1、-1-本科毕业论文外文文献及译文文献、资料题目：GlobalPositioningSystem文献、资料来源：http//en/wikipedia/org/wiki/Global_Positioning_System文献、资料发表（出版）日期：2009/01/03院（部）：土木工程学院专业：土木工程班级：姓名：学号：指导教师：翻译日期：外文文献：-2-GlobalPositioningSystemTheGlobalPositioningSystem(GPS)isaglobalnavigationsatellitesystem(GNSS)developedbytheUnitedStatesDep
2、artmentofDefenseandmanagedbytheUnitedStatesAirForce50thSpaceWing/ItistheonlyfullyfunctionalGNSSintheworld/canbeusedfreely/andisoftenusedbyciviliansfornavigationpurposes/TheGlobalPositioningSystem(GPS)isasatellite-basednavigationsystemmadeupofanetworkof24satellitesplacedintoorbitbytheU/S/Departmentof
3、Defense/GPSwasoriginallyintendedformilitaryapplications/butinthe1980s/thegovernmentmadethesystemavailableforcivilianuse/GPSworksinanyweatherconditions/anywhereintheworld/24hoursaday/TherearenosubscriptionfeesorsetupchargestouseGPS/Itusesaconstellationofbetween24and32mediumEarthorbitsatellitesthattra
4、nsmitpreciseradiowavesignals/whichallowGPSreceiverstodeterminetheircurrentlocation/thetime/andtheirvelocity/ItsofficialnameisNAVSTARGPS/AlthoughNAVSTARisnotanacronym/1afewbackronymshavebeencreatedforit/Sinceitbecamefullyoperationalin1993/GPShasbecomeawidelyusedaidtonavigationworldwide/andausefultool
5、formap-making/landsurveying/commerce/scientificuses/andhobbiessuchasgeocaching/Also/theprecisetimereferenceisusedinmanyapplicationsincludingthescientificstudyofearthquakesandasarequiredtimesynchronizationmethodforcellularnetworkprotocolssuchastheIS-95standardforCDMA/GPSsatellitescircletheearthtwicea
6、dayinaverypreciseorbitandtransmitsignalinformationtoearth/GPSreceiverstakethisinformationandusetriangulationtocalculatetheusersexactlocation/Essentially/theGPSreceivercomparesthetimeasignalwastransmittedbyasatellitewiththetimeitwasreceived/ThetimedifferencetellstheGPSreceiverhowfarawaythesatelliteis
7、/Now/withdistancemeasurementsfromafewmoresatellites/thereceivercandeterminetheuserspositionanddisplayitontheunitselectronicmap/AGPSreceivermustbelockedontothesignalofatleastthreesatellitestocalculatea2Dposition(latitudeandlongitude)andtrackmovement/Withfourormoresatellitesinview/thereceivercandeterm
8、inetheusers3Dposition(latitude/longitudeandaltitude)/Oncetheuserspositionhasbeendetermined/theGPSunitcancalculateotherinformation/suchasspeed/bearing/track/tripdistance/distancetodestination/sunriseandsunsettimeandmore/-3-HistoryThefirstsatellitenavigationsystem/Transit/usedbytheUnitedStatesNavy/was
9、firstsuccessfullytestedin1960/Usingaconstellationoffivesatellites/itcouldprovideanavigationalfixapproximatelyonceperhour/In1967/theU/S/NavydevelopedtheTimationsatellitewhichprovedtheabilitytoplaceaccurateclocksinspace/atechnologythatGPSreliesupon/Inthe1970s/theground-basedOmegaNavigationSystem/based
10、onsignalphasecomparison/becamethefirstworldwideradionavigationsystem/ThedesignofGPSisbasedpartlyonsimilarground-basedradionavigationsystems/suchasLORANandtheDeccaNavigatordevelopedintheearly1940s/andusedduringWorldWarII/AdditionalinspirationfortheGPScamewhentheSovietUnionlaunchedthefirstman-madesate
11、llite/Sputnikin1957/AteamofU/S/scientistsledbyDr/RichardB/KershnerweremonitoringSputniksradiotransmissions/Theydiscoveredthat/becauseoftheDopplereffect/thefrequencyofthesignalbeingtransmittedbySputnikwashigherasthesatelliteapproached/andlowerasitcontinuedawayfromthem/Theyrealizedthatsincetheyknewthe
12、irexactlocationontheglobe/theycouldpinpointwherethesatellitewasalongitsorbitbymeasuringtheDopplerdistortion/AfterKoreanAirLinesFlight007wasshotdownin1983afterstrayingintotheUSSRsprohibitedairspace/3PresidentRonaldReaganissuedadirectivemakingGPSfreelyavailableforcivilianuseasacommongood/4Thesatellite
13、swerelaunchedbetween1989and1993/Initiallythehighestqualitysignalwasreservedformilitaryuse/whilethesignalavailableforcivilianusewasintentionallydegraded(SelectiveAvailability/SA)/SelectiveAvailabilitywas-4-endedin2000/improvingtheprecisionofcivilianGPSfromabout100mtoabout20m/Ofcrucialimportanceforthe
14、functionofGPSistheplacementofatomicclocksinthesatellites/firstproposedbyFriedwardtWinterbergin1955/5Onlythencantherequiredpositionaccuracybereached/TimelineIn1972/theUSAirForceCentralInertialGuidanceTestFacility(HollomanAFB)conducteddevelopmentalflighttestsoftwoprototypeGPSreceiversoverWhiteSandsMissileRange/usingground-basedpseudo-satellites/SatellitenumbersBlockLaunchPeriodSatelliteslaunchedCurrentlyinserviceI1978198510+110II1985199090IIA199019971913IIR1997200412+1112IIR-M200520097+126IIF200920110+1020
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