The study of inter-system bias(ISB)is important for multi-system fusion and the performance of different signal compatibility.In this paper,the stability of ISB at the BDS3/BDS2 receiver end is calculated and analyzed...The study of inter-system bias(ISB)is important for multi-system fusion and the performance of different signal compatibility.In this paper,the stability of ISB at the BDS3/BDS2 receiver end is calculated and analyzed for different time spans(DOY 060~090 in 2021)from a total of 31 MGEX and iGMAS stations.We adopted two estimation strategies,random walk and constant approach,using the precision products of orbit and clock bias provided by WUM,the influence of which on ISB was also analyzed.Our results showed that the ISB value varied little within a day,and the mean of daily ISB standard deviation was only 0.037 m when the observation condition was good.The signal reception was continuous,indicating a high ISB stability for one day.If extending the time series to one month,however,the ISB standard deviation calculated by constant approach,in which a constant ISB is estimated on a daily basis was about 0.1 m,and the results of adjacent days were not continuous,with no apparent pattern.Concerning the random walk approach,the obtained ISB time series also had a jump,and the conclusion was the same as that of the constant strategy.Besides,receiver types showed a strong regularity in ISB numerical situation,and the distribution of ISB values corresponding to the same receiver type was relatively close.Therefore,we conclude that the ISB parameters remain stable in the short term(one day)and less stable in the long-term period.It is recommended that the ISB term should be set as a constant estimate every day in BDS3/BDS2 solutions,regardless of receiver type consistency.展开更多
Vertical errors often present in multibeam swath bathymetric data. They are mainly sourced by sound refraction, internal wave disturbance, imperfect tide correction, transducer mounting, long period heave, static draf...Vertical errors often present in multibeam swath bathymetric data. They are mainly sourced by sound refraction, internal wave disturbance, imperfect tide correction, transducer mounting, long period heave, static draft change, dynamic squat and dynamic motion residuals, etc. Although they can be partly removed or reduced by specific algorithms, the synthesized depth biases are unavoidable and sometimes have an important influence on high precise utilization of the final bathymetric data. In order to confidently identify the decimeter-level changes in seabed morphology by MBES, we must remove or weaken depth biases and improve the precision of multibeam bathymetry further. The fixed-interval profiles that are perpendicular to the vessel track are generated to adjust depth biases between swaths. We present a kind of postprocessing method to minimize the depth biases by the histogram of cumulative depth biases. The datum line in each profile can be obtained by the maximum value of histogram. The corrections of depth biases can be calculated according to the datum line. And then the quality of final bathymetry can be improved by the corrections. The method is verified by a field test.展开更多
本文介绍了车载双偏振雷达参数ZDR的处理方法,首先分析了信噪比SNR对ZDR参数的影响,得出信噪比SNR至少要>18 d B,ZDR数据才可信;其次分析了雷达附近的不同类型遮挡物对ZDR参数的影响,结果表明,尖状的遮挡物容易造成ZDR正的偏差,房屋...本文介绍了车载双偏振雷达参数ZDR的处理方法,首先分析了信噪比SNR对ZDR参数的影响,得出信噪比SNR至少要>18 d B,ZDR数据才可信;其次分析了雷达附近的不同类型遮挡物对ZDR参数的影响,结果表明,尖状的遮挡物容易造成ZDR正的偏差,房屋等遮挡物容易造成负偏差,而对树林等遮挡物,偏差的正负变化很大。随着遮挡程度的减小,ZDR的变化幅度变小;针对ZDR的系统误差,使用反射率因子结合ΦDP增量可以很好的进行计算,ZDR系统误差在短时间内变化不大,但是,随时间变化而逐渐变化,需要进行实时订正;最后,使用FIR滤波方法进行KDP参数计算并用于ZDR衰减订正,取得了不错的效果。针对业务应用,给出了实时处理ZDR参数的业务流程图。展开更多
高压系统中直流偏磁对换流变压器和交直流输电产生巨大的危害,限流和隔直是抑制直流偏磁的主要方法,目前广泛采用的是通过中性点串联电容的方法,对电容的保护研究很少。本文利用PSCAD/EMTDC建立500 k V的高压直流输电电磁暂态仿真平台,...高压系统中直流偏磁对换流变压器和交直流输电产生巨大的危害,限流和隔直是抑制直流偏磁的主要方法,目前广泛采用的是通过中性点串联电容的方法,对电容的保护研究很少。本文利用PSCAD/EMTDC建立500 k V的高压直流输电电磁暂态仿真平台,在发生工频过电压时,对换流变压器中性点处串联电容的过电压,以及其2端保护装置火花间隙进行了仿真和分析,选择了最佳容抗值的电容器,并探究了火花间隙对中性点串联电容器的保护,结果表明:火花间隙对换流变压器中性点接地电容以及变压器中性点起到保护作用。展开更多
地磁感应电流、直流输电系统接地极电流侵入电网,对电网内变压器造成直流偏磁危害,影响变压器安全、稳定运行。针对该问题,设计了一种基于通用无线分组业务(general packet radio service,GPRS)网络的变压器直流偏磁电流在线监测系统,...地磁感应电流、直流输电系统接地极电流侵入电网,对电网内变压器造成直流偏磁危害,影响变压器安全、稳定运行。针对该问题,设计了一种基于通用无线分组业务(general packet radio service,GPRS)网络的变压器直流偏磁电流在线监测系统,并研制了专门用于变压器直流偏磁电流监测的装置。该设计在电气上完全切断了过电压及各种干扰的传播路径,能有效保证监测装置工作的稳定性、可靠性。展开更多
基金the Natural Science Innovation Group Foundation of China under Grants NO.41721003the Science and Technology Support Project of Department of Natural Resources of Hubei Province under Grants NO.ZRZY2022KJ29+1 种基金the Special Fund of Hubei Luojia Laboratory under Grants NO.220100020the National Natural Science Foundation of China under Grants NO.42174030.
文摘The study of inter-system bias(ISB)is important for multi-system fusion and the performance of different signal compatibility.In this paper,the stability of ISB at the BDS3/BDS2 receiver end is calculated and analyzed for different time spans(DOY 060~090 in 2021)from a total of 31 MGEX and iGMAS stations.We adopted two estimation strategies,random walk and constant approach,using the precision products of orbit and clock bias provided by WUM,the influence of which on ISB was also analyzed.Our results showed that the ISB value varied little within a day,and the mean of daily ISB standard deviation was only 0.037 m when the observation condition was good.The signal reception was continuous,indicating a high ISB stability for one day.If extending the time series to one month,however,the ISB standard deviation calculated by constant approach,in which a constant ISB is estimated on a daily basis was about 0.1 m,and the results of adjacent days were not continuous,with no apparent pattern.Concerning the random walk approach,the obtained ISB time series also had a jump,and the conclusion was the same as that of the constant strategy.Besides,receiver types showed a strong regularity in ISB numerical situation,and the distribution of ISB values corresponding to the same receiver type was relatively close.Therefore,we conclude that the ISB parameters remain stable in the short term(one day)and less stable in the long-term period.It is recommended that the ISB term should be set as a constant estimate every day in BDS3/BDS2 solutions,regardless of receiver type consistency.
基金supported by the project of Shandong Provincial National Science Foundation for Distinguished Young Scholars(Grant No.JQ201113)SDUST's National Science Foundation for Distinguished Young Scholars(Grant No.2010KYJQ102)
文摘Vertical errors often present in multibeam swath bathymetric data. They are mainly sourced by sound refraction, internal wave disturbance, imperfect tide correction, transducer mounting, long period heave, static draft change, dynamic squat and dynamic motion residuals, etc. Although they can be partly removed or reduced by specific algorithms, the synthesized depth biases are unavoidable and sometimes have an important influence on high precise utilization of the final bathymetric data. In order to confidently identify the decimeter-level changes in seabed morphology by MBES, we must remove or weaken depth biases and improve the precision of multibeam bathymetry further. The fixed-interval profiles that are perpendicular to the vessel track are generated to adjust depth biases between swaths. We present a kind of postprocessing method to minimize the depth biases by the histogram of cumulative depth biases. The datum line in each profile can be obtained by the maximum value of histogram. The corrections of depth biases can be calculated according to the datum line. And then the quality of final bathymetry can be improved by the corrections. The method is verified by a field test.
文摘本文介绍了车载双偏振雷达参数ZDR的处理方法,首先分析了信噪比SNR对ZDR参数的影响,得出信噪比SNR至少要>18 d B,ZDR数据才可信;其次分析了雷达附近的不同类型遮挡物对ZDR参数的影响,结果表明,尖状的遮挡物容易造成ZDR正的偏差,房屋等遮挡物容易造成负偏差,而对树林等遮挡物,偏差的正负变化很大。随着遮挡程度的减小,ZDR的变化幅度变小;针对ZDR的系统误差,使用反射率因子结合ΦDP增量可以很好的进行计算,ZDR系统误差在短时间内变化不大,但是,随时间变化而逐渐变化,需要进行实时订正;最后,使用FIR滤波方法进行KDP参数计算并用于ZDR衰减订正,取得了不错的效果。针对业务应用,给出了实时处理ZDR参数的业务流程图。
文摘高压系统中直流偏磁对换流变压器和交直流输电产生巨大的危害,限流和隔直是抑制直流偏磁的主要方法,目前广泛采用的是通过中性点串联电容的方法,对电容的保护研究很少。本文利用PSCAD/EMTDC建立500 k V的高压直流输电电磁暂态仿真平台,在发生工频过电压时,对换流变压器中性点处串联电容的过电压,以及其2端保护装置火花间隙进行了仿真和分析,选择了最佳容抗值的电容器,并探究了火花间隙对中性点串联电容器的保护,结果表明:火花间隙对换流变压器中性点接地电容以及变压器中性点起到保护作用。
文摘地磁感应电流、直流输电系统接地极电流侵入电网,对电网内变压器造成直流偏磁危害,影响变压器安全、稳定运行。针对该问题,设计了一种基于通用无线分组业务(general packet radio service,GPRS)网络的变压器直流偏磁电流在线监测系统,并研制了专门用于变压器直流偏磁电流监测的装置。该设计在电气上完全切断了过电压及各种干扰的传播路径,能有效保证监测装置工作的稳定性、可靠性。
