This paper presents a source localization algorithm based on the source signal's time-difference-of-arrival(TDOA) for asynchronous wireless sensor network.To obtain synchronization among anchors,all anchors broadc...This paper presents a source localization algorithm based on the source signal's time-difference-of-arrival(TDOA) for asynchronous wireless sensor network.To obtain synchronization among anchors,all anchors broadcast signals periodically,the clock offsets and skews of anchor pairs can be estimated using broadcasting signal's time-of-arrivals(TOA) at anchors.A kalman filter is adopted to improve the accuracy of clock offsets and track the clock drifts due to random fluctuations.Once the source transmits signal,the TOAs at anchors are stamped respectively and source's TDOA error due to clock offset and skew of anchor pair can be mitigated by a compensation operation.Based on a Gaussian noise model,maximum likelihood estimation(MLE) for the source position is obtained.Performance issues are addressed by evaluating the Cramer-Rao lower bound and the selection of broadcasting period.The proposed algorithm is simple and effective,which has close performance with synchronous TDOA algorithm.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
为考虑产品综合与服务中心(Integration and Service Center,ISC)采用的钟差综合方法中的GNSS 4系统卫星间的周期性差异,提出了一种基于多项式附加周期项模型的钟差综合方法。该方法对钟差进行拟合,求得拟合值与原始值的差值,以拟合差...为考虑产品综合与服务中心(Integration and Service Center,ISC)采用的钟差综合方法中的GNSS 4系统卫星间的周期性差异,提出了一种基于多项式附加周期项模型的钟差综合方法。该方法对钟差进行拟合,求得拟合值与原始值的差值,以拟合差值构造抗差估计,对钟差进行动态加权综合,得到钟差综合值。选择长安大学、中科院国家授时中心、武汉大学、西安测绘研究所4家分析中心提供的最终钟差产品进行了钟差综合实验,对获得的钟差综合值与ISC提供的钟差以及iGMAS各分析中心提供的钟差进行精度与稳定性比较,并采用5个MGEX测站数据进行北斗单系统静态精密单点定位(Precise point positioning,PPP)实验。结果表明:BDS与GLONASS卫星的钟差综合值精度与ISC提供的钟差精度相比,分别提高了2.6、0.3 ns;而GPS与Galileo卫星的钟差综合值精度略低于ISC提供的钟差精度。采用钟差综合值进行PPP时,综合钟差定位精度基本稳定在3 cm左右。该方法可作为ISC钟差综合方法的一个补充。展开更多
基金supported by the National Natural Science Foundation of China under Grant No.61571452 and No.61201331
文摘This paper presents a source localization algorithm based on the source signal's time-difference-of-arrival(TDOA) for asynchronous wireless sensor network.To obtain synchronization among anchors,all anchors broadcast signals periodically,the clock offsets and skews of anchor pairs can be estimated using broadcasting signal's time-of-arrivals(TOA) at anchors.A kalman filter is adopted to improve the accuracy of clock offsets and track the clock drifts due to random fluctuations.Once the source transmits signal,the TOAs at anchors are stamped respectively and source's TDOA error due to clock offset and skew of anchor pair can be mitigated by a compensation operation.Based on a Gaussian noise model,maximum likelihood estimation(MLE) for the source position is obtained.Performance issues are addressed by evaluating the Cramer-Rao lower bound and the selection of broadcasting period.The proposed algorithm is simple and effective,which has close performance with synchronous TDOA algorithm.
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.
文摘为考虑产品综合与服务中心(Integration and Service Center,ISC)采用的钟差综合方法中的GNSS 4系统卫星间的周期性差异,提出了一种基于多项式附加周期项模型的钟差综合方法。该方法对钟差进行拟合,求得拟合值与原始值的差值,以拟合差值构造抗差估计,对钟差进行动态加权综合,得到钟差综合值。选择长安大学、中科院国家授时中心、武汉大学、西安测绘研究所4家分析中心提供的最终钟差产品进行了钟差综合实验,对获得的钟差综合值与ISC提供的钟差以及iGMAS各分析中心提供的钟差进行精度与稳定性比较,并采用5个MGEX测站数据进行北斗单系统静态精密单点定位(Precise point positioning,PPP)实验。结果表明:BDS与GLONASS卫星的钟差综合值精度与ISC提供的钟差精度相比,分别提高了2.6、0.3 ns;而GPS与Galileo卫星的钟差综合值精度略低于ISC提供的钟差精度。采用钟差综合值进行PPP时,综合钟差定位精度基本稳定在3 cm左右。该方法可作为ISC钟差综合方法的一个补充。
