificates are in progress including airplanes from other companies such as Airbus or Lockheed Martin.[8]

Aircraft equipped with WAAS compliant avionics may take benefit from the more than 2000 LPV/LP approaches approved in USA and Canada airports [4] (see the article WAAS Services).


The non-safety-of-life devices comprise low cost, general purpose GPS equipment that uses the WAAS signal-in-space (SIS) to provide the user with an enhanced accuracy performance in comparison with the one provided by a standalone GPS device. In comparison with the certification requirements of the safety-of-life user equipment, the general-purpose equipment is not necessarily compliant with the RTCA MOPS DO 229 processing rules, but might only make use of the processing algorithms that render the accuracy corrections provided by the SBAS SIS.

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. ^ a b 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. ^ List of available SBAS receivers, ESA, March 2006.
  8. ^ a b c WAAS Program Update, 2011, FAA
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