共查询到17条相似文献，搜索用时 109 毫秒
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研究了NeQuick2算法改进及其实现方法,从不同角度分析了NeQuick2模型在全球区域和中国区域内的性能优势。一个太阳活动周期内,中国区域NeQuick2模型计算的电子总含量（total electron content,TEC）比NeQuick1模型精度有显著提升,改正精度与太阳活动水平具有较强的相关性,低年比高年的改善效果更为显著。以全球电离层数据（global ionosphere maps,GIM）为参考标准,中国中高纬区域太阳活动低年NeQuick2模型TEC的系统年平均偏差减少了76%,年平均均方根（root mean square,RMS）值减少了约72%。太阳活动高年NeQuick2模型TEC的系统年平均偏差减少了38%,平均RMS减少了13%左右,且中高纬区域改正精度优于低纬区域11%~13%。全球区域太阳活动峰值期间NeQuick2模型TEC比NeQuick1模型日平均偏差改善了25%,日平均RMS改善了30%左右。分别用NeQuick1和NeQuick2模型得出F2层顶部区域在太阳活动峰值期电子密度随高度剖面分布,顶部电子密度剖面精度改善近40%。最后分别得出了两个模型中国区域中高纬地区E和F1层区域在100 km、150 km和200 km高度的电子密度分布图,结果显示NeQuick2模型改善了电子密度分布状况,有效避免了NeQuick1在底部区域电子密度梯度不连续以及电离层异常结构的情况。 相似文献
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电离层总电子含量(TEC)是描述电离层变化特性的关键参量,构建实时电离层TEC模型可为实时导航定位用户提供电离层延迟改正,加快精密单点定位收敛速度,实现对空间天气的精准监测。基于此,论文以构建实时电离层TEC模型为目标,从融合多源电离层数据构建电离层TEC模型和高精度电离层TEC预报模型的构建展开研究,主要研究内容及贡献如下:(1)使用不同方法评估了2002年001天-2018年365天IRI-2016模型、NeQuick2模型与IGS提供的电离层最终产品(IGSG)的精度。 相似文献
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F2层临界频率foF2是高频通信的重要参数,目前获取F2层临界频率(foF2)最有效的手段是电离层测高仪,但磁暴期间电离层自身剧烈变化会造成测高仪foF2数据严重缺失。经验模型如NeQuick虽能给出foF2估计值,但磁暴期精度却不及磁静日水平。本文选取2015年12月19日至2015年12月22日磁暴期中国地壳运动监测网GNSS双频数据进行区域建模并估算出电子总含量(total electron content,TEC),利用实测区域TEC对NeQuick模型有效电离参数Az进行估计,得出NeQuick模型优化后TEC总含量和F2层临界频率foF2,并反演出磁暴期初相,主相及恢复相阶段变化过程。以中国地区台站实测数据作为参考对比,结果表明:GNSS数据优化后的NeQuick模型TEC精度大概提升了20%~40%,foF2的实时精度提升了10%~25%。GNSS优化后NeQuick模型能准确反演出电离层的由正相暴转为负相暴演化过程,而原始模型由于仅依赖于输入的太阳活动水平,只能反映出与磁静日水平相当的日变化趋势值。利用该方法可以有效提高磁暴期TEC和foF2的经验模型的计算精度,特别是弥补磁暴期foF2数据缺失的不足,可以作为磁暴期电离层垂直探测仪的有益补充或者有效参考。 相似文献
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电离层延迟是影响全球卫星导航系统精密定位的主要误差源之一。本文介绍了常用的NeQuick模型和IRI模型,利用两模型进行了中国地区电离层TEC相关计算,将计算值与电离层参考值进行比较,得出了关于区域电离层TEC的有益结论。 相似文献
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电离层总电子含量(TEC)是电离层探测与研究工作的重要特征参量之一．利用地基GPS接收站台网,可以获得大量的垂直TEC数据．本文提出一种高精度TEC地图重构方法,基于Kriging法对垂直TEC进行插值处理,实现了亚大区域高分辨率TEC二维分布的重构,并与实测数据对比验证了本方法的精度和有效性．基于此二维分布,分析了区域TEC值随时间、纬度的变化情况;重点分析了磁静日与磁暴期间南北半球不同纬度TEC值的不同表现特征,并给出了磁暴期间不同纬度TEC的变化趋势所存在的差异及其解释,相关研究成果可为区域高分辨率电离层监测系统的建立提供方法支撑． 相似文献
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不同NeQuick电离层模型参数的应用精度分析 总被引：3，自引：2，他引：1
Galileo采用NeQuick作为全球广播电离层模型,其实际应用中以有效电离水平因子Az代替太阳活动指数作为NeQuick的输入参数,并利用二次多项式拟合得到广播星历中播发的3个电离层参数。本文在总结和讨论NeQuick模型参数估计方法及其变化特征的基础上,分别以全球电离层格网、GPS基准站及JASON-2测高卫星提供的电离层TEC为参考,分析不同NeQuick模型参数(包括以太阳活动参数F10.7为输入的NeQuick2、以本文解算参数为输入的NeQuickC和以Galileo广播电离层参数为输入的NeQuickG)在全球大陆及海洋地区的应用精度,并与GPS广播的Klobuchar模型对比。结果表明,NeQuickG在全球范围内的修正精度为54.2%~65.8%,NeQuickC的修正精度为71.1%~74.2%,NeQuick2的修正精度与NeQuickG相当,略优于GPS广播星历中播发的Klobuchar模型。 相似文献
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电离层是影响卫星导航系统传输时延的重要因素之一,电离层总电子含量(TEC)地图重构是消除电离层传输时延的重要手段。GPSTk作为GPS数据处理的重要软件之一,可以满足区域电离层TEC地图的重构要求。本文针对GPSTk的特点,深入研究了GPSTk的电离层TEC计算原理、数据处理流程及具体的软件操作方法,该研究对基于GPS数据的电离层数据处理软件的研制具有一定的参考意义。 相似文献
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《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
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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
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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
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.
Application of the TaiWan Ionospheric Model to single-frequency ionospheric delay corrections for GPS positioning 总被引：2，自引：2，他引：0
The performance of a three-dimensional ionospheric electron density model derived from FormoSat3/COSMIC GPS Radio Occultation measurements, called the TaiWan Ionosphere Model (TWIM), in removing the ionospheric delays in single-frequency pseudorange observations is presented. Positioning results using TWIM have been compared with positioning results using other ionospheric models, such as the Klobuchar (KLOB) and the global ionospheric model (GIM). C/A code pseudoranges have been observed at three International GPS Service reference stations that are representative of mid-latitude (BOR1 and IRKJ) and low-latitude (TWTF) regions of the ionosphere. The observations took place during 27 geomagnetically quiet days from April 2010 to October 2011. We perform separate solutions using the TWIM, KLOB, GIM ionospheric models and carry out a solution applying no ionospheric correction at all. We compute the daily mean horizontal errors (DMEAN) and the daily RMS (DRMS) for these solutions with respect to the published reference station coordinates. It has demonstrated that TEC maps generate using the TWIM exhibit a detailed structure of the ionosphere, particularly at low-latitude region, whereas the Klobuchar and the GIM only provide the basic diurnal and geographic features of the ionosphere. Also, it is shown that even for lower satellite elevations, the TWIM provides better positioning than the Klobuchar and GIM models. Specifically, using TWIM, the difference of the uncorrected solution (no ionospheric correction), and the other solutions, relative to the uncorrected solution, is 45 % for the mean horizontal error (DMEAN) and 42 % for the horizontal root-mean-square error (DRMS). Using Klobuchar and GIM, the percent for DMEAN only reaches to about 12 % and 3 %, while the values for the DRMS are only 12 and 4 %, respectively. In the vertical direction, all models have a percentage of about 99 and 70 % for the mean vertical error (VMEAN) and vertical root-mean-square error (VRMS), respectively. These percentages show the greater impact of TWIM on the ionospheric correction compared to the other models. In at least 40 % of the observed days and across all stations, TWIM has the smallest DMEAN, VMEAN, DRMS, and VRMS daily values. These values reach 100 % at station TWTF. This shows the overall performance of TWIM is better than the Klobuchar and GIM. 相似文献
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Differential ionospheric slant delays are obtained from a quiet-time, three-dimensional ionospheric electron density model, called the TaiWan Ionosphere Model (TWIM), to be used in code-based differential GPS positioning. The code observations are acquired from nine continuously operating GPS stations around Taiwan whose baseline ranged from 19 to 340 km. Daily 24-hour epoch-per-epoch positioning obtained for 70 most geomagnetic quiet days (2008–2010) for each of the 72 baselines. The performance of TWIM has been compared with the standard operational Klobuchar model (KLB) used by typical single-frequency receivers and the IGS global ionospheric model (GIM). Generally, TWIM performed well in reducing the differential ionospheric delay especially for long baselines and different levels of low solar activity. It has a much better performance compared to the operational KLB model. TWIM also performed similarly with GIM, though GIM has the best performance overall. GIM has the best ionospheric gradient estimates among the three models whose differential ionospheric delay-to-horizontal error ratio is more than 0.25. This is followed closely by TWIM with about 0.20. KLB only has a ratio of <0.10. The similarity of the performance of TWIM and GIM demonstrates the feasibility of TWIM in correcting for differential ionospheric delays in the C/A code pseudorange that is caused by electron density gradients in the ionosphere. It can provide decimeter-to-centimeter level accuracy in differential GPS positioning for single-frequency receivers during geomagnetic quiet conditions across all seasons and different levels of low solar activities. 相似文献
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Impact of the Halloween 2003 ionospheric storm on kinematic GPS positioning in Europe 总被引：2，自引：0，他引：2
N. Bergeot C. Bruyninx P. Defraigne S. Pireaux J. Legrand E. Pottiaux Q. Baire 《GPS Solutions》2011,15(2):171-180
Using dual-frequency data from 36 GPS stations from the EUREF Permanent Network (EPN), the influence of the October 30, 2003
Halloween geomagnetic storm on kinematic GPS positioning is investigated. The Halloween storm induced ionospheric disturbances
above the northern part of Europe and Scandinavia. It is shown that kinematic position repeatabilities for this period are
mainly affected for stations in northern Europe with outliers reaching 12 cm in the horizontal, and 26 cm in the vertical.
These magnitudes are shown to be possibly due to the second-order ionospheric delays on GPS signals, not accounted for in
the kinematic GPS positioning analysis performed. In parallel, we generate hourly TEC (Total Electron Content) maps on a 1° × 1°
grid using the dense EPN network. These TEC maps do not use any interpolation but provide a high resolution in the time and
space and therefore allow to better evidence small structures in the ionosphere than the classical 2-hourly 2.5° × 5° grid
Global Ionospheric TEC Maps (GIM). Using the hourly 1° × 1° TEC maps, we reconstruct and refine exactly the zones of intense
ionosphere activity during the storm, and we show the correlation between the ionospheric activity and assess the quality
of GPS-based kinematic positioning performed in the European region. 相似文献