卫星定位导航外文翻译文献

卫星定位导航外文翻译文献（文档含中英文对照即英文原文和中文翻译）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)一丝】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.亘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.现代大地测量参考框架进行精确的卫星定位导航J.库巴和J.Popelar大地测量部，测绘加拿大，加拿大自然资源部（NRCan）615展位街，渥太华，安大略省，加拿大K1AEO9在NAD83和WGS84坐标参考框架建立超过十年前，以满足大多数测绘，制图，定位和导航应用。他们是在分别于大陆和全球范围内的1-2米的水平相一致，反映了现有数据和技术的局限性。随着定位准确迅速改善，主要是由于全球定位系统，submetre导航已成为实用和参考帧在厘米至毫米级所需的最苛刻的用户。该IERS地球参考框架（ITRF）成立于1988年由国际地球自转服务组织（IERS），以促进基于国家的最先进的，如甚长基线干涉（技术精确监测地球定向参数（EOP）的丫181）和卫星激光测距（SLR）。随着在1994年成立了国际GPS服务的地球动力学（IGS）的，在ITRF是直接通过精确的GPS全球卫星轨道/时钟解决方案和大量IGS监测站进行访问的用户全世界。最新的ITRF解决方案，指定ITRF92和ITRF93，基于空间大地测量观测数据，包括GPS到1993年年底在厘米级提供全球一致性。加拿大主动控制系统（CACS）通过IGS和VLBI积极参与有利于获得ITRF。包括在NAD83基准VLBI点提供了直接链接到ITRF，并有可能升级NAD83，以满足与厘米的精确定位和导航的要求，在未来的坐标。CACS方便最有效的连接，通过GPS高精度定位以及为一般空间参考需要在加拿大的ITRF和NAD83参考帧。1引言在大地测量参考坐标系表示的规模，方向和坐标原点为参考系，其中也包括地球的行星模型和必要的卫星定轨，GE-odynamic和地球物理数据分析常量的一部分。卫星导航系统使我们能够建立一个真正的全球地心参照系统，它很快就被改编为精确的大地测量定位，尤其是长距离。这是第一次有可能确定的扭曲和世界各地的经典大地测量网的取向差。美国海军导航卫星系统（NNSS），也称为运输或干脆多普勒（克什纳和牛顿，1962）成为基础的美国国防部部世界大地测量系统1972（WGS72），后来WGS84它定义全球地心参考系一致时约1-2米的水平。要升级和经典北美洲基准面1927（NAD27），在加拿大，美国，墨西哥和格陵兰的大地测量网络的调整的正确扭曲共同承担。这个新的基准，指定NAD83（北美基准），名义上是用做兼容的WGS84由是地心，并根据多普勒变换位置的导向，但在另外的NAD83调整包括VLBI（甚长基线干涉）的基线。因此，这两个，WGS84和NAD83，是在约一米的一致，主要是由于多普勒技术（库巴，1993）的限制。GPS和测距（SLR）提供的数据具有较高的精度，支持地壳动力学和极移，需要一个更精确的全球参考框架的研究等基础空间技术，如VLBI观测和卫星激光。该IERS地球参考框架（ITRF）成立于1988年，更新每年由国际地球自转服务组织（IERS），以保持它的电流和改善站速度所必需的维持这个全球基准的精度知识框架。NAD83可以与ITRF正是基于共同的VLBI站通过变换一个时代。加拿大主动控制系统（CACS）提供了最有效的方法来升级在加拿大，以满足未来与厘米的精确定位和导航要求NAD83坐标。2北美大地基准点：NAD83北美洲基准面1927（NAD27）采用欧式三角网与在Meades牧场在美国堪萨斯州（罗斯，1936年），一个位于中心的基准点成立于本世纪初。在60年代和70年代卫星大地测量检测到大约100米NAD27原点相对于地心以及扭曲超过几十米的大地控制网（米勒，1974）的某些部分抵销。一个新的参照系wasrequired，方便使用的测量和导航效率和精确的卫星大地测量技术。其中有1986年底前建立卫星多普勒位置和几个VLBI基线，被用来提供一个框架，并定义了新的途径大地基准点。北美洲基准面1983（NAD83）是基于多普勒站坐标变换，以符合对地心的起源，规模和参考椭球（NOAA，1989）取向的国际公约。经典大地测量观测值超过260,000的控制点进行了调整和整合的框架，提供了平面控制网的纪念碑实际使用的NAD83坐标范围内。因此，NAD83在其原始版本提供了水平定位精度与基准帧在对应于卫星多普勒精度多少有些误差通过在包含在NAD83网络调整经典三角弧稀释一米的水平。在这种精度级别没有必要引进台速度和NAD83被认为是连接到北美板块。制图，制图，导航和空间参照北美在不需要亚米级精度的NAD83坐标系满足最实际的需求。然而，今天的大地测量GPS测量的精度提高，需要在厘米级这将有利于涉及与地震或火山活动相关的板块构造和自然灾害等地壳动力学研究的参考帧一致性的VLBI基线贡献的精度到NAD83的定义不仅提供了有关NAD83一种有效的方法来在2cm的水平（索勒等人，1992）更准确的参考帧，但是也使用精确的大地测量空间技术有利于精确的升级。这样的做法将保证定位精度不断提高，以及可追溯至NAD83这是具有重大的现实意义。3世界大地测量系统：WGS84WGS84是已建立并保持了美国国防部部，以方便定位和导航世界各地（DMA,1991）的全球大地测量参考系统。对应于WGS84地面坐标参考框架已经更新，以保持与一般使用的GPS定位和导航技术的精确度提高的步伐。原始WGS84陆地参考系WGS84世界各地的地球参考框架最初仅基于卫星多普勒坐标变换中的相同的方式NAD83。然而，一组不同的多普勒台站使用，没有VLBI基线测量，包括在网络调整。这种方法产生了具有1-2米，反映了多普勒技术的局限性,精确度在全球同质的大地测量参考框架。站速度被忽略,因为他们并不重要。虽然多普勒WGS84坐标系是与NAD83在北美相媲美，缺乏精确的VLBI框架使得它无法与WGS84到目前，更准确，精度大于1m更好的参考帧。显著改善，如果可以的GPS运营所采用的WGS84框架被认为是可以实现的。这WGS84（GPS）地球参考框架是基于对代运营（直播）卫星轨道和时钟参数采用美国国防部10GPS跟踪站的WGS84坐标。修订WGS84（G730）陆地参考系已作出修订，使用几个星期从全球32个站（10国防部+22IGS）在同时调整卫星轨道和测站坐标网GPS观测的WGS84（GPS）的10GPS跟踪站的坐标;8个IGS站的坐标是约束通过的国际地球自转服务组织（IERS），并用引力的地心恒定的IERS值的值。对于GPS这种改进的参考框架，指定WGS84（G730）是指GPS周730，显示在大约10厘米水平全球一致性和使用的站速度（雨燕，1994NUVEL-1板块运动模型；。德大都会在人，1990）。自1994年开始，DMA已经使用WGS84（G730）的后处理，预计要为业务（广播）的GPS卫星轨道计算在不久的将来（Malys和斯莱特，1994）4日前地面参考系：ITRF为了通过现代空间大地测量技术，方便精确的地球自转和极移的监测局国际DEL'HEURE（BIH）成立于1984年，主要基于波黑地面系统（BTS84）对VLBI，SLR和卫星多普勒观测。1988年，当BIH被取代了IERS的IERS地球参考框架（ITRF88）的建立是为了满足以下要求（布歇，1990）：

(1)它是地心与原点在整个地球的质量中心包括海洋和大气；(2)其方向与BIH地球定向参数(EOP)系列的划时代1984.0一致;(3)站速度模型不得生产对于地球地壳的任何残余旋转；HolberWilliam1(4)规模相当于地球的局部坐标系中引力的相对论理论的意义。HolberWilliam1duduVictoriaAPciiuaiicntCACStrackingsite口nqu'n■WesternCanadaDeforniationxAiray(WCDA)•MomnneiitedtemporaiyCACSti'ackiiigsite图1：对CACSNAD83和ITRF92(1994.0)之间的残余差异监测站：自1988年以来，一个ITRF解决方案已经产生每年把新的观测站，并适当满足上述要求。板块运动模型NUVEL-1被用来推导站速度，同时强制执行无残余旋转的要求。这种结合ITRF站的有点不平衡的全球分布产生ITRF和IERS的EOP(IERS年报1992年的报告)，其中1992年累计约1MAS一个显著偏差之间的0.2MAS/年轮换。该NUVEL-1型台的速度进行了修订，以考虑到观测的VLBI和SLR站速度如果有的话，产生ITRF92，其中包括约150台。GPS观测提供最有效的技术ITRF时，集成在VLBI框架，保持绝对的方向和规模的致密化。意味着VLBI并列入ITRF92GPS网站位置误差列于表1,其显示了全球解决方案(鲍彻等人，1993)厘米级的一致性。在测定站速度，并进一步致密化的改进，在所有大陆获得更均匀的覆盖范围将是维持和提高ITRF精度在未来的发展至关重要。表1.致性的VLBI和GPS全球解决方案包括在ITRF92解决方案N权均方根值(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.地面参考帧之间的转换不同地球参考框架之间实际有用的转换是基于他们最准确的组常用电台这是用来确定7转换参数，并提供有关的关系的一致性基本RMS的信息。残留的系统性差异可以被映射或解析地表示，如果他们超过的坐标差显著的RMS值转换后。NAD83和ITRF92（历元1994.0）为加拿大主动控制系统（CACS）监测站示于图1中的位置之间的残余差异。然而，这样的偏差应该进行调查，如果它们表示系统误差的累积校正。这种修改提供自然升级路径的任何地球参考框架，并逐步消除不可接受的错误，显著提高其实际意义。在WGS84（G730）参考框架是为了应对全球定位系统应用的实际需求进行全面修订的一个例子。表2列出了上面和ITRF92（历元1988.0）讨论地球参考框架之间的7转换参数。地球参考框架的全球一致性数量级在过去十年从表2可见，几乎两个数量已有所改善。已通过VLBI和卫星大地测量的互补技术的细致应用程序实现的。在厘米级地球参考框架的一致性的维护需要地壳和地形的动态，包括纪念碑稳定的系统监测。连续监测地球旋转动力通过VLBI是必要为其在全球大地测量可能有这样的快速进步卫星定位导航系统的高精度应用。表2：转换参数对ITRF92（1988.0时代）Ref.FrameD工DY[cm]JZRXRY[mas'RZSCL:PPF]RMS[cm]-94L98542^,515万10.7-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进入现代陆地参考系全球范围和精度高，动态特性的空间技术，特别是GPS在普遍使用的今天,新方法的需求维护和访问地球参考框架。正如上面指出的,现代地球参考框架必须连接到最好的实现提供的惯性坐标系VLBI和必须促进决心站地心坐标系中的速度。这目前通过综合解决方案的全球网络VLBI站的单反和GPS基准站的地心坐标和速度得到了从一系列观测和地球动力学的模型,解决方案定义了一个“控制网络”对于一个给定的时期，例如I