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1.
《武汉大学学报(信息科学版)》2020,(4)
卫星测高、DORIS(Doppler Orbitography and Radio-positioning Integrated by Satellite)和无线电掩星等星基观测技术具有不受地表形态限制的全球观测范围,能够作为地基全球导航卫星系统(Global Navigation Satellite System,GNSS)电离层反演在海洋区域的补充观测。然而星基观测电离层高度范围仅限于低轨卫星轨道面以下,无法覆盖整个电离层高度范围,因此不能直接用于与地基GNSS反演的电离层总电子含量(total electron content, TEC)格网融合。针对DORIS观测反演的相对斜向总电子含量(slant total electron content,STEC),以全球电离层TEC格网(global ionosphere maps total electron content, GIM TEC)为基准,采用整体偏移方法将两者归算至统一观测尺度上;而卫星测高和GNSS掩星电离层产品则选取国际GNSS服务(International GNSS Service, IGS)组织提供的全球电离层TEC格网中均方根(root mean square, RMS)误差小于2 TECU的区域作为基准,采用2014年1月份低轨卫星观测值反演的TEC和GIM TEC数据进行对比,统计Jason-2和COSMIC(Constellation Observing System for Meteorology, Ionosphere and Climate)卫星反演的TEC与GIM TEC之间基于比例因子的函数关系,并将不同的观测手段归算到统一的观测尺度上,对比归算前后的TEC产品差异。并根据反演产品附近的全球定位系统(Global Positioning System,GPS)电离层穿刺点数量进行分类,验证星基电离层反演精度的有效性。对比结果显示,卫星测高、DORIS和掩星3种星基技术归算后的TEC产品与GIM TEC的匹配度在地基观测密集区域均能达到较好的符合度,而在地基观测不足区域符合度存在明显差异。考虑星基观测精度不受地域限制的特性,可认为该海洋区域的差异是由于星基观测在海洋区域观测精度比地基GNSS观测精度更高,星基观测反演的电离层TEC产品可作为海洋地区地基电离层TEC观测的有效补充。 相似文献
2.
电离层延迟是GNSS导航定位中重要的误差源,对电离层进行监测和建模具有重要的意义。GNSS具有覆盖范围广、观测时间长、反演精度高等特点,为电离层监测和建模提供了一种有效的手段。差分码偏差(differential code bias,DCB)包含在电离层观测值中,与电离层总电子含量(total electron content,TEC)参数相互耦合,在电离层建模时需要被精确分离和确定。 相似文献
3.
《武汉大学学报(信息科学版)》2016,(6)
电离层总电子含量TEC(total electron content)是影响卫星导航定位的主要误差源之一。为了构建精确的电离层TEC模型,基于Chapman函数建立了基于物理机制的电离层TEC同化模型背景场,并着重以IGS发布的2008年4个时段低纬度、中纬度和高纬度地区的电离层TEC数据为样本,同化稀疏点上的已知电离层TEC值,分析模型计算值的残差和相对精度分布,利用模型对电离层TEC进行了2h短期预报和1d预报,并将1d的预报值和IGS发布值进行对比。实验结果表明:(1)由同化模型计算得到的TEC残差值超过92%分布在±2TECU以内,并且除边缘区域外,同化模型TEC计算值的相对精度均在90%以上;(2)2h和1d预报残差小于±3TECU的比例分别为81.8%和81.5%。 相似文献
4.
胡文权 《测绘与空间地理信息》2023,(8):164-167
为了提高电离层TEC值的预报精度,建立更高精度的电离层TEC预报模型,本文在RBF神经网络模型的基础上引入奇异谱分析(Singular Spectrum Analysis, SSA)方法,构建新的电离层TEC预报模型。该组合模型首先通过SSA提取原始序列中的特征分量,避免噪声分量对预报结果的影响,其次将去噪后特征分量作为RBF神经网络模型的输入值。使用IGS中心提供的TEC数据序列进行模型验证,结果表明,无论是对平静期电离层TEC预报还是磁暴期电离层TEC预报,相比于单一的RBF神经网络模型预报结果,本文提出的SSA-RBF神经网络模型的预报结果均更优,其中平静期预报残差在2 TECU以内,磁暴期预报残差在3—4 TECU以内,验证了本文提出组合模型的优越性。 相似文献
5.
为分析磁暴期间电离层扰动规律及GNSS定位性能变化，基于国际GNSS服务(International GNSS Service,IGS)全球观测数据及全球电离层图(global ionospheric map,GIM)，对2018年8月26日地磁暴事件引发的北半球地区电离层总电子含量(total electron content,TEC)异常变化和GPS定位性能进行分析.结果表明：北半球TEC异常存在纬度差异，高纬地区响应快，低纬地区异常值变化大，达12 TECU；磁暴期间高纬地区观测数据周跳变化明显，周跳比数值与磁静日相比最大下降61.84%；磁暴期间所有测站数据完整率下降，高纬地区下降响应快，下降严重，达38.65%，研究区所有测站数据完整率下降出现在磁暴恢复相，数据质量与TEC异常变化规律较为一致；对GPS双频动态精密单点定位(precise point positioning,PPP)结果进行分析发现，磁暴期间高纬地区测站定位误差显著增大，水平和垂直方向均方根误差(root mean squared error,RMSE)增至约0.7 m及1.8 m. 相似文献
6.
应用半参数AR模型的电离层TEC建模与预测 总被引：1，自引：0，他引：1
本文基于时间序列分析的DDS(Dynamic Data System)建模法,对季节性的电离层总电子含量(TEC)时间序列观测值平稳化后建立自回归AR模型,提出以半参数AR模型对普通AR模型精化,并利用半参数AR模型对电离层TEC预报。实例分析表明:利用半参数AR模型对电离层TEC进行预报,在短期内半参数模型预报效果优于普通AR模型,但随着预报时间变长,则半参数模型预报精度明显下降,其预报效果则不如普通的AR模型。 相似文献
7.
太阳活跃期受太阳风高能粒子影响易发生磁暴,使得电离层总电子含量异常扰动,其非平稳性与非线性特征较平静期明显增强。分别利用2011年区域内多个测站的实测数据与IGS（International GNSS Service）发布的全球电离层模型（global ionosphere model,GIM）进行逐点建模,选取db4小波基对样本序列进行分解后,采用时间序列模型对各分量进行预报并重构,实现对ARIMA（auto regressive integrated moving average）模型的改进。通过分析ARIMA模型与改进模型预报值的残差比例和实验区域内均方根误差的分布情况,来评定改进模型的预报精度与适用性。结果表明,改进模型的残差与实验区域内的均方根误差较ARIMA模型总体减小,且该模型对区域内均方根误差峰值能起到较大的削弱作用。 相似文献
8.
基于球谐函数模型的GPS差分码延迟估计 总被引：1，自引：0，他引：1
电离层延迟是GNSS观测值中最大的误差源,因此如何利用GNSS观测值确定高精度电离层模型逐渐成为实时导航、定位及大气相关研究的重要内容。在通常采用组合观测值建立模型的方法中,精确估计电离层总电子含量（TEC）的重要误差之一是差分码硬件延迟（DCBs）。为了实时得到P1、P2、C2相互间硬件差分码延迟偏差,本文采用IGS跟踪站的观测数据并利用载波平滑后的差分伪距建立观测方程,对卫星和接收机硬件差分码延迟偏差进行实时解算。经比较模型解算DCB值与IGS最大差异不超过0.8 ns,C1、P1码延迟偏差72%差异值小于0.3 ns,P1、P2的74%差异值小于0.3 ns。 相似文献
9.
《测绘地理信息》2017,(5)
基于国际GNSS服务(International GNSS Service,IGS)WUHN、BJFS站GPS观测数据,利用码与相位观测值联合解算北京时间2010-01-15、2012-05-21日偏食前后电离层总电子含量(total electronic content,TEC),以此探测两次日偏食过程中的电离层效应。研究分析表明,日偏食期间电离层效应微弱,电离层TEC存在异常扰动,异常过程为先减少、达到最大变化量、逐步恢复正常,该过程与测站日偏食过程具有时间一致性,电离层TEC最大变化量不足1TECU,最大变化时刻滞后食甚时刻1~13min,不存在电离层TEC长时间异常现象。 相似文献
10.
自回归移动平均模型的电离层总电子含量短期预报 总被引：2，自引：1，他引：1
摘 要：本文在充分考虑乘积性季节模型的情况下,利用差分法对电离层总电子含量（Total Electron Content,TEC）样本序列进行平稳化处理后,采用时间序列分析中的求和自回归移动平均模型（简称ARIMA,Autoregressive Integrated Moving Average)对TEC值序列进行预报分析。以欧洲定轨道中心（CODE）提供的2008-2012年电离层TEC值为样本数据,分析了该方法在电离层平静期、活跃期预报高、中、低不同纬度电离层TEC值的精度以及TEC样本数据的长短对预报精度的影响等。实验结果表明：在电离层平静期和活跃期预报6天的平均相对精度可达83.3%和86.6%;而平均预报残差分别为0.18±1.9TECU和0.69±2.6TECU,其中预报残差小于3TECU分别达到90%和81%以上;而且两个时期都具有纬度越高相对精度越低而绝对精度越高的规律。此外,预报精度会随TEC样本序列长度增加而提高,但40天左右为其最佳样本长度,如超过此长度,其精度会逐渐降低;而相同样本数据的预报精度会随预报长度的增加而减小,初期并不明显,但超过30天其相对精度将随时间明显降低。 相似文献
11.
Application of SWACI products as ionospheric correction for single-point positioning: a comparative study 总被引：1，自引：0，他引：1
In Global Navigation Satellite Systems (GNSS) using L-band frequencies, the ionosphere causes signal delays that correspond with link related range errors of up to 100 m. In a first order approximation the range error is proportional to the total electron content (TEC) of the ionosphere. Whereas this first order range error can be corrected in dual-frequency measurements by a linear combination of carrier phase- or code-ranges of both frequencies, single-frequency users need additional information to mitigate the ionospheric error. This information can be provided by TEC maps deduced from corresponding GNSS measurements or by ionospheric models. In this paper we discuss and compare different ionospheric correction methods for single-frequency users. The focus is on the comparison of the positioning quality using dual-frequency measurements, the Klobuchar model, the NeQuick model, the IGS TEC maps, the Neustrelitz TEC Model (NTCM-GL) and the reconstructed NTCM-GL TEC maps both provided via the ionosphere data service SWACI (http://swaciweb.dlr.de) in near real-time. For that purpose, data from different locations covering several days in 2011 and 2012 are investigated, including periods of quiet and disturbed ionospheric conditions. In applying the NTCM-GL based corrections instead of the Klobuchar model, positioning accuracy improvements up to several meters have been found for the European region in dependence on the ionospheric conditions. Further in mid- and low-latitudes the NTCM-GL model provides results comparable to NeQuick during the considered time periods. Moreover, in regions with a dense GNSS ground station network the reconstructed NTCM-GL TEC maps are partly at the same level as the final IGS TEC maps. 相似文献
12.
13.
Experimental analysis was performed using multiplicative algebraic reconstruction technique (MART) to map the ionosphere over Brazil. Code and phase observations from the global navigation satellite system (GNSS) together with the international reference ionosphere (IRI) enabled the estimation of ionospheric profiles and total electron content (TEC) over the entire region. Twenty-four days of data collected from existing ground-based GNSS receivers during the recent solar maximum period were used to analyze the performance of the MART algorithm. The results were compared with four ionosondes. It was demonstrated that MART estimated the electron density peak with the same degree of accuracy as the IRI model in regions with appropriate geometrical coverage by GNSS receivers for tomographic reconstruction. In addition, the slant TEC, as estimated with MART, presented lower root-mean-square error than the TEC calculated by ionospheric maps available from the International GNSS Service (IGS). Furthermore, the daily variations of the ionosphere were better represented with the algebraic techniques, compared to the IRI model and IGS maps, enabling a correlation of the elevation of the ionosphere at higher altitudes with the equatorial ionization anomaly intensification. The tomographic representations also enabled the detection of high vertical gradients at the same instants in which ionospheric irregularities were evident. 相似文献
14.
Ionospheric delay is a dominant error source in Global Navigation Satellite System (GNSS). Single-frequency GNSS applications require ionospheric correction of signal delay caused by the charged particles in the earth’s ionosphere. The Chinese Beidou system is developing its own ionospheric model for single-frequency users. The number of single-frequency GNSS users and applications is expected to grow fast in the next years in China. Thus, developing an appropriate ionospheric model is crucially important for the Chinese Beidou system and worldwide single-frequency Beidou users. We study the performance of five globally accessible ionospheric models Global Ionospheric Map (GIM), International Reference Ionosphere (IRI), Parameterized Ionospheric Model (PIM), Klobuchar and NeQuick in low- and mid-latitude regions of China under mid-solar activity condition. Generally, all ionospheric models can reproduce the trend of diurnal ionosphere variations. It is found that all the models have better performances in mid-latitude than in low-latitude regions. When all the models are compared to the observed total electron content (TEC) data derived from GIM model, the IRI model (2012 version) has the best agreement with GIM model and the NeQuick has the poorest agreement. The RMS errors of the IRI model using the GIM TEC as reference truth are about 3.0–10.0 TECU in low-latitude regions and 3.0–8.0 TECU in mid-latitude regions, as observed during a period of 1 year with medium level of solar activity. When all the ionospheric models are ingested into single-frequency precise point positioning (PPP) to correct the ionospheric delays in GPS observations, the PIM model performs the best in both low and mid-latitudes in China. In mid-latitude, the daily single-frequency PPP accuracy using PIM model is ~10 cm in horizontal and ~20 cm in up direction. At low-latitude regions, the PPP error using PIM model is 10–20 cm in north, 30–40 cm in east and ~60 cm in up component. The single-frequency PPP solutions indicate that NeQuick model has the lowest accuracy among all the models in both low- and mid-latitude regions of China. This study suggests that the PIM model may be considered for single-frequency GNSS users in China to achieve a good positioning accuracy in both low- and mid-latitude regions. 相似文献
15.
Single layer ionosphere models are frequently used for ionospheric modeling and estimation using GPS measurements from a network of GPS reference stations. However, the accuracies of single layer models are inherently constrained by the assumption that the ionospheric electrons are concentrated in a thin shell located at an altitude of about 350 km above Earths surface. This assumption is only an approximation to the physical truth because the electrons are distributed in the entire ionosphere region approximately from 50 to 1,000 km. To provide instantaneous ionospheric corrections for the real-time GPS positioning applications, the ionospheric corrections need to be predicted in advance to eliminate the latency caused by the correction computation. This paper will investigate ionospheric total electron content (TEC) predictions using a multiple-layer tomographic method for ionospheric modeling over a local area GPS reference network. The data analysis focuses on the accuracy evaluation of short-term (5 min in this study) TEC predictions. The results have indicated that the obtainable TEC prediction accuracy is at a level of about 2.8 TECU in the zenith direction and 95% of the total electron content can be recovered using the proposed tomography-based ionosphere model. 相似文献
16.
GAMIT／GLOBK是全球应用最广泛的高精度GPS数据处理软件之一,不仅在高精度定位方面得到应用,而且在全球地壳板块运动监测、电离层监测和GPS气象学等领域也得到广泛应用。本文介绍了在Windows7系统下实现Ubunru Kylin16.04桌面版系统的安装,并在Ubuntu Kylin系统平台下安装、更新最新版GAMIT／GLOBK10.60,并利用中国及其周边IGS站观测数据进行基线解算和网平差,验证了软件安装的正确性。 相似文献
17.
电离层延迟是影响导航定位精度的最主要因素。北斗卫星导航系统采用Klobuchar模型修正单频接收机用户的电离层延迟误差,对于双频接收机,可以利用不同频率信号的伪距观测数据解算得到电离层延迟值。为比较两种方法在天津地区的电离层延迟修正效果,利用NovAtel GPStation6接收机(GNSS电离层闪烁和TEC监测接收机)采集到的卫星实测数据进行计算。以国际全球导航卫星系统服务组织(IGS)发布的全球电离层格网数据为参考,对两种方法的修正效果进行比较分析。结果表明,在天津地区,利用双频观测值解算电离层延迟比Klobuchar模型计算结果更加精确,且平均每天的修正值达到IGS发布数据的82.11％,比Klobuchar模型计算值高948％ 相似文献
18.
Local variability in total electron content can seriously affect the accuracy of GNSS real-time applications. We have developed
software to compute the positioning error due to the ionosphere for all baselines of the Belgian GPS network, called the Active
Geodetic Network (AGN). In a first step, a reference day has been chosen to validate the methodology by comparing results
with the nominal accuracy of relative positioning at centimeter level. Then, the effects of two types of ionospheric disturbances
on the positioning error have been analyzed: (1) Traveling ionospheric disturbances (TIDs) and (2) noise-like variability
due to geomagnetic storms. The influence of baseline length on positioning error has been analyzed for these three cases.
The analysis shows that geomagnetic storms induce the largest positioning error (more than 2 m for a 20 km baseline) and that
the positioning error depends on the baseline orientation. Baselines oriented parallel to the propagation direction of the
ionospheric disturbances are more affected than others. The positioning error due to ionospheric small-scale structures can
be so identified by our method, which is not always the case with the modern ionosphere mitigation techniques. In the future,
this ionospheric impact formulation could be considered in the development of an integrity monitoring service for GNSS relative
positioning users. 相似文献
19.
Ionospheric correction using NTCM driven by GPS Klobuchar coefficients for GNSS applications 总被引：1，自引：1，他引：0
Global Navigation Satellite Systems (GNSS) require mitigation of ionospheric propagation errors because the ionospheric range errors might be larger than tens of meters at the zenith direction. Taking advantage of the frequency-dispersive property of ionospheric refractivity, the ionospheric range errors can be mitigated in dual-frequency applications to a great extent by a linear combination of carrier phases or pseudoranges. However, single-frequency GNSS operations require additional ionospheric information to apply signal delay or range error corrections. To aid single-frequency operations, the global positioning system (GPS) broadcasts 8 coefficients as part of the navigation message to drive the ionospheric correction algorithm (ICA) also known as Klobuchar model. We presented here an ionospheric correction algorithm called Neustrelitz TEC model (NTCM) which can be used as complementary to the GPS ICA. Our investigation shows that the NTCM can be driven by Klobuchar model parameters to achieve a significantly better performance than obtained by the mother ICA algorithm. Our research, using post-processed reference total electron content (TEC) data from more than one solar cycle, shows that on average the RMS modeled TEC errors are up to 40% less for the proposed NTCM model compared to the Klobuchar model during high solar activity period, and about 10% less during low solar activity period. Such an approach does not require major technology changes for GPS users rather requires only introducing the NTCM approach a complement to the existing ICA algorithm while maintaining the simplicity of ionospheric range error mitigation with an improved model performance. 相似文献
20.
本文在研究了目前存在方法的基础上,将数理统计中的方差分析周期叠加外推法应用于电离层短期预报,并对其作了改进。采用IGS提供的电离层TEC数据作为原始数据比较了该方法改进前后的预报精度,分别利用中国区域内不同地理位置的40天的数据进行分析预报,预报结果显示改进后的方法预报精度可达到1.1TECU左右,优于改进前。改进后的预报效果依然与经纬度有关,在中国区域内随着纬度的减小、经度的增加,预报精度会降低。通过与目前常用方法比较分析,该方法预报结果精度较高、所需计算参数少、简单易行,可以较好地应用于电离层短期预报。 相似文献