A Beidou 3(BD3)system-based power reference station can provide high-precision time synchronization for power distribution systems by sending synchronization data packets to devices in a multi-hop routing fashion.Howe...A Beidou 3(BD3)system-based power reference station can provide high-precision time synchronization for power distribution systems by sending synchronization data packets to devices in a multi-hop routing fashion.However,optimizing route selection to reduce both time synchronization error and delay is a challenging problem.In this paper,we establish a software-defined network-enabled power reference station time synchronization framework based on BD3.Then,we formulate the joint problem to minimize cumulative synchronization error and delay through multi-hop route selection optimization.A back propagation(BP)neural network-improved intelligent time synchronization route selection algorithm named BP-RS is proposed to learn the optimal route selection,which uses a BP neural network to dynamically adjust the exploration factor to achieve rapid convergence.Simulation results show the superior performance of BP-RS in synchronization delay,synchronization error,and adaptability with changing routing topologies.展开更多
The Real-Time Kinematic(RTK)positioning method of the Global Navigation Satellite System(GNSS)has been widely used for landslide monitoring.The stability of its reference station is crucial to obtain accurate and reli...The Real-Time Kinematic(RTK)positioning method of the Global Navigation Satellite System(GNSS)has been widely used for landslide monitoring.The stability of its reference station is crucial to obtain accurate and reliable monitoring results.Unstable reference stations due to the geological environment and human activities are difficult to detect and in practical applications often ignored.As a result,it affects the positioning solutions and subsequently the interpretation and detection of landslide motions,which must be addressed in GNSS landslide monitoring.To solve this problem,we propose using the Precise Point Positioning(PPP)technique to analyze the stability of the reference station by verifying its position.The deformations of the monitoring stations are then compensated.First,the reference station coordinates are obtained by the PPP technique and tectonic motion is considered in data processing.The change or breakout of the reference station position is then determined using a cumulative sum control chart method.Finally,each monitoring station’s displacements are compensated according to the displacements of the reference station.According to the results of the Tengqing landslide experiment,the PPP technique can be used in GNSS landslide monitoring to analyze the stability of reference stations.With PPP,millimeter-level accuracy for the coordinates of reference stations is achieved.Compared to the traditional deformation series,the compensated displacement series more reliably reflects the landslide motions.This study will increase the reliability of monitoring results and contribute to implementing GNSS in monitoring landslides.展开更多
To study the crustal movement in the vicinity of the epicenter before the Zhangye MS5.0 earthquake in 2019, the characteristics of crustal deformation before the earthquake are discussed through the GPS velocity field...To study the crustal movement in the vicinity of the epicenter before the Zhangye MS5.0 earthquake in 2019, the characteristics of crustal deformation before the earthquake are discussed through the GPS velocity field analysis based on the CMONOC data observed from GPS. The baseline time series between two continuous GPS stations and the strain time series of an area among several stations are analyzed in the epicenter area. The resulting time series of baseline azimuth around the epicenter reflects that the energy of the fault in the northern margin of Qilian Mountain is accumulated continuously before 2017. Besides,the movement trend of azimuth slows down after 2017,indicating the stress accumulation on both sides of the seismogenic fault zone has reached a certain degree. The first shear strain and EWdirection linear strain in the epicentral area of the Zhangye MS5.0 earthquake remain steady after 2017,and the surface strain rate decreases gradually after 2016. It is illustrated that there is an obvious deformation loss at the epicentral region three years before the earthquake,indicating that a certain degree of strain energy is accumulated in this area before the earthquake.展开更多
Wanshan area has been chosen to be the specified field to calibrate and validate(Cal/Val)the HY-2 altimeter and its follow-on satellites.In March 2018,an experiment has been conducted to determine the sea surface heig...Wanshan area has been chosen to be the specified field to calibrate and validate(Cal/Val)the HY-2 altimeter and its follow-on satellites.In March 2018,an experiment has been conducted to determine the sea surface height(SSH)under the HY-2 A ground track(Pass No.203).A GPS towing-body(GPS-TB)was designed to measure the SSH covering an area of about 6 km×28 km wide centered on the HY-2 A altimeter satellite ground track.Three GPS reference stations,one tide gauge and a GPS buoy were placed in the research area,in order to process and resolve the kinematic solution and check the precision of the GPS-TB respectively.All the GPS data were calculated by the GAMIT/GLOBK software and TRACK module.The sea surface was determined by the GPS-TB solution and the tide gauge placed on Zhiwan Island.Then the sea surface of this area was interpolated by Arc GIS10.2 with ordinary Kriging method.The results showed that the precision of the GPS-TB is about 1.10 cm compared with the tide gauge placed nearby,which has an equivalent precision with the GPS buoy.The interpolated sea surface has a bias of–1.5–4.0 cm with standard deviation of 0.2–2.4 cm compared with the checking line.The gradient of the measured sea surface is about 1.62 cm/km along the HY-2 orbit which shows a good agreement compared with the CLS11 mean sea surface(MSS).In the Cal/Val of satellites,the sea surface between the tide gauge/GPS buoy and the footprint of altimeter can be improved by this work.展开更多
According to the Technical Guide for Climatic Feasibility Demonstration of Airport Project Site Selection,via statistical analysis on historical climate data of reference weather station,climatic background characteri...According to the Technical Guide for Climatic Feasibility Demonstration of Airport Project Site Selection,via statistical analysis on historical climate data of reference weather station,climatic background characteristics and meteorological disaster situation of preselected site,and characteristics of seasonal distribution,interannual variation and long-term trend of main meteorological elements and disasters were summarized.The difference of meteorological elements between preselected site and reference weather station and its cause were analyzed,and fine analysis of fog,low visibility event,wind,cloud and other meteorological elements or weather with high influence in preselected site was conducted.Climatic feasibility,advantages and disadvantages of meteorological conditions and possible meteorological risks in preselected site were evaluated.The research could provide decision-making basis for site selection of Lingling Airport and airport engineering design.Moreover,key technology route and research results were extracted,and technical analysis process of demonstration report was integrated,which could provide reference for climate feasibility demonstration on site selection of similar airports in China.展开更多
基于上海市连续运行基准站(continuously operating reference station,CORS)系统中10个基准站2021-09-10—2021-09-14的观测数据,采用实时精密单点定位(precise point positioning,PPP)技术反演大气可降水量(precipitable water vapor,...基于上海市连续运行基准站(continuously operating reference station,CORS)系统中10个基准站2021-09-10—2021-09-14的观测数据,采用实时精密单点定位(precise point positioning,PPP)技术反演大气可降水量(precipitable water vapor,PWV),探究了台风“灿都”期间PWV与实际降雨量的时空交互特征。结果表明,PWV含量与降雨量显著相关,即PWV在降雨发生前激增,降雨期间保持稳定,降雨完成后回落至原水平。此外,PWV的空间演变还可揭示台风影响期间的水汽输送路径。上述特征证明,实时PWV有预警极端降雨的潜力,未来可在CORS系统部署降雨预警模块,进一步拓宽其服务领域。展开更多
Initialization speed is one of the most important factors in network real time kinematic(NRTK)performance.Owing to the low correlation among the error sources of reference stations,it is difficult to fix reference sta...Initialization speed is one of the most important factors in network real time kinematic(NRTK)performance.Owing to the low correlation among the error sources of reference stations,it is difficult to fix reference station ambiguities of long-range NRTK quickly.In traditional reference stations ambiguity resolution(AR)methods,baselines are usually solved independently which is called baseline solution(BS)mode in this study.Because the correlations among baselines are not taken into consideration in ambiguities estimation,the AR speed is slow.Generally,tens of minutes or longer time is required to initialize.We propose a network solution(NS)mode approach,in which the correlations among the double-difference ambiguities(DDAs)as well as double-difference ionospheric delays(DDIDs)of different baselines are considered in estimating float ambiguity solutions.Experimental results show that the float ambiguity solutions obtained are more accurate with an improved consistency.Thus,initialization speed is significantly increased by 18%in NS mode.展开更多
基金supported by the Science and Technology Project of the China Southern Power Grid Company Limited under grant number GDKJXM20202032。
文摘A Beidou 3(BD3)system-based power reference station can provide high-precision time synchronization for power distribution systems by sending synchronization data packets to devices in a multi-hop routing fashion.However,optimizing route selection to reduce both time synchronization error and delay is a challenging problem.In this paper,we establish a software-defined network-enabled power reference station time synchronization framework based on BD3.Then,we formulate the joint problem to minimize cumulative synchronization error and delay through multi-hop route selection optimization.A back propagation(BP)neural network-improved intelligent time synchronization route selection algorithm named BP-RS is proposed to learn the optimal route selection,which uses a BP neural network to dynamically adjust the exploration factor to achieve rapid convergence.Simulation results show the superior performance of BP-RS in synchronization delay,synchronization error,and adaptability with changing routing topologies.
基金This work was funded by the National Natural Science Foundation of China(41941019,42090053,and 42127802)the Key R&D Program of Shaanxi Province(2022ZDLSF07-12)the Fundamental Research Funds for the Central Universities of CHD(300102263401).
文摘The Real-Time Kinematic(RTK)positioning method of the Global Navigation Satellite System(GNSS)has been widely used for landslide monitoring.The stability of its reference station is crucial to obtain accurate and reliable monitoring results.Unstable reference stations due to the geological environment and human activities are difficult to detect and in practical applications often ignored.As a result,it affects the positioning solutions and subsequently the interpretation and detection of landslide motions,which must be addressed in GNSS landslide monitoring.To solve this problem,we propose using the Precise Point Positioning(PPP)technique to analyze the stability of the reference station by verifying its position.The deformations of the monitoring stations are then compensated.First,the reference station coordinates are obtained by the PPP technique and tectonic motion is considered in data processing.The change or breakout of the reference station position is then determined using a cumulative sum control chart method.Finally,each monitoring station’s displacements are compensated according to the displacements of the reference station.According to the results of the Tengqing landslide experiment,the PPP technique can be used in GNSS landslide monitoring to analyze the stability of reference stations.With PPP,millimeter-level accuracy for the coordinates of reference stations is achieved.Compared to the traditional deformation series,the compensated displacement series more reliably reflects the landslide motions.This study will increase the reliability of monitoring results and contribute to implementing GNSS in monitoring landslides.
基金sponsored by the Fund of Science for Earthquake Resilience(XH21035Y,XH20057)the Earthquake Tracking Track of CEA(2020010211,2018010204)+1 种基金the Earthquake Science and Technology Development Fund of CEA(2016M02,2017IESLZ07)National Natural Science Foundation of China(51478444,41304048)。
文摘To study the crustal movement in the vicinity of the epicenter before the Zhangye MS5.0 earthquake in 2019, the characteristics of crustal deformation before the earthquake are discussed through the GPS velocity field analysis based on the CMONOC data observed from GPS. The baseline time series between two continuous GPS stations and the strain time series of an area among several stations are analyzed in the epicenter area. The resulting time series of baseline azimuth around the epicenter reflects that the energy of the fault in the northern margin of Qilian Mountain is accumulated continuously before 2017. Besides,the movement trend of azimuth slows down after 2017,indicating the stress accumulation on both sides of the seismogenic fault zone has reached a certain degree. The first shear strain and EWdirection linear strain in the epicentral area of the Zhangye MS5.0 earthquake remain steady after 2017,and the surface strain rate decreases gradually after 2016. It is illustrated that there is an obvious deformation loss at the epicentral region three years before the earthquake,indicating that a certain degree of strain energy is accumulated in this area before the earthquake.
基金The National Key R&D Program of China under contract No.2018YFB0504900the National Natural Science Foundation of China under contract Nos 41406204 and 41501417Operational Support Service System For Natural Resources Satellite Remote Sensing。
文摘Wanshan area has been chosen to be the specified field to calibrate and validate(Cal/Val)the HY-2 altimeter and its follow-on satellites.In March 2018,an experiment has been conducted to determine the sea surface height(SSH)under the HY-2 A ground track(Pass No.203).A GPS towing-body(GPS-TB)was designed to measure the SSH covering an area of about 6 km×28 km wide centered on the HY-2 A altimeter satellite ground track.Three GPS reference stations,one tide gauge and a GPS buoy were placed in the research area,in order to process and resolve the kinematic solution and check the precision of the GPS-TB respectively.All the GPS data were calculated by the GAMIT/GLOBK software and TRACK module.The sea surface was determined by the GPS-TB solution and the tide gauge placed on Zhiwan Island.Then the sea surface of this area was interpolated by Arc GIS10.2 with ordinary Kriging method.The results showed that the precision of the GPS-TB is about 1.10 cm compared with the tide gauge placed nearby,which has an equivalent precision with the GPS buoy.The interpolated sea surface has a bias of–1.5–4.0 cm with standard deviation of 0.2–2.4 cm compared with the checking line.The gradient of the measured sea surface is about 1.62 cm/km along the HY-2 orbit which shows a good agreement compared with the CLS11 mean sea surface(MSS).In the Cal/Val of satellites,the sea surface between the tide gauge/GPS buoy and the footprint of altimeter can be improved by this work.
文摘According to the Technical Guide for Climatic Feasibility Demonstration of Airport Project Site Selection,via statistical analysis on historical climate data of reference weather station,climatic background characteristics and meteorological disaster situation of preselected site,and characteristics of seasonal distribution,interannual variation and long-term trend of main meteorological elements and disasters were summarized.The difference of meteorological elements between preselected site and reference weather station and its cause were analyzed,and fine analysis of fog,low visibility event,wind,cloud and other meteorological elements or weather with high influence in preselected site was conducted.Climatic feasibility,advantages and disadvantages of meteorological conditions and possible meteorological risks in preselected site were evaluated.The research could provide decision-making basis for site selection of Lingling Airport and airport engineering design.Moreover,key technology route and research results were extracted,and technical analysis process of demonstration report was integrated,which could provide reference for climate feasibility demonstration on site selection of similar airports in China.
文摘基于上海市连续运行基准站(continuously operating reference station,CORS)系统中10个基准站2021-09-10—2021-09-14的观测数据,采用实时精密单点定位(precise point positioning,PPP)技术反演大气可降水量(precipitable water vapor,PWV),探究了台风“灿都”期间PWV与实际降雨量的时空交互特征。结果表明,PWV含量与降雨量显著相关,即PWV在降雨发生前激增,降雨期间保持稳定,降雨完成后回落至原水平。此外,PWV的空间演变还可揭示台风影响期间的水汽输送路径。上述特征证明,实时PWV有预警极端降雨的潜力,未来可在CORS系统部署降雨预警模块,进一步拓宽其服务领域。
基金supported in part by the National Key Research and Development Program of China(Grant No.2016YFB0800401)in part by the National Natural Science Foundation of China(Grant Nos.61621003,61532020&11472290).
文摘Initialization speed is one of the most important factors in network real time kinematic(NRTK)performance.Owing to the low correlation among the error sources of reference stations,it is difficult to fix reference station ambiguities of long-range NRTK quickly.In traditional reference stations ambiguity resolution(AR)methods,baselines are usually solved independently which is called baseline solution(BS)mode in this study.Because the correlations among baselines are not taken into consideration in ambiguities estimation,the AR speed is slow.Generally,tens of minutes or longer time is required to initialize.We propose a network solution(NS)mode approach,in which the correlations among the double-difference ambiguities(DDAs)as well as double-difference ionospheric delays(DDIDs)of different baselines are considered in estimating float ambiguity solutions.Experimental results show that the float ambiguity solutions obtained are more accurate with an improved consistency.Thus,initialization speed is significantly increased by 18%in NS mode.
