简介:Inthispaper,wedescribetheestimationoflow-altituderefractivitystructurefromsimulationandrealground-basedGPSdelays.Theverticalstructureoftherefractiveenvironmentismodeledusingthreeparameters,i.e.,ductheight,ductthickness,andductslope.Therefractivitymodelisimplementedwithaprioriconstraintsontheductheight,thickness,andstrength,whichmightbederivedfromsoundingsornumericalweather-predictionmodels.Araypropagationmodelmapstherefractivitystructureintoareplicafield.Replicafieldsarecomparedwiththesimulationobserveddatausingasquarederrorobjectivefunction.Aglobalsearchforthethreeenvironmentalparametersisperformedusingageneticalgorithm.Theinversionisassessedbycomparingtherefractivityprofilesfromtheradiosondestothoseestimated.Thistechniquecouldprovidenear-real-timeestimationoftheductingeffect.Theresultssuggestthatground-basedGPSprovidessignificantatmosphericrefractivityinformation,despitecertainfundamentallimitationsofground-basedmeasurements.Radiosondesaretypicallylaunchedjustafewtimesdaily.Consequently,estimatesoftemporallyandspatiallyvaryingrefractivitythatassimilateGPSdelayscouldsubstantiallyimproveover-estimatescausedbyusingradiosondedataalone.
简介:Verticaltotalelectroncontent(VTEC)timeserieswereobtainedfrom22GPSstationsneartheepicenteroftheLushanearthquake.Inthispaper,wehaveadoptedaslidingaveragemethodtodetectandanalyzeanomalousVTECassociatedwiththeearthquake.Theresultsshowthatsignificant,negativeionosphereVTECanomaliesappearedoverthe5daysbeforetheearthquake,andonthedaywhenearthquakeoccurred.ThemaximumvalueofVTECanomaliesthatexceededthelowerboundreached20TECU.ThespatialdistributionofVTECanomaliesshowedaconjugatestructure,whichshiftedtothemagneticequator,andsubsequentlymovedwestwards.
简介:在最近的年里,全球航行卫星系统反射计(GNSS-R)被开发作为一个新遥感工具估计土壤潮湿内容(SMC)。全球放的系统(GPS)bistatic雷达的信号错误是影响SMC评价的精确性的一个重要因素。在这份报纸,直接、反映的信号被介绍的包含两个的GPS信号刻度的二个方法,和如此的方法的理论基础的详细解释被给。利用校准的GPSL乐队信号的一个改进SMC评价模型被建议,并且评价精确性在2002从土壤潮湿实验用在空中的GPS数据被验证(SMEX02)。我们为确认在US的核桃溪区域与大豆和玉米选择21个地点。这些地点根据他们的植被盖子被划分成三个范畴:赤裸的土壤,中间植被的盖子(中间蔬菜),并且高植被的盖子(高蔬菜)。SMC评价的精确性为赤裸的土壤是11.17%并且8.12%为中间蔬菜的地点,比传统的模型的好一些。为高蔬菜的地点,信号变细的效果preliminarily由于植被盖子被考虑,与规范的差别植被索引(NDVI)有关的一个线性模特儿被收养为修正在刻度上,和错误获得一个因素因为高蔬菜的地点最后被归结为3.81%。