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WAAS Ground Segment

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


The Wide Area Augmentation System (WAAS) is an GPS Augmentation system developed by the 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.[1]

WAAS Ground Segment

WAAS System

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.[2]

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.

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

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.[2] Listed below are the coordinates of the site centroids in North America:

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 CYFB 63.731446844ºN 68.543393603ºW 9.998 m
Gander, Newfoundland and Labrador CYQX Template:Coord 146.891 m
Winnipeg, Manitoba CYWG Template:Coord 222.046 m
Goose Bay, Newfoundland and Labrador CYYR Template:Coord 37.842 m
Albuquerque, New Mexico KZAB Template:Coord 1620.154 m
Anchorage, Alaska PAZA Template:Coord 80.654 m
Aurora, Illinois KZAU Template:Coord 195.922 m
Nashua, New Hampshire KZBW Template:Coord 39.141 m
Leesburg, Virginia KZDC Template:Coord 80.085 m
Longmont, Colorado KZDV Template:Coord 1541.389 m
Fort Worth, Texas KZFW Template:Coord 155.604 m
Houston, Texas KZHU Template:Coord 10.947 m
Hilliard, Florida KZJX Template:Coord 2.141 m
Olathe, Kansas KZKC Template:Coord 305.814 m
Palmdale, California KZLA Template:Coord 763.546 m
Salt Lake City, Utah KZLC Template:Coord 1287.420 m
Miami, Florida KZMA Template:Coord -7.882 m
Memphis, Tennessee KZME Template:Coord 68.788 m
Farmington, Minnesota KZMP Template:Coord 262.667 m
Ronkonkoma, New York KZNY Template:Coord 6.108 m
Fremont, California KZOA Template:Coord -3.459 m
Oberlin, Ohio KZOB Template:Coord 224.115 m
Auburn, Washington KZSE Template:Coord 82.128 m
San Juan, Puerto Rico TJZS Template:Coord -28.547 m
Hampton, Georgia KZTL Template:Coord 261.142 m

Notes

References

  1. ^ WAAS in Wikipedia
  2. ^ a b WAAS and LAAS Status,FAA presentation at 47th meeting of the Civil Global Positioning System Service Interface Committee, September 25, 2008