Real-time satellite orbit and clock corrections obtained from the broadcast ephemerides can be improved using IGS real-time service (RTS) products. Recent research showed that applying such corrections for broadcast e...Real-time satellite orbit and clock corrections obtained from the broadcast ephemerides can be improved using IGS real-time service (RTS) products. Recent research showed that applying such corrections for broadcast ephemerides can significantly improve the RMS of the estimated coordinates. However, unintentional streaming interruption may happen for many reasons such as software or hardware failure. Streaming interruption, if happened, will cause sudden degradation of the obtained solution if only the broadcast ephemerides are used. A better solution can be obtained in real-time if the predicted part of the ultra-rapid products is used. In this paper, Harmonic analysis technique is used to predict the IGS RTS corrections using historical broadcasted data. It is shown that using the predicted clock corrections improves the RMS of the estimated coordinates by about 72%, 58%, and 72% in latitude, longitude, and height directions, respectively and reduces the 2D and 3D errors by about 80% compared with the predicted part of the IGS ultra-rapid clock corrections.展开更多
The analysis centers of the Multi-GNSS Pilot Project of the International GNSS Service provide orbit and clock products for the global navigation satellite systems(GNSSs)Global Positioning System(GPS),GLONASS,Galileo,...The analysis centers of the Multi-GNSS Pilot Project of the International GNSS Service provide orbit and clock products for the global navigation satellite systems(GNSSs)Global Positioning System(GPS),GLONASS,Galileo,and BeiDou,as well as for the Japanese regional Quasi-Zenith Satellite System(QZSS).Due to improved solar radiation pressure modeling and other more sophisticated models,the consistency of these products has improved in recent years.The current orbit consistency between different analysis centers is on the level of a few centimeters for GPS,around one decimeter for GLONASS and Galileo,a few decimeters for BeiDou-2,and several decimeters for QZSS.The clock consistency is about 2 cm for GPS,5 cm for GLONASS and Galileo,and 10 cm for BeiDou-2.In terms of carrier phase modeling error for precise point positioning,the various products exhibit consistencies of 2–3 cm for GPS,6–14 cm for GLONASS,3–10 cm for Galileo,and 10–17 cm for BeiDou-2.展开更多
Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position ac...Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position accuracy is affected by several factors such as satellite clock error, propagation path delays and receiver noise due to which the GPS does not meet the requirements of critical navigation applications such as missile navigation and category I/II/III aircraft landings. This paper emphasizes on modelling the satellite clock error and orbital solution (satellite position) error considering the signal emission time. The transmission time sent by each satellite in broadcast ephemerides is not accurate. This has to be corrected in order to obtain correct satellite position and in turn a precise receiver position. Signal transmission time or broadcast time from satellite antenna phase center is computed at the receiver using several parameters such as signal reception time, propagation time, pseudorange observed and satellite clock error correction parameters. This corrected time of transmission and broadcast orbital parameters are used for estimation of the orbital solution. The estimated orbital solution was validated with the precise ephemerides which are estimated by Jet Propulsion Laboratory (JPL), USA. The errors are estimated for a typical day data collected on 11th March 2011 from dual frequency GPS receiver located at Department of Electronics and Communication Engineering, Andhra University College of Engineering, Visakhapatnam (17.73°N/83.319°E).展开更多
Accurate estimation of clocks, for example for the Gravity Recovery And Climate Experiment(GRACE)twin-satellites, is a critical part of precise orbit determination(POD) that ensures temporal gravity inversion. Charact...Accurate estimation of clocks, for example for the Gravity Recovery And Climate Experiment(GRACE)twin-satellites, is a critical part of precise orbit determination(POD) that ensures temporal gravity inversion. Characterizing the periodic variations of the receiver clocks is critical for precise clock modeling and prediction. In this study, the receiver clock is estimated using two different POD procedure: kinematic and reduced-dynamic approaches. Choices and the number of orbital parameters estimated in POD process affect the clock estimates, e.g., there are 8895 and 34,560 total parameters in the reduced-dynamic and kinematic approaches, respectively. In the both cases, the periodic variations of GRACE receiver clock are mainly dominated by the GPS orbit period, as well as once-(1-pr) and twiceper-revolution(2-pr) effects. Here the 1-pr effect is coupled with the relativistic effect, resulting in a difficulty to separate both signals. The clock amplitudes caused by the GPS orbit period, 1-pr and 2-pr are about 0.1, 0.03 and 0.01 ns, respectively. The GPS orbit period is almost one order magnitude larger than the 1-and 2-pr effect. The 0.1-ns amplitude of the 12-h periodic variation is equivalent to a 3-cm error in range. Such a systematic error should be considered in the receiver clock modeling for both the improvement of positioning accuracy and the reduction of number of unknown parameters, if the precise point positioning(PPP) technique is used for the orbit determination of the GRACE.展开更多
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 ...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 detail.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 constellation.The 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, respectively.The 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 and 8.64 cm, respectively,after convergence. The obtainable positioning and convergence performances are comparable to those using products generated by global tracking networks.展开更多
近年来,随着多系统全球导航卫星系统(global navigation satellite system,GNSS)的迅速发展以及实时高精度应用需求的日益增长,国际GNSS服务分析中心(International GNSS Service,IGS)提供的状态空间表述(state space representation,S...近年来,随着多系统全球导航卫星系统(global navigation satellite system,GNSS)的迅速发展以及实时高精度应用需求的日益增长,国际GNSS服务分析中心(International GNSS Service,IGS)提供的状态空间表述(state space representation,SSR)产品越来越丰富。评估不同分析中心的GNSS实时产品及其定位性能对用户具有重要参考价值。对中国科学院(Chinese Academy of Sciences,CAS)、法国太空研究中心(Centre National d’Etudes Spatiales,CNE)、德国宇航中心(Deutsches Zentrum für Luft-und Raumfahrt,DLR)、西班牙航天与防务公司(GMV Aerospace and Defense,GMV)、德国地学研究中心(Deutsches GeoForschungsZentrum,GFZ)、武汉大学(Wuhan University,WHU)6个分析中心的GPS/北斗卫星导航系统(BeiDou satellite navigation system,BDS)SSR产品的可用性、精度和实时精密单点定位性能进行了评估。实验结果表明:CAS播发的GPS卫星可用性最高,提供了所有32颗GPS卫星的SSR改正数;CAS、GFZ、WHU 3家分析中心的BDS卫星可用性相对较高,提供了15(BDS-2)+27(BDS-3)卫星的SSR改正数。在6个分析中心中,WHU的GPS卫星的三维轨道精度和钟差精度均为最佳;不同分析中心GPS卫星的信号空间测距误差(signal-in-space ranging errors,SISRE)普遍优于5 cm,不同分析中心GPS卫星的SISRE值的大小顺序为:WHU<GMV<CNE<DLR<GFZ<CAS;BDS卫星轨道钟差精度相对较差,表现最优的WHU分析中心的BDS-2和BDS-3的中地球轨道卫星精密产品的SISRE值分别为8.83、5.91 cm。在单GPS动态PPP模式下,DLR的收敛速度最慢,GFZ收敛速度最快;加入BDS卫星以后,定位精度无显著差异,但能够有效提升收敛速度。展开更多
利用CNES 1 a的实时轨道与钟差产品,以用户测距误差(user range error,URE)为评价指标,通过与事后产品对比的方法分析GPS、Galileo、BDS-2和BDS-3的故障率、故障类型、故障来源及故障排除后的精度与PPP性能。结果显示,GPS与Galileo的故...利用CNES 1 a的实时轨道与钟差产品,以用户测距误差(user range error,URE)为评价指标,通过与事后产品对比的方法分析GPS、Galileo、BDS-2和BDS-3的故障率、故障类型、故障来源及故障排除后的精度与PPP性能。结果显示,GPS与Galileo的故障率低于BDS,BDS-3与BDS-2的故障率存在显著差异;对于故障类型而言,突变故障最少,而钟差为主要故障来源(大于65%);故障排除后,GPS、Galileo、BDS-3的用户测距精度(user range accuracy,URA)均值分别为0.02 m、0.03 m、0.05 m,BDS-2中不同卫星URA差异较大。全球测站仿动态PPP测试显示,剔除卫星故障时段可有效保障定位精度。展开更多
实时轨道、钟差产品的精度和完好性是实现全球卫星导航系统精准可信定位服务的重要前提。以2022年中国科学院(Chinese Academy of Sciences,CAS)实时轨道、钟差产品为例,从产品精度及精密单点定位精度两个方面评估实时轨道、钟差产品性...实时轨道、钟差产品的精度和完好性是实现全球卫星导航系统精准可信定位服务的重要前提。以2022年中国科学院(Chinese Academy of Sciences,CAS)实时轨道、钟差产品为例,从产品精度及精密单点定位精度两个方面评估实时轨道、钟差产品性能,并根据全球均匀分布的100个虚拟测站计算得到的瞬时空间信号用户测距误差(instantaneous signal-in-space user range error,IURE),分析实时轨道、钟差产品的空间信号用户测距误差分布特性,计算CAS实时轨道、钟差产品的完好性支持信息。试验结果表明,以德国地学研究中心提供的事后精密产品为参考,GPS和Galileo的轨道精度优于5 cm,钟差标准差(standard deviation,STD)优于0.08 ns,BDS和GLONASS的轨道精度优于15 cm,STD优于0.3 ns;选取全球分布测站以静态仿动态方式进行精密单点定位测试,四系统组合定位的3D方向精度均方根(root mean square,RMS)优于4 cm,收敛时间优于11 min。GPS和Galileo的IURE RMS优于4 cm,同时IURE分布峰度基本在10以内,偏度绝对值基本在0.5以内,可接受为高斯分布;GLONASS的IURE RMS在10 cm以内,但是各卫星IURE的偏度和峰度之间差异较大,尖峰厚尾情况较为严重;BDS的IURE RMS优于11 cm,但是不同类型卫星的IURE分布不同,且BDS-3上海微小卫星工程中心的卫星具有较为明显的双峰特性。对于星座故障和卫星故障先验概率,GPS星座故障先验概率最小为5.2×10^(-5),除BDS-2外,其他系统星座故障先验概率小于1.0×10^(-3);GLONASS卫星故障先验概率达到2.7×10^(-3),Galileo卫星故障先验概率最小为8.7×10^(-4)。对于空间信号用户测距误差的包络标准差和标准差,GPS和Galileo卫星的两种标准差差异均在4 cm以内;GLONASS卫星的两种标准差差异基本大于5 cm;相较于标准差,BDS-2和BDS-3的包络标准差差异较大。展开更多
Stable and reliable high-precision satellite orbit products are the prerequisites for the positioning services with high performance.In general,the positioning accuracy depends strongly on the quality of satellite orb...Stable and reliable high-precision satellite orbit products are the prerequisites for the positioning services with high performance.In general,the positioning accuracy depends strongly on the quality of satellite orbit and clock products,especially for absolute positioning modes,such as Precise Point Positioning(PPP).With the development of real-time services,real-time Precise Orbit Determination(POD)is indispensable and mainly includes two methods:the ultra-rapid orbit prediction and the real-time filtering orbit determination.The real-time filtering method has a great potential to obtain more stable and reliable products than the ultra-rapid orbit prediction method and thus has attracted increasing attention in commercial companies and research institutes.However,several key issues should be resolved,including the refinement of satellite dynamic stochastic models,adaptive filtering for irregular satellite motions,rapid convergence,and real-time Ambiguity Resolution(AR).This paper reviews and summarizes the current research progress in real-time filtering POD with a focus on the aforementioned issues.In addition,the real-time filtering orbit determination software developed by our group is introduced,and some of the latest results are evaluated.The Three-Dimensional(3D)real-time orbit accuracy of GPS and Galileo satellites is better than 5 cm with AR.In terms of the convergence time and accuracy of kinematic PPP AR,the better performance of the filter orbit products is validated compared to the ultra-rapid orbit products.展开更多
Real-time satellite orbit and clock estimations are the prerequisite for Global Navigation Satellite System(GNSS)real-time precise positioning services.To meet the high-rate update requirement of satellite clock corre...Real-time satellite orbit and clock estimations are the prerequisite for Global Navigation Satellite System(GNSS)real-time precise positioning services.To meet the high-rate update requirement of satellite clock corrections,the computational efficiency is a key factor and a challenge due to the rapid development of multi-GNSS constellations.The Square Root Information Filter(SRIF)is widely used in real-time GNSS data processing thanks to its high numerical stability and computational efficiency.In real-time clock estimation,the outlier detection and elimination are critical to guarantee the precision and stability of the product but could be time-consuming.In this study,we developed a new quality control procedure including the three standard steps:i.e.,detection,identification,and adaption,for real-time data processing of huge GNSS networks.Effort is made to improve the computational efficiency by optimizing the algorithm to provide only the essential information required in the processing,so that it can be applied in real-time and high-rate estimation of satellite clocks.The processing procedure is implemented in the PANDA(Positioning and Navigation Data Analyst)software package and evaluated in the operational generation of real-time GNSS orbit and clock products.We demonstrated that the new algorithm can efficiently eliminate outliers,and a clock precision of 0.06 ns,0.24 ns,0.06 ns,and 0.11 ns can be achieved for the GPS,GLONASS,Galileo,and BDS-2 IGSO/MEO satellites,respectively.The computation time per epoch is about 2 to 3 s depending on the number of existing outliers.Overall,the algorithm can satisfy the IGS real-time clock estimation in terms of both the computational efficiency and product quality.展开更多
文摘Real-time satellite orbit and clock corrections obtained from the broadcast ephemerides can be improved using IGS real-time service (RTS) products. Recent research showed that applying such corrections for broadcast ephemerides can significantly improve the RMS of the estimated coordinates. However, unintentional streaming interruption may happen for many reasons such as software or hardware failure. Streaming interruption, if happened, will cause sudden degradation of the obtained solution if only the broadcast ephemerides are used. A better solution can be obtained in real-time if the predicted part of the ultra-rapid products is used. In this paper, Harmonic analysis technique is used to predict the IGS RTS corrections using historical broadcasted data. It is shown that using the predicted clock corrections improves the RMS of the estimated coordinates by about 72%, 58%, and 72% in latitude, longitude, and height directions, respectively and reduces the 2D and 3D errors by about 80% compared with the predicted part of the IGS ultra-rapid clock corrections.
基金We would like to acknowledge the efforts of the MGEX station operators,data,and analysis centers,as well as the ILRS for providing SLR normal points.
文摘The analysis centers of the Multi-GNSS Pilot Project of the International GNSS Service provide orbit and clock products for the global navigation satellite systems(GNSSs)Global Positioning System(GPS),GLONASS,Galileo,and BeiDou,as well as for the Japanese regional Quasi-Zenith Satellite System(QZSS).Due to improved solar radiation pressure modeling and other more sophisticated models,the consistency of these products has improved in recent years.The current orbit consistency between different analysis centers is on the level of a few centimeters for GPS,around one decimeter for GLONASS and Galileo,a few decimeters for BeiDou-2,and several decimeters for QZSS.The clock consistency is about 2 cm for GPS,5 cm for GLONASS and Galileo,and 10 cm for BeiDou-2.In terms of carrier phase modeling error for precise point positioning,the various products exhibit consistencies of 2–3 cm for GPS,6–14 cm for GLONASS,3–10 cm for Galileo,and 10–17 cm for BeiDou-2.
文摘Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position accuracy is affected by several factors such as satellite clock error, propagation path delays and receiver noise due to which the GPS does not meet the requirements of critical navigation applications such as missile navigation and category I/II/III aircraft landings. This paper emphasizes on modelling the satellite clock error and orbital solution (satellite position) error considering the signal emission time. The transmission time sent by each satellite in broadcast ephemerides is not accurate. This has to be corrected in order to obtain correct satellite position and in turn a precise receiver position. Signal transmission time or broadcast time from satellite antenna phase center is computed at the receiver using several parameters such as signal reception time, propagation time, pseudorange observed and satellite clock error correction parameters. This corrected time of transmission and broadcast orbital parameters are used for estimation of the orbital solution. The estimated orbital solution was validated with the precise ephemerides which are estimated by Jet Propulsion Laboratory (JPL), USA. The errors are estimated for a typical day data collected on 11th March 2011 from dual frequency GPS receiver located at Department of Electronics and Communication Engineering, Andhra University College of Engineering, Visakhapatnam (17.73°N/83.319°E).
基金funded by the Ministry of Science and Technology of Taiwan, under grant numbers 103-2116-M-008-014
文摘Accurate estimation of clocks, for example for the Gravity Recovery And Climate Experiment(GRACE)twin-satellites, is a critical part of precise orbit determination(POD) that ensures temporal gravity inversion. Characterizing the periodic variations of the receiver clocks is critical for precise clock modeling and prediction. In this study, the receiver clock is estimated using two different POD procedure: kinematic and reduced-dynamic approaches. Choices and the number of orbital parameters estimated in POD process affect the clock estimates, e.g., there are 8895 and 34,560 total parameters in the reduced-dynamic and kinematic approaches, respectively. In the both cases, the periodic variations of GRACE receiver clock are mainly dominated by the GPS orbit period, as well as once-(1-pr) and twiceper-revolution(2-pr) effects. Here the 1-pr effect is coupled with the relativistic effect, resulting in a difficulty to separate both signals. The clock amplitudes caused by the GPS orbit period, 1-pr and 2-pr are about 0.1, 0.03 and 0.01 ns, respectively. The GPS orbit period is almost one order magnitude larger than the 1-and 2-pr effect. The 0.1-ns amplitude of the 12-h periodic variation is equivalent to a 3-cm error in range. Such a systematic error should be considered in the receiver clock modeling for both the improvement of positioning accuracy and the reduction of number of unknown parameters, if the precise point positioning(PPP) technique is used for the orbit determination of the GRACE.
基金supported by the National Natural Science Foundation of China(No.41804030)。
文摘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 detail.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 constellation.The 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, respectively.The 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 and 8.64 cm, respectively,after convergence. The obtainable positioning and convergence performances are comparable to those using products generated by global tracking networks.
文摘近年来,随着多系统全球导航卫星系统(global navigation satellite system,GNSS)的迅速发展以及实时高精度应用需求的日益增长,国际GNSS服务分析中心(International GNSS Service,IGS)提供的状态空间表述(state space representation,SSR)产品越来越丰富。评估不同分析中心的GNSS实时产品及其定位性能对用户具有重要参考价值。对中国科学院(Chinese Academy of Sciences,CAS)、法国太空研究中心(Centre National d’Etudes Spatiales,CNE)、德国宇航中心(Deutsches Zentrum für Luft-und Raumfahrt,DLR)、西班牙航天与防务公司(GMV Aerospace and Defense,GMV)、德国地学研究中心(Deutsches GeoForschungsZentrum,GFZ)、武汉大学(Wuhan University,WHU)6个分析中心的GPS/北斗卫星导航系统(BeiDou satellite navigation system,BDS)SSR产品的可用性、精度和实时精密单点定位性能进行了评估。实验结果表明:CAS播发的GPS卫星可用性最高,提供了所有32颗GPS卫星的SSR改正数;CAS、GFZ、WHU 3家分析中心的BDS卫星可用性相对较高,提供了15(BDS-2)+27(BDS-3)卫星的SSR改正数。在6个分析中心中,WHU的GPS卫星的三维轨道精度和钟差精度均为最佳;不同分析中心GPS卫星的信号空间测距误差(signal-in-space ranging errors,SISRE)普遍优于5 cm,不同分析中心GPS卫星的SISRE值的大小顺序为:WHU<GMV<CNE<DLR<GFZ<CAS;BDS卫星轨道钟差精度相对较差,表现最优的WHU分析中心的BDS-2和BDS-3的中地球轨道卫星精密产品的SISRE值分别为8.83、5.91 cm。在单GPS动态PPP模式下,DLR的收敛速度最慢,GFZ收敛速度最快;加入BDS卫星以后,定位精度无显著差异,但能够有效提升收敛速度。
文摘利用CNES 1 a的实时轨道与钟差产品,以用户测距误差(user range error,URE)为评价指标,通过与事后产品对比的方法分析GPS、Galileo、BDS-2和BDS-3的故障率、故障类型、故障来源及故障排除后的精度与PPP性能。结果显示,GPS与Galileo的故障率低于BDS,BDS-3与BDS-2的故障率存在显著差异;对于故障类型而言,突变故障最少,而钟差为主要故障来源(大于65%);故障排除后,GPS、Galileo、BDS-3的用户测距精度(user range accuracy,URA)均值分别为0.02 m、0.03 m、0.05 m,BDS-2中不同卫星URA差异较大。全球测站仿动态PPP测试显示,剔除卫星故障时段可有效保障定位精度。
文摘实时轨道、钟差产品的精度和完好性是实现全球卫星导航系统精准可信定位服务的重要前提。以2022年中国科学院(Chinese Academy of Sciences,CAS)实时轨道、钟差产品为例,从产品精度及精密单点定位精度两个方面评估实时轨道、钟差产品性能,并根据全球均匀分布的100个虚拟测站计算得到的瞬时空间信号用户测距误差(instantaneous signal-in-space user range error,IURE),分析实时轨道、钟差产品的空间信号用户测距误差分布特性,计算CAS实时轨道、钟差产品的完好性支持信息。试验结果表明,以德国地学研究中心提供的事后精密产品为参考,GPS和Galileo的轨道精度优于5 cm,钟差标准差(standard deviation,STD)优于0.08 ns,BDS和GLONASS的轨道精度优于15 cm,STD优于0.3 ns;选取全球分布测站以静态仿动态方式进行精密单点定位测试,四系统组合定位的3D方向精度均方根(root mean square,RMS)优于4 cm,收敛时间优于11 min。GPS和Galileo的IURE RMS优于4 cm,同时IURE分布峰度基本在10以内,偏度绝对值基本在0.5以内,可接受为高斯分布;GLONASS的IURE RMS在10 cm以内,但是各卫星IURE的偏度和峰度之间差异较大,尖峰厚尾情况较为严重;BDS的IURE RMS优于11 cm,但是不同类型卫星的IURE分布不同,且BDS-3上海微小卫星工程中心的卫星具有较为明显的双峰特性。对于星座故障和卫星故障先验概率,GPS星座故障先验概率最小为5.2×10^(-5),除BDS-2外,其他系统星座故障先验概率小于1.0×10^(-3);GLONASS卫星故障先验概率达到2.7×10^(-3),Galileo卫星故障先验概率最小为8.7×10^(-4)。对于空间信号用户测距误差的包络标准差和标准差,GPS和Galileo卫星的两种标准差差异均在4 cm以内;GLONASS卫星的两种标准差差异基本大于5 cm;相较于标准差,BDS-2和BDS-3的包络标准差差异较大。
基金National Natural Science Foundation of China(Grand No.41904021).
文摘Stable and reliable high-precision satellite orbit products are the prerequisites for the positioning services with high performance.In general,the positioning accuracy depends strongly on the quality of satellite orbit and clock products,especially for absolute positioning modes,such as Precise Point Positioning(PPP).With the development of real-time services,real-time Precise Orbit Determination(POD)is indispensable and mainly includes two methods:the ultra-rapid orbit prediction and the real-time filtering orbit determination.The real-time filtering method has a great potential to obtain more stable and reliable products than the ultra-rapid orbit prediction method and thus has attracted increasing attention in commercial companies and research institutes.However,several key issues should be resolved,including the refinement of satellite dynamic stochastic models,adaptive filtering for irregular satellite motions,rapid convergence,and real-time Ambiguity Resolution(AR).This paper reviews and summarizes the current research progress in real-time filtering POD with a focus on the aforementioned issues.In addition,the real-time filtering orbit determination software developed by our group is introduced,and some of the latest results are evaluated.The Three-Dimensional(3D)real-time orbit accuracy of GPS and Galileo satellites is better than 5 cm with AR.In terms of the convergence time and accuracy of kinematic PPP AR,the better performance of the filter orbit products is validated compared to the ultra-rapid orbit products.
基金the project“Early-Warning and Rapid Impact Assessment with real-time GNSS in the Mediterranean(EWRICA)”Funded by the Federal Ministry of Education and Research,Germany.
文摘Real-time satellite orbit and clock estimations are the prerequisite for Global Navigation Satellite System(GNSS)real-time precise positioning services.To meet the high-rate update requirement of satellite clock corrections,the computational efficiency is a key factor and a challenge due to the rapid development of multi-GNSS constellations.The Square Root Information Filter(SRIF)is widely used in real-time GNSS data processing thanks to its high numerical stability and computational efficiency.In real-time clock estimation,the outlier detection and elimination are critical to guarantee the precision and stability of the product but could be time-consuming.In this study,we developed a new quality control procedure including the three standard steps:i.e.,detection,identification,and adaption,for real-time data processing of huge GNSS networks.Effort is made to improve the computational efficiency by optimizing the algorithm to provide only the essential information required in the processing,so that it can be applied in real-time and high-rate estimation of satellite clocks.The processing procedure is implemented in the PANDA(Positioning and Navigation Data Analyst)software package and evaluated in the operational generation of real-time GNSS orbit and clock products.We demonstrated that the new algorithm can efficiently eliminate outliers,and a clock precision of 0.06 ns,0.24 ns,0.06 ns,and 0.11 ns can be achieved for the GPS,GLONASS,Galileo,and BDS-2 IGSO/MEO satellites,respectively.The computation time per epoch is about 2 to 3 s depending on the number of existing outliers.Overall,the algorithm can satisfy the IGS real-time clock estimation in terms of both the computational efficiency and product quality.
