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{{Article Infobox2
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|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 and operated 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 [[GNSS Augmentation|GPS Augmentation]] system developed by the [http://www.faa.gov Federal Aviation Administration (FAA)], WAAS is an extremely accurate navigation system developed for civil aviation. Before WAAS, the U.S. National Airspace System (NAS) did not have the potential to provide horizontal and vertical navigation for approach operations for all users at all locations. With WAAS, this capability is a reality. WAAS provides service for all classes of aircraft in all phases of flight - including en route navigation, airport departures, and airport arrivals. This includes vertically-guided landing approaches in instrument meteorological conditions at all qualified locations throughout the NAS.
It currently achieves excellent coverage over the vast majority of North America, providing corrections to the GPS L1 signal. However, when the ionosphere is disturbed or when the constellation is weak, its availability may be reduced. Using both the L1 and L5 signals in the aircraft will remove the primary dependence on the state of the ionosphere. Removing this largest source of uncertainty allows service to be provided under more conditions than are allowed today. Thus, the use of L1 and L5 together as it is being defined in the evolution of SBAS standards will provide very robust coverage of vertical guidance.<ref name="article">[https://www.researchgate.net/profile/Todd_Walter/publication/261537494_Evolving_WAAS_to_serve_L1L5_users/links/5a6a0f5c4585154d15466882/Evolving-WAAS-to-serve-L1-L5-users.pdf Todd Walter, Juan Blanch, R. Eric Phelts, and Per Enge, "Evolving WAAS to Serve L1/L5 Users", Stanford University, 2020]</ref>
   
   
==WAAS Services==
==WAAS Services==
[[File:Airports_with_wass_supported_approaches.jpg‎ |CONUS airports with WAAS procedures.|300px|thumb|right]]
[[File:Alaska_Airports_with_WAAS_approches.jpg‎ |Alaska airports with WAAS procedures.|300px|thumb|right]]
The objectives of the WAAS are to provide improved [[Integrity|integrity]], [[Accuracy|accuracy]], [[Availability|availability]], and [[Continuity|continuity]] of service to the [[GPS Services|GPS Standard Positioning Service]] (SPS) for the Civil Aviation community. The ultimate objective is to provide a navigation system for all phases of flight through precision approach.<ref name=SpecWAAS>[http://www.faa.gov ''Specification for the Wide Area Augmentation System(WAAS)''], FAA-E- 2892b, August 13, 2001.</ref>


The objectives of the WAAS are to provide improved: [[Integrity|integrity]],[[Accuracy|accuracy]],[[Availability|availability]], and [[Continuity|continuity]] of service to the [[GPS Services|GPS Standard Positioning Service]] (SPS). The ultimate objective is to provide a navigation system for all phases of flight through precision approach.<ref> FAA.[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/library/documents/media/waas/2892bC2a.pdf ''Specification for the Wide Area Augmentation System(WAAS)'']. FAA-E- 2892b. August 13, 2001.</ref>
The WAAS is a safety-critical system which augments Global Positioning System (GPS) Standard Positioning Service (SPS). The WAAS provides a signal-in-space to WAAS users, i.e. all aircraft with approved WAAS avionics, to support en route through precision approach navigation. The WAAS GEO satellites have ranging capabilities, i.e., they can be used as extra GPS satellites to enhance the performance achieved in the user location because of the additional statistics and the improved geometry. In addition, the WAAS signals broadcast augmentation information that corrects GPS ephemeris and ensures the integrity meeting the [[WAAS Performances|WAAS performance requirements]].<ref name=SpecWAAS/><ref>[https://www.gps.gov/technical/ps/2008-WAAS-performance-standard.pdf WAAS Performance Standard]</ref>  


The WAAS is a safety-critical system consisting of the equipment and software which augments Global Positioning System (GPS) Standard Positioning Service (SPS). The WAAS provides a signal-in-space to WAAS users to support en route through precision approach navigation. The WAAS users include all aircraft with approved WAAS avionics using the WAAS for any approved phase of flight. The signal in space provides two services: (1) data on GPS and GEO satellites, and (2) a ranging capability. In addition to providing GPS integrity, the WAAS verifies its own integrity and takes any necessary action to ensure that the system meets the WAAS performance requirements. The WAAS also has a system operations and maintenance function that provides information to FAA Airway Facilities (AF) National Airspace System (NAS) personnel.
In order to take benefit from the signal in space provided by WAAS, aircraft need to be equipped with certified receivers meeting the corresponding standards, i.e. RTCA MOPS DO 229 for current WAAS services or the future SBAS DFMC standards for next evolutions of WAAS (see article [[SBAS Standards]]).


The WAAS has a single state - ''normal state''. Periodic maintenance and corrective maintenance do not interrupt the normal state. There are two modes for  the normal state.
On July 10, 2003, the WAAS system was declared operational for safety-of-life aviation, with a service area consisting in 95% of the United States, and part of Alaska,<ref name="STANFORD_WAAS"/><ref>[http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System Wide Area Augmentation System in Wikipedia]</ref> to be expanded in 2007 to include Canada and Mexico.<ref name="EXTENSION"/> At present, WAAS supports en-route, terminal and approach operations down to a full LPV-200 (CAT-I like Approach Capability) for the WAAS service area that includes CONUS, Alaska and Canada.<ref name="APPROACHES"/><ref name="WAASExpanded"/>
*'''Continuous Service Mode''':  In the normal state, the WAAS shall possess an operational mode of continuous service meeting all of the [[Work in Progress:WAAS Performances|performance requirements]], both for the ''precision approach'' and ''non-precision approach'' phases of flight.
*'''Military Emergency Mode''': In the normal state, the WAAS shall possess a military emergency mode that only meets the performance requirements for en route through ''non-precision approach'' services.


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. 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.
Currently, WAAS supports the following flight procedures, as well as airport departures and airport arrivals:<ref name="APPROACHES"/><ref>[http://aviationglossary.com Aviation Glossary]</ref>
* LNAV  (Lateral Navigation).
* LNAV/VNAV (Lateral Navigation/Vertical Navigation).
* LP (Localizer Performance).
* LPV (Localizer Performance with Vertical guidance).


On July 10, 2003, the WAAS signal was activated for safety-of-life aviation, covering 95% of the United States, and portions of Alaska.<ref name="WAAS WIKI"/> At present, WAAS supports en-route, terminal and approach operations down to a full LPV-200 (CAT-I like Approach Capability) for the CONUS, Mexico and Canada.
The WAAS service is interoperable with other regional SBAS services, including those operated by Japan (MSAS), Europe (EGNOS), and India (GAGAN).


==Notes==
==Notes==

Latest revision as of 09:11, 16 February 2021


WAASWAAS
Title WAAS Services
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 and operated 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]

It currently achieves excellent coverage over the vast majority of North America, providing corrections to the GPS L1 signal. However, when the ionosphere is disturbed or when the constellation is weak, its availability may be reduced. Using both the L1 and L5 signals in the aircraft will remove the primary dependence on the state of the ionosphere. Removing this largest source of uncertainty allows service to be provided under more conditions than are allowed today. Thus, the use of L1 and L5 together as it is being defined in the evolution of SBAS standards will provide very robust coverage of vertical guidance.[7]

WAAS Services

CONUS airports with WAAS procedures.
Alaska airports with WAAS procedures.

The objectives of the WAAS are to provide improved integrity, accuracy, availability, and continuity of service to the GPS Standard Positioning Service (SPS) for the Civil Aviation community. The ultimate objective is to provide a navigation system for all phases of flight through precision approach.[8]

The WAAS is a safety-critical system which augments Global Positioning System (GPS) Standard Positioning Service (SPS). The WAAS provides a signal-in-space to WAAS users, i.e. all aircraft with approved WAAS avionics, to support en route through precision approach navigation. The WAAS GEO satellites have ranging capabilities, i.e., they can be used as extra GPS satellites to enhance the performance achieved in the user location because of the additional statistics and the improved geometry. In addition, the WAAS signals broadcast augmentation information that corrects GPS ephemeris and ensures the integrity meeting the WAAS performance requirements.[8][9]

In order to take benefit from the signal in space provided by WAAS, aircraft need to be equipped with certified receivers meeting the corresponding standards, i.e. RTCA MOPS DO 229 for current WAAS services or the future SBAS DFMC standards for next evolutions of WAAS (see article SBAS Standards).

On July 10, 2003, the WAAS system was declared operational for safety-of-life aviation, with a service area consisting in 95% of the United States, and part of Alaska,[3][10] to be expanded in 2007 to include Canada and Mexico.[6] At present, WAAS supports en-route, terminal and approach operations down to a full LPV-200 (CAT-I like Approach Capability) for the WAAS service area that includes CONUS, Alaska and Canada.[4][5]

Currently, WAAS supports the following flight procedures, as well as airport departures and airport arrivals:[4][11]

  • LNAV (Lateral Navigation).
  • LNAV/VNAV (Lateral Navigation/Vertical Navigation).
  • LP (Localizer Performance).
  • LPV (Localizer Performance with Vertical guidance).

The WAAS service is interoperable with other regional SBAS services, including those operated by Japan (MSAS), Europe (EGNOS), and India (GAGAN).

Notes

References

  1. ^ Navigation Services - History - Satellite Navigation, FAA.
  2. ^ Navigation Services - Wide Area Augmentation System (WAAS), FAA.
  3. ^ a b Wide Area Differential GPS (WADGPS), Stanford University
  4. ^ a b c GNSS - GPS/WAAS Approaches, Federal Aviation Agency (FAA).
  5. ^ a b WAAS Service Expanded into Canada and Mexico, September 28, 2007, Federal Aviation Agency (FAA).
  6. ^ a b SatNav News, Vol. 33, March 2008, Federal Aviation Agency (FAA).
  7. ^ Todd Walter, Juan Blanch, R. Eric Phelts, and Per Enge, "Evolving WAAS to Serve L1/L5 Users", Stanford University, 2020
  8. ^ a b Specification for the Wide Area Augmentation System(WAAS), FAA-E- 2892b, August 13, 2001.
  9. ^ WAAS Performance Standard
  10. ^ Wide Area Augmentation System in Wikipedia
  11. ^ Aviation Glossary
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