Global modeling 2^(nd)-order ionospheric delay and its effects on GNSS precise positioning

查看全文 作　　者：ZHANG [1,2]HongPing;LV [3]HaiXia;LI [2]Min;SHI [1,2]Chuang

机构地区：[1]State Key Laboratory of Information Engineering in Surveying,Mapping and Remote Sensing,Wuhan University,Wuhan 430070,China;[2]GNSS Research Center,Wuhan University,Wuhan 430079,China;[3]School of Geodesy and Geomatics,Wuhan University,Wuhan 430079,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》索引2011年第54卷第6期,共9页

基　　金：supported by the National Basic Research Project of China (Grant No.2009CB72400205);the National Natural Science Foundation of China (Grant No.40804005);the National High Technology Research and Development Program of China (Grant No.2009AA121401) 摘　　要：Ionospheric delay is one of the major error sources in GNSS navigation and positioning.Nowadays,the dual-frequency technique is the most widely used in ionospheric refraction correction.However,dual-frequency measurements can only eliminate the first-order term of ionospheric delay,while the effect of the second-order term on GNSS observations may be several centimeters.In this paper,two models,the International Reference Ionosphere (IRI) 2007 and International Geomagnetic Reference Field (IGRF) 11 are used to estimate the second-order term through the integral calculation method.Besides,the simplified single layer ionosphere model in a dipole moment approximation for the earth magnetic field is used.Since the traditional integral calculation method requires large calculation load and takes much time,it is not convenient for practical use.Additionally,although the simplified single layer ionosphere model is simple to implement,it results in larger errors.In this study,second-order term ionospheric correction formula proposed by Hoque (2007) is improved for estimating the second-order term at a global scale.Thus,it is more practicable to estimate the second-order term.More importantly,its results have a higher precision of the sub-millimeter level for a global scale in normal conditions.Compared with Hoque's original regional correction model,which calculates coefficients through polynomial fitting of elevation and latitudes,this study proposes a piece-wise look-up table and interpolation technique to modify Hoque model.Through utilizing a table file,the modified Hoque model can be conveniently implemented in an engineering software package,like as PANDA in this study.Through applying the proposed scheme for the second-order ionospheric correction into GNSS precise positioning in both PPP daily and epoch solutions,the results have shown south-shift characteristics in daily solution at a global scale and periodic change with VTEC daily variation in epoch positioning solution. 关键词：全球导航卫星系统电离层延迟精确定位二阶国际地磁参考场电离层模型积分计算建模

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Global modeling 2^(nd)-order ionospheric delay and its effects on GNSS precise positioning

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