In cross-country skiing,athletes expend large amounts of energy to overcome friction as their skis interact with snow.Even minor reductions in the friction can significantly influence race outcomes.Over the years,rese...In cross-country skiing,athletes expend large amounts of energy to overcome friction as their skis interact with snow.Even minor reductions in the friction can significantly influence race outcomes.Over the years,researchers have found many ways of quantifying ski–snow friction,but there are only a few methods that consider the glide of real-sized skis under natural conditions during both accelerating and decelerating movements.This study introduces a novel experimental setup,consisting of a sled equipped with authentic cross-country skis and a base station that uses satellite receivers to communicate via radio,constituting a real-time kinematic positioning system with centimetre accuracy.While the sled was running on a classic ski track with natural height variations,altitude and velocity data were recorded for quantification of the coefficient of friction(COF),both for accelerating and decelerating motion,employing a model based on Newton’s second law.The results show that the COF during acceleration was more than 20%higher than during deceleration,demonstrating dynamic changes in the frictional behaviour between these phases.This finding is crucial for the execution of all types of cross-country skiing techniques,where the athlete either accelerates or decelerates while moving forward.The ability of the current experimental set-up to distinguish between the COF during acceleration and deceleration has considerable implications for further developments.展开更多
In the case of a medium-long baseline, for real-time kinematic (RTK) positioning, the fixed rate of integer ambiguity is low due to the distance between the base station and the observation station. Moreover, the atmo...In the case of a medium-long baseline, for real-time kinematic (RTK) positioning, the fixed rate of integer ambiguity is low due to the distance between the base station and the observation station. Moreover, the atmospheric delay after differential processing cannot be ignored. For correcting the residual atmospheric errors, we proposed a GPS/BDS/Galileo/GLONASS four-system fusion RTK positioning algorithm, which is based on the extended Kalman filter (EKF) algorithm. After realizing the spatio-temporal unification of multiple global navigation satellite systems (GNSSs), we introduced a parameter estimation of atmospheric errors based on the EKF model, using the least-squares integer ambiguity decorrelation adjustment (LAMBDA) to calculate the integer ambiguity. After conducting experiments for different baselines, the proposed RTK positioning algorithm can achieve centimeter-level positioning accuracy in the case of medium-long baselines. In addition, the time required to solve the fixed solution is shorter than that of the traditional RTK positioning algorithm.展开更多
随着北京城市化进程的加速,越来越多的规划监督项目远离了繁闹的市区,六环外、各郊区县项目的暴增给网络实时动态载波相位差分技术(Real Time Kinematic,RTK)的使用带来更多难题。由于偏远地区通信设施建设滞后导致网络不稳定,网络RTK...随着北京城市化进程的加速,越来越多的规划监督项目远离了繁闹的市区,六环外、各郊区县项目的暴增给网络实时动态载波相位差分技术(Real Time Kinematic,RTK)的使用带来更多难题。由于偏远地区通信设施建设滞后导致网络不稳定,网络RTK初始化时间和收敛精度受到极大影响,需要采取有效技术手段进行解决、改善。分别阐述全球定位系统(Global Positioning System,GPS)GPS-RTK和网络RTK的原理及作业差异,对GPS-RTK的测量精度进行理论推导,并通过实验数据分析各项结果,最终结果表明,在通信网络不佳,小范围作业采用GPS-RTK进行放线,数据整体稳定性较网络RTK更好,可以满足相关规范要求。展开更多
The joint utilization of the Fifth Generation Communications Technology(5G)and the Global Navigation Satellite System(GNSS)serves as a promising solution to address the challenges associated with insufficient visible ...The joint utilization of the Fifth Generation Communications Technology(5G)and the Global Navigation Satellite System(GNSS)serves as a promising solution to address the challenges associated with insufficient visible satellites and lower observation quality in urban environments.5G allows for the angle and distance measurements,augmenting the performance of Real-Time Kinematic(RTK)positioning.To quantify the improvement of 5G observations on RTK positioning,this paper proposes a float solution gain factor and the Ambiguity Dilution of Precision(ADOP)gain factor.Based on these gain factors,the theoretical analysis and simulation are performed.This study designs an extended Kalman filter for 5G-assisted BeiDou Navigation Satellite System(BDS)RTK positioning,employing both the Full Ambiguity Resolution(FAR)and Partial Ambiguity Resolution(PAR)modes.Our experiment verified the effectiveness of 5G-assisted BDS RTK positioning in mitigating outlier occurrences and improving the ambiguity fixing rate as well as the positioning accuracy.In the FAR and PAR modes,the Three-Dimensional(3D)spatial accuracy increased by 48%and 18.8%,respectively,and the results are consistent with theoretical analysis based on gain factors.The fixing rate of RTK increased from 11.11%to 13.93%,while it increased from 32.58%to 44.43%for the PAR mode.The assistance of 5G observations reduced the median error for the FAR mode from over 1.3m to 0.9 m,and the third quartile from 2.1m to 1.05 m.For the PAR mode,the median error decreased from 0.5m to 0.12 m,and the third and fourth quartiles decreased from 0.65m to 0.38 m.展开更多
基金supported by the Swedish Olympic Committee(SOK)and the Kempe Foundation#JCK-2107.
文摘In cross-country skiing,athletes expend large amounts of energy to overcome friction as their skis interact with snow.Even minor reductions in the friction can significantly influence race outcomes.Over the years,researchers have found many ways of quantifying ski–snow friction,but there are only a few methods that consider the glide of real-sized skis under natural conditions during both accelerating and decelerating movements.This study introduces a novel experimental setup,consisting of a sled equipped with authentic cross-country skis and a base station that uses satellite receivers to communicate via radio,constituting a real-time kinematic positioning system with centimetre accuracy.While the sled was running on a classic ski track with natural height variations,altitude and velocity data were recorded for quantification of the coefficient of friction(COF),both for accelerating and decelerating motion,employing a model based on Newton’s second law.The results show that the COF during acceleration was more than 20%higher than during deceleration,demonstrating dynamic changes in the frictional behaviour between these phases.This finding is crucial for the execution of all types of cross-country skiing techniques,where the athlete either accelerates or decelerates while moving forward.The ability of the current experimental set-up to distinguish between the COF during acceleration and deceleration has considerable implications for further developments.
文摘In the case of a medium-long baseline, for real-time kinematic (RTK) positioning, the fixed rate of integer ambiguity is low due to the distance between the base station and the observation station. Moreover, the atmospheric delay after differential processing cannot be ignored. For correcting the residual atmospheric errors, we proposed a GPS/BDS/Galileo/GLONASS four-system fusion RTK positioning algorithm, which is based on the extended Kalman filter (EKF) algorithm. After realizing the spatio-temporal unification of multiple global navigation satellite systems (GNSSs), we introduced a parameter estimation of atmospheric errors based on the EKF model, using the least-squares integer ambiguity decorrelation adjustment (LAMBDA) to calculate the integer ambiguity. After conducting experiments for different baselines, the proposed RTK positioning algorithm can achieve centimeter-level positioning accuracy in the case of medium-long baselines. In addition, the time required to solve the fixed solution is shorter than that of the traditional RTK positioning algorithm.
文摘随着北京城市化进程的加速,越来越多的规划监督项目远离了繁闹的市区,六环外、各郊区县项目的暴增给网络实时动态载波相位差分技术(Real Time Kinematic,RTK)的使用带来更多难题。由于偏远地区通信设施建设滞后导致网络不稳定,网络RTK初始化时间和收敛精度受到极大影响,需要采取有效技术手段进行解决、改善。分别阐述全球定位系统(Global Positioning System,GPS)GPS-RTK和网络RTK的原理及作业差异,对GPS-RTK的测量精度进行理论推导,并通过实验数据分析各项结果,最终结果表明,在通信网络不佳,小范围作业采用GPS-RTK进行放线,数据整体稳定性较网络RTK更好,可以满足相关规范要求。
基金supported by the National Key R&D Program of China under Grant No.2021YFA0716603the 6th Young Elite Scientist Sponsorship Program through the China Association for Science and Technology under Grant YESS20200226.
文摘The joint utilization of the Fifth Generation Communications Technology(5G)and the Global Navigation Satellite System(GNSS)serves as a promising solution to address the challenges associated with insufficient visible satellites and lower observation quality in urban environments.5G allows for the angle and distance measurements,augmenting the performance of Real-Time Kinematic(RTK)positioning.To quantify the improvement of 5G observations on RTK positioning,this paper proposes a float solution gain factor and the Ambiguity Dilution of Precision(ADOP)gain factor.Based on these gain factors,the theoretical analysis and simulation are performed.This study designs an extended Kalman filter for 5G-assisted BeiDou Navigation Satellite System(BDS)RTK positioning,employing both the Full Ambiguity Resolution(FAR)and Partial Ambiguity Resolution(PAR)modes.Our experiment verified the effectiveness of 5G-assisted BDS RTK positioning in mitigating outlier occurrences and improving the ambiguity fixing rate as well as the positioning accuracy.In the FAR and PAR modes,the Three-Dimensional(3D)spatial accuracy increased by 48%and 18.8%,respectively,and the results are consistent with theoretical analysis based on gain factors.The fixing rate of RTK increased from 11.11%to 13.93%,while it increased from 32.58%to 44.43%for the PAR mode.The assistance of 5G observations reduced the median error for the FAR mode from over 1.3m to 0.9 m,and the third quartile from 2.1m to 1.05 m.For the PAR mode,the median error decreased from 0.5m to 0.12 m,and the third and fourth quartiles decreased from 0.65m to 0.38 m.
