利用中国区域电离层数据拟合 Klobuchar参数

对于单频G PS用户而言,电离层延迟是最重要的误差来源之一。G PS系统使用Klobuchar模型对电离层延迟进行改正,其改正数从根据经验模型和历史数据得到的370组常数选取。在缺少全球观测数据的情况下,仅利用中国区域观测数据拟合电离层模型参数,存在区域外精度下降,参数超限等问题。针对这些问题,提出了利用经验模型外推进行参数拟合的方法。相比广播Klobuchar参数,在太阳活动高峰年RMS误差减小接近7 TECU ,正常年减小1.5 T EC U ,平静年精度也略有提升。2001年至2012年的拟合参数不存在参数超限现象,且量化后或者使用预报的电离层数据进行拟合,精度下降很小,可以用于预报全球电离层模型参数。     

Modification Of Sporadic E-Layers Caused By Seismic Activity

Among all earthquake precursors, those related to electromagneticeffects are the most puzzling, and the many possible sources ofnoise are cause of lively controversies. A large number oflaboratory experiments clearly suggest that micro-fracturingis associated with the appearance of spontaneous charge production(electrification) and transient Electric or ElectroMagnetic (EM)Emission. Many electric and magnetic pre-seismic and co-seismiceffects have been reported in the past as well as ionosphericperturbations. The aim of this paper is to review some of theseionospheric perturbations performed in the former Soviet Union.The importance of sporadic E-layer formation is underlined.Statistical studies with the available observations are done.At the end, a physical model of lithosphere-ionosphere couplingis presented in order to explain the observations. This modeltakes into account the following effects at the Earth's surface:electric charge generation, emanation of radioactive gas,temperature variation, and surface vibration. It is shown thatthese effects can trigger sporadic E-layer formation.     

Failure time variation derived from R-S relation： the role of the static stress perturbation

In general, earthquake cycle related to earthquake faulting could include four major processes which could be described by(1) fault locking,(2) self-acceleration or nucleation(possible foreshocks),(3) coseismic slip, and(4) post-stress relaxation and afterslip. A sudden static stress change/perturbation in the surrounding crust can advance/ delay the fault instability or failure time and modify earthquake rates. Based on a simple one-dimensional spring-slider block model with the combination of rate-and-statedependent friction relation, in this study, we have approximately derived the simple analytical solutions of clock advance/delay of fault failures caused by a sudden static Coulomb stress change applied in the different temporal evolution periods during an earthquake faulting. The results have been used in the physics-based explanation of delayed characteristic earthquake in Parkfield region, California, in which the next characteristic earthquake of M 6.0 after 1966 occurred in 2004 instead of around 1988 according to its characteristic return period of 22 years. At the same time, the analytical solutions also indicate that the time advance/ delay in Coulomb stress change derived by the dislocation model has a certain limitation and fundamental flaw. Furthermore, we discussed the essential difference between rate- and state-variable constitutive(R–S) model and Coulomb stress model used commonly in current earthquake triggering study, and demonstrated that, in fact, the Coulomb stress model could be involved in the R–S model. The results, we have obtained in this study, could be used in the development of time-dependent fault interaction model and the probability calculation related to the time-dependent and renewal earthquake prediction model.     

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北斗电离层模型精度分析

北斗电离层模型包括基本导航的BDSKlob模型、BDGIM模型及广域差分格网电离层模型,本文详细分析2种基本导航的电离层模型因相邻模型参数更新引起的延迟跳变,基于CODE格网电离层模型对比2种电离层模型随空间和时间的变化情况,分析不同电离层模型在不同时段不同纬度的改正精度及定位精度,并利用2018年数据对北斗格网点电离...     

GNSS多频观测值线性组合研究

以Galileo四频为例,组合其不同频率间的相位观测值,给出以周为单位和以m为单位的相位组合观测模型的通用形式,系统分析组合后的电离层误差、波长以及观测噪声|在保持整周模糊度整数特性的前提下,研究电离层误差小、波长长、观测噪声小的组合|最后,按照合适的原则,编程计算出不同导航系统不同形式的组合观测系数,并给出几组典型组合。     

基于CORS的DInSAR大气延迟校正方法研究

针对利用GPS数据改正DInSAR大气延迟误差中存在CORS站点稀疏的问题,给出一种广义曲面拟合插值模型,并基于北京地区的GPS观测数据和SAR影像对比较了反距离加权插值模型（IDW）和曲面拟合插值模型（CSF）用于区域对流层延迟建模的精度,然后对SAR差分干涉图进行大气延迟校正。结果表明,曲面拟合模型比反距离加权模型更能反映区域单差对流层延迟特性,两次实验的插值精度分别达到了7.1和3.5 mm。采用CORS观测数据和曲面拟合内插模型,可有效削弱DInSAR中的大气延迟误差,提高DInSAR测量结果的精度。     

基于GPS电离层层析技术的地震电离层异常研究

采用电离层层析成像技术（CIT）研究日本、苏门答腊岛、中国台湾、新疆地区上空不同震级地震前后的电离层三维分布。利用异常探测方法对反演出的电子密度值进行探测并用统计学方法统计地震电离层异常规律,结论如下： 1）在地震前几天或者前几个小时出现电离层明显异常,尤其是在地震前1～2 d震中附近,排除太阳活动和地球磁场影响,初步认为该异常与地震有关|2)电离层电子密度出现异常区域一般涵盖震中区域,与震中位置有少量偏移,而且离震中区域越近,电离层异常变化越大|3)未发现正、负异常的比例与地震之间有明确的对应关系。     

高阶电离层延迟对中国区域双差定位影响研究

给出顾及高阶电离层延迟改正的双差定位模型,探讨中国区域VTEC的时空变化规律,分析高阶电离层延迟对L3观测值的影响。利用41个陆态网测站2015年全年的GNSS数据,基于Bernese 5.2软件的双差定位技术,系统研究高阶电离层延迟对中国区域双差定位的影响及其时空分布规律。结果表明,高阶电离层延迟对中国区域双差定位的影响与测站网型结构相关,明显存在0.5 a的周期变化,影响年均值大小为0～2 mm,且具有方向性差异,对高纬度测站的影响有向北偏移趋势,对低纬度测站的影响有向南偏移趋势。     

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