衛(wèi)星定位導(dǎo)航外文翻譯文獻(xiàn)

衛(wèi)星定位導(dǎo)航外文翻譯文獻(xiàn)（文檔含中英文對照即英文原文和中文翻譯）原文：MODERNGEODETICREFERENCEFRAMESFORPRECISESATELLITEPOSITIONINGANJ.KoubaandJ.PopelarGeodeticSurveyDivision,GeomaticsCanada,NaturalResourcesCanada(NRCan)615BoothStreet,Ottawa,Ontario,CanadaK1AEO9ABSTRACTTheNAD83andWGS84referencecoordinateframeswereestablishedmorethanadecadeagotosatisfymostmapping,charting,positioningandnavigationapplications.Theyareconsistentatthe1-2metrelevelonacontinentalandglobalscalesrespectively,reflectingthelimitationsofavailabledataandtechniques.Withrapidimprovementsinpositioningaccuracy,mainlyduetoGPS,submetrenavigationhasbecomepracticalandreferenceframesatthecmtommlevelarerequiredbythemostdemandingusers.TheIERSTerrestrialReferenceFrame(ITRF)wasestablishedin1988bytheInternationalEarthRotationService(IERS)tofacilitateprecisemonitoringoftheEarthOrientationParameters(EOP)basedonstate-of-the-arttechniquessuchasVeryLongBaselineInterferometry(VLBI)andSatelliteLaserRanging(SLR).WiththeestablishmentoftheInternationalGPSServiceforGeodynamics(IGS)in1994,theITRFisdirectlyaccessibletousersworld-widebymeansofpreciseglobalGPSsatelliteorbit/clocksolutionsandalargenumberofIGSmonitoringstations.ThemostrecentITRFsolutions,designatedITRF92andITRF93,arebasedonspacegeodeticobservationsincludingGPSuptotheendof1993providingglobalconsistencyatthecmlevel.TheCanadianActiveControlSystem(CACS)facilitatesaccesstoITRFthroughactiveparticipationinIGSandVLBI.FiducialVLBIpointsincludedinNAD83provideadirectlinktoITRFandmakeitpossibletoupgradeNAD83coordinatesinordertosatisfypositioningandnavigationrequirementswithcmprecisioninthefuture.CACSfacilitatesthemostefficientconnectionstotheITRFandNAD83referenceframesforhighprecisionpositioningbyGPSaswellasforgeneralspatialreferencingneedsinCanada.INTRODUCTIONIngeodesyareferencecoordinateframeimpliesascale,orientationandcoordinateoriginaspartofareferencesystemwhichalsoincludesEarthplanetarymodelsandconstantsnecessaryforsatelliteorbitdetermination,ge-odynamicandgeophysicaldataanalysis.Satellitenavigationsystemsmadeitpossibletoestablishatrulyglobalgeocentricreferencesystemwhichwasquicklyadaptedforprecisegeodeticpositioning,especiallyoverlongdistances.Forthefirsttimeitwaspossibletodeterminedistortionsandmisorientationofclassicalgeodeticnetworksaroundtheworld.TheU.S.NavyNavigationSatelliteSystem(NNSS),alsocalledTransitorsimplyDoppler(KershnerandNewton,1962)becamethebasisfortheU.S.DepartmentofDefenseWorldGeodeticSystem1972(WGS72)andlaterWGS84whichdefineglobalgeocentricreferenceframesconsistentataboutthe1-2metrelevel.ToupgradeandcorrectdistortionsoftheclassicalNorthAmericanDatum1927(NAD27),areadjustmentofthegeodeticnetworksinCanada,USA,MexicoandGreenlandwasjointlyundertaken.Thisnewdatum,designatedNAD83,wasnominallymadecompatiblewithWGS84bybeinggeocentricandorientedaccordingtotransformedDopplerpositions,butinadditiontheNAD83adjustmentincludedVLBI(VeryLongBaselineInterferometry)baselines.Thusboth,WGS84andNAD83,areconsistentataboutonemetre,mainlyduetothelimitationsoftheDopplertechniques(Kouba,1993).GPSandotherspacebasedtechniquessuchasVLBIandSatelliteLaserRanging(SLR)providedatawithhigherprecisionstosupportstudiesofcrustaldynamicsandpolarmotionwhichrequireamoreaccurateglobalreferenceframe.TheIERSTerrestrialReferenceFrame(ITRF)wasestablishedin1988andisupdatedonanannualbasisbytheInternationalEarthRotationService(IERS)tokeepitcurrentandtoimproveknowledgeofstationvelocitieswhicharenecessaryformaintainingtheaccuracyofthisglobalreferenceframe.NAD83canberelatedtoITRFpreciselyforagivenepochbyatransformationbasedoncommonVLBIstations.TheCanadianActiveControlSystem(CACS)providesthemostefficientmethodtoupgradeNAD83coordinatesinCanadainordertomeetpositioningandnavigationrequirementswithcmprecisioninthefuture.NORTHAMERICANGEODETICDATUM:NAD83TheNorthAmericanDatum1927(NAD27)wasestablishedatthebeginningofthiscenturyusingcontinentaltriangulationwithacentrallylocateddatumpointatMeadesRanchinKansas,USA(Ross,1936).Satellitegeodesyinthe60'sand70'sdetectedtheapproximately100moffsetoftheNAD27originwithrespecttothegeocenteraswellasdistortionsexceedingtensofmetersinsomepartsofthegeodeticcontrolnetwork(Mueller,1974).Anewreferenceframewasrequiredtofacilitateuseofefficientandprecisesatellitegeodetictechniquesinsurveyingandnavigation.SatelliteDopplerpositionsandseveralVLBIbaselineswhichhadbeenestablishedbeforetheendof1986,wereusedtoprovideaframeworkandtodefinethegeodeticdatuminanewway.TheNorthAmericanDatum1983(NAD83)wasbasedonDopplerstationcoordinatestransformedtoconformwiththeinternationalconventionforgeocentricorigin,scaleandorientationofthereferenceellipsoid(NOAA,1989).Classicalgeodeticobservationsformorethan260,000controlpointshavebeenreadjustedandintegratedwithintheframeworktoprovidetheNAD83coordinatesofthehorizontalcontrolnetworkmonumentsforpracticaluse.Thus,NAD83initsoriginalversionprovidesareferenceframeforhorizontalpositioningwithaccuraciesattheonemeterlevelcorrespondingtosatelliteDopplerprecisionsomewhatdilutedbyerrorsintheclassicaltriangulationarcsincludedintheNAD83networkadjustment.AtthislevelofprecisiontherewasnoneedtointroducestationvelocitiesandNAD83isconsideredtobeattachedtotheNorthAmericantectonicplate.TheNAD83referenceframesatisfiesmostpracticalneedsformapping,charting,navigationandspatialreferencinginNorthAmericawheresub-meteraccuracyisnotrequired.However,todaytheincreasedprecisionofgeodeticGPSmeasurementsrequiresareferenceframeconsistencyatacmlevelwhichwouldfacilitatestudiesofcrustaldynamicsrelatedtoplatetectonicsandnaturalhazardsassociatedwithseismicorvolcanicactivities,etc.TheaccuracyoftheVLBIbaselineswhichcontributedtothedefinitionofNAD83notonlyprovidesaneffectivewaytorelateNAD83tomoreaccuratereferenceframesata2cmlevel(Soleretal.,1992)butalsofacilitatesprecisionupgradesusingaccurategeodeticspacetechniques.SuchanapproachwillassurecontinuousimprovementsofpositioningaccuracyaswellastraceabilitytoNAD83whichisofgreatpracticalimportance.WORLDGEODETICSYSTEM:WGS84WGS84isaglobalgeodeticreferencesystemwhichhasbeenestablishedandmaintainedbytheU.S.DepartmentofDefensetofacilitatepositioningandnavigationworldwide(DMA,1991).TheterrestrialcoordinatereferenceframecorrespondingtoWGS84hasbeenupdatedtokeeppacewithincreasingprecisionofGPSpositioningandnavigationtechnologyingeneraluse.ORIGINALWGS84TERRESTRIALEFERENCEFRAMEWGS84worldwideterrestrialreferenceframewasinitiallybasedonlyonsatelliteDopplercoordinatestransformedinthesamewayasforNAD83.However,adifferentsetofDopplerstationswasusedandnoVLBIbaselinemeasurementswereincludedinthenetworkadjustment.Thisapproachproducedagloballyhomogeneousgeodeticreferenceframewithanaccuracyof1-2mreflectingthelimitationsoftheDopplertechnique.Stationvelocitieswereignoredastheywereoflittleimportance.AlthoughtheDopplerWGS84referenceframeiscomparablewiththatofNAD83inNorthAmerica,thelackofpreciseVLBIframeworkmakesitimpossibletorelateWGS84tocurrent,moreaccuratereferenceframeswithaprecisionbetterthan1m.SignificantimprovementcanbeachievediftheWGS84frameworkadoptedforGPSoperationsisconsidered.ThisWGS84(GPS)terrestrialreferenceframeisbasedonWGS84coordinatesof10GPStrackingstationsusedbytheU.S.DoDforgenerationofoperational(broadcast)satelliteorbitsandclockparameters.REVISEDWGS84(G730)TERRESTRIALREFERENCEFRAMETheWGS84(GPS)coordinatesofthe10GPStrackingstationshavebeenrevisedusingseveralweeksofGPSobservationsfromaglobalnetworkof32stations(10DoD+22IGS)inasimultaneousadjustmentofsatelliteorbitsandstationcoordinates;thecoordinatesof8IGSstationswereconstrainedtothevaluesadoptedbytheInternationalEarthRotationService(IERS)andtheIERSvalueofthegeocentricconstantofgravitationwasused.ThisimprovedreferenceframeforGPS,designatedWGS84(G730)torefertoGPSweek730,showsglobalconsistencyataboutthe10cmlevelandusesNUVEL-1platemotionmodelforstationvelocities(Swift,1994;DeMetsatal.,1990).Sincethebeginningof1994,DMAhasusedWGS84(G730)inpostprocessinganditisexpectedtobeadoptedforthecomputationofoperational(broadcast)GPSsatelliteorbitsinthenearfuture(MalysandSlater,1994).

IERSTERRESTRIALREFERENCEFRAME:ITRFInordertofacilitatepreciseEarthrotationandpolarmotionmonitoringbymodernspacegeodetictechniquestheBureauInternationalde1'Heure(BIH)establishedin1984theBIHTerrestrialSystem(BTS84)basedmainlyonVLBI,SLRandsatelliteDopplerobservations.In1988whenBIHwassupersededbyIERStheIERSTerrestrialReferenceFrame(ITRF88)wascreatedtomeetthefollowingrequirements(Boucher,1990):▲PennanentCACStrackingsite3■WesternCanadaDefbrnKitionArray(WCDA)?MomnnentedtempoiaiyCACStrackingsiteFigure1.ResidualdifferencesbetweenNAD83andITRF92(1994.0)fortheCACSmonitoringstations.itisgeocentricwiththeoriginatthecenterofmassofthewholeEarthincludingtheoceansandtheatmosphere;itsorientationisconsistentwiththeBIHEarthOrientationParameter(EOP)seriesfortheepoch1984.0;thestationvelocitymodelshallnotproduceanyresidualrotationwithrespecttotheEarthcrust;thescalecorrespondstothelocalcoordinatesystemoftheEarthinthesense

oftherelativistictheoryofgravitation.Since1988,anITRFsolutionhasbeenproducedonanannualbasistoincorporatenewobservationsandstationsasappropriatetosatisfytheaboverequirements.ThetectonicplatemotionmodelNUVEL-1wasusedtoderivestationvelocitieswhileenforcingthenoresidualrotationrequirement.ThiscombinedwiththesomewhatunevenglobaldistributionoftheITRFstationsproduceda0.2mas/yearrotationbetweenITRFandIERSEOP(IERSAnnualReport1992)whichaccumulatedby1992toasignificantmisalignmentofabout1mas.TheNUVEL-1modelstationvelocitieswererevisedtotakeintoaccountobservedVLBIandSLRstationvelocitieswhereavailable,toproduceITRF92whichincludedabout150stations.GPSobservationsofferthemostefficienttechniqueforthedensificationofITRFwhenintegratedintheVLBIframeworkwhichmaintainstheabsoluteorientationandscale.MeanstationpositionerrorsforVLBIandGPSnetworksincludedinITRF92aresummarizedinTable1whichshowscmlevelconsistencyfortheglobalsolutions(Boucheratal.,1993).ImprovementsindeterminationofstationvelocitiesandfurtherdensificationtoobtainmorehomogeneouscoverageonallcontinentswillbecriticalformaintainingandincreasingtheITRFaccuracyinthefuture.Table1.ConsistencyofVLBIandGPSglobalsolutionsincludedinITRF92SolutionNWeightedRMS[cm]2D3DVLBI(GIUB)70.60.7VLBI(GSFC)700.40.6VLBI(JPL)71.11.5VLBI(NOAA)550.30.5VLBI(USNO)150.70.7GPS(CODE)120.40.7GPS(CSR)241.21.3GPS(EMR)170.40.6GPS(ESA)323.13.4GPS(JPL)390.60.7GPS(SIO)401.31.85.TRANSFORMATIONBETWEENTERRESTRIALREFERENCEFRAMESPracticallyusefultransformationsbetweendifferentterrestrialreferenceframesarebasedontheirmostaccuratecommonsetofstationswhicharethenusedtodetermineseventransformationparametersandprovidebasicRMSinformationontheconsistencyoftherelationship.ResidualsystematicdifferencescanbemappedorrepresentedanalyticallyiftheyexceedsignificantlytheRMSvalueofthecoordinatedifferencesafterthetransformation.TheresidualdifferencesbetweenNAD83andITRF92(epoch1994.0)positionsfortheCanadianActiveControlSystem(CACS)monitoringstationsareshowninFigure1.However,suchdeviationsshouldbeinvestigatedandcorrectediftheyrepresentaccumulationofsystematicerrors.Revisionsofthiskindprovidenaturalupgradepathforanyterrestrialreferenceframeandenhancesignificantlyitspracticalimportancebygraduallyeliminatingunacceptableerrors.TheWGS84(G730)referenceframeisanexampleofacomprehensiverevisioninresponsetopracticalneedsofGPSapplications.Table2liststhe7transformationparametersbetweentheterrestrialreferenceframesdiscussedaboveandITRF92(epoch1988.0).TheglobalconsistencyoftheterrestrialreferenceframeshasimprovedbyalmosttwoordersofmagnitudeoverthelastdecadeasevidentfromTable2.IthasbeenachievedbyameticulousapplicationofthecomplementarytechniquesofVLBIandsatellitegeodesy.Themaintenanceofthecmlevelterrestrialreferenceframeconsistencyrequiressystematicmonitoringofcrustalandterraindynamicsincludingmonumentstability.ContinuousmonitoringoftheEarthrotationaldynamicsbyVLBIisnecessaryforhighprecisionapplicationsofsatellitepositioningandnavigationsystemswhichhavemadethisrapidprogressinglobalgeodesypossible.Table2.TransformationparameterswithrespecttoITRF92(epoch1988.0)Ref.FrameDXDY3]DZWXRY[mas]RZSCL[ppm]RMS[cm]-941985427.515.510.7-0.0052WGS84-6+52+22-18.4-0.3.00.011<200WGS84(GPS)-4-J.-204.2-4.0-15.6-0.21Q94WGS84(G730)0-34-2.6-2.5-0.40.0006二TRF9MC.20.70.7-3.39o.ao-0.96-0.0012<1ACCESSTOMODERNTERRESTRIALREFERENCEFRAMESThehighprecision,globalscopeanddynamicnatureofspacetechniques,particularlyGPSingeneralusetoday,demandnewapproachestothemaintenanceandaccesstoterrestrialreferenceframes.Aspointedoutabove,themodernterrestrialreferenceframesmustbeconnectedtothebestavailablerealizationoftheinertialframeprovidedbyVLBIandmustfacilitatedeterminationofstationvelocitiesinthegeocentriccoordinatesystem.ThisispresentlyaccomplishedbyacombinedsolutionforaglobalnetworkoffiducialVLBIstationsaugmentedbySLRandGPSstationsforwhichgeocentriccoordinatesandvelocitiesareobtainedfromseriesofobservationsandgeodynamicmodels;thesolutiondefinesa"controlnetwork"foragivenepoch,e.g.1988forITRF.Monitoringof"controlstation"velocitiesandtheEarthrotationparameters(ERP),neededforinertialreference,requirescontinuousobservationatsomeofthe"controlnetworkstations"whichcreatesanActiveControlSystem(ACS).Suchreferencesystemofferstwocomplementarymodesofaccesstoitsterrestrialreferenceframeandsupportsreal-timehighprecisionglobalpositioningandnavigation.CANADIANACTIVECONTROLSYSTEMCACSTheGeodeticSurveyDivision(GSD),GeomaticsCanadaincollaborationwiththeGeologicalSurveyofCanada(GSC)hasestablishedCACSasanessentialcomponentamodernfullyintegratedspatialreferencesystemtosupportgeodeticpositioning,navigationandgeneralpurposespatialreferencing.CACSrepresentstheCanadiancontributiontotheInternationalGPSServiceforGeodynamics(IGS)andfacilitates

directintegrationofCanadianstationswithinITRF.TheCACSnetworkconfiguration(Fig.1)augmentedbyaboutl8globallydistributedIGSstationsprovidescontinuousdatafordailypreciseGPSsatelliteorbitandclockoffsetdeterminationconstrainedbyabout13fiducialVLBIstationstofacilitatepositioningwithhighestprecisionforgeodeticcontrolnetworksandcrustaldynamicstudiesaswellasgenerationofhighqualityorbitpredictionsforreal-timeapplications.ThequalityoftheCACSresultsincomparisontotheotherIGSAnalysisCenterscanbeseeninTable3.GSDisalsoresponsibleforcoordinationoftheIGSAnalysisCentersandcombinationoftheirresultsintotheofficialIGSproducts(Beutleratal.,1993).Table3.IGSCombinedOrbitSummary,week0758(July17-July23,1994)Meanandstandarddeviationsoftransformationparameters.WRMS-orbitRMSweightedbytheorbitaccuracycodes.ThreestrategieshavebeendevelopedfortheintegrationofregionalGPSThreestrategieshavebeendevelopedfortheintegrationofregionalGPSUnits:meters,mas,ppb,nano-sec,nano-sec/day.C3ETIBXDYDZRYRZSCLRMSWRMSTOFTTDRFTRMScod.01.02-.01-1.66-1.44,08.0.13,11-3.,_.775.4.01QI.13.32a￡』emr,00--01-1.73-1.08“17-.1,13-417..1-1.01,01,58.43.10a67.3e.9esa.00.00-.01-1.56-1.S9-.24.口.20.L8-.01.01.01,41,22.2gfz-.04.02-.02-1.70-.92-.36--1.14.LI-411.S-24.39.a,01.01,01.72,27“13.16E.e10.0二Pl.00-.01.01-1.86-1.76-418.2.11.LI-412.S-1.01.01.56,1667.3ngs.05-.01-.03-1.91-.6?,57-2.9_.97S.4,03.01,03.81.40“3E.33.1G.Gsio.00-.04,10-1.94-.95,85-..0.0.01.01,02.68,20“17.1z.0stationsandnetworksinITRForrelatedterrestrialreferenceframes,e.g.NAD83,WGS84.Thefirststrategyusessequentialglobalprocessingforadditionofdatafromregionalstationstothesystemofnormalequationsandobtainupdatedglobalsolutionwithcoordinatesoftheregionalstations.ThesecondstrategyusestheCACS/IGSpreciseorbitsinbaselinedouble-differenceprocessingtoestablishhighprecisionregionalnetworksforspecialgeodeticandgeodynamicapplicationswithmmorppb

precision(Fig.2).ThethirdstrategyusestheCACS/IGSprecisesatelliteephemeridesandclockoffsetdataandundifferencedGPSobservationsforsinglepointpositioningwithaccuracycorrespondingtothepseudorangemeasurementprecisionoftheGPSreceiverused.30ooooo

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(LULU)一絲】ID三一3z3rs_111P-君XDRAO-ALBHBaseline,Length301.768387kmSigma=32..95mmEMe二至一8.E6S9M661FE66一ns6一要一8H66I9766一o3VariationsintheDRAO(Penticton)-ALBH(Victoria)baselinelengthsolutions(afterDragertatal.,1994).Thisrathersimpleapproachcansatisfywiderangeofspatialreferencingandnavigationrequirementswithonemeterorbetterprecision(Fig.3).Real-timewideareadifferentialGPS(WADGPS)servicecanonlybesupportedbyanactivecontrolsystemlikeCACSwhichassurescontinuous,efficientandeconomicalaccesstothereferenceframe.Inthiswayallactivitiesandoperationscanberelatedtoacommon,accurateandreliableglobalspatialreferenceframebymeansofGPS.CACSsatisfiesbothrequirementsofamodernterrestrialreferenceframe:maintainsanetworkoffiducialreferencestationsandprovidescontinuousmonitoringandupdatingofallvariablesystemparameterswhicharenecessaryforpreciseandconsistentuserpositioning.Latitude'LonaiTiicle◎Elevation8642u248642u24o.sso.亙8至碧a-OS0:006:0012:00L8:0024:00Avei^isiiisTimeCACSUSERPOSITIONINGINTERFACE:InitialconvergencetestsbasedonCACSpost-processedorbits/clocksandasinglereceiverpseudorange/phaseata.CANADIANBASENETWORK-CBNThetraditionalmethodofaccesstoareferenceframeisbasedondifferentialpositioningwithrespecttocontrolstationswith"known"coordinatesintherequiredreferenceframe.Thesearedeterminedeitherduringthereferenceframedefinitionorthelaterintegrationofsocalledcontrolsurveys.Suchanapproachwasnecessaryduetotheelaborateandtimeconsumingproceduresusedinthepasttoobtainreferencestationcoordinateswithrequiredaccuracy.Nevertheless,theneedtomaintainanaccurateterrestrialnetworkofmonumentedreferencestationsinadditiontoanactivecontrolsystemistwofold.Firstly,itprovidescontrolpointsfortecniquesotherthanGPSandfacilitatescalibrationandperformanceanalysisofsurveyinstrumentationandprocedures.Secondly,itdensifiesthenetworkofactivecontrolpointswhileprovidingdirectconnectionstoclassicalgeodetichorizontalandverticalcontrolnetworks.Stationspacingisgenerallygreaterandspecialconsiderationsarerequiredforsiteselectionandmonumentationtosupporthigherprecisionandefficiencyofoperations.Thedeterminationofstationvelocities

requiresregularreoccupationsandsystematicanalysisofmonumentstabilityandcrustaldynamics.TheCanadianBaseNetwork(Fig.4)istoplayanimportantroleintheintegrationofthehorizontalandverticalgeodeticcontrolnetworksandsupportstudiesofcrustaldeformationsandseismichazardsinCanada.Figure4.ProposedstationspacingfortheCanadianBaseNetwork(CBN).CONCLUSIONSGPStechnologyoffersusersthemostversatile,accurateandeconomicalsystemforgeodeticpositioning,navigationandgeneralpurposespatialreferencingtodate.Inordertomaximizesystemperformanceandeffectiveness,GPSapplicationsdependoncontinuousmonitoringoftheGPSsatelliteswithrespecttoconventionalterrestrialandcelestialreferenceframes.ModernterrestrialreferenceframesarebasedonthespacetimecoordinatesystemcenteredatthegeocenterandmusttakeaccountofEarthtectonicplatemotionanddeformationtoprovideacmlevelaccuracypotential.ITRFhasbeenimplementedandmaintainedtosatisfythehighestaccuracypositioningrequirementsontheglobalscale.NAD83hasbeenimplementedtosatisfymapping,chartingandnavigationapplicationswheresub-meteraccuracyisnotrequired;howevertheVLBIframeworkprovidesanupgradepathtoacmaccuracyNAD83referenceframerigidlyconnectedtotheNorthAmericanplate.Thetransformationparameters(Table2)facilitatetransformationsbetweenthereferenceframestoaccommodateuserneeds.Theactivecontrolsystem(ACS)providesefficientandeconomicaldirectaccesstotheterrestrialreferenceframeswiththerequiredaccuracyandfacilitatereal-timehighprecisionspatialreferencingandnavigation.REFERENCESBeutler,G.,J.Kouba,T.Springer,CombiningtheorbitsoftheIGSProcessingcenters,Proc.IGSAnalysisCenterWorkshop,20-56,1993.Boucher,C.,DefinitionandRealizationofTrrestrialReferenceSystemsforMonitoringEarthRotation,inVariationsinEarthRotation,D.D.McCarthyandW.E.Carter(eds),197-201,1990.Boucher,C.,Z.AltamimiandL.Daniel,ITRFstationcoordinates,apaperpresebtedattheIGSNetworkOperationsWorkshop,SilverSpring,Md.,USA,Oct.18-21,1993.DeMets,C.,R.G.Gordon,D.F.ArgusandS.Stein,Currentplatemotions,Geophys.J.Int.,101,425-,1990.Dragert,H.,M.SchmidtandX.Chen,TheContinuousGPSTrackingforDeformationStudiesinSouthwesternBritishColumbia,IONGPS94,SaltLakeCity,Utah,September20-23,1994.DMATR8350.2,DepartmentofDefenseWorldGeodeticSystem1984,ItsDefinitionandRelationshipswithLocalGeodeticSystem,2ndEd.,Sep.1991.IERS1992AnnualReport,InternationalEarthRotationService(IERS),ObservatoiredeParis,July1993.IERS1993AnnualReport,InternationalEarthRotationService(IERS),ObservatoiredeParis,July1994.Kershner,R.B.andR.R.Newton,TheTRANSITSystem,J.Inst.Navigation,15,129-144,1962.Kouba,J.,AreviewofgeodeticandgeodynamicsatelliteDopplerpositioning,ReviewofSpacePhysics,21(1),27-40,1983.Kouba,J.,P.Tetrault,R.FerlandandF.Lahaye,IGSdataprocessingattheEMRMasterActiveControlSystemCentre,Proc.of1993IGSWorkshop,123-132,1993.Malys,S.,andJ.A.Slater,MaintenanceandenhancemensoftheWGS84,IONGPS,SaltLakeCity,Utah,September20-23,1994.McCarthy,D.D.,IERSStandards(1992),IERSTechnicalNote13,ObservatoiredeParis,July1992.Mueller,I.I.,Reviewofproblemsassociatedwithconventionalgeodeticdatums,TheCanadianSurveyor,Vol.28,No.5,514-523,December,1974.NOAAProfessionalPaperNOS2,NorthAmericanDatumof1983,EditedbyC.R.Schwarz,NationalGeodeticSurvey,NOS,NOAA,U.S.DepartmentofCommerce,1989.Ross,J.E.R.,TriangualtioninOntarioandQuebec,GeodeticSurveyofCanadaPublicationNo.90,DepartmentonInterior,Ottawa,Canada,1936.Soler,T.,J.D.Love,L.W.Hall,R.H.Foote,GPSresultsfromstatewideHighPrecisionNetworksintheUnitedStates,Proc.Int.Geod.Symp.onSatell.Positioning6th,573-582,1992.Swift,E.,ImprovedWGS84CoordinatesfortheDefenseMappingAgencyandAirForceGPSTrackingSites,IONGPS94,SaltLakeCity,Utah,September20-23,1994.現(xiàn)代大地測量參考框架進(jìn)行精確的衛(wèi)星定位導(dǎo)航J.庫巴和J.Popelar大地測量部，測繪加拿大，加拿大自然資源部（NRCan）615展位街，渥太華，安大略省，加拿大K1AEO9在NAD83和WGS84坐標(biāo)參考框架建立超過十年前，以滿足大多數(shù)測繪，制圖，定位和導(dǎo)航應(yīng)用。他們是在分別于大陸和全球范圍內(nèi)的1-2米的水平相一致，反映了現(xiàn)有數(shù)據(jù)和技術(shù)的局限性。隨著定位準(zhǔn)確迅速改善，主要是由于全球定位系統(tǒng)，submetre導(dǎo)航已成為實(shí)用和參考幀在厘米至毫米級(jí)所需的最苛刻的用戶。該IERS地球參考框架（ITRF）成立于1988年由國際地球自轉(zhuǎn)服務(wù)組織（IERS），以促進(jìn)基于國家的最先進(jìn)的，如甚長基線干涉（技術(shù)精確監(jiān)測地球定向參數(shù)（EOP）的丫181）和衛(wèi)星激光測距（SLR）。隨著在1994年成立了國際GPS服務(wù)的地球動(dòng)力學(xué)（IGS）的，在ITRF是直接通過精確的GPS全球衛(wèi)星軌道/時(shí)鐘解決方案和大量IGS監(jiān)測站進(jìn)行訪問的用戶全世界。最新的ITRF解決方案，指定ITRF92和ITRF93，基于空間大地測量觀測數(shù)據(jù)，包括GPS到1993年年底在厘米級(jí)提供全球一致性。加拿大主動(dòng)控制系統(tǒng)（CACS）通過IGS和VLBI積極參與有利于獲得ITRF。包括在NAD83基準(zhǔn)VLBI點(diǎn)提供了直接鏈接到ITRF，并有可能升級(jí)NAD83，以滿足與厘米的精確定位和導(dǎo)航的要求，在未來的坐標(biāo)。CACS方便最有效的連接，通過GPS高精度定位以及為一般空間參考需要在加拿大的ITRF和NAD83參考幀。1引言在大地測量參考坐標(biāo)系表示的規(guī)模，方向和坐標(biāo)原點(diǎn)為參考系，其中也包括地球的行星模型和必要的衛(wèi)星定軌，GE-odynamic和地球物理數(shù)據(jù)分析常量的一部分。衛(wèi)星導(dǎo)航系統(tǒng)使我們能夠建立一個(gè)真正的全球地心參照系統(tǒng)，它很快就被改編為精確的大地測量定位，尤其是長距離。這是第一次有可能確定的扭曲和世界各地的經(jīng)典大地測量網(wǎng)的取向差。美國海軍導(dǎo)航衛(wèi)星系統(tǒng)（NNSS），也稱為運(yùn)輸或干脆多普勒（克什納和牛頓，1962）成為基礎(chǔ)的美國國防部部世界大地測量系統(tǒng)1972（WGS72），后來WGS84它定義全球地心參考系一致時(shí)約1-2米的水平。要升級(jí)和經(jīng)典北美洲基準(zhǔn)面1927（NAD27），在加拿大，美國，墨西哥和格陵蘭的大地測量網(wǎng)絡(luò)的調(diào)整的正確扭曲共同承擔(dān)。這個(gè)新的基準(zhǔn)，指定NAD83（北美基準(zhǔn)），名義上是用做兼容的WGS84由是地心，并根據(jù)多普勒變換位置的導(dǎo)向，但在另外的NAD83調(diào)整包括VLBI（甚長基線干涉）的基線。因此，這兩個(gè)，WGS84和NAD83，是在約一米的一致，主要是由于多普勒技術(shù)（庫巴，1993）的限制。GPS和測距（SLR）提供的數(shù)據(jù)具有較高的精度，支持地殼動(dòng)力學(xué)和極移，需要一個(gè)更精確的全球參考框架的研究等基礎(chǔ)空間技術(shù)，如VLBI觀測和衛(wèi)星激光。該IERS地球參考框架（ITRF）成立于1988年，更新每年由國際地球自轉(zhuǎn)服務(wù)組織（IERS），以保持它的電流和改善站速度所必需的維持這個(gè)全球基準(zhǔn)的精度知識(shí)框架。NAD83可以與ITRF正是基于共同的VLBI站通過變換一個(gè)時(shí)代。加拿大主動(dòng)控制系統(tǒng)（CACS）提供了最有效的方法來升級(jí)在加拿大，以滿足未來與厘米的精確定位和導(dǎo)航要求NAD83坐標(biāo)。2北美大地基準(zhǔn)點(diǎn)：NAD83北美洲基準(zhǔn)面1927（NAD27）采用歐式三角網(wǎng)與在Meades牧場在美國堪薩斯州（羅斯，1936年），一個(gè)位于中心的基準(zhǔn)點(diǎn)成立于本世紀(jì)初。在60年代和70年代衛(wèi)星大地測量檢測到大約100米NAD27原點(diǎn)相對于地心以及扭曲超過幾十米的大地控制網(wǎng)（米勒，1974）的某些部分抵銷。一個(gè)新的參照系wasrequired，方便使用的測量和導(dǎo)航效率和精確的衛(wèi)星大地測量技術(shù)。其中有1986年底前建立衛(wèi)星多普勒位置和幾個(gè)VLBI基線，被用來提供一個(gè)框架，并定義了新的途徑大地基準(zhǔn)點(diǎn)。北美洲基準(zhǔn)面1983（NAD83）是基于多普勒站坐標(biāo)變換，以符合對地心的起源，規(guī)模和參考橢球（NOAA，1989）取向的國際公約。經(jīng)典大地測量觀測值超過260,000的控制點(diǎn)進(jìn)行了調(diào)整和整合的框架，提供了平面控制網(wǎng)的紀(jì)念碑實(shí)際使用的NAD83坐標(biāo)范圍內(nèi)。因此，NAD83在其原始版本提供了水平定位精度與基準(zhǔn)幀在對應(yīng)于衛(wèi)星多普勒精度多少有些誤差通過在包含在NAD83網(wǎng)絡(luò)調(diào)整經(jīng)典三角弧稀釋一米的水平。在這種精度級(jí)別沒有必要引進(jìn)臺(tái)速度和NAD83被認(rèn)為是連接到北美板塊。制圖，制圖，導(dǎo)航和空間參照北美在不需要亞米級(jí)精度的NAD83坐標(biāo)系滿足最實(shí)際的需求。然而，今天的大地測量GPS測量的精度提高，需要在厘米級(jí)這將有利于涉及與地震或火山活動(dòng)相關(guān)的板塊構(gòu)造和自然災(zāi)害等地殼動(dòng)力學(xué)研究的參考幀一致性的VLBI基線貢獻(xiàn)的精度到NAD83的定義不僅提供了有關(guān)NAD83一種有效的方法來在2cm的水平（索勒等人，1992）更準(zhǔn)確的參考幀，但是也使用精確的大地測量空間技術(shù)有利于精確的升級(jí)。這樣的做法將保證定位精度不斷提高，以及可追溯至NAD83這是具有重大的現(xiàn)實(shí)意義。3世界大地測量系統(tǒng)：WGS84WGS84是已建立并保持了美國國防部部，以方便定位和導(dǎo)航世界各地（DMA,1991）的全球大地測量參考系統(tǒng)。對應(yīng)于WGS84地面坐標(biāo)參考框架已經(jīng)更新，以保持與一般使用的GPS定位和導(dǎo)航技術(shù)的精確度提高的步伐。原始WGS84陸地參考系WGS84世界各地的地球參考框架最初僅基于衛(wèi)星多普勒坐標(biāo)變換中的相同的方式NAD83。然而，一組不同的多普勒臺(tái)站使用，沒有VLBI基線測量，包括在網(wǎng)絡(luò)調(diào)整。這種方法產(chǎn)生了具有1-2米，反映了多普勒技術(shù)的局限性,精確度在全球同質(zhì)的大地測量參考框架。站速度被忽略,因?yàn)樗麄儾⒉恢匾?。雖然多普勒WGS84坐標(biāo)系是與NAD83在北美相媲美，缺乏精確的VLBI框架使得它無法與WGS84到目前，更準(zhǔn)確，精度大于1m更好的參考幀。顯著改善，如果可以的GPS運(yùn)營所采用的WGS84框架被認(rèn)為是可以實(shí)現(xiàn)的。這WGS84（GPS）地球參考框架是基于對代運(yùn)營（直播）衛(wèi)星軌道和時(shí)鐘參數(shù)采用美國國防部10GPS跟蹤站的WGS84坐標(biāo)。修訂WGS84（G730）陸地參考系已作出修訂，使用幾個(gè)星期從全球32個(gè)站（10國防部+22IGS）在同時(shí)調(diào)整衛(wèi)星軌道和測站坐標(biāo)網(wǎng)GPS觀測的WGS84（GPS）的10GPS跟蹤站的坐標(biāo);8個(gè)IGS站的坐標(biāo)是約束通過的國際地球自轉(zhuǎn)服務(wù)組織（IERS），并用引力的地心恒定的IERS值的值。對于GPS這種改進(jìn)的參考框架，指定WGS84（G730）是指GPS周730，顯示在大約10厘米水平全球一致性和使用的站速度（雨燕，1994NUVEL-1板塊運(yùn)動(dòng)模型；。德大都會(huì)在人，1990）。自1994年開始，DMA已經(jīng)使用WGS84（G730）的后處理，預(yù)計(jì)要為業(yè)務(wù)（廣播）的GPS衛(wèi)星軌道計(jì)算在不久的將來（Malys和斯萊特，1994）4日前地面參考系：ITRF為了通過現(xiàn)代空間大地測量技術(shù)，方便精確的地球自轉(zhuǎn)和極移的監(jiān)測局國際DEL'HEURE（BIH）成立于1984年，主要基于波黑地面系統(tǒng)（BTS84）對VLBI，SLR和衛(wèi)星多普勒觀測。1988年，當(dāng)BIH被取代了IERS的IERS地球參考框架（ITRF88）的建立是為了滿足以下要求（布歇，1990）：

(1)它是地心與原點(diǎn)在整個(gè)地球的質(zhì)量中心包括海洋和大氣；(2)其方向與BIH地球定向參數(shù)(EOP)系列的劃時(shí)代1984.0一致;(3)站速度模型不得生產(chǎn)對于地球地殼的任何殘余旋轉(zhuǎn)；HolberWilliam1(4)規(guī)模相當(dāng)于地球的局部坐標(biāo)系中引力的相對論理論的意義。HolberWilliam1duduVictoriaAPciiuaiicntCACStrackingsite口nqu'n■WesternCanadaDeforniationxAiray(WCDA)?MomnneiitedtemporaiyCACSti'ackiiigsite圖1：對CACSNAD83和ITRF92(1994.0)之間的殘余差異監(jiān)測站：自1988年以來，一個(gè)ITRF解決方案已經(jīng)產(chǎn)生每年把新的觀測站，并適當(dāng)滿足上述要求。板塊運(yùn)動(dòng)模型NUVEL-1被用來推導(dǎo)站速度，同時(shí)強(qiáng)制執(zhí)行無殘余旋轉(zhuǎn)的要求。這種結(jié)合ITRF站的有點(diǎn)不平衡的全球分布產(chǎn)生ITRF和IERS的EOP(IERS年報(bào)1992年的報(bào)告)，其中1992年累計(jì)約1MAS一個(gè)顯著偏差之間的0.2MAS/年輪換。該NUVEL-1型臺(tái)的速度進(jìn)行了修訂，以考慮到觀測的VLBI和SLR站速度如果有的話，產(chǎn)生ITRF92，其中包括約150臺(tái)。GPS觀測提供最有效的技術(shù)ITRF時(shí)，集成在VLBI框架，保持絕對的方向和規(guī)模的致密化。意味著VLBI并列入ITRF92GPS網(wǎng)站位置誤差列于表1,其顯示了全球解決方案(鮑徹等人，1993)厘米級(jí)的一致性。在測定站速度，并進(jìn)一步致密化的改進(jìn)，在所有大陸獲得更均勻的覆蓋范圍將是維持和提高ITRF精度在未來的發(fā)展至關(guān)重要。表1.致性的VLBI和GPS全球解決方案包括在ITRF92解決方案N權(quán)均方根值(cm)2D3D

VLBI(GIUB)70.60.7VLBI(GSFC)700.40.6VLBI(JPL)71.11.5VLBI(NOAA)550.30.5VLBI(USNO)150.70.7GPS(CODE)120.40.7GPS(CSR)241.21.3GPS(EMR)170.40.6GPS(ESA)323.13.4GPS(JPL)390.60.7GPS(SIO)401.31.85.地面參考幀之間的轉(zhuǎn)換不同地球參考框架之間實(shí)際有用的轉(zhuǎn)換是基于他們最準(zhǔn)確的組常用電臺(tái)這是用來確定7轉(zhuǎn)換參數(shù)，并提供有關(guān)的關(guān)系的一致性基本RMS的信息。殘留的系統(tǒng)性差異可以被映射或解析地表示，如果他們超過的坐標(biāo)差顯著的RMS值轉(zhuǎn)換后。NAD83和ITRF92（歷元1994.0）為加拿大主動(dòng)控制系統(tǒng)（CACS）監(jiān)測站示于圖1中的位置之間的殘余差異。然而，這樣的偏差應(yīng)該進(jìn)行調(diào)查，如果它們表示系統(tǒng)誤差的累積校正。這種修改提供自然升級(jí)路徑的任何地球參考框架，并逐步消除不可接受的錯(cuò)誤，顯著提高其實(shí)際意義。在WGS84（G730）參考框架是為了應(yīng)對全球定位系統(tǒng)應(yīng)用的實(shí)際需求進(jìn)行全面修訂的一個(gè)例子。表2列出了上面和ITRF92（歷元1988.0）討論地球參考框架之間的7轉(zhuǎn)換參數(shù)。地球參考框架的全球一致性數(shù)量級(jí)在過去十年從表2可見，幾乎兩個(gè)數(shù)量已有所改善。已通過VLBI和衛(wèi)星大地測量的互補(bǔ)技術(shù)的細(xì)致應(yīng)用程序?qū)崿F(xiàn)的。在厘米級(jí)地球參考框架的一致性的維護(hù)需要地殼和地形的動(dòng)態(tài)，包括紀(jì)念碑穩(wěn)定的系統(tǒng)監(jiān)測。連續(xù)監(jiān)測地球旋轉(zhuǎn)動(dòng)力通過VLBI是必要為其在全球大地測量可能有這樣的快速進(jìn)步衛(wèi)星定位導(dǎo)航系統(tǒng)的高精度應(yīng)用。表2：轉(zhuǎn)換參數(shù)對ITRF92（1988.0時(shí)代）Ref.FrameD工DY[cm]JZRXRY[mas'RZSCL:PPF]RMS[cm]-94L98542^,515萬10.7-a.0052WGS34-6-52-22-IB.4-0.3-7.00.01L<200WGS34(GPS：-4-1-284.2-4..0-15.6-0.21B94WGS34(G730)0-14-2.6-2.5-0.46ZTEF9-0.39o.ao-0.96-0.0012<16進(jìn)入現(xiàn)代陸地參考系全球范圍和精度高，動(dòng)態(tài)特性的空間技術(shù)，特別是GPS在普遍使用的今天,新方法的需求維護(hù)和訪問地球參考框架。正如上面指出的,現(xiàn)代地球參考框架必須連接到最好的實(shí)現(xiàn)提供的慣性坐標(biāo)系VLBI和必須促進(jìn)決心站地心坐標(biāo)系中的速度。這目前通過綜合解決方案的全球網(wǎng)絡(luò)VLBI站的單反和GPS基準(zhǔn)站的地心坐標(biāo)和速度得到了從一系列觀測和地球動(dòng)力學(xué)的模型,解決方案定義了一個(gè)“控制網(wǎng)絡(luò)”對于一個(gè)給定的時(shí)期，例如I