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| 1 | A new global zenith tropospheric delay model IGGtrop for GNSS applications显示文摘Tropospheric delay is one of the main sources of measurement error in global navigation satellite systems.It is usually compensated by using an empirical correction model.In this paper,temporal and spatial variations of the global zenith tropospheric delay(ZTD) are further analyzed by ZTD time series from global International GNSS Service stations and annual ZTDs derived from global National Centers for Environmental Prediction reanalysis data,respectively.A new ZTD correction model,named IGGtrop,is developed based on the characteristics of ZTD.Experimental results show that this new 3D-grid-based model that accommodates longitudinal as well as latitudinal variations of ZTD performs better than latitude-only based models(such as UNB3,EGNOS,and UNB3m).The global average bias and RMS for IGGtrop are about-0.8 cm and 4.0 cm,respectively.Bias values for UNB3,EGNOS,and UNB3m are 2.0,2.0,and 0.7 cm,respectively,and respective RMS values 5.4,5.4,and 5.0 cm.IGGtrop shows much more consistent prediction errors for different areas than EGNOS and UNB3m,In China,the performance of IGGtrop(bias values from-2.0 to 0.4 cm and RMS from 2.1 to 6.4 cm) is clearly superior to those of EGNOS and UNB3m.It is also demonstrated that IGGtrop biases vary little with height,and its RMS values tend to decrease with increasing height.In addition,IGGtrop generally estimates ZTD with greater accuracy than EGNOS and UNB3m in the Southern Hemisphere. | LI Wei YUAN YunBin OU JiKun LI Hui LI ZiShen | 2012 | Chinese Science Bulletin2012，57，17： | 32 |
| 2 | Models and methods for precise determination of ionospheric delay using GPS显示文摘为精确在 GPS 观察决定 ionospheric 延期的基本原则和方法是 intorduced 并且讨论。为基于 GPS 适合 ionospheric delyas 的各种各样的方法和模型被比较并且分析,并且到研究和工程的方法和模型的应用被总结。 | YUAN Yunbin HUO Xingliang OU Jikun | 2007 | Progress in Natural Science:Materials International2007，17，2： | 25 |
| 3 | Preliminary results and analyses of using IGS GPS data to determine global ionospheric TEC显示文摘Using the spherical harmonic (SH) function model and the dual frequency GPS data of 139 International GPS Service (IGS) stations for July 15 of 2000, the global ionospheric total electron content (TEC) is calculated and the basic method is investigated. Here, preliminary results are reported and the problems and difficulties to be solved for using GPS data to determine the global ionospheric TEC are discussed. | YUAN Yunbin and OU Jikun(Laboratory of Dynamic Geodesy, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China) | 2003 | Progress in Natural Science:Materials International2003，13，6： | 20 |
| 4 | Extraction of line-of-sight ionospheric observables from GPS data using precise point positioning显示文摘Here we propose a method for extracting line-of-sight ionospheric observables from GPS data using precise point positioning(PPP).The PPP-derived ionospheric observables(PIOs) have identical form with their counterparts obtained from leveling the geometry-free GPS carrier-phase to code(leveling ionospheric observables,LIOs),and are affected by the satellite and receiver inter-frequency biases(IFBs).Based on the co-location experiments,the effects of extracting error arising from the observational noise and multipath on the PIOs and the LIOs are comparatively assessed,and the considerably reduced effects ranging from 70% to 75% on the PIOs with respect to the LIOs can be verified in our case.In addition,based on 26 consecutive days' GPS observations from two international GNSS service(IGS) sites(COCO,DAEJ) during disturbed ionosphere period,the extracted PIOs and LIOs are respectively used as the input of single-layer ionospheric model to retrieve daily satellite IFBs station-by-station.The minor extracting errors underlying the PIOs in contrast to the LIOs can also be proven by reducing day-to-day scatter and improving between-receiver consistency in the retrieved satellite IFBs values. | ZHANG BaoCheng OU JiKun YUAN YunBin LI ZiShen | 2012 | Science China Earth Sciences2012，55，11： | 19 |
| 5 | Model analysis method (MAM) on the effect of the second-order ionospheric delay on GPS positioning solution显示文摘In this paper,we develop an approach to study the effect of second-order ionospheric delay on GPS positioning based on the ionosphere-free combination (abbreviated to Lc) of GPS dual-frequency carrier phase observables,in which the first-order ionospheric delay has been eliminated.GPS data from IGS WUHN tracking station during April 9 23,2003 is used to perform the above approach,and results show that the second-order ionospheric delay in GPS so-called ionosphere-free observables will result in the regular southward shift of GPS positioning solution.Additionally,the influence of the Earth's magnetic field on second-order ionospheric delay over the Wuhan area is discussed,and it indicates that the Earth's magnetic field is one of the main factors why second-order ionospheric delay results in the regular southward shift of GPS positioning solution over Wuhan area. | LIU XiFeng YUAN YunBin HUO XingLiang LI ZiShen LI Wei | 2010 | Chinese Science Bulletin2010，55，15： | 15 |
| 6 | Yaw attitude of eclipsing GPS satellites and its impact on solutions from precise point positioning显示文摘During the period when a GPS satellite,the Earth and the Sun are approximately collinear,the phenomenon of eclipsing the satellite occurs,when the satellite yaw attitude deviates from its nominal case,i.e. the body X-axis cannot point towards the Sun for Block II&IIA or away from it for Block IIR satellites. The yaw attitude of the eclipsing satellites has a significant influence on both the satellite clock estimation at each International GNSS Service (IGS) Analysis Center (AC) and for users of the precise point positioning (PPP) implementations. It is known that,during the eclipsing periods,inconsistent yaw attitude models among the ACs will contribute to the errors of the IGS combined clock products. As for the PPP user,the influence of the eclipsing satellite is two-fold. First,as the satellite clocks are always kept fixed during PPP implementation,the above-mentioned problematic IGS clocks will inevitably be passed on to the PPP estimates. Second,the improper yaw attitude modeling of the eclipsing satellite will cause a correction bias exceeding 1 dm for the two kinds of attitude-related systematic errors,namely the phase wind-up and satellite antenna phase center offset,which will further deteriorate the accuracy of the PPP solutions. A yaw attitude model is introduced in this paper with the aim of improving the reliability of PPP solutions during the satellite eclipsing period. | ZHANG BaoCheng OU JiKun YUAN YunBin ZHONG ShiMing | 2010 | Chinese Science Bulletin2010，55，32： | 8 |
| 7 | Initial assessment of single-and dual-frequency BDS-3 RTK positioning显示文摘The BeiDou navigation satellite system with global coverage(BDS-3)has been fully operational since July 2020 and provides comprehensive services to global users.BDS-3 transmits several new navigational signals based on the signals inherited from the BeiDou navigation satellite(regional)system(BDS-2).Previous studies focused on the positioning performance of BDS-2 plus BDS-3 and that of combining BDS-3 and other Global Navigation Satellite Systems(GNSSs),but there was no in-depth discussion on the positioning performance of the BDS-3-only.In this contribution,the BDS-3-only Real-Time Kinematic(RTK)positioning is analysed using the data collected in zero and short baselines in Wuhan,China.The RTK model based on Single-Differenced is first presented,and the BDS-3-only RTK positioning in cases of single and dual-frequencies is evaluated with the model in terms of the empirical integer ambiguity resolution success rates and positioning accuracy.Our numerical tests suggest two major findings.First,the positioning performance for the B1I and B3I retained from BDS-2 and the new frequency B1C is comparable,while that for the new frequency B2a is poorer.Second,the positioning performance of the new frequency combination of the B1C+B2a is not as good as that of the B1C only,owing to the unrealistic stochastic model used. | Yunbin Yuan Xiaolong Mi Baocheng Zhang | 2020 | Satellite Navigation2020，1，1： | 7 |
| 8 | Monitoring the ionosphere based on the Crustal Movement Observation Network of China显示文摘The Global Navigation Satellite System(GNSS) is becoming important for monitoring the variations in the earth's ionosphere based on the total electron content(TEC) and ionospheric electron density(IED). The Crustal Movement Observation Network of China(CMONOC), which includes GNSS stations across China's Mainland, enables the continuous monitoring of the ionosphere over China as accurately as possible. A series of approaches for GNSS-based ionospheric remote sensing and software has been proposed and developed by the Institute of Geodesy and Geophysics(IGG) in Wuhan. Related achievements include the retrieval of ionospheric observables from raw GNSS data, differential code biases estimations in satellites and receivers, models of local and regional ionospheric TEC,and algorithms of ionospheric tomography. Based on these achievements, a software for processing GNSS data to determine the variations in ionospheric TEC and IED over China has been designed and developed by IGG. This software has also been installed at the CMONOC data centers belonging to the China Earthquake Administration and China Meteorological Administration. This paper briefly introduces the related research achievements and indicates potential directions of future work. | Yuan Yunbin Li Zishen Wang Ningbo Zhang Baocheng Li Hui Li Min Huo Xingliang Ou Jikun | 2015 | Geodesy and Geodynamics2015，6，2： | 5 |
| 9 | Optimal carrier-smoothed-code algorithm for dual-frequency GPS data显示文摘Carrier-smoothed-code (CSC) algorithm is an e ective pseudorange multipath mitigation technique, which can alleviate the compu- tational burden and reduce the communication bandwidth needed for the transmission of GPS observations. This paper presents an improved Hatch lter and addresses the optimal CSC algorithm for dual-frequency GPS data based on the optimal parameter estimation theory. The smoothed observations have the same information content as that of the raw dual-frequency GPS data from which these are derived. Consequently, the optimal CSC algorithm is equivalent to the uncombined algorithm. Theoretical analyses show that the data precision of the optimal CSC algorithm is better than that of Hatch lter and its improved version. | Jianfeng Guo Jikun Ou Yunbin Yuan Haitao Wang | 2008 | Progress in Natural Science:Materials International2008，18，5： | 4 |
| 10 | Initial orbit determination of BDS-3 satellites based on new code signals显示文摘For the two newly launched satellites(PRN number 27 and 28) of the future global BeiDou navigation satellite system(BDS-3), there is no available broadcast ephemeris data and other initial orbit information, but the initial orbit is the fundamental of the comprehensive analysis of the satellites and their signals. Precise orbit determination(POD) also requires determination of a priori initial value with a certain precision in order to avoid problems such as filter divergence during POD. Compared with the Newton iteration method, which relies on the initial value, this study utilizes the Bancroft algorithm to directly solve the nonlinear equations with the advantage of numerical stability. The initial orbits of these two satellites are calculated based on new code signals, and their results are analyzed and discussed. The experimental results show that, with the exception of very few epochs, when the new code signal is utilized, the median and robust variance factor of the observed residuals computed using pseudo-range observations and the solved initial orbits are less than 4 and 2 m, respectively. It also shows that this solution can be used for rapid initial orbit recovery after maneuvers of the new BeiDou satellites. | Fei Ye Yunbin Yuan Jikun Ou | 2018 | Geodesy and Geodynamics2018，9，4： | 2 |
| 11 | An improvement to ionospheric delay correction for single frequency GPS user the APR-I scheme显示文摘 | Yuan Yunbin and Ou Jikun | 2001 | Journal of Geodesy2001，75，56： | 1 |
| 12 | Auto-covariance estimation of variable samples (ACEVS) and its application for monitoring random ionosphere using GPS显示文摘 | Yuan Yunbin and Ou Jikun | 2001 | Journal of Geodesy2001，75，78： | 1 |
| 13 | Refining the Klobuchar Lonospheric Coefficients Based onGPS Observations显示文摘 | YUAN YUNBIN HUO XINGLIANG OU JIKUN | 2008 | IEEE Transactions on Aerospaceand Electronic Systems2008，44，4： | 1 |
| 14 | An Improvement to Ionospheric Delay Correction for Single-frequency GPS User--the APR-I Scheme显示文摘 | YUAN Yunbin OU Jikun | 2001 | Journal of Geodesy2001，75，56： | 1 |
| 15 | Three-dimensional ionospheric tomography by an improved algebraic reconstruction technique显示文摘 | Wen Debao Yuan Yunbin Ou Jikun | | 0，，11： | 1 |
| 16 | Status of CAS global ionospheric maps after the maximum of solar cycle 24显示文摘As a new Ionosphere Associate Analysis Center(IAAC)of the International GNSS Service(IGS),Chinese Academy of Sciences(CAS)started the routine computation of the real-time,rapid,and final Global Ionospheric Maps(GIMs)in 2015.The method for the generation of CAS rapid and final GIMs and recent updates are presented in the paper.The quality of CAS post-processed GIMs is assessed during 2015-2018 after the maximum of solar cycle 24.To perform an independent and fair assessment,Jason-2/3 Vertical Total Electron Contents(VTEC)are first used as the references over the ocean.GPS differential Slant TECs(dSTEC)generated from 55 Multi-GNSS Experimental(MGEX)stations of the IGS are also employed,which provides a complementing way to evaluate the ability of electron content models to reproduce the spatial and temporal gradients in the ionosphere.During the test period,Jet Propulsion Laboratory(JPL)GIMs present significantly positive deviations compared to the Jason VTEC and GPS dSTEC.Technical University of Catalonia(UPC)rapid GIM UQRG exhibits the best performance in both Jason VTEC and GPS dSTEC analysis.The CAS GIMs show comparable performance with the results of the first four IAACs of the IGS.As expected,the poor performance of all GIMs is in equatorial regions and the high latitudes of the southern hemisphere.The consideration of generating multi-layer or three-dimensional ionospheric maps is emphasized to mitigate the inadequacy of ionospheric single-layer assumption in the presence of pronounced latitudinal gradients.The use of ionospheric observations from the new GNSS constellations and other space-or ground-based observation techniques is also suggested in the generation of future GIMs,given the sparse GPS/GLONASS stations in the southern hemisphere. | Zishen Li Ningbo Wang Ang Liu Yunbin Yuan Liang Wang Manuel Hernández-Pajares Andrzej Krankowski Hong Yuan | 2021 | Satellite Navigation2021，2，1： | 1 |
| 17 | The Ionospheric Eclipse Factor Method(IEFM)andIts Application to Determining the Ionospheric Delay forGPS显示文摘 | YUAN YUNBIN TSCHERNING C C KNUDSEN P etal | 2008 | Journal of Geodesy2008，82，1： | 1 |
| 18 | Research on both models and schemes for precisely determining the ionospheric delays using GPS data 显示文摘 | Yuan Yunbin Huo Xingliang Ou Jikun | 2007 | Progress in Nature Science (S1002-0071)2007，17，2： | 1 |
| 19 | Reliability Analysis for a Robust M-estimator显示文摘 | Guo Jianfeng Ou Jikun Yuan Yunbin | | 0，，01： | 1 |
| 20 | Determination of the Differential Code Bias for Current BDS Satellites显示文摘 | ZISHEN LI YUNBIN YUAN LEI FAN | 2014 | IEEE Transactions on Geoscience and Remote Sensing2014，52，7： | 1 |
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