The White House announced May 1, 2000 the United States will discontinue “selective availability” of the global positioning system signals available to the public.
What is selective availability?
Selective availability is the intentional degradation of signals transmitted by Navstar GPS satellites, providing civilian users with accuracy less than what’s used by the military.
With the removal of SA, GPS accuracy improves up to tenfold, according to Air Force Space Command officials. The new policy went into effect immediately.
GPS constellation
GPS is a dual-use, satellite-based system that provides accurate location and timing data to users worldwide. The 24-satellite GPS constellation is operated and controlled by Air Force Space Command’s 50th Space Wing at Schriever Air Force Base, Colo.
GPS provides 24-hour navigation services to military and civilians users worldwide.
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Why was selective availability discontinued?
In his announcement, President Bill Clinton said that in his goals for GPS he wanted to “encourage acceptance and integration of GPS into peaceful civil, commercial and scientific applications worldwide; and to encourage private sector investment in and the use of … GPS technologies and services. To meet these goals, I committed the U.S. to discontinuing the use of (selective availability)…”
Clinton said the decision to discontinue SA was based “upon a recommendation by the secretary of defense in coordination with the departments of State, Transportation, Commerce, the director of Central Intelligence, and other Executive Branch departments and agencies. They realized that worldwide transportation safety, scientific, and commercial interests could best be served by discontinuation of SA.”
The president said the decision to discontinue SA is “coupled with…continuing efforts to upgrade the military utility of our systems that use GPS, and is supported by threat assessments which conclude that setting SA to zero at this time would have minimal impact on national security.”
In the White House announcement the president indicated that future threats could be dealt with by applying SA on a regional basis as needed.
“We have demonstrated the capability to selectively deny GPS signals on a regional basis when our security is threatened,” Clinton said.
Originally developed by the Department of Defense as a military system, GPS is now used around the world in many applications, including air, road, marine, and rail navigation, telecommunications and emergency response.
by Maj. LeWonnie Belcher
Air Force Space Command Public Affairs
