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GNSS rapid precise point positioning enhanced by low Earth orbit satellites

Satellite Navigation 2023年第1期4卷 41-53,I0003页

作者： Ju Hong Rui Tu Pengfei Zhang Rui Zhang Junqiang Han Lihong Fan Siyao Wang Xiaochun Lu National Time Service Center Chinese Academy of SciencesShu Yuan RoadXi’an 710600China University of Chinese Academy of Sciences Yu Quan RoadBeijing 100049China

The Low Earth Orbit(LEO)satellites can be used to efectively speed up precise point positioning(PPP)*** this study,180 LEO satellites with a global distribution are simulated to evaluate their contribution to the PPP *** satellites can give more redundant observations and improve satellite geometric distributions,particularly for a single Global Navigation Satellite System(GNSS).The convergence speed of the PPP foat solution using the Global positioning System(GPS,G)or BeiDou Navigation Satellite System(BDS,C)single system as well as the G/C/Galileo navigation satellite system(Galileo,E)/GLObal NAvigation Satellite System(GLONASS,R)combined system with LEO satellites added is improved by 90.0%,91.0%,and 90.7%,respectively,with respect to the system without LEO satellites *** introduced LEO observations to assist GNSS in PPP-AR(Ambiguity Resolution)and PPP-RTK(Real Time Kinematic).The success fx rate of a single system is signifcantly improved,and the Time-To-First-Fix(TTFF)of G and G/C/E is reduced by 86.4%and 82.8%,respectively,for the PPP-AR *** analyzed the positioning performance of LEO satellite assisted G/C/E PPP-RTK in the reference networks of diferent scales,namely diferent atmospheric delay interpolation *** success fx rate of the G/C/E combined system is improved from 86.8 to 94.9%,and the TTFF is reduced by 36.8%,with the addition of LEO satellites in the 57 km reference *** the 110 km reference network,the success fx rate of the G/C/E combined system is improved from 64.0 to 88.6%,and the TTFF is reduced by 32.1%.GNSS PPP-RTK with adding the LEO satellites in the reference networks of diferent scales shows obvious improvement because the atmospheric correlation decreases with increasing distance from the reference networks.

关键词： precise point positioning Low earth orbit LEO enhanced global navigation satellite system Rapid positioning

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Inter-satellite link augmented BeiDou-3 orbit determination for precise point positioning

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Chinese Journal of Aeronautics 2022年第4期35卷 332-343页

作者： Liqian ZHAO Xiaogong HU Chengpan TANG Shanshi ZHOU Yueling CAO Qianxin WANG Ranran SU Space Star Technology Co. Ltd.Beijing 100095China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China School of Environment Science and Spatial Informatics China University of Mining and TechnologyXuzhou 221116China Beijing Satellite Navigation Center Beijing 100094China

precise point positioning(PPP) requires precise products, including high-accuracy satellite orbit and clock parameters. It is impossible to obtain an orbit solution that is sufficiently accurate for PPP services with a regional tracking network;therefore, satellite orbits are usually estimated by a global tracking network with a large number of ground stations. However, it is expensive to build globally distributed stations. Fortunately, BeiDou-3 satellites carry an InterSatellite Link(ISL) payload, which can track the whole arc of the BeiDou-3 satellites and enhance the orbit determination accuracy with regional ground stations. In this contribution, a novel orbit determination strategy for BeiDou-3 PPP is proposed, in which the BeiDou-3 satellite orbits are enhanced by the ISL. First, the generation of precise satellite products is demonstrated in *** addition, the products are assessed by Satellite Laser Ranging(SLR) residuals and overlap comparisons. Moreover, the products are used for receivers in China's Mainland to carry out the static and kinematic modes to research the PPP performance of Bei Dou-3’s 3IGSO/24MEO *** SLR validations of the satellite orbits demonstrate an accuracy better than 0.1 m in the radial component, and the orbit overlap comparisons show accuracies of 0.016 m in the radial component,0.088 m in the along-track component and 0.087 m in the cross-track component. The Standard Deviation(STD) in the differences in overlapping arcs for the estimated satellite clocks is approximately 0.10 ns. The static PPP results demonstrate that the error in both the horizontal and vertical components is smaller than 10 cm after 30 minutes of convergence. After 24 hours of convergence,the errors are 0.70 cm, 0.63 cm and 1.99 cm for the north, east and up components, *** kinematic PPP experiment illustrates that the Root Mean Square(RMS) position errors in the north, east and up components are approximately 3.23 cm, 5.27 cm a

关键词： BeiDou-3 Clock offsets Convergence Inter-satellite link precise point positioning Regional ground stations Satellite orbits

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Real-time GNSS precise point positioning with smartphones for vehicle navigation

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Satellite Navigation 2022年第3期3卷 140-161,I0004页

作者： Zishen Li Liang Wang Ningbo Wang Ran Li Ang Liu Aerospace Information Research Institute(AIR) Chinese Academy of Sciences(CAS)Beijing100094China School of Electronic Electrical and Communicating EngineeringUniversity of Chinese Academy of Sciences19A Yuquan RoadShijingshan DistrictBeijing100049China

The availability of raw Global Navigation Satellite System(GNSS)measurements from Android smart devices gives new possibilities for precise positioning solutions,e.g.,precise point positioning(PPP).However,the accuracy of the PPP with smart devices currently is a few meters due to the poor quality of the raw GNSS measurements in a kinematic scenario and in urban environments,particularly when the smart devices are placed inside *** promote the application of GNSS PPP for land vehicle navigation with smart devices,this contribution studies the real-time PPP with *** data quality analysis and positioning performance validation,two vehicle-based kinematic positioning tests were carried out using two Huawei Mate30 smartphones and two Huawei P40 smartphones with different installation modes:the vehicle-roof mode with smartphones mounted on the top roof outside the vehicle,and the dashboard mode with smartphones stabilized on the dashboard inside the *** realize high accuracy positioning,we proposed a real-time smartphone PPP method with the data processing strategies adapted for smart *** results show that the real-time PPP can achieve the horizontal positioning accuracy of about 1–1.5 m in terms of root-mean-square and better than 2.5 m at the 95th percentile for the vehicle-based kinematic positioning with the experimental smartphones mounted on the dashboard inside the vehicle,which is the real scenario in vehicle navigation.

关键词： Global Navigation Satellite System Smartphone positioning precise point positioning Raw GNSS measurements Land vehicle navigation

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Functional model modification of precise point positioning considering the time-varying code biases of a receiver

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Satellite Navigation 2021年第1期2卷 158-167页

作者： Baocheng Zhang Chuanbao Zhao Robert Odolinski Teng Liu State Key Laboratory of Geodesy and Earth’s Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhanChina University of Chinese Academy of Sciences BeijingChina National School of Surveying University of OtagoDunedinNew Zealand.

precise point positioning(PPP),initially developed for the analysis of the Global Positing System(GPS)data from a large geodetic network,gradually becomes an effective tool for positioning,timing,remote sensing of atmospheric water vapor,and monitoring of Earth’s ionospheric Total Electron Content(TEC).The previous studies implicitly assumed that the receiver code biases stay constant over time in formulating the functional model of *** this contribution,it is shown this assumption is not always valid and can lead to the degradation of PPP performance,especially for Slant TEC(STEC)retrieval and *** this reason,the PPP functional model is modified by taking into account the time-varying receiver code biases of the two *** is different from the Modified Carrier-to-Code Leveling(MCCL)method which can only obtain the variations of Receiver Differential Code Biases(RDCBs),i.e.,the difference between the two frequencies’code *** the Modified PPP(MPPP)model,the temporal variations of the receiver code biases become estimable and their adverse impacts on PPP parameters,such as ambiguity parameters,receiver clock offsets,and ionospheric delays,are *** is confirmed by undertaking numerical tests based on the real dual-frequency GPS data from a set of global continuously operating reference *** results imply that the variations of receiver code biases exhibit a correlation with the ambient *** the modified functional model,an improvement by 42%to 96%is achieved in the Differences of STEC(DSTEC)compared to the original PPP model with regard to the reference values of those derived from the Geometry-Free(GF)carrier phase *** medium and long term(1×10^(4) to 1.5×10^(4) s)frequency stability of receiver clocks are also signifi-cantly improved.

关键词： Global positioning system International GNSS service precise point positioning Receiver code bias Slant total electron content Timing

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Signal quality analysis and quality check of BDS3 precise point positioning in the Arctic Ocean

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Acta Oceanologica Sinica 2022年第2期41卷 166-179页

作者： Xiaoguo Guan Hongzhou Chai Guorui Xiao Zhenqiang Du Wenlong Qi Xueping Wang College of Urban and Environmental Sciences Xuchang UniversityXuchang 461000China Institute of Geospatial Information Information Engineering UniversityZhengzhou 450001China Department of Civil Engineering Henan Vocational College of Water Conservancy and EnvironmentZhengzhou 450001China

This study analyzes the signal quality and the accuracy of BeiDou 3 rd generation Satellite Navigation System(BDS3) precise point positioning(PPP) in the Arctic Ocean. Assessment of signal quality of BDS3 includes signal to noise ratio(SNR), multipath(MP), dilution of precision(DOP), and code-minus-carrier combination(CC). The results show that, 5 to 13 satellites are visible at any time in the Arctic Ocean area as of September 2018, which are sufficient for positioning. In the mid-latitude oceanic region and in the Arctic Ocean, the SNR is 25–52 dB Hz and the MP ranges from-2 m to 2 m. As the latitude increases, the DOP values show large variation, which may be related to the distribution of BDS satellites. The CC values of signals B1 I and BIC range from-5 m to 5 m in the mid-latitude sea area and the Arctic Ocean, which means the effect of pseudorange noise is small. Moreover, as to obtain the external precise reference value for GNSS positioning in the Arctic Ocean region is difficult, it is hard to evaluate the accuracy of positioning results. An improved isotropy-based protection level method based on Receiver Autonomous Integrity Monitoring is proposed in the paper, which adopts median filter to smooth the gross errors to assess the precision and reliability of PPP in the Arctic Ocean. At first, the improved algorithm is verified with the data from the International GNSS Service Station Tixi. Then the accuracy of BDS3 PPP in the Arctic Ocean is calculated based on the improved algorithm. Which shows that the kinematic accuracy of PPP can reach the decimeter level in both the horizontal and vertical directions, and it meets the precision requirements of maritime navigation.

关键词： BDS3 Arctic Ocean signal quality analysis protection level quality check precise point positioning satellite navigation

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A resilient adjustment method to weigh pseudorange observation in precise point positioning

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Satellite Navigation 2022年第3期3卷 125-139,I0004页

作者： Qieqie Zhang Long Zhao Jianhua Zhou College of Automation Engineering Nanjing University of Aeronautics and AstronauticsNanjing211106China Digital Navigation Center School of Automation Science and Electrical EngineeringBeihang UniversityBeijing100191China Beijing Satellite Navigation Center Beijing100094China

The accurate weighting of pseudorange observations is important to improve the convergence time and positioning quality of precise point positioning(PPP).Currently,the weight of a pseudorange observation is mainly determined with empirical stochastic ***,in a complex environment,due to the inability to adapt for the dynamic changes of the user environment,the empirical stochastic models usually cannot reflect the real error level of pseudorange *** address this problem,a resilient adjustment method to weigh pseudorange observations is proposed,which constructs the real-time estimation and inflation model for the variance of pseudorange multipath error and measurement noise to replace the empirical stochastic model to determine the weights of pseudorange observations.A set of static and dynamic Global positioning System(GPS)test data are used to verify the effectiveness of the proposed *** test results indicate that the proposed real-time estimation model can provide a better representation of the pseudorange accuracy,and the positioning performance of PPP using the real-time estimation model is better than that with the empirical stochastic *** with the optimal empirical stochastic model,the positioning accuracy of PPP with the real-time estimation model is improved by at least 20%,and the convergence time is reduced by at least 50%.

关键词： precise point positioning Stochastic model Resilient adjustment Complex environments

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Multi-constellation GNSS precise point positioning with multi-frequency raw observations and dual-frequency observations of ionospheric-free linear combination

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Satellite Navigation 2020年第1期1卷 68-80页

作者： Xiangdong An Xiaolin Meng Weiping Jiang GNSS Research Center Wuhan University129 Luoyu RoadWuhan 430079China Nottingham Geospatial Institute University of NottinghamNottingham NG72TUUK.

precise point positioning(PPP)is famous for its capability of high-precision positioning with just one station as long as the receiver can receive global navigation satellite system(GNSS)*** the rapid development of BDS and Galileo,the number of available satellites for positioning has increased *** addition,GPS III,GLONASS-K,BDS,and Galileo satellites can transmit triple-frequency *** potentials of multi-constellation GNSS PPP requires further analysis on a global ***,we selected 96 multi-GNSS experiment(MGEX)stations with a global distribution and used 1 week’s data to assess the PPP *** results show that the PPP based on multi-frequency raw observations with spatial and temporal constraints has better performance than PPP using dual-frequency ionospheric-free *** main contribution of multi-constellation GNSS PPP is to shorten the convergence *** convergence time for GPS PPP is approximately 40 min,which can be shortened to less than 20 min in multi-GNSS *** convergence,the positioning accuracy of multi-GNSS PPP is improved by 0.5 to 1.0 cm compared with GPS or GLONASS *** positioning accuracy of multi-GNSS could be further improved in the future with the BDS and Galileo precise products of orbits,clock and phase center offset/variation.

关键词： precise point positioning Multi-frequency and multi-constellation GNSS PPP convergence Multi-GNSS experiment

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An ERA5 tropospheric parameters-augmented approach for improving GNSS precise point positioning

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Geodesy and Geodynamics 2023年第5期14卷 467-476页

作者： Liangke Huang Feifan Liu Lijie Guo Guiwen Lan Lv Zhou Cheng Wang Lilong Liu College of Geomatics and Geoinformation Guilin University of TechnologyGuilin 541006China Wuhan Changjiang Waterway Rescue and Salvage Bure Wuhan 430014China Guangxi Institute of Natural Resources Survey and Monitoring Nanning530023China

precise point positioning(PPP) technology has developed into a potent instrument for geodetic positioning, ionospheric modeling, tropospheric atmospheric parameter detection, and seismic *** atmospheric reanalysis data products’ accuracy and spatiotemporal resolution have improved recently, it has become important to apply these products to obtain high-accuracy tropospheric delay parameters, like zenith tropospheric delay(ZTD) and tropospheric horizontal gradient. These tropospheric delay parameters can be applied to PPP to reduce the convergence time and to increase the accuracy in the vertical direction of the position. The European Centre for Medium-Range Weather Forecasts Reanalysis 5(ERA5) atmospheric reanalysis data is the latest product with a high spatiotemporal resolution released by the European Center for Medium-Range Weather Forecasts(ECMWF). Only a few researches have evaluated the application of ERA5 data to Global Navigation Satellite System(GNSS)PPP. Therefore, this study compared and validated the ZTD products derived from ERA5 data using ZTD values provided by 290 global International GNSS Service(IGS) stations for 2016-2017. The results indicated a stable performance for ZTD, with annual average bias and RMS values of 0.23 cm and 1.09 cm,respectively. Further, GNSS observations for one week in each of the four seasons(spring: DOY 92-98;summer: DOY 199-205;autumn: DOY 275-281;and winter: DOY 22-28) from 34 multi-GNSS experiments(MGEX) stations distributed globally in 2016 were considered to evaluate the performance of ERA5-derived tropospheric delay products in GNSS PPP. The performance of ERA5-enhanced PPP was compared with that of the two standard GNSS PPP schemes(without estimated tropospheric horizontal gradient and with estimated tropospheric horizontal gradient). The results demonstrated that ERA5-enhanced GNSS PPP showed no significant improvement in the convergence times in both the Eastern(E) and Northern(N) directions, while the

关键词： precise point positioning ERA5 atmospheric reanalysis data Multi-GNSS Tropospheric delay

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Impact of Sampling Rate of IGS Satellite Clock on precise point positioning

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Geo-Spatial Information Science 2010年第2期13卷 150-156页

作者： GUO Fei ZHANG Xiaohong LI Xingxing CAI Shixiang School of Geodesy and Geomatics Wuhan University 129 Luoyu Road Wuhan 430079 China

Both static and kinematic testings are investigated by using IGS 5rain, 30s and 5s-interval precise satellite clock prod- ucts in precise point positioning （PPP） solution. Test results show that the sampling rate oflGS satellite clock has very little effect on the static PPP solution. All the three types of sampling intervals of precise satellite clock can satisfy mm-cm level of positioning accuracy; higher sampling rate has no significant improvement for PPP solution. However, sampling rate of satellite clock has a significant impact on the PPP solution in kinematic PPP. The higher the interval of satellite clock, the better the accuracy achieved. The accuracy of kinematic PPP achieved by using 30s-interval precise satellite clock is improved by nearly 30-50 percent with re- spect to the solution by using 5min-interval precise satellite clock, but using 5s and 30s-interval satellite clock can almost produce the same accuracy of kinematic solution. Moreover, the use of precise satellite clock products from different analysis centers may also produce more or less effect on the PPP solution.

关键词： precise satellite clock error sampling rate precise point positioning accuracy

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Accuracy Improvement of Zenith Tropospheric Delay Estimation Based on GPS precise point positioning Algorithm

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Geo-Spatial Information Science 2010年第4期13卷 306-310页

作者： ZHU Qinglin ZHAO Zhenwei LIN Leke WU Zhensen China Research Institute of Radio Wave Propagation 36 West Xianshan Road Qingdao 266107 China School of Science Xidian University 2 South Taida Road Xi'an 710071 China

In the precise point positioning(PPP),some impossible accurately simulated systematic errors still remained in the GPS observations and will inevitably degrade the precision of zenith tropospheric delay(ZTD) *** stochastic models used in the GPS PPP mode are *** this paper,the research results show that the precision of PPP-derived ZTD can be obviously improved through selecting a suitable stochastic model for GPS ***-elevation observations can cover more troposphere information that can improve the estimation of ZTD.A new stochastic model based on satellite low elevation cosine square is *** results show that the stochastic model using satellite elevation-based cosine square function is better than previous stochastic models.

关键词： precise point positioning stochastic model zenith tropospheric delay cosine GPS

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