區(qū)域電離層提取算法及延遲改正模型研究中期報(bào)告

區(qū)域電離層提取算法及延遲改正模型研究中期報(bào)告（英文）Mid-TermReportonAlgorithmandDelayCorrectionModelforExtractingRegionalIonosphericLayersAbstract:IonosphericdelayisoneofthemainsourcesoferrorinGPSpositioningandnavigation.AccuratelyestimatingtheionosphericdelayisimportantforimprovingtheaccuracyofGPSpositioning.RegionalionosphericlayershavesignificantimpactsonGPSsignalswithincertainregions.Inthisstudy,analgorithmforextractingregionalionosphericlayersbasedontheInternationalGNSSService(IGS)GlobalIonosphereMap(GIM)isproposed.ThealgorithmusesthesphericalharmonicanalysismethodtofittheIGSGIMdataandobtaintheionosphericdelayparameters.Thealgorithmwillbefurtheroptimizedbasedonthefeedbackfromexperimentaldata.Additionally,adelaycorrectionmodelwillbeestablishedbasedonthepreviousalgorithm,andtheaccuracyofthemodelwillbevalidatedbycomparingitwiththeIGSproducts.Theresearchiscurrentlyinthemid-termstage,andasummaryoftheresearchprogressandfutureworkispresentedinthisreport.Introduction:WiththedevelopmentofGlobalPositioningSystem(GPS),theapplicationofGPShasbeenwidelyusedincivilianandmilitaryfields.However,theionosphericdelayisoneofthemainsourcesoferrorinGPSpositioningandnavigation.Ionosphericdelayfluctuateswithtimeandlocationandisaffectedbyvariousfactors,suchassolaractivityandtheEarth'smagneticfield.AccuratelyestimatingtheionosphericdelayiscrucialforimprovingtheaccuracyofGPSpositioning.Amongthevariousionosphericmodels,theglobalionosphericmodelscanprovideaglobalionosphericdelaymapwithahightemporalandspatialresolution.However,duetothelimitationoftheionosphericobservationdata,theaccuracyoftheglobalionosphericmodelsisdifficulttofurtherimprove.Incontrast,regionalionosphericmodelsfocusonlocalionosphericfluctuationcharacteristicsthatcansignificantlyimpactGPSsignalswithincertainareas.Therefore,extractingregionalionosphericlayerparameterscanimproveGPSpositioningaccuracywithinthosespecificregions.Initially,aregionalgrid-basedionosphericmodelwasproposed.However,themodelfailedtoachievebetteraccuracyinareaswithrelativelylargeionosphericdisturbances.Basedonthislimitation,theconceptofregionalionosphericlayerswasproposed.Theregionalionosphericlayersaredefinedasasetofthinandhorizontalionosphericlayers,andeachlayerrepresentstheverticalandhorizontalionosphericdelaycharacteristicsinaspecificheightrangeandposition.Theregionalionosphericlayerscanbetterreflecttheionosphericdelaycharacteristicsinaregionofinterest,andtheextractionoftheregionalionosphericlayershasbecomearesearchhotspot.Inthisstudy,analgorithmforextractingregionalionosphericlayersbasedontheIGSGIMisproposed.Additionally,adelaycorrectionmodelwillbeestablishedbasedonthealgorithmtoimprovetheaccuracyofGPSpositioning.Methodology:TheproposedalgorithmaimstoextracttheregionalionosphericlayerparametersbyfittingtheIGSGIMdatausingthesphericalharmonicanalysismethod.Thealgorithmconsistsofthreesteps:datapreprocessing,sphericalharmonicanalysis,andextractionofregionalionosphericlayers.1.DataPreprocessing:Thepreprocessingstageincludesthefollowingsteps:a)Datascreening:screeningouttheionospheredatawithintheregionofinterest.b)Temporalfiltering:removingthediurnalvariationandotherperiodiccomponentsoftheionosphericdelaytoextracttheresidualionosphere.c)Spatialfiltering:removingthelarge-scaleionosphericdelayusingaspatialfilteringmethod.2.Sphericalharmonicanalysis:Thesphericalharmonicanalysismethodisadoptedtofittheresidualionospheredatatoobtainthesphericalharmoniccoefficientsoftheionosphericdelay.Thehigher-ordercoefficientsusuallyreflecttheregionalionosphericlayerparameters,suchasthethickness,height,andposition.3.ExtractionofRegionalionosphericlayers:Basedonthesphericalharmoniccoefficients,theregionalionosphericlayerparametersinaspecificheightrangeandpositioncanbeestimated.Theregionalionosphericlayerparametersincludeionosphericdelay,thickness,height,andposition.TheionosphericdelaycanbeusedtocorrecttheGPSpositioningerrorinaparticularregionofinterest.ResultsandDiscussion:Thealgorithmwillbeoptimizedbasedonthefeedbackfromexperimentaldata.ThemodelvalidationwillbeconductedbycomparingthedelaycorrectionmodelwiththeIGSproducts.Inaddition,theaccuracyofthealgorithmandmodelfordifferentregionswillbeevaluated.Finally,theimpactoftheregionalionosphericlayersonGPSpositioningaccuracywillbestudied.ConclusionsandFutureWork:Inthisstudy,analgorithmforextractingregionalionosphericlayersbasedontheIGSGIMisproposed.ThealgorithmusesthesphericalharmonicanalysismethodtofittheIGSGIMdataandobtaintheionosphericdelayparameters.Thealgorithmwillbeoptimizedbasedonthefeedbackfro