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report of the action team on global navigation satellite systems (gnss)

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Service Availability Standard62. The United States Government commits to maintaining <str<strong>on</strong>g>the</str<strong>on</strong>g> Positi<strong>on</strong> Diluti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> Precisi<strong>on</strong>(PDOP) in accordance with <str<strong>on</strong>g>the</str<strong>on</strong>g> following tolerances:= 98% <strong>global</strong> Positi<strong>on</strong> Diluti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> Precisi<strong>on</strong> (PDOP) <str<strong>on</strong>g>of</str<strong>on</strong>g> 6 or less.= 88% worst site PDOP <str<strong>on</strong>g>of</str<strong>on</strong>g> 6 or less.• Defined for positi<strong>on</strong> soluti<strong>on</strong> meeting <str<strong>on</strong>g>the</str<strong>on</strong>g> representative user c<strong>on</strong>diti<strong>on</strong>s and operatingwithin <str<strong>on</strong>g>the</str<strong>on</strong>g> service volume over any 24-hour interval.• Based <strong>on</strong> using <strong>on</strong>ly <strong>satellite</strong>s transmitting standard code and indicating “healthy” in <str<strong>on</strong>g>the</str<strong>on</strong>g>broadcast navigati<strong>on</strong> message (sub-frame 1).• In support <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> service availability standard, 24 operati<strong>on</strong>al <strong>satellite</strong>s must be available<strong>on</strong> orbit with 0.95 probability (averaged over any day). At least 21 <strong>satellite</strong>s in <str<strong>on</strong>g>the</str<strong>on</strong>g> 24nominal plane/slot positi<strong>on</strong>s must be set healthy and transmitting a navigati<strong>on</strong> signal with0.98 probability (yearly averaged).• C<strong>on</strong>stellati<strong>on</strong> availability: Representative Performance <str<strong>on</strong>g>of</str<strong>on</strong>g> 25-28 healthy <strong>satellite</strong>s.63. The United States Government’s commitments for maintaining PDOP and c<strong>on</strong>stellati<strong>on</strong>SPS SIS URE result in support for a service availability standard as presented below.SPS Service Availability Standard/Service Availability Standard C<strong>on</strong>diti<strong>on</strong>s and C<strong>on</strong>straints:= 99% Horiz<strong>on</strong>tal Service Availability average locati<strong>on</strong>.= 99% Vertical Service Availability average locati<strong>on</strong>.• 36 meter horiz<strong>on</strong>tal (SIS <strong>on</strong>ly) 95% threshold.• 77 meter vertical (SIS <strong>on</strong>ly) 95% threshold.• Defined for positi<strong>on</strong> soluti<strong>on</strong> meeting <str<strong>on</strong>g>the</str<strong>on</strong>g> representative user c<strong>on</strong>diti<strong>on</strong>s and operatingwithin <str<strong>on</strong>g>the</str<strong>on</strong>g> service volume over any 24-hour interval.• Based <strong>on</strong> using <strong>on</strong>ly <strong>satellite</strong>s transmitting standard code and indicating “healthy” in <str<strong>on</strong>g>the</str<strong>on</strong>g>broadcast navigati<strong>on</strong> message (sub-frame 1).= 90% Horiz<strong>on</strong>tal Service Availability worst case locati<strong>on</strong>.= 90% Vertical Service Availability worst case locati<strong>on</strong>.• 36 meter horiz<strong>on</strong>tal (SIS <strong>on</strong>ly) 95% threshold.• 77 meter vertical (SIS <strong>on</strong>ly) 95% threshold.• Defined for positi<strong>on</strong> soluti<strong>on</strong> meeting <str<strong>on</strong>g>the</str<strong>on</strong>g> representative user c<strong>on</strong>diti<strong>on</strong>s and operatingwithin <str<strong>on</strong>g>the</str<strong>on</strong>g> service volume over any 24-hour interval.• Based <strong>on</strong> using <strong>on</strong>ly <strong>satellite</strong>s transmitting standard code and indicating “healthy” in <str<strong>on</strong>g>the</str<strong>on</strong>g>broadcast navigati<strong>on</strong> message (sub-frame 1).• C<strong>on</strong>stellati<strong>on</strong> RMS User Range Error = SPS Performance Standard (October 2001) = 6meters with Representative Performance = 1.6 meters.• Service Reliability = SPS Performance Standard (October 2001) = 99.94% <strong>global</strong>,99.79% worst site, with Representative Performance = 100% <strong>global</strong> and 100% worst site.17

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