GPS是怎样工作的课件.ppt

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1、StudentSupportServicesByAndyWilliamsonHowGPSWorksWhatisGPS?GPS,whichstandsforGlobalPositioningSystem,istheonlysystemtodayabletoshowyouyourexactpositionontheEarthanytime,inanyweather,anywhere.ThethreepartsofGPSare:SatellitesReceiversSoftwareWhatisGPS?Isalocatio

2、nsystembasedonaconstellationof24satellitesorbitingtheearthataltitudesofapproximately11,000miles.CanaccuratelydeterminelocationsofHistoryInitiatedbyU.S.DepartmentofDefenseMilitaryplannerswantedatechnologywhereapositioncouldbeobtainedwithouttheuseofradiotransmis

3、sionsOfficiallynamedNavigationSystemwithTimingandRanging(NAVSTAR)Firstsatellitelaunchedin1974(satellitesbyRockwellCollins)SatellitesTherearequiteanumberofsatellitesoutthereinspace.Theyareusedforawiderangeofpurposes:satelliteTV,cellularphones,militarypurposesan

4、detc.SatellitescanalsobeusedbyGPSreceivers.GPSSatellitesTheGPSOperationalConstellationconsistsof24satellitesthatorbittheEarthinverypreciseorbitstwiceaday.GPSsatellitesemitcontinuousnavigationsignals.ReceiversandSatellitesGPSunitsaremadetocommunicatewithGPSsate

5、llites(whichhaveamuchbetterviewoftheEarth)tofindoutexactlywheretheyareontheglobalscaleofthings.GPSSignalsEachGPSsatellitetransmitsdatathatindicatesitslocationandthecurrenttime.AllGPSsatellitessynchronizeoperationssothattheserepeatingsignalsaretransmittedatthes

6、ameinstant.Physicallythesignalisjustacomplicateddigitalcode,orinotherwords,acomplicatedsequenceof“on”and“off”pulses.PseudoRandomNoiseCodeReceiverPRNSatellitePRNTimeDifferenceTimeDifferenceTheGPSreceivercomparesthetimeasignalwastransmittedbyasatellitewiththetim

7、eitwasreceived.ThetimedifferencetellstheGPSreceiverhowfarawaythesatelliteis.CalculatingDistanceVelocityxTime=DistanceRadiowavestravelatthespeedoflight,roughly186,000milespersecond(mps)Ifittook0.06secondstoreceiveasignaltransmittedbyasatellitefloatingdirectlyov

8、erhead,usethisformulatofindyourdistancefromthesatellite.186,000mpsx0.06seconds=11,160milesTriangulationGeometricPrinciple:Youcanfindonelocationifyouknowitsdistancefromother,already