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Saito Susumu Sunda Surendra Lee Jiyun Pullen Sam Supriadi Slamet Yoshihara Takayuki Terkildsen Michael Lecat Frédéric 《GPS Solutions》2017,21(4):1937-1947
GPS Solutions - We investigated characteristics of anomalous spatial gradients in ionospheric delay on GNSS signals in the Asia-Pacific (APAC) low-magnetic latitude region in the context of the... 相似文献
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《测绘科学》2020,(1):48-53
针对电离层延迟改正对单频接收机用户带来误差较大的问题,该文基于球谐函数借助山东区域CORS双频观测数据建立山东区域电离层模型,并对硬件延迟偏差(DCB)和电子含量进行可靠性、稳定性分析,进一步使用单频精密单点定位(PPP)验证山东区域电离层模型的有效性。实验结果表明:测站DCB解算精度稳定在0.4ns内,解算卫星DCB与欧洲定轨中心(CODE)的偏差总体稳定在0.5ns内,区域电离层模型与CODE解算VTEC差值的均方根为1.22TECU,STD为0.93TECU,对山东区域单频PPP而言,山东区域电离层模型比CODE发布全球电离层模型在N、E、U方向精度明显提高。同时,建立的山东区域电离层模型从时间分辨率、空间分辨率上均优于CODE中心发布全球电离层模型。 相似文献
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Satellite-Based Augmentation Systems (SBASs) enhance the global navigation satellite system (GNSS) to support all phases of flight by providing required accuracy, integrity, continuity, and availability. The Korean SBAS program was recently initiated to develop a single-frequency SBAS aiming to provide Approach Procedure with Vertical guidance (APV)-I Safety-of-Life (SoL) service to aviation users by 2022 within the Korean region. We assess the preliminary availability of the single-frequency SBAS which will be deployed in the Korean peninsula. The resulting system performance shall be used as a baseline to design system components and specifications. The fundamental components of SBAS architecture, SBAS monitor network, geostationary earth orbiting satellite parameters, and ionospheric grid point mask, are defined and their effects on system performance are investigated. Ionospheric correction and integrity algorithm parameters including an ionospheric irregularity threat model are determined using data collected from the Korean GNSS network. The coverage of 99.9 % availability for APV-I service increases from approximately 70 % for the baseline case to 100 % when SBAS monitor stations are expanded to overseas. Even with the expanded monitor network, however, 90 % and less than 95 % availability for LPV-200 service can be achieved only in a very limited region. 相似文献
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针对如何有效地对各类电离层模型在建模实现、模型精度、模型时效性等方面进行综合评估问题,该文提出一种基于改进CODE模型(CODE+模型)全球电离层图(GIM)的预报电离层精度评估方法,通过增加我国陆态网监测站数据,提高我国及周边地区的电离层建模精度,弥补了CODE GIM在我国及周边地区因观测数据少而精度受限的不足。通过试验分析表明,改进CODE GIM能够满足精度要求,且更好地与我国实际电离层情况相吻合;并以此为基准评估GNSS广播电离层精度,对比分析了GPS、BDS、Galileo电离层模型的精度,得到一些初步结论。 相似文献
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Simulation study of the influence of the ionospheric layer height in the thin layer ionospheric model 总被引:2,自引:1,他引:1
This work aims to contribute to the understanding of the influence of the ionospheric layer height (ILH) on the thin layer
ionospheric model (TLIM) used to retrieve ionospheric information from the GNSS observations. Particular attention is paid
to the errors caused on the estimation of the vertical total electron content (vTEC) and the GNSS satellites and receivers inter-frequency biases (IFB), by the use of an inappropriate ILH. The work relies
upon numerical simulations performed with an empirical model of the Earth’s ionosphere: the model is used to create realistic
but controlled ionospheric scenarios and the errors are evaluated after recovering those scenarios with the TLIM. The error
assessment is performed in the Central and the northern part of the South American continents, a region where large errors
are expected due to the combined actions of the Appleton Anomaly of the ionosphere and the South-Atlantic anomaly of the geomagnetic
field. According to this study, there does not exist a unique ILH that cancels the vTEC error for the whole region under consideration. The ILH that cancels the regional mean vTEC error varies with the solar activity and season. The latitude-dependent conversion error propagates to the parameters of
the model used to represent the latitudinal variation on the vTEC on the ionospheric layer, and to the IFB, when these values are simultaneously estimated from the observed sTEC. Besides, the ILH that cancels the regional mean vTEC error is different from the one that cancels the IFB error and the difference between both ILH varies with the solar activity
and season. 相似文献
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多系统全球卫星导航系统(GNSS)的出现为天基增强系统(SBAS)电离层格网模型的性能提升提供了可能,但多系统GNSS测量对电离层格网模型性能提升是有条件的. 为此,利用中国区域GPS观测模拟分析了多系统GNSS测量对中国区域电离层格网模型可用性的影响. 结果表明:多系统GNSS测量可有效提高电离层格网模型的覆盖范围. 中国南方地区存在低纬赤道电离异常(EIA)现象,严重影响SBAS电离层格网模型实现性能,单纯增加GNSS测量不能有效应对低纬电离异常现象影响. 中国北方地区电离层延迟变化平缓,在多系统GNSS测量情况下可以考虑减少地面监测站数量,仍能保持系统原有性能. 相似文献
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太阳活动高峰年山东区域电离层时空变化研究 总被引:1,自引:1,他引:0
2012年为太阳活动高峰年份,为了研究太阳活动高年区域电离层的变化特征,该文选取了山东区域内的SDCORS站点,构建了山东区域垂直电子含量(VTEC)球谐格网模型,对该年山东区域电离层时空变化规律进行分析。实验研究表明,在空间变化上山东区域电离层表现出较强的纬度相关性,出现了明显的分层现象。同时给出了山东电离层在时间上呈现出的时段变化、日变化、月变化、季节变化,发现VTEC受太阳活动影响较大,除了存在明显的单峰和双峰结构外,该年还发生了半年度异常现象。 相似文献
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Improving the GNSS positioning stochastic model in the presence of ionospheric scintillation 总被引:1,自引:0,他引:1
M. Aquino J. F. G. Monico A. H. Dodson H. Marques G. De Franceschi L. Alfonsi V. Romano M. Andreotti 《Journal of Geodesy》2009,83(10):953-966
Ionospheric scintillations are caused by time- varying electron density irregularities in the ionosphere, occurring more often
at equatorial and high latitudes. This paper focuses exclusively on experiments undertaken in Europe, at geographic latitudes
between ~50°N and ~80°N, where a network of GPS receivers capable of monitoring Total Electron Content and ionospheric scintillation parameters was
deployed. The widely used ionospheric scintillation indices S4 and sj{\sigma_{\varphi}} represent a practical measure of the intensity of amplitude and phase scintillation affecting GNSS receivers. However, they
do not provide sufficient information regarding the actual tracking errors that degrade GNSS receiver performance. Suitable
receiver tracking models, sensitive to ionospheric scintillation, allow the computation of the variance of the output error
of the receiver PLL (Phase Locked Loop) and DLL (Delay Locked Loop), which expresses the quality of the range measurements
used by the receiver to calculate user position. The ability of such models of incorporating phase and amplitude scintillation
effects into the variance of these tracking errors underpins our proposed method of applying relative weights to measurements
from different satellites. That gives the least squares stochastic model used for position computation a more realistic representation,
vis-a-vis the otherwise ‘equal weights’ model. For pseudorange processing, relative weights were com- puted, so that a ‘scintillation-mitigated’
solution could be performed and compared to the (non-mitigated) ‘equal weights’ solution. An improvement between 17 and 38%
in height accuracy was achieved when an epoch by epoch differential solution was computed over baselines ranging from 1 to
750 km. The method was then compared with alternative approaches that can be used to improve the least squares stochastic
model such as weighting according to satellite elevation angle and by the inverse of the square of the standard deviation
of the code/carrier divergence (sigma CCDiv). The influence of multipath effects on the proposed mitigation approach is also
discussed. With the use of high rate scintillation data in addition to the scintillation indices a carrier phase based mitigated
solution was also implemented and compared with the conventional solution. During a period of occurrence of high phase scintillation
it was observed that problems related to ambiguity resolution can be reduced by the use of the proposed mitigated solution. 相似文献
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针对电离层延迟误差目前是GNSS导航定位精度最重要误差源的现状,通过GNSS参考站或跟踪站实测数据计算电子总含量值,建立区域电离层模型,监测区域电离层变化,进而找到削弱或消除电离层延迟误差影响方法。利用曲面拟合实现建模,在模型的建立过程中通过对不同的模型阶数进行设置,对比不同情况下的模型精度,从而确定特定区域内最佳数据采样间隔及阶数设置,并在最佳阶数设置情况下,比较了预报不同时段的精度,进而对延迟量预报问题进行探讨,得出一些有益结论。可以通过该模型单独解算流动站站点的实时电离层延迟信息,这对多基站CORS的站间距离选择和单基站CORS基准站和流动站之间距离设计,尤其对提高单频接收机以及GIS产品用户的定位精度和差分模型的覆盖范围都具有实际参考意义。 相似文献
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Zhang Ming Liu Hui Bai Zhengdong Qian Chuang Fan Chengcheng Zhou Peng Shu Bao 《GPS Solutions》2017,21(2):617-626
GPS Solutions - Ambiguity resolution (AR) speed is one of the most important performance indicators of a network RTK (real-time kinematics) system. Given the low correlation between the error... 相似文献
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Quality assessment of GPS rapid static positioning with weighted ionospheric parameters in generalized least squares 总被引:3,自引:2,他引:1
Pawel Wielgosz 《GPS Solutions》2011,15(2):89-99
Precise GPS positioning requires the processing of carrier-phase observations and fixing integer ambiguities. With increasing
distance between receivers, ambiguity fixing becomes more difficult because ionospheric and tropospheric effects do not cancel
sufficiently in double differencing. A popular procedure in static positioning is to increase the length of the observing
session and/or to apply atmospheric (ionospheric) models and corrections. We investigate the methodology for GPS rapid static
positioning that requires just a few minutes of dual-frequency GPS observations for medium-length baselines. Ionospheric corrections
are not required, but the ionospheric delays are treated as pseudo-observations having a priori values and respective weights.
The tropospheric delays are reduced by using well-established troposphere models, and satellite orbital and clock errors are
eliminated by using IGS rapid products. Several numerical tests based on actual GPS data are presented. It is shown that the
proposed methodology is suitable for rapid static positioning within 50–70 km from the closest reference network station and
that centimeter-level precision in positioning is feasible when using just 1 min of dual-frequency GPS data. 相似文献
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The ionospheric eclipse factor method (IEFM) and its application to determining the ionospheric delay for GPS 总被引:3,自引:1,他引:3
A new method for modeling the ionospheric delay using global positioning system (GPS) data is proposed, called the ionospheric
eclipse factor method (IEFM). It is based on establishing a concept referred to as the ionospheric eclipse factor (IEF) λ
of the ionospheric pierce point (IPP) and the IEF’s influence factor (IFF) . The IEF can be used to make a relatively precise distinction between ionospheric daytime and nighttime, whereas the IFF
is advantageous for describing the IEF’s variations with day, month, season and year, associated with seasonal variations
of total electron content (TEC) of the ionosphere. By combining λ and with the local time t of IPP, the IEFM has the ability to precisely distinguish between ionospheric daytime and nighttime, as well as efficiently
combine them during different seasons or months over a year at the IPP. The IEFM-based ionospheric delay estimates are validated
by combining an absolute positioning mode with several ionospheric delay correction models or algorithms, using GPS data at
an international Global Navigation Satellite System (GNSS) service (IGS) station (WTZR). Our results indicate that the IEFM
may further improve ionospheric delay modeling using GPS data. 相似文献
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Ionospheric delays compensation is a mandatory step for precise absolute and relative positioning of Low Earth Orbit Satellites (LEO) by GPS measurements. The most frequently used ionosphere model for real-time GPS-based navigation in LEO is an isotropic model proposed by Lear, which uses the Vertical Total Electron Content (VTEC) above the receiver and a mapping function for TEC evaluation along a given ray path. Based on significant assessed results available for ground-based GPS receivers, we propose the use of a different model relying on the thin shell assumption and a bilinear horizontal variation of the VTEC as a function of latitude and longitude in the shell. It is expected that this model is capable of better describing horizontal gradients in the ionosphere, thus improving ionospheric delay estimation, especially in intense ionospheric conditions. This model is referred to as Linear Thin Shell (LTS). LTS performance in estimating undifferenced and double-differenced ionospheric delays is checked by comparing measured and predicted delays computed using flight data from the GRACE mission. Results show that the LTS always outperforms the isotropic model, especially in case of high solar activity. Moreover, the LTS model provides a higher performance uniformity over a wide range of ionospheric delays, thus ensuring good performance in different conditions. The results obtained demonstrate that the LTS model improves the ionosphere delays estimation accuracy by 20 and 40% for undifferenced and double-differenced delays, respectively. This suggests the LTS model can effectively contribute to improving precision in LEO positioning applications. 相似文献