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Wide Area Augmentation System ( WAAS ) Fact Sheet by FAA


The FAA has produced the following fact sheet regarding the Wide Area Augmentation System, or WAAS. Most recreational GPS users probably don’t know that the WAAS system was developed by an aircraft company (Raytheon who also produces aircraft under the Beechcraft name) and was designed specifically with aviation needs in mind.

The Wide Area Augmentation System (WAAS) is a navigational tool representing an enormous leap forward in air navigation, providing precision approach guidance to thousands of airports and airstrips where there is no precision landing capability. It is a core element in transitioning to the satellite-based air traffic control system of the future.

WAAS is designed to improve the accuracy and ensure the integrity of information coming from Global Positioning System (GPS) satellites.

  • GPS alone does not meet FAA’s navigation requirements for accuracy, integrity and availability. Nor does it provide the necessary guarantees that its signal will be accurate and available at all times.
  • WAAS corrects for ionospheric and other disturbances in the GPS signal, making the signal more accurate and dependable.
  • More importantly, WAAS warns the pilot when WAAS or GPS are not functioning correctly and should not be used for navigation.
  • Currently, precision approach capability is limited to major airports. WAAS will make precision approaches available at any airport that has WAAS procedures.

Although the WAAS was designed for aviation users, it supports a wide variety of non-aviation uses including agriculture, surveying, recreation, and surface transportation, just to name a few. The WAAS signal has been available for non safety-of-life applications since August 2000, and numerous manufacturers have developed WAAS-enabled GPS receivers for the consumer market. Today, there are millions of non-aviation WAAS-enabled GPS receivers in use.

WAAS was developed for the FAA by Raytheon Corp.

How WAAS Works
WAAS uses a network of precisely-located ground reference stations that monitor GPS satellite signals. These stations are located throughout the continental U.S., Hawaii, Puerto Rico, Alaska, Canada and Mexico. The stations collect and process GPS information and send the information to WAAS master stations. The WAAS master stations develop a WAAS correction message that is sent to user receivers via navigation transponders on geostationary satellites. The WAAS message improves the accuracy, availability, and safety of GPS-derived position information. Using WAAS, GPS signal accuracy is improved from 20 meters to approximately 1.5– 2 meters in both the horizontal and vertical dimensions. WAAS hardware consists of: 25 ground reference stations, 2 master stations, 2 INMARSAT satellites and the terrestrial communications network.

Two of the FAA’s top goals are increased safety and greater capacity. WAAS provides both. Additional significant benefits include:

  • More direct, fuel efficient and timely routings through the air traffic control system.
  • More flexible approach and departure routings, which will cut arrival times as well as enhance safety and noise abatement.
  • Automatic Dependent Surveillance-Broadcast (ADS-B) that will increase the amount of traffic that can be handled by air traffic control. ADS-B uses the aircraft’s knowledge of its position using WAAS to report a more accurate position to controllers.
  • Terrain Avoidance Warning Systems, which warn pilots and controllers of proximity to the ground.
  • Significant government cost savings due to the elimination of maintenance costs associated with older, more expensive ground-based navigation aids.

WAAS is a pioneering technology. Currently, no other navigation technologies exist to meet FAA requirements and user needs for the expansion of precision landing capabilities at thousands of additional airports.


  • The FAA commissioned WAAS in July 2003 for instrument flight use and today more than 4,000 aircraft are equipped with WAAS capable avionics.
  • In October 2004, FAA Administrator Marion C. Blakey urged aviation users to equip with WAAS. Blakey announced that U.S. avionics manufacturers were building new WAAS receivers or upgrading existing GPS receivers to WAAS capability.
  • The first commercial flight with a certified TSO-145 GPS/WAAS receiver was flown in March 2003 by FAA’s Capstone program in Alaska. Garmin and Chelton Flight Systems have certified WAAS receivers.
  • The FAA installed four additional WAAS reference stations in Barrow, Bethel, Fairbanks, and Kotzebue, AK in December 2004. The agency is adding 13 additional ground reference stations in Alaska, Canada, and Mexico and 1 additional master station, replacing the aging INMARSAT satellite communications links, and is modernizing the terrestrial communications network.
  • In March 2005, the FAA finalized the Geostationary Satellite Communications Control Segment contract with Lockheed Martin for WAAS geostationary satellite leased services through 2016. The initial contract was awarded to Lockheed Martin in March 2003 and provided the FAA the capability of ordering two satellites, PanAmSat Galaxy XV and Telesat Anik F1R, both scheduled for launch in 2005 and planned to be operational in late 2006. The Telesat launched September 9, 2005.
  • In June 2005, WAAS achieved a major milestone toward full localizer performance with vertical guidance (LPV) approach capability throughout the continental U.S. with the installation of the first international WAAS reference station in Canada.

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