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1.
Xiaohong Zhang Fujian Ma Xiaodong Ren Weiliang Xie Feng Zhu Xin Li 《GPS Solutions》2017,21(4):1535-1548
Ionospheric delay is a dominant factor that affects the accuracy of single-frequency positioning. Thus, an empirical ionospheric model with high accuracy is very important for single-frequency users. This study proposes a modified empirical broadcast ionospheric model, called MNTCM-BC, based on the Neustrelitz Total Electron Content (TEC) broadcast model NTCM-BC. Nine daily ionospheric coefficients of these models are estimated using datasets of the previous day from 30 globally distributed Global Navigation Satellite System monitor stations, and the prediction performance of the MNTCM-BC is evaluated with the datasets of the current day from all 300 verification stations. The results show that the complex behavior of the ionosphere is well described by the MNTCM-BC, including the visibility of two ionization crests on both sides of the geomagnetic equator and the TEC variations that depend on the local time and geomagnetic latitude. In terms of the prediction accuracy, compared with the NTCM-BC, the main improvement in the MNTCM-BC is achieved in summer, whereas the accuracy is comparable in other seasons. Hence, the following analyses are focused on summer. In the low-solar activity year of 2009, the prediction accuracy of the MNTCM-BC is improved by 0.11 TECU compared with that of the NTCM-BC. As to the high-solar activity year of 2014, the corresponding improvement is 0.35 TECU. In addition, when the number of monitor stations is increased from 30 to 300, the prediction accuracy of two models can be slightly improved by 0.06 TECU in 2009 and 0.13 TECU in 2014, respectively, while reliability enhances. Furthermore, the average three-dimensional positioning accuracy of 160 globally distributed stations for single-frequency point positioning using the Klobuchar model, the NTCM-BC and the MNTCM-BC is 1.83, 1.21 and 1.20 m during quiet day and 3.15, 2.31 and 2.21 m during perturbed day, respectively. Relative to the Klobuchar model and the NTCM-BC, the average accuracy improvements in the MNTCM-BC are about 30 and 3%, respectively. 相似文献
2.
An approach to modeling the regional ionospheric total electron content (TEC) based on spherical cap harmonic analysis is
presented. This approach not only provides a better regional TEC mapping accuracy, but also the capability for ionospheric
model prediction based on spectrum analysis and least squares collocation. Unlike conventional approaches, which predict the
immediate TEC with models using current observations, the spherical cap harmonic approach utilizes models using past observations
to predict a model which will provide future TEC values. A significant advantage in comparison with conventional approaches
is that the spherical cap harmonic approach can be used to predict the long-term TEC with reasonable accuracy. This study
processes a set of GPS data with an observation time span of 1 year from two GPS networks in China. The TEC mapping accuracy
of the spherical cap harmonic model is compared with the polynomial model and the global ionosphere model from IGS. The results
show that the spherical cap harmonic model has a better TEC mapping accuracy with smoother residual distributions in both
temporal and spatial domains. The TEC prediction with the spherical cap harmonic model has been investigated for both short-
and long-term intervals. For the short-term interval, the prediction accuracies for the latencies of 1-day, 2-days, and 3-days
are 2.5 TECU, 3.5 TECU, and 4.5 TECU, respectively. For the long-term interval, the prediction accuracy is 4.5 TECU for a
2-month latency. 相似文献
3.
为了分析单站区域电离层总电子含量(total electron content,TEC)模型的适用范围和精度,基于2～15阶次球谐函数,分别建立了欧洲区域16个单站区域电离层TEC模型,生成了区域格网TEC,并与欧洲定轨中心(Center for Orbit Determination in Europe,CODE)、... 相似文献
4.
Global Ionosphere Maps of VTEC from GNSS,satellite altimetry,and formosat-3/COSMIC data 总被引：1，自引：1，他引：0
For space geodetic techniques, operating in microwave band, ionosphere is a dispersive medium; thus signals traveling through
this medium are in the first approximation affected proportional to inverse of the square of their frequencies. This effect
allows gaining information about the parameters of the ionosphere in terms of Total Electron Content (TEC) or the electron
density (N
e
). TEC or electron density can then be expressed by means of spherical harmonic base functions to provide a Global Ionosphere
Map (GIM). The classical input data for development of GIMs are obtained from dual-frequency observations carried out at Global
Navigation Satellite Systems (GNSS) stations. However, GNSS stations are in-homogeneously distributed around the world, with
large gaps particularly over the oceans; this fact reduces the precision of the GIM over these areas. On the other hand, dual-frequency
satellite altimetry missions such as Jason-1 provide information about the ionosphere precisely above the oceans; and furthermore
Low Earth Orbiting (LEO) satellites, such as Formosat-3/COSMIC (F/C) provide well-distributed information of ionosphere globally.
This study investigates on global modeling of TEC through combining GNSS and satellite altimetry data with global TEC data
derived from the occultation measurements of the F/C mission. The combined GIMs of vertical TEC (VTEC) show a maximum difference
of 1.3–1.7 TEC units (TECU) with respect to the GNSS-only GIMs in the whole day. The root mean square error (RMS) maps of
combined solution show a reduction of about 0.1 TECU in the whole day. This decrease of RMS can reach up to 0.5 TECU in areas
where no or few GNSS observations are available, but high number of F/C measurement is carried out. This proves that the combined
GIMs provide a more homogeneous global coverage and higher reliability than results of each single method. All comparisons
and validations made within this study provide vital information regarding combination and integration of various observation
techniques in the Global Geodetic Observing System of the International Association of Geodesy. 相似文献
5.
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
6.
7.
针对区域电离层变化情况较为复杂,所确定的电离层模型系数难以反映其短时间内的变化情况问题,该文提出了利用旋转地图内插结合曲面拟合模型实现区域电离层实时监测方法。采用旋转地图内插IGS提供的电离层数据,能够有效补偿电离程度与太阳位置的强相关性,提高总电子含量内插精度;基于曲面拟合模型对区域电离层进行实时监测,实现了模型系数的实时更新。利用JSCORS网的双频观测数据,采用曲面拟合模型建立了实时的区域电离层监测模型,数据计算结果表明,其网内外精度分别优于0.81TECU和0.96TECU。 相似文献
8.
Current dual-frequency GPS measurements can only eliminate the first-order ionospheric term and may cause a higher-order range
bias of several centimeters. This research investigates the second-order ionospheric effect for GNSS users in Europe. In comparison
to previous studies, the electron density profiles of the ionosphere/plasmasphere are modeled as the sum of three Chapman
layers describing electron densities of the ionospheric F2, F1 and E layers and a superposed exponential decay function describing the plasmasphere. The International Geomagnetic Reference
Field model is used to calculate the geomagnetic field vectors at numerous points along the incoming ray paths. Based on extended
simulation studies, we derive a correction formula to compute the average value of the longitudinal component of the earth’s
magnetic field along the line-of-sight as a function of geographic latitude and longitude, and geometrical parameters such
as elevation and azimuth angles. Using our correction formula in conjunction with the total electron content (TEC) along the
line-of-sight, the second-order ionospheric term can be corrected to the millimeter level for a vertical TEC level of 1018 electrons/m2. 相似文献
9.
Patricia Doherty joins the regular contributors of this column to discuss the correlation between measurements of solar 10.7
cm radio flux and ionospheric range delay effects on GPS. Mrs. Doherty has extensive experience in the analysis of ionospheric
range delays from worldwide systems and in the utilization and development of analytical and theoretical models of the Earth's
ionosphere.
Ionospheric range delay effects on GPS and other satellite ranging systems are directly proportional to the Total Electron
Content (TEC) encountered along slant paths from a satellite to a ground location. TEC is a highly variable and complex parameer
that is a function of geographic location, local time, season, geomagnetic activity, and solar activity. When insufficiently
accounted for, ionospheric TEC can seriously limit the performance of satellite ranging applications. Since the ionosphere
is a dispersive medium, dual-frequency Global Positoning System (GPS) users can make automatic corrections for ionospheric
range delay by computing the apparent difference in the time delays between the two signals. Single-frequency GPS users must
depend on alternate methods to account for the ionospheric range delay. Various models of the ionosphere have been used to
provide estimates of ionospheric range delay. These models range from the GPS system's simple eight-coefficient algorithm
designed to correct for approximately 50% rms of the TEC, to state-of-the-art models derived from physical first principles,
which can correct for up to 70 to 80% rms of the TEC but at a much greater computational cost.
In an effort to improve corrections for the day-to-day variability of the ionosphere, some attempts have been made to predict
the TEC by using the daily values of solar 10.7 cm radio flux (F10,7). The purpose of this article is to show that this type of prediction is not useful due to irregular, and sometimes very
poor, correlation between daily values of TEC and F10.7. Long-term measurements of solar radio flux, however, have been shown to be well correlated with monthly mean TEC, as well
as with the critical frequency of the inonospheric F2 region (foF2), which is proportional to the electron density at the
peak of the ionospheric F2 region. ? 2000 John Wiley & Sons, Inc. 相似文献
10.
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
11.
Jian Kong Yibin Yao Chen Zhou Yi Liu Changzhi Zhai Zemin Wang Lei Liu 《Journal of Geodesy》2018,92(11):1255-1266
The Co-Seismic Ionospheric Disturbance of the 2015 Nepal earthquake is analyzed in this paper. GNSS data are used to obtain the Satellite-Station TEC sequences. After removing the de-trended TEC variation, a clear ionospheric disturbance was observed 10 min after the earthquake, while the geomagnetic conditions, solar activity, and weather condition remained calm according to the Kp, Dst, F10.7 indices and meteorological records during the period of interest. Computerized ionosphere tomography (CIT) is then used to present the tridimensional ionosphere variation with a 10-min time resolution. The CIT results indicate that (1) the disturbance of the ionospheric electron density above the epicenter during the 2015 Nepal earthquake is confined at a relatively low altitude (approximately 150–300 km); (2) the ionospheric disturbances on the west side and east sides of the epicenter are precisely opposite. A newly established electric field penetration model of the lithosphere–atmosphere–ionosphere coupling is used to investigate the potential physical mechanism. 相似文献
12.
Twenty-seven-day variation caused by solar rotation is one of the main periodic effects of solar radiation influence on the ionosphere, and there have been many studies on this periodicity using peak electron density \(\mathrm{N_{m}F_{2}}\) and solar radio flux index F10.7. In this paper, the global electron content (GEC) and observation of Solar EUV Monitor (SEM) represent the whole ionosphere and solar EUV flux, respectively, to investigate the 27-day variation. The 27-day period components of indices \((\hbox {GEC}_{27}\), \(\hbox {SEM}_{27}\), \(\hbox {F10.7}_{27}\), \(\hbox {Ap}_{27})\) are obtained using Chebyshev band-pass filter. The comparison of regression results indicates that the index SEM has higher coherence than F10.7 with 27-day variation of the ionosphere. The regression coefficients of \(\hbox {SEM}_{27 }\) varied from 0.6 to 1.4 and the coefficients of \(\hbox {Ap}_{27}\) varied from \({-}\)0.6 to 0.3, which suggests that EUV radiation seasonal variations are the primary driver for the 27-day variations of the ionosphere for most periods. TEC map grid points on three meridians where IGS stations are dense are selected for regression, and the results show that the contribution of solar EUV radiation is positive at all geomagnetic latitudes and larger than geomagnetic activity in most latitudes. The contribution of geomagnetic activity is negative at high geomagnetic latitude, increasing with decreasing geomagnetic latitudes, and positive at low geomagnetic latitudes. The global structure of 27-day variation of ionosphere is presented and demonstrates that there are two zonal anomaly regions along with the geomagnetic latitudes lines and two peaks in the north of Southeast Asia and the Middle Pacific where \(\hbox {TEC}_{27}\) magnitude values are notably larger than elsewhere along zonal anomaly regions. 相似文献
13.
The Doppler orbitography and radiopositioning integrated by satellite (DORIS) system was originally developed for precise orbit determination of low Earth orbiting (LEO) satellites. Beyond that, it is highly qualified for modeling the distribution of electrons within the Earth’s ionosphere. It measures with two frequencies in L-band with a relative frequency ratio close to 5. Since the terrestrial ground beacons are distributed quite homogeneously and several LEOs are equipped with modern receivers, a good applicability for global vertical total electron content (VTEC) modeling can be expected. This paper investigates the capability of DORIS dual-frequency phase observations for deriving VTEC and the contribution of these data to global VTEC modeling. The DORIS preprocessing is performed similar to commonly used global navigation satellite systems (GNSS) preprocessing. However, the absolute DORIS VTEC level is taken from global ionospheric maps (GIM) provided by the International GNSS Service (IGS) as the DORIS data contain no absolute information. DORIS-derived VTEC values show good consistency with IGS GIMs with a RMS between 2 and 3 total electron content units (TECU) depending on solar activity which can be reduced to less than 2 TECU when using only observations with elevation angles higher than \(50^\circ \) . The combination of DORIS VTEC with data from other space-geodetic measurement techniques improves the accuracy of global VTEC models significantly. If DORIS VTEC data is used to update IGS GIMs, an improvement of up to 12 % can be achieved. The accuracy directly beneath the DORIS satellites’ ground-tracks ranges between 1.5 and 3.5 TECU assuming a precision of 2.5 TECU for altimeter-derived VTEC values which have been used for validation purposes. 相似文献
14.
利用IGS中心提供的全球电离层TEC数据,建立集合经验模态分解与Holt-Winters组合的预报模型。根据地磁活动情况,选取地磁平静时段和地磁活跃时段的低、中纬度TEC序列,分别采用EEMD-Holt-Winters组合模型和单一Holt-Winters模型进行建模预报。实验结果表明,地磁平静期文中模型的相对精度最优可达91.71%,均方根误差最优可达1.54 TECu,地磁活跃期文中模型的相对精度最优可达86.83%,均方根误差最优可达2.18 TECu,预报结果较单一模型有显著提高。 相似文献
15.
为了分析与评估国际GNSS监测评估系统(iGMAS)全球电离层TEC格网产品精度,该文基于iGMAS及IGS各电离层分析中心发布的全球电离层TEC格网产品,进行了精度比较分析,结果表明:iGMAS与IGS、CODE、JPL、ESOC、UPC等IGS电离层工作组发布的全球电离层TEC格网产品,在全球、不同纬度带和欧洲等不同区域均表现出较高的一致性和强相关性,互差为0~2.0 TECU;JPL分析中心GIM的内符合精度约为2.5 TECU,iGMAS、IGS、CODE、ESOC和UPC等分析中心GIM的内符合精度均小于1.5 TECU;在2~8 TECU的精度范围内,iGMAS全球电离层TEC格网产品的精度总体与IGS、CODE、JPL、ESOC、UPC等IGS电离层工作组的精度相当。 相似文献
16.
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
17.
利用GPS研究电离层,具有其他探测技术所没有的全天候、高分辨率、大范围等优点.本文采用双频GPS数据提取区域电离层电子浓度总含量（TEC）,并结合全球电离层地理（GIM）数据,借助滑动四分位距法建立TEC背景值.研究了台风“莫兰蒂”对其经过区域及登陆地点电离层TEC的影响.分析表明,台风登陆厦门前一天,厦门地区电离层TEC发生了较强的正扰动,登陆后第二天,TEC发生了小尺度的负扰动;台风临近台湾岛前,东南沿海和台湾岛区域电离层出现了大范围的正异常扰动,其值为15～20 TECU,持续时间10 h.结合厦门和台湾岛的地形,推测此次TEC异常原因是由于台风所激发的声重力波传播到电离层高度,造成了电离层的异常扰动. 相似文献
18.
利用中国区域电离层数据拟合 Klobuchar参数 总被引：3，自引：0，他引：3
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。 相似文献
19.
基于北斗GEO卫星独有的静地特性,本文利用其观测数据提取电离层TEC进行磁暴期间电离层TEC时空变化研究。同时利用全球电离层格网图GIM值进行试验对比,结果表明：北斗GEO卫星提取的TEC与GIM模型值变化趋势一致,并且前者可更有效地监测电离层的细微扰动变化。在此次磁暴发生期间,亚太地区电离层TEC变化及扰动响应特征在纬度方向差异明显。其中南北半球较高纬度区域,电离层TEC在磁暴主相阶段主要表现为正响应扰动,而赤道及北半球较低纬度区域,电离层TEC在磁暴主相及恢复相阶段均产生了强度更大、持续时间更长的正响应扰动。结合现有研究,认为造成此次电离层异常扰动的激励因素主要为东向快速穿透电场的增强及热层中性成分的变化。试验结果也证明了GEO卫星可以精准有效地监测在磁暴发生时电离层TEC的变化规律及不同空间位置处TEC产生的扰动响应特征。 相似文献