Editing Galileo (satellite navigation) (section)

==== GPS and Galileo ====
{{Comparison satellite navigation orbits}}

One of the reasons given for developing Galileo as an independent system was that position information from GPS can be made significantly inaccurate by the deliberate application of universal [[Error analysis for the Global Positioning System|selective availability]] (SA) by the US military. GPS is widely used worldwide for civilian applications; Galileo's proponents argued that civil infrastructure, including aircraft navigation and landing, should not rely solely upon a system with this vulnerability.

On 2 May 2000, the selective availability was disabled by the President of the United States, [[Bill Clinton]]; in late 2001 the entity managing the GPS confirmed that it did not intend to enable selective availability ever again.<ref>{{citation-attribution|1={{Cite web |date=13 November 2014 |title=Satellite Navigation - GPS - Policy - Selective Availability |url=https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/gps/policy/availability/index.cfm |website=faa.gov}}}}</ref> Though Selective Availability capability still exists, on 19 September 2007 the US Department of Defense announced that newer GPS satellites would not be capable of implementing Selective Availability;<ref>{{cite web|url=http://www.defenselink.mil/releases/release.aspx?releaseid=11335|title=DoD Permanently Discontinues Procurement of Global Positioning System Selective Availability |publisher=DefenseLink|date=18 September 2007|access-date=17 December 2007|url-status=dead|archive-url=https://web.archive.org/web/20080218050849/http://www.defenselink.mil/releases/release.aspx?releaseid=11335 |archive-date=18 February 2008}}</ref> the wave of [[GPS Block IIF|Block IIF]] satellites launched in 2009, and all subsequent GPS satellites, are stated not to support selective availability. As old satellites are replaced in the [[GPS Block III]] programme, selective availability will cease to be an option.<ref>{{citation-attribution|1={{cite web|url=https://www.gps.gov/systems/gps/modernization/sa/|title=GPS.gov: Selective Availability |website=www.gps.gov|access-date=4 February 2018}} }}</ref> The modernisation programme also contains standardised features that allow GPS III and Galileo systems to inter-operate, allowing receivers to be developed to utilise GPS and Galileo together to create an even more accurate GNSS.