Error analysis for the Global Positioning System: Difference between revisions

Revision as of 00:24, 22 January 2022

Revision as of 12:40, 13 March 2022

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During the 1990–91 [[Gulf War]], the shortage of military GPS units caused many troops and their families to buy readily available civilian units. Selective Availability significantly impeded the U.S. military's own battlefield use of these GPS, so the military made the decision to turn it off for the duration of the war.

In the 1990s, the [[Federal Aviation Administration|FAA]] started pressuring the military to turn off SA permanently. This would save the FAA millions of dollars every year in maintenance of their own [[radio navigation]] systems. The amount of error added was "set to zero"<ref name="FAA">{{Cite web |date=May 1, 2000 |title=Statement by the President regarding the United States' Decision to Stop Degrading Global Positioning System Accuracy |url=http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/gps/policy/presidential/index.cfm?print=go#1 |access-date=2013-01-04 |publisher=[[Federal Aviation Administration]] |archive-url=https://web.archive.org/web/20111021210058/http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/gps/policy/presidential/index.cfm?print=go#1 |archive-date=2011-10-21 |url-status=dead}}</ref> at midnight on May 1, 2000 following an announcement by U.S. President [[Bill Clinton]], allowing users access to the error-free L1 signal. Per the directive, the induced error of SA was changed to add no error to the public signals (C/A code). Clinton's executive order required SA to be set to zero by 2006; it happened in 2000 once the U.S. military developed a new system that provides the ability to deny GPS (and other navigation services) to hostile forces in a specific area of crisis without affecting the rest of the world or its own military systems.<ref name="FAA" />

On 19 September 2007, the [[United States Department of Defense]] announced that future [[GPS modernization|GPS III]] satellites will not be capable of implementing SA,<ref>{{Cite web |date=September 18, 2007 |title=DoD Permanently Discontinues Procurement Of Global Positioning System Selective Availability |url=http://www.defenselink.mil/releases/release.aspx?releaseid=11335 |url-status=dead |archive-url=https://web.archive.org/web/20080218050849/http://www.defenselink.mil/releases/release.aspx?releaseid=11335 |archive-date=February 18, 2008 |access-date=2008-02-20 |publisher=DefenseLink}}</ref> eventually making the policy permanent.<ref>{{Cite web |title=Selective Availability |url=http://pnt.gov/public/sa/ |url-status=dead |archive-url=https://web.archive.org/web/20080113123316/http://pnt.gov/public/sa/ |archive-date=January 13, 2008 |access-date=2008-02-20 |publisher=National space-based Positioning, Navigation, and Timing Executive Committee}}</ref>