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Global Positioning System: Difference between revisions
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The orbital planes are centered on the Earth, not rotating with respect to the distant stars.<ref>[http://metaresearch.org/cosmology/gps-relativity.asp What the Global Positioning System Tells Us about Relativity]. Accessed [[January 2]], [[2007]].</ref> The six planes have approximately 55° [[inclination]] (tilt relative to Earth's [[equator]]) and are separated by 60° [[right ascension]] of the [[orbital node|ascending node]] (angle along the equator from a reference point to the orbit's intersection).<ref name="GPS overview from JPO">[http://gps.losangeles.af.mil/jpo/gpsoverview.htm GPS Overview from the NAVSTAR Joint Program Office]. Accessed [[December 15]], [[2006]].</ref> | The orbital planes are centered on the Earth, not rotating with respect to the distant stars.<ref>[http://metaresearch.org/cosmology/gps-relativity.asp What the Global Positioning System Tells Us about Relativity]. Accessed [[January 2]], [[2007]].</ref> The six planes have approximately 55° [[inclination]] (tilt relative to Earth's [[equator]]) and are separated by 60° [[right ascension]] of the [[orbital node|ascending node]] (angle along the equator from a reference point to the orbit's intersection).<ref name="GPS overview from JPO">[http://gps.losangeles.af.mil/jpo/gpsoverview.htm GPS Overview from the NAVSTAR Joint Program Office]. Accessed [[December 15]], [[2006]].</ref> | ||
Orbiting at an altitude of approximately 20,200 | Orbiting at an altitude of approximately 20,200 kilometers (12,600 miles or 10,900 nautical miles; orbital radius of 26,600 km (16,500 mi or 14,400 NM)), each SV makes two complete orbits each [[sidereal day]], so it passes over the same location on Earth once each day. The orbits are arranged so that at least six satellites are always within [[line of sight]] from almost anywhere on Earth.<ref>[http://www.navcen.uscg.gov/faq/gpsfaq.htm USCG Navcen: GPS Frequently Asked Questions]. Accessed [[January 3]], [[2007]].</ref> | ||
[[As of February 2007]], there are 30 actively broadcasting satellites in the GPS [[satellite constellation|constellation]]. The additional satellites improve the precision of GPS receiver calculations by providing redundant measurements. With the increased number of satellites, the constellation was changed to a nonuniform arrangement. Such an arrangement was shown to improve reliability and availability of the system, relative to a uniform system, when multiple satellites fail.<ref>Massatt, Paul and Brady, Wayne. "[http://www.aero.org/publications/crosslink/summer2002/index.html Optimizing performance through constellation management]", ''Crosslink'', Summer 2002, pages 17-21.</ref> | [[As of February 2007]], there are 30 actively broadcasting satellites in the GPS [[satellite constellation|constellation]]. The additional satellites improve the precision of GPS receiver calculations by providing redundant measurements. With the increased number of satellites, the constellation was changed to a nonuniform arrangement. Such an arrangement was shown to improve reliability and availability of the system, relative to a uniform system, when multiple satellites fail.<ref>Massatt, Paul and Brady, Wayne. "[http://www.aero.org/publications/crosslink/summer2002/index.html Optimizing performance through constellation management]", ''Crosslink'', Summer 2002, pages 17-21.</ref> | ||
