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将香港地区某天由电离层层析反演得到的电子密度值分成6组,利用神经网络方法对该6组数据分别进行了拟合建模及预报。实验结果表明,采用电离层层析技术并经神经网络模型预报得出的电子密度值精度明显高于由IRI2007模型提供的电子密度值,其预报的30min及60min的电子密度值精度可分别达到0.45TECU和1.34TECU。 相似文献
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在利用GNSS进行像素基电离层层析时,多尺度层析方法利用权重因子将反演区域不同像素层析模型结合在一起,最终得到电离层电子密度反演结果,可以有效地解决电离层层析过程中不适应问题和最终的电离层电子密度失真现象。在多尺度电离层层析中,不同像素尺度层析模型之间权重是影响最终的电离层电子密度精度的重要因素。为了获得高精度电离层层析模型,考虑到权重因子存在着等式和不等式限制条件,采用解决最优化问题的罚函数法确定不同像素尺度电离层层析模型之间的权重。通过采用实测GNSS观测数据进行电离层多尺度电离层层析,对比了多尺度层析模型的各个子模型建模精度并进行分析,同时将罚函数法获得的模型精度与其他确权方法进行了对比,该方法可以有效地应用于多尺电离层度层析,且最终的层析模型精度优于其他确权方法,更优于单尺度电离层层析模型精度。 相似文献
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《武汉大学学报(信息科学版)》2021,(11)
三维电子密度是研究电离层空间结构的关键参数,现有的技术和方法存在空间分辨率不足的缺陷。基于此,提出一种联合全极化合成孔径雷达(synthetic aperture radar, SAR)和国际参考电离层(international reference ionosphere,IRI)模型估计高空间分辨率三维电子密度分布的方法。首先利用全极化SAR计算法拉第旋转(Faraday rotation,FR)角;然后根据FR角结合磁场信息估计垂直总电子含量(vertical total electron content,VTEC);最后联合估计的VTEC和IRI电子密度剖线求解三维空间电子密度分布。为了验证所提方法的可行性,利用覆盖美国阿拉斯加地区的先进陆地观测卫星(advanced land observing satellite, ALOS)-1全极化SAR影像进行了实验,并获取GPS及Poker Flat测站的非相干散射雷达(incoherent scattering radar, ISR)数据对实验结果进行验证。结果发现,相对于IRI三维电子密度,所提方法获取的高空间分辨率三维电子密度整体误差减少了33.57%,其中高于133 km的电子密度误差减少了47.98%。 相似文献
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电离层是日地空间环境的重要组成部分,电离层异常对无线电通讯和人类空间活动的影响不容忽视.电离层异常监测,在高精度GNSS PNT 服务与深空探测误差修正、空间天气预报预警及日地空间环境动态监测等方面具有重要科学意义和实用价值.海量地基、天基多源电离层观测数据,为电离层异常监测及电离层精细化时空变化反演提供了丰富的数据源.论文利用全球约250个Multi-GNSS站和COSMIC掩星观测数据,采用并行计算10 m in内实现全球数据处理,近实时构建了三维电子密度模型,融合掩星数据使得海洋地区的精度明显改善;搭建了天地联合多源电离层观测数据融合处理试验平台,在线提供近实时三维电离层产品,可为地球空间飞行器的空间环境信息支持、空间环境异常监测及预报、导航系统全球电离层延迟修正等提供服务.基于近实时三维电子密度模型,开展了电离层异常的立体监测,较IRI模型能够更好地监测磁暴期间电离层异常与演化过程,实现了全球大尺度、区域精细化电离层动态监测.同时,论文针对电离层异常对GNSS影响效应展开了较为全面的研究,分析了磁暴、太阳耀斑对GNSS信号、电离层模型精度、服务性能的影响. 相似文献
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随着GALILEO、GLONASS和BDS等系统的快速发展,全球导航卫星系统GNSS(Global Navigation Satellite System)为电离层层析技术的应用带来大量的观测数据,可弥补单星座条件下地面观测站点少和观测视角有限等不足。本文利用多星座GNSS的观测数据,通过融合定权的方式,提出一种基于地基GNSS的电离层层析方法,求解出高精度的电离层电子含量值。利用该方法反演出欧洲区域上空的电子密度。实验结果表明,多星座GNSS反演的精度要优于使用单GPS数据的结果。并将该方法应用到磁暴探测中,与垂测仪的观测结果进行比较,验证了多星座GNSS电离层层析方法的可行性和优越性。 相似文献
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奥斯特/GPS掩星与地面雷达联合观测电离层电子密度的初步结果 总被引：10，自引：3，他引：7
张训械 P.Hoeg G.B.Larsen Stig Syndergaard Martin B.S Jakob G.R S.Fukao Kiyoshi lgarashi Seiji Kawamura 《全球定位系统》2000,(3)
1999年2月丹麦发射了一颗奥斯特小卫星,它装载了两台GPS接收机,其中一台用于电离层和中性大气掩星测量,另一台用于自主定位。本文给出了1999年10月奥斯特/GPS掩星与日本MU雷达和数字测高仪的联合观测结果。奥斯特掩星反演得到的电子密度剖面与地面雷达观测的进行了比较,结果表明:天基和地基雷达观测的电子密度是一致的。文章还给出利用GPS的单频信号反演电离层电子密度剖面技术和3维射线追踪技术模拟掩星结果。 相似文献
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奥斯特／GPS掩星与地面雷达联合观测电码离层电子密度的初步结果 总被引：8，自引：0，他引：8
《全球定位系统》2000,25(3):1-5
1999年2月丹麦发射了一颗奥斯特小卫星,它装载了两台GPS接收机,其中一台用于电离层和中性大气掩星测量,另一台用于自主定位,本文给出了1999年10月奥斯特/GPS掩星与日本MU雷达和数字测高仪的联合观测结果。奥斯特掩星反演得到的电子密度剖面与地面雷达观测的进行了比较。结果表明：天基和地基雷达观测的电子密度是一致的。文章还给出利用GPS的单频信号反演电离层电子密度剖面技术和3维射线追踪技术模拟掩星结果。 相似文献
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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
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威德尔海异常是西南极沿海地区在夏季出现的电离层异常现象。本文用西南极地区的GPS跟踪站数据和测高卫星Jason-2数据,分别提取了陆地和海洋地区大范围的电离层TEC参数。GPS反演结果的优势是获取测站上空高精度的TEC时间序列,测高反演的结果整体与GPS的结果精度相当,虽然测高的时间分辨率较低,但其优势是获取海洋广大区域的TEC值。两种观测手段的研究区域互补,可以充分观测威德尔海异常在西南极的变化特征,从空间上来看,威德尔海异常出现在以别林斯高晋海为中心的广大区域,而威德尔海异常也是覆盖了西南极的别林斯高晋海、威德尔海以及可达80°S的西南极陆地区域。从时间上来看,出现时段在每年的10月底到次年3月初,夜晚电子密度增加,白天电子密度降低,随着太阳活动的增强,其异常程度也变大。 相似文献
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Electron density profiles in the equatorial ionosphere observed by the FORMOSAT-3/COSMIC and a digisonde at Jicamarca 总被引：1，自引：0，他引：1
Jann-Yenq Liu Chien-Chih Lee Jhih-Yung Yang Chao-Yen Chen Bodo W. Reinisch 《GPS Solutions》2010,14(1):75-81
We examine for the first time the ionospheric electron density profiles concurrently observed by the GPS occultation experiment
(GOX) onboard the FORMOSAT-3/COSMIC (F3/C) and the ground-based digisonde portable sounder DPS-4 at Jicamarca (12°S, 283°W,
1°N geomagnetic) in 2007. Our results show that the F3/C generally underestimates the F2-peak electron density NmF2 and the
F2-peak height hmF2. On the other hand, when the equatorial ionization anomaly (EIA) pronouncedly appears during daytime,
the total electron content (TEC) derived from the radio occultation of the GPS signal recorded by the F3/C GOX is significantly
enhanced. This results in the NmF2 at Jicamarca being overestimated by the Abel inversion on the enhanced TEC during the afternoon
period. 相似文献
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Using the global positioning system (GPS) measurements, the total electron content (TEC) at station Bangalore (13.02°N, 77.57°E geographic; 04.44°N, 150.84°E geomagnetic), lying at the equatorial region, and station Lucknow (26.91°N, 80.95°E geographic; 17.96°N, 155.24°E geomagnetic), lying at equatorial ionospheric anomaly (EIA) crest region, have been estimated for the year 2012–2013. In order to evaluate the International Reference Ionosphere (IRI) model regarding simulation/modeling of ionospheric studies specially at equatorial and EIA crest regions, we have compared the TEC derived from the recent version of the IRI-2012 model and the older IRI-2007 with its three topside options, namely IRI-NeQuick (IRI-NeQ), IRI-2001, and IRI01-corr, with that of GPS-TEC over Bangalore and Lucknow. For the EIA station Lucknow, the IRI-2012 model with IRI-NeQ and IRI01-corr topside is found in good agreement with GPS-TEC during summer and equinox season, while the IRI-2012 model for all three topside options significantly overestimates the GPS-TEC during winter season. The IRI-2001 topside overestimates the GPS-TEC over both the stations during all seasons. The anomalous difference between the IRI-2012 model prediction and ground-based GPS-TEC in daytime hours during the winter season observed at Lucknow could be attributed to discrepancies in the slab thickness predicted by the model, which is more during the winter season as compared to summer and equinox. These large discrepancies in the slab thickness predicted by the IRI-2012 as well as the IRI-2007 model during the winter season have been supported by using the foF2 data from Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation-based measurements. We also observed that the discrepancies in the recent IRI-2012 model with respect to GPS-TEC are found to be slightly larger than those with the older IRI-2007 model over the EIA region Lucknow. However, over the equatorial region Bangalore, the discrepancy with the older model IRI-2007 was found to be larger than with the recent IRI-2012 model. This suggests that the performance of the IRI-2012 model is poorer than the IRI-2007 model at the EIA region while better at equatorial region, and that further improvements in the IRI-2012 models are required particularly in the low-latitude and EIA regions. The GPS-TEC showed disappearance of the winter anomaly during 2012–2013, while the IRI model failed to predict the disappearance of winter anomaly. 相似文献
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A new two-step algorithm for ionospheric tomography solution 总被引：3，自引：2，他引：1
Ionospheric tomography inverse algorithms are usually an ill-conditioned problem because the geometric distribution of continuously
operating reference GPS stations is not ideal for this task. In order to cope with such ill-conditioning, a new tomographic
algorithm, termed two-step algorithm (TSA), is presented. The electron density is estimated in two steps: Phillips smoothing
method (PSM) is first used to resolve the ill-conditioned problem in the ionospheric tomography system, and then, the PSM
solution is input as an initial value to the multiplicative algebraic reconstruction technique (MART) and iteratively improved.
Numerical simulations using the International Reference Ionosphere 2007 model demonstrate that the TSA is applicable to GPS-based
ionospheric tomography reconstruction and is superior to PSM and MART when these techniques are used alone. The new algorithm
is applied to reconstruct the ionospheric electron density distribution over China using GPS observations, and a comparison
with ionosonde observations is made. 相似文献
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Ionospheric electron density observed by FORMOSAT-3/COSMIC over the European region and validated by ionosonde data 总被引：4，自引：0，他引：4
Andrzej Krankowski Irina Zakharenkova Anna Krypiak-Gregorczyk Irk I. Shagimuratov Pawel Wielgosz 《Journal of Geodesy》2011,85(12):949-964
This research is motivated by the recent IGS Ionosphere Working Group recommendation issued at the IGS 2010 Workshop held
in Newcastle, UK. This recommendation encourages studies on the evaluation of the application of COSMIC radio occultation
profiles for additional IGS global ionosphere map (GIM) validation. This is because the reliability of GIMs is crucial to
many geodetic applications. On the other hand, radio occultation using GPS signals has been proven to be a promising technique
to retrieve accurate profiles of the ionospheric electron density with high vertical resolution on a global scale. However,
systematic validation work is still needed before using this powerful technique for sounding the ionosphere on a routine basis.
In this paper, we analyze the properties of the ionospheric electron density profiling retrieved from COSMIC radio occultation
measurements. A comparison of radio occultation data with ground-based measurements indicates that COSMIC profiles are usually
in good agreement with ionosonde profiles, both in the F2 layer peak electron density and the bottom side of the profiles.
For this comparison, ionograms recorded by European ionospheric stations (DIAS network) in 2008 were used. 相似文献