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卫星导航系统SatelliteNavigationSystem任课教师：赵琳课程内容Syllabus§1卫星导航系统发展概述§2

GPS系统组成§3GPS定位原理§4GPS信号与导航电文§5GPS系统误差分析及补偿§6GPS应用§1

卫星导航系统发展概述IntroductiontotheDevelopmentofSatelliteNavigation§1卫星导航系统发展概述HistorychangedonOctober4,1957,whentheSovietUnionsuccessfullylaunchedSputnikI(СпутникI).Thatlaunchusheredinnewpolitical,military,technological,andscientificdevelopments.1.1.人造卫星的发射使卫星导航成为可能SputnikI§1卫星导航系统发展概述On4October1957,launchofSputnikI.On3November1957,SputnikIIwasputintoorbit.SputnikIIIwaslaunchedon18September1958.OrbitofsputnikI,II,III§1卫星导航系统发展概述AtAppliedPhysicsLab(APL),JohnsHopkinsUniversityatBaltimore,twojuniorphysicists,GeorgeWeiffenbachandWilliamGuier,wereregardedastheGENESIS&PIONEERSOFSATELLITENAVIGATION.TheyfiguredoutawaytodetermineSputnik'sorbitsimplybymeasuringtheDoppler-inducedchangesinthefrequency.

George(left)andWilliam(right)

atarecentsymposiumontheLegacyofTransit.§1卫星导航系统发展概述JohaanChristianDoppler,anAustriaphysician,foundDopplerEffectin1842.

JohaanChristianDoppler1803-1853

DopplerShiftisaneffectthatisassociatedwithanywavephenomena(suchassoundwaves).§1卫星导航系统发展概述DopplerShift§1卫星导航系统发展概述ROYGBIV：Red,Orange,Yellow,Green,Blue,Indigo,Violet

Ifyoudriveyourcarto

movesoquicklytowardsaredtrafficlightthatitwouldappeargreentoyou,willthepolicefineyou?§1卫星导航系统发展概述JohnsHopkinsUniversitysignedacontract(PlanTRANSIT)withAmericanNavyin1960;NavyNavigationSatelliteSystem(NNSS)wasbuiltupinJanuary1964;1.2.子午仪计划（PlanTRANSIT）§1卫星导航系统发展概述RichardB.KerschnerAwardThisawardisfortherecognitionofanindividualwhohasmadeasubstantialcontributiontothetechnologyofnavigationandpositioningequipment,systems,orpractices.Initiatedin1986,itispresentedatthebiennialPositionLocationandNavigation(PLANS)Conference.

WilliamH.Guier,FrankT.McClure,andGeorgeC.

Weiffenbach(ltor)discusstheprinciplesoftheTransitNavigation

System(latercalledtheNavyNavigationSatelliteSystem).§1卫星导航系统发展概述NavyNavigationSatelliteSystem—NNSSTransitConstellation§1卫星导航系统发展概述NavyNavigationSatelliteSystem—NNSSTheOrbitIntervalofTRANSITsatellite§1卫星导航系统发展概述NavyNavigationSatelliteSystem—NNSSTheOrbitofTRANSITsatellite§1卫星导航系统发展概述NavyNavigationSatelliteSystem—NNSSTwoNNSSSatellites§1卫星导航系统发展概述NavyNavigationSatelliteSystem—NNSSNNSSReceiver§1卫星导航系统发展概述NavyNavigationSatelliteSystem—NNSSNavigationPrinciple§1卫星导航系统发展概述NNSSNavigationPrinciplet1t2t3OrbitD1D2D3§1卫星导航系统发展概述NNSSNavigationAccuracy

In1967,thesystemwasopenedtothecivilapplicationoftheworld;In1968,theaccuracyofNNSS:~70mIn1976,

itwasimprovedtobe:~30m§1卫星导航系统发展概述In1967,VicePresidentHubertHumphreyreleasedthesystemforpublicandcommercialusebyshipsofallfriendlynations,andinOctoberhepresentedDr.KershnerwithaDistinguishedPublicServiceAward.

Attheendof1996Transit,theNavyNavigationSatelliteSystem,wasretiredaftermorethan32yearsofcontinuous,successfulservicetotheU.S.Navy.Duringits32yearsofoperation,theTransitNavigationSystemprovidedanextremelyaccurateandreliableglobalnavigationsystemfortheU.S.Navyandtheciviliancommunity.Thesystemwascontinuouslyimprovedthroughtheyearsandcontributedtonumerousadvancesinspacescience,engineering,andtechnology.NavyNavigationSatelliteSystem—NNSS§1卫星导航系统发展概述TheTransitsystemspawnedanumberofspace"firsts,"includs:thetwo-frequencymethodforcorrectingionosphericerror,solarattitudedetectors,dual-launchpayloads,satelliteelectronicmemoryanuplinkauthenticationsystem,gravity-gradientstabilization.developmentofsatellitecompensationfordragandradiationpressure,theuseofpulsedplasmamicro-thrusters,andhardeningofthespacecraftagainstanenhancedradiationenvironment.§1卫星导航系统发展概述NavyNavigationSatelliteSystem—NNSS1.3NAVSTARGPSNAVigation

SatelliteTimingAndRangingGlobalPositioningSystemDevelopedandmaintainedbytheDepartmentofDefenseOperatestwopositioningservicesPrecisePositioningService(PPS)StandardPositioningService(SPS)Consistsofthreesegments:User–handheldreceiverSpace–satelliteconstellationControl–trackingandcorrections

§1卫星导航系统发展概述NAVSTARGPSGenerationsofthecurrentsystemBlockISeriesof11experimentalsatellites1stsatellitelaunchedin1978,thelastin1985Lastsatellitedecommissionedin1995BlockII/IIAlaunched1989-19974atomicclocksIncreasedsatellitelifetimeMoredatastoragecapabilitiesNucleardetonationdetectorBlockIIRAbilitytooperateautonomouslyforlongperiodsUpto5carriersignals§1卫星导航系统发展概述CurrentGPSCapabilitiesThecurrentsystememploys24activesatellites,atleast6backupsCosttomaintainsystem:$750millionperyearCombinationofBlockII,IIAandIIR1995useofGPSbecameavailabletothepublic,freeofchargeLevelsofservice:SPSchannelL1Predictedaccuracy:13mhorizontal,22mvertical,200nsPPSchannelL2Predictedaccuracy:8mhorizontalandvertical,40ns§1卫星导航系统发展概述1.4OtherSystemsGLONASSBeidouGalileoWAASLAASEGNOSMSAS§1卫星导航系统发展概述GLONASSGlobalNavigationSystemdevelopedbyRussiaNominallyconsistsof21satellitesplus3spares8satellitesarrangedin3orbitalplaneswithaninclinationof64.8ºOrbitsareapproximatelycircularwithaperiodof11h15m§1卫星导航系统发展概述GLONASSAlsotransmitsL1&L2carriers,C/A&PcodesL1isin1602-1615.5MHzbandTobeshiftedto(1598.0625-1604.25MHz)L2isin1246-1256.5MHzbandTobeshiftedto(1242.9365-1247.75MHz)C/Acodeis0.5MpsPCodeis5.11Mbps§1卫星导航系统发展概述GLONASSCarrierfrequencydependsonthesatelliteEachoneiscurrentlyuniqueAftershift,eachpairofsatelliteswillbeassignedthesamefrequencyPairsonoppositesidesoftheEarth(antipodal)Usesfrequencychannelratherthancodetoidentifysatellite§1卫星导航系统发展概述GLONASSThesystemisnotasrobustaspredictedEconomiccrisishasseverelyhurttheRussianspaceprogramFewersatellitesinorbitthanexpectedAslittleas7inMay2001Newclassofsatellites(GLONASS-M)shouldbelaunchedsoon§1卫星导航系统发展概述GLONASSCanbeusedinconjunctionwithGPStoimprovenavigation/positioningNeedtoaccountfor2differencesinreferenceNeedtotransformEarthParameterSystem1990(PZ-90)toWGS84Candifferbyupto20mNeedtorelateRussiantimescaletoGPStimeCandifferby10sofμs§1卫星导航系统发展概述Beidou北斗系统ChineseregionalsatellitenavigationsystemConsistsof2satellitesingeostationaryorbitsAltitudeof36000kmUsedinlandandmarinetransportationPlansfornextgenerationsystem§1卫星导航系统发展概述地面中心站S1S2D1D2DS1DS2用户北斗系统§1卫星导航系统发展概述GalileoSystem伽利略系统

SystemSpecification：PositioningAccuracy:10m(95%);TimingAccuracy:<33ns;TTFF:<15s;GlobalAvailability:>99.7%;30satellites;

§1卫星导航系统发展概述系统将耗资24~30亿欧元；推行公方和私方联营体制（PublicPrivatePartnership）；中国已于2003年9月18日正式成为该系统的投资方。Galileo§1卫星导航系统发展概述GalileoProposedandbeingplannedbyEuropeItwillbecontrolledbyciviliansPlanscallfor30mediumEarthorbitsatellitesDistributedin3orbitalplanesAltitudeof23000km§1卫星导航系统发展概述GalileoWillprovide2levelsofserviceBasic(free-of-charge)Chargeableservice3phasesofdevelopmentDefinitionphase(alreadycompleted)DevelopmentandvalidationphaseDeploymentphaseScheduledtobeginin2006/7timeframeServiceby2008(?)§1卫星导航系统发展概述GalileoBecauseitiscivilianoperated,itwillhaveadvantagesinthemarketplaceAlreadypromisingtoprovideaservicethatwillmeetlegalstandardsGPScan’tdothisIfthelawyersarehappy,thebusinessmoneyismorelikelyintoGalileoproducts§1卫星导航系统发展概述WAASWideAreaAugmentationSystem(WAAS)CoversNorthAmericaSouthAmericacouldbecoveredlaterUtilizesGPSbutaugmentsitwithadditionalsatelliteinformationUsegeostationarysatellitesInternationalMaritimeSatellite(Inmarsat)ProvidesadditionalreliabilityandaccuracyUsedforaircraftnavigationNotnecessarilyfortakeoffandlanding§1卫星导航系统发展概述LAASLocalAreaAugmentationSystem(LAAS)UtilizesGPSbutaugmentsitwithpseudoliteinformationatcriticallocationsTypicallyaroundairportsbutcouldbeusedinotherlocationstheoreticallyUsedforaircrafttakeoffandlandingIncludingcategoryII/III§1卫星导航系统发展概述EGNOSEuropeanGeostationaryNavigationOverlaySystem(EGNOS)EuropeanversionofWAASCoversallofEuropeandNorthAfricaCouldbeextendedtocoverallofAfricaandMiddleEastWilleventuallybesupercededbyGalileo§1卫星导航系统发展概述MSASMTSATSatellite-BasedAugmentationSystem(MSAS)Multi-functionalTransportSatellite(MTSAT)JapaneseversionofWAASCoverspartsofAsiaandthePacific§1卫星导航系统发展概述§2GPS系统组成GPSSystemComposition§2GPS系统组成TheGlobalPositioningSystemConstellationof24satellitesoperatedbytheU.S.DepartmentofDefenseOriginallyintendedformilitaryapplicationsbutextendedtocivilianuseEachsatellite’sorbitalperiodis12hours6satellitesvisibleineachhemisphere§2GPS系统组成GPSStructures

SpaceSegmentControlSegmentUserSegment§2GPS系统组成GPSStructures§2GPS系统组成GPSSpaceSegment§2GPS系统组成GPSSpaceSegment§2GPS系统组成GPSSpaceSegment§2GPS系统组成GPSSatellitesBLOCK-IBLOCK-II§2GPS系统组成GPSSatellitesBLOCK-IIRBLOCK-II§2GPS系统组成GPS系统卫星的作用接收和储存由地面注入站发送的导航电文和其他有关信息，并通过GPS信号形成电路，适时地发送给用户；连续地向用户发送导航定位信号，并通过导航电文报告自己的现势位置、状态和其他在轨卫星的概略位置；接收并执行地面主控站发送的卫星调度命令，如适时地改正运行偏差、调整卫星姿态或者启用备用时钟等；卫星上设有微处理机，进行部分必要的数据处理工作；通过星载的高精度原子钟提供精密的时间标准。钟型时钟频率（Hz）每日稳定度差1s所需时间石英钟

5000000

109

30年铷钟

6834682613

1012

30000年铯钟

9192631770

1013

300000年氢钟

1420405751

1015

30000000年§2GPS系统组成GPSControlSegment§2GPS系统组成GPSControlSegment§2GPS系统组成GPS地面监控系统的作用根据本站和其他监测站的观测资料编制各卫星的星历、卫星钟差和大气层的修正参数等，并把数据传送到注入站；提供全球定位系统的时间基准，各监控站和GPS卫星的原子钟均应与主控站的原子钟同步或测出其间的钟差，并把这些钟差信息编入导航电文；对地面监控系统的工作状况及卫星的健康状况进行诊断，调整偏离轨道的卫星，使之沿预定轨道运行；进行卫星调度，控制启用备用卫星以替代失效的工作卫星。§2GPS系统组成GPSUserSegmentMilitary.Searchandrescue.Disasterrelief.Surveying.Marine,aeronauticalandterrestrialnavigation.Remotecontrolledvehicleandrobotguidance.Satellitepositioningandtracking.Shipping.GeographicInformationSystems(GIS).Recreation.§2GPS系统组成GPSUserSegment(Receiver)AshtechG8OEMGarmin

StreetPilotGarminGPSMap185WithSounder§2GPS系统组成GPSUserSegment(Receiver)Garmin

NavTalkTrimbleNT300DGarminVHF725§2GPS系统组成CompositionofGPSReceiver

GPS接收机主要由天线单元、主机单元和电源三部分组成。接收机主机由变频器、信号通道、微处理器、存储器及显示模块组成：§2GPS系统组成ClassificationofGPSReceiver1．按照用途分类（1）导航型接收机（2）测地型接收机（3）授时型接收机2．按照接收机的工作原理分类（1）码相关型（CorrelationChannel）接收机（2）平方型（SquaringChannel）接收机（3）混合型（HybridChannel）接收机（4）码相位型（CodePhaseChannel）接收机（5）干涉型（InterferometryChannel）接收机3．按照信号通道分类（1）多通道（Multi-Channel）接收机（2）序贯通道（SequencingChannel）接收机（3）多路复用通道（MultiplexingChannel）接收机4．根据接收的卫星信号频率分类（1）单频（L1）接收机（2）双频（L1+L2）接收机。§2GPS系统组成§3GPS定位原理GPSPositioningTheory§3GPS定位原理PositionisBasedonTimeT+3Distancebetweensatelliteandreceiver=“3timesthespeedoflight”TSignalleavessatelliteattime“T”Signalispickedupbythereceiverattime“T+3”§3GPS定位原理PseudoRandomNoiseCodeReceiverPRNSatellitePRNTimeDifference§3GPS定位原理WhatTimeisitAnyway?ZuluTimeMilitaryTime

(localtimeona24hourclock)UniversalCoordinatedTimeGreenwichMeanTimeLocalTime:AMandPM(adjustedforlocaltimezone)GPSTime-13**GPSTimeiscurrentlyaheadofUTCby13seconds.§3GPS定位原理SignalFromOneSatelliteThereceiverissomewhereonthissphere.§3GPS定位原理SignalsFromTwoSatellites§3GPS定位原理ThreeSatellites(2DPositioning)§3GPS定位原理TriangulatingCorrectPosition§3GPS定位原理ThreeDimensional(3D)Positioning§3GPS定位原理FundamentalsofPositionFixingTherangebasedonmeasuringthetime-of-flightofaRFsignalthatleavesthetransmitteratt=t1andarrivesattheuseratt=t2isgivenby:Inthepresenceofaclockerror,dt(=b/c),therangeestimate(ormeasurement)becomes:§3GPS定位原理GPSPositionFixing§3GPS定位原理SV#1SV#2SV#3AsauserlocatedatpointX,thetruerangemeasurementstothethreeGPSsatellitesare:YourGPSreceiver,however,measuresr1,r2

andr3.Theserangemeasurementarecalledpseudoranges.GPSPseudoranges§3GPS定位原理SolvingNavigationEquationsSolvether-requationsEasyandgiveyouinsightintothelinearizationprocessGPSnavigationequations.The

r-rpositionfixingsystemofequationswherethreeindependentrangemeasurementsareavailablewasgivenas:§3GPS定位原理LinearizationbyExpansionExactEquationsyouwouldsolveinanidealworldEquationstheyoucanorwillsolve§3GPS定位原理LinearizationbyExpansion(2)(droppedhigherorderterms)Fortherangemeasurements,Forthepositioncoordinatex,Forthepositioncoordinatey,Where,§3GPS定位原理LinearizationbyExpansion(3)Takingthedifferencebetweenthetrueandestimatedvalues,Normallyyouhavemoreequationsthanunknowns.Thus,youcandoaleastsquaressolution.Thatis,§3GPS定位原理LinearizationbyExpansion(4)Becausewedon’thavetrueranges,butpseudo-ranges,weaugmenttheGmatrixwithacolumnofonesforthetimebias.Weneedatleast3measurementsforthe2-Dsolution.§3GPS定位原理LeastSquaresSolutionForthemoment,withoutproof,westatethattheleastsquaressolutionisgivenby,Algorithmforsolvingthenavigationequation:1)Pickaninitialguessforxandy2)Computeforasmanymeasurementsasyouhave3)Formforallmeasurementsandthenform4)Solvefor5)Updateyourinitialguessesforxandyasfollows:6)Repeatuntilconvergence§3GPS定位原理§4GPS信号与导航电文GPSSignalsandNavigationMessage§4

GPS信号与导航电文TheSignalsCarriersignalsL1andL2aremodulatedwithothersignals:Rangingcodes–binaryPRNCoarseacquisition(C/A)code-L1only1,023bitcodebroadcast@1.023Mbps,repeatseverymsEachsatellitehasitsownuniqueC/Acode.Precision(P)code–L1andL2AlsoaPRN,butis266dayslong@10.23Mbps–about2.35x10^14bitslong!DividedintoweeklongsegmentsandassignedtoeachsatelliteAlsousedforidentificationbutismoresecure,suitableformilitary.§4

GPS信号与导航电文TheSignalsReceiverscarryalistofidenticalcodesinorderto:Identifywhichsatellitethesignalisfromand,Asakindofruler,tomeasuretimedelayofsignal.Clocksmustbesynchronized§4

GPS信号与导航电文TheSignalsThenavigationmessageisalsomodulatedintobothcarriersignals37,500bitcode@50bpstakes750s–12andahalfminutesContainsvariousformsofinformationSatellitehealthstatusClockcorrectionsSatellitealmanac–predictedpositionsofsatellitesEphemeris–positionsofallsatellitesasafunctionoftime§4

GPS信号与导航电文TheWholeMessageTotalinformationbroadcast:Carriersignal-1575.42or1227.6MHzsinwaveNavigationmessageEphemerisdataprovidesthereceiverwiththeexactpositionsandtimesofall24satellitesatthetimeofbroadcastConstantlysynchronizesreceiver’squartzclockwithGPStimeC/AcodeandPcodeidentifyeachsatelliteandprovideastandardbywhichtomeasuretimedelay§4

GPS信号与导航电文FindingyourPositionThereceivermakesaroughestimate,apseudorangetoasatellitebyaligningtheC/AandPcodes.Usuallyaccuratetoafewhundredyards.EphemerisdatagivesexactlocationandtimeofthesatelliteatthebeginningofitstransmissionsCorrectionstoephemerissenttosatelliteshourlyQuartzclockinreceiverresynchronizesitselfwithGPStime,synchronizedwithin10nsReceiverhasallitneeds:locationsoffourormoresatellitesandthedistancetothem.3Dtrilaterationwillyieldanaccuratelocation§4

GPS信号与导航电文§5GPS系统误差分析及补偿GPSErrorandErrorMitigation§5GPS系统误差分析及补偿SourcesOfErrorGeometricDegreeofPrecision(GDOP)SelectiveAvailabilityDiscontinuedin5/1/2000AtmosphericEffectsIonosphericTroposphericMultipathEphemerisError (satellitepositiondata)SatelliteClockErrorReceiverClockError§5GPS系统误差分析及补偿

Source

AmountofErrorSatelliteclocks: 1.5to3.6metersOrbitalerrors: <1meterIonosphere: 5.0to7.0metersTroposphere: 0.5to0.7metersReceivernoise: 0.3to1.5metersMultipath: 0.6to1.2metersSelectiveAvailability (seenotes)Usererror: UptoakilometerormoreErrorsarecumulativeandincreasedbyPDOP.§5GPS系统误差分析及补偿GeometricDegreeofPrecision(GDOP)RelativegeometryofsatelliteconstellationtoreceiverWithfoursatellitesbestGDOPoccurswhenThreesatellitesjustabovethehorizonspacedevenlyaroundthecompassOnesatellitedirectlyoverheadSatelliteselectionminimizesGDOPerror§5GPS系统误差分析及补偿GoodGeometricDegreeofPrecision§5GPS系统误差分析及补偿BadGeometricDegreeofPrecision§5GPS系统误差分析及补偿ErrorMitigationTechniquesCarriersatL1andL2frequenciesIonosphericerrorisfrequencydependentsousingtwofrequencieshelpstolimiterrorDifferentialGPSPost-ProcessusermeasurementsusingmeasurederrorvaluesSpaceBasedAugmentationSystems(SBAS)ExamplesareU.S.WideAreaAugmentationSystem(WAAS),EuropeanGeostationaryNavigationalOverlayService(EGNOS)SBASprovidesatmospheric,ephemerisandsatelliteclockerrorcorrectionvaluesinrealtime。§5GPS系统误差分析及补偿DifferentialGPSUsesaGPSreceiveratafixed,surveyedlocationtomeasureerrorinpseudorangesignalsfromsatellitesPseudorangeerrorforeachsatelliteissubtractedfrommobilereceiverbeforecalculatingposition(typicallypostprocessed)§5GPS系统误差分析及补偿DifferentialGPS§5GPS系统误差分析及补偿GeostationaryWAASsatellitesGPSConstellationWAASControlStation(WestCoast)LocalAreaSystem(LAAS)WAASControlStation(EastCoast)WideAreaAugmentationSystem§5GPS系统误差分析及补偿+-

3meters+-15metersWithSelectiveAvailabilitysettozero,andunderidealconditions,aGPSreceiverwithoutWAAScanachievefifteenmeteraccuracymostofthetime.*UnderidealconditionsaWAASequippedGPSreceivercanachievethreemeteraccuracy95%ofthetime.**Precisiondependsongoodsatellitegeometry,openskyview,andnouserinducederrors.HowgoodisWAAS?§5GPS系统误差分析及补偿§6GPS应用GPSApplications§6GPS应用FourPrimaryFunctionsofGPSPositionandcoordinates.Thedistanceanddirectionbetweenanytwowaypoints,orapositionandawaypoint.Travelprogressreports.Accuratetimemeasurement.§6GPS应用Applications–MilitaryMilitaryGPSuserequipmenthasbeenintegratedintofighters,bombers,tankers,helicopters,ships,submarines,tanks,jeeps,andsoldiers'equipment.Inadditiontobasicnavigationactivities,militaryapplicationsofGPSincludetargetdesignationofcruisemissilesandprecision-guidedweaponsandcloseairsupport.TopreventGPSinterceptionbytheenemy,thegovernmentcontrolsGPSreceiverexportsGPSsatellitesalsocancontainnucleardetonationdetectors.§6GPS应用Applications–CivilianAutomobilesareoftenequippedGPSreceivers.Theyshowmovingmapsandinformationaboutyourpositiononthemap,speedyouaretraveling,buildings,highways,exitsetc.SomeofthemarketleadersinthistechnologyareGarminandTomTom,nottomentionthebuiltinGPSnavigationalsystemsfromautomotivemanufacturers.§6GPS应用Applications–CivilianForaircraft,GPSprovidesContinuous,reliable,andaccuratepositioninginformationforallphasesofflightonaglobal