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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 on July 10, 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 Ground Segment==
WAAS works by processing GPS data collected by a network of reference stations to generate the SBAS message which is uploaded to the GEO satellites. The GEO satellites broadcast this information to the user receivers, which compute the aircraft positioning and inform on potential alert messages.<ref name=WAASWorks>[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/waas/howitworks/ FAA WAAS: How it works]</ref>
[[File:FAA WAAS System Overview.jpg|WAAS System|250px|thumb]]


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 system components are typically divided in three different segments: the ground segment, encompassing the system assets located on ground, the [[ WAAS Space Segment|space segment]], including the GEO satellites used to broadcast the information to the users, and the [[ WAAS User Segment|user segment]], consisting in the users themselves.
 
==WAAS Ground Segment==
[[File:FAA WAAS System Overview.jpg|WAAS System|300px|thumb]]


The WAAS Ground Segment is composed of multiple Wide-area Reference Stations (WRS). These precisely surveyed ground stations monitor and collect information on the GPS signals, then send their data to three Wide-area Master Stations (WMS) using a terrestrial communications network. The reference stations also monitor signals from WAAS geostationary satellites, providing integrity information regarding them as well. As of October 2008 there were 38 WRSes: twenty in the contiguous United States (CONUS), seven in Alaska, one in Hawaii, one in Puerto Rico, five in Mexico, and four in Canada.<ref name="FAA_WAAS_LAAS">[http://www.navcen.uscg.gov/pdf/cgsicMeetings/47/%5B12%5D%20WAAS-LAAS-CGSIC-07.pdf WAAS and LAAS Status],FAA presentation at 47th meeting of the Civil Global Positioning System Service Interface Committee, September 25, 2008</ref>
The WAAS Ground segment is composed of:<ref name=WAASWorks/>


Using the data from the WRS sites, the WMSes generate two different sets of corrections: fast and slow. The fast corrections are for errors which are changing rapidly and primarily concern the GPS satellites' instantaneous positions and clock errors. These corrections are considered user position-independent, which means they can be applied instantly by any receiver inside the WAAS broadcast footprint. The slow corrections include long-term ephemeric and clock error estimates, as well as ionospheric delay information. WAAS supplies delay corrections for a number of points (organized in a grid pattern) across the WAAS service area.
* 38 widely-spaced Wide-area Reference Stations (WRS), located in North America (continental U.S., Puerto Rico, Alaska, Canada and Mexico) and Hawaii: the WRS stations collect GPS data.
* 3 WAAS Master Station (WMS): the WRS collected data are forwarded to the WAAS Master Station (WMS) via a terrestrial communications network. At the WMS, the WAAS augmentation messages are generated.
* 6 Ground Uplink Stations (GUS): they are in charge of the transmission of the WAAS messages generated by WMS stations to the navigation payloads on [[WAAS Space Segment|Geostationary communications satellites]] for rebroadcast to the [[WAAS User Segment|users]].
* 2 Operational Control Centers (OCC), used to monitor the system performance and to carry out the necessary corrective and periodic maintenance operations located at the National Operations and Control Center (NOCC) and Pacific Operations Control Center (POCC).<ref>[http://www.faa.gov Specification for the Wide Area Augmentation System (WAAS), U.S. Department of Transportation Federal Aviation Administration]</ref>
* WAAS terrestrial communications network that provides the communications link between the WAAS subsystems for transmitting WAAS data.


Once these correction messages are generated, the WMSes send them to two pairs of Ground Uplink Stations (GUS), which then transmit to satellites in the Space segment for rebroadcast to the User segment.
===List of reference stations===
[[File:WAAS Reference Station Barrow Alaska.jpg|WAAS Reference Station Barrow, Alaska|250px|thumb]]


==List of reference stations==
The WAAS Wide-area Reference Stations (WRS) are located in USA, Canada, Mexico and Puerto Rico. Regarding the US stations, each of the FAA Air Traffic Control Centers, but Indianapolis, hosts one WRS.<ref name="FAA_WAAS_LAAS">WAAS and LAAS Status,FAA presentation at 47th meeting of the Civil Global Positioning System Service Interface Committee, September 25, 2008</ref>


Each FAA Air Route Traffic Control Center in the 50 states has a WAAS reference station, except for Indianapolis. There are also stations positioned in Canada, Mexico and Puerto Rico.<ref name="FAA_WAAS_LAAS" /> Listed below are the coordinates of the site centroids in North America:
For completeness, the list of WRS stations with their coordinates are shown in the next table (taken from WAAS article in Wikipedia<ref name="WAAS_WIKI">[https://en.wikipedia.org/wiki/List_of_WAAS_reference_stations List of WAAS reference stations in Wikipedia website]</ref>
):


{| class="wikitable sortable"
{| class="wikitable sortable"
Line 48: Line 54:
| Puerto Vallarta, Jalisco (Mexico) || MMPR || 20.679034758ºN 105.249200735ºW || 11.077 m
| Puerto Vallarta, Jalisco (Mexico) || MMPR || 20.679034758ºN 105.249200735ºW || 11.077 m
|-
|-
| San José del Cabo, Baja California (Mexico)]] || MMSD || 23.160416093ºN 109.717667886ºW || 104.286 m
| San José del Cabo, Baja California (Mexico) || MMSD || 23.160416093ºN 109.717667886ºW || 104.286 m
|-
|-
| Tapachula, Chiapas (Mexico) || MMTP || 14.791340027ºN 92.367991216ºW || 54.922 m
| Tapachula, Chiapas (Mexico) || MMTP || 14.791340027ºN 92.367991216ºW || 54.922 m

Latest revision as of 09:12, 16 February 2021


WAASWAAS
Title WAAS Ground 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 on July 10, 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 Ground Segment

WAAS works by processing GPS data collected by a network of reference stations to generate the SBAS message which is uploaded to the GEO satellites. The GEO satellites broadcast this information to the user receivers, which compute the aircraft positioning and inform on potential alert messages.[7]

WAAS System

The WAAS system components are typically divided in three different segments: the ground segment, encompassing the system assets located on ground, the space segment, including the GEO satellites used to broadcast the information to the users, and the user segment, consisting in the users themselves.

The WAAS Ground segment is composed of:[7]

  • 38 widely-spaced Wide-area Reference Stations (WRS), located in North America (continental U.S., Puerto Rico, Alaska, Canada and Mexico) and Hawaii: the WRS stations collect GPS data.
  • 3 WAAS Master Station (WMS): the WRS collected data are forwarded to the WAAS Master Station (WMS) via a terrestrial communications network. At the WMS, the WAAS augmentation messages are generated.
  • 6 Ground Uplink Stations (GUS): they are in charge of the transmission of the WAAS messages generated by WMS stations to the navigation payloads on Geostationary communications satellites for rebroadcast to the users.
  • 2 Operational Control Centers (OCC), used to monitor the system performance and to carry out the necessary corrective and periodic maintenance operations located at the National Operations and Control Center (NOCC) and Pacific Operations Control Center (POCC).[8]
  • WAAS terrestrial communications network that provides the communications link between the WAAS subsystems for transmitting WAAS data.

List of reference stations

WAAS Reference Station Barrow, Alaska

The WAAS Wide-area Reference Stations (WRS) are located in USA, Canada, Mexico and Puerto Rico. Regarding the US stations, each of the FAA Air Traffic Control Centers, but Indianapolis, hosts one WRS.[9]

For completeness, the list of WRS stations with their coordinates are shown in the next table (taken from WAAS article in Wikipedia[10] ):

City ICAO airport code Location Elevation
Bethel, Alaska PABE 60.787898226ºN 161.841705626ºW 52.202 m
Billings, Montana KBIL 45.803726761ºN 108.539727967ºW 1112.261 m
Barrow, Alaska PABR 71.282786134ºN 156.789914977ºW 15.581 m
Cold Bay, Alaska PACD 55.200376531ºN 162.718528459ºW 53.652 m
Fairbanks, Alaska PAFA 64.809686817ºN 147.847403468ºW 149.888 m
Honolulu, Hawaii PHNL 21.312783159ºN 157.920876933ºW 24.922 m
Juneau, Alaska PAJN 58.362530123ºN 134.585495176ºW 16.024 m
Mérida, Yucatán (Mexico) MMMD 20.931919004ºN 89.662872977ºW 29.157 m
Mexico City (Mexico) MMMX 19.431653193ºN 99.068389463ºW 2236.638 m
Puerto Vallarta, Jalisco (Mexico) MMPR 20.679034758ºN 105.249200735ºW 11.077 m
San José del Cabo, Baja California (Mexico) MMSD 23.160416093ºN 109.717667886ºW 104.286 m
Tapachula, Chiapas (Mexico) MMTP 14.791340027ºN 92.367991216ºW 54.922 m
Kotzebue, Alaska PAOT 66.887352636ºN 162.611355542ºW 10.911 m
Iqaluit, Nunavut (Canada) CYFB 63.731446844ºN 68.543393603ºW 9.998 m
Gander, Newfoundland and Labrador (Canada) CYQX 48.966447828ºN 54.597532074ºW 146.891 m
Winnipeg, Manitoba (Canada) CYWG 49.900606898ºN 97.259280113ºW 222.046 m
Goose Bay, Newfoundland and Labrador(Canada) CYYR 53.308720955ºN 60.419401330ºW 37.842 m
Albuquerque, New Mexico KZAB 35.173560874ºN 106.567308273ºW 1620.154 m
Anchorage, Alaska PAZA 61.229174557ºN 149.780364869ºW 80.654 m
Aurora, Illinois KZAU 41.782616622ºN 88.331308050ºW 195.922 m
Nashua, New Hampshire KZBW 42.735705193ºN 71.480378445ºW 39.141 m
Leesburg, Virginia KZDC 39.101556058ºN 77.542750106ºW 80.085 m
Longmont, Colorado KZDV 40.187286655ºN 105.127181633ºW 1541.389 m
Fort Worth, Texas KZFW 32.830614792ºN 97.066488376ºW 155.604 m
Houston, Texas KZHU 29.961833882ºN 95.331462501ºW 10.947 m
Hilliard, Florida KZJX 30.698824796ºN 81.908178358ºW 2.141 m
Olathe, Kansas KZKC 38.880140378ºN 94.790729104ºW 305.814 m
Palmdale, California KZLA 34.603503189ºN 118.083872233ºW 763.546 m
Salt Lake City, Utah KZLC 40.786007936ºN 111.952158417ºW 1287.420 m
Miami, Florida KZMA 25.824644475ºN 80.319246501ºW -7.882 m
Memphis, Tennessee KZME 35.067423639ºN 89.955391700ºW 68.788 m
Farmington, Minnesota KZMP 44.637444415ºN 93.152039309ºW 262.667 m
Ronkonkoma, New York KZNY 40.784293219ºN 73.097181151ºW 6.108 m
Fremont, California KZOA 37.543019928ºN 122.015922570ºW -3.459 m
Oberlin, Ohio KZOB 41.297135898ºN 82.206391657ºW 224.115 m
Auburn, Washington KZSE 47.286919203ºN 122.188372739ºW 82.128 m
San Juan, Puerto Rico TJZS 18.431249167ºN 65.993480433ºW -28.547 m
Hampton, Georgia KZTL 33.379671593ºN 84.296678124ºW 261.142 m

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: How it works
  8. ^ Specification for the Wide Area Augmentation System (WAAS), U.S. Department of Transportation Federal Aviation Administration
  9. ^ WAAS and LAAS Status,FAA presentation at 47th meeting of the Civil Global Positioning System Service Interface Committee, September 25, 2008
  10. ^ List of WAAS reference stations in Wikipedia website
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