Elements and Experiments of Shenzhen Continuous Operating Reference Stations (SZCORS) System

Real-time kinematic GPS precise positioning has been playing an increasing role in both surveying and navigation. Based on the city’s fibre LAN network, Shenzhen Continuous Operating Reference Stations (SZCORS) system has been established and consists of GPS reference stations, system control center, user’s data center, and real-time datacom network. The SZCORS system provides users the real-time centimeter positioning or post-processing millimeter positioning. This paper makes discussion on the structure of SZCORS system. Some experiments have been made to test the usablity, and then the data has been analyzed.

Accurate time synchronization of power reference station based on BD3 system

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.

Stability analysis of reference station and compensation for monitoring stations in GNSS landslide monitoring

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.

Measurement of the sea surface using a GPS towing-body in Wanshan area

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.

Quasi-real time inversion method of three-dimensional epicenter coordinate, trigger time, and magnitude based on CORS

This study explores the quasi-real time inversion principle and precision estimation of three-dimensional coordinates of the epicenter, trigger time and magnitude of earthquakes with the aim to improve traditional methods, which are flawed due to missing information or distortion in the seismograph records. The epicenter, trigger time and magnitude from the Lushan earthquake are inverted and analyzed based on high-frequency GNSS data. The inversion results achieved a high precision, which are consistent with the data published by the China Earthquake Administration. Moreover, it has been proven that the inversion method has good theoretical value and excellent application prospects.

Analysis of Anomalous Characteristics of Regional Crustal Deformation before the September 16^th,2019 Zhangye MS5.0 Earthquake,Gansu,China

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.

Analysis of Abnormal Characteristics of Regional Crustal Deformation before the Menyuan MS6.4 Earthquake by GPS Continuous Data

In order to study the characteristics of crustal deformation around the epicenter before the 2016 M_S6. 4 Menyuan earthquake,the GPS continuous stations of the period from 2010 to 2016 were selected according to the observation data of the tectonic environment monitoring network in Chinese Mainland. The deformation characteristics of the crust before the earthquake were discussed through inter-station baseline time series analysis and the strain time series analysis in the epicentral region. The results show that a trend turn of the baseline movement state around the epicenter region occurred after 2014,and the movement after 2014 reflects an obvious decreasing trend of compressional deformation.During this period,the stress field energy was in a certain accumulation state. Since the beginning of 2014,the EW-component linear strain and surface strain rate weakened gradually before the earthquake. It shows that there was an obvious deformation deficit at the epicentral area in the past two years,which indicates that the region accumulated a high degree of strain energy before the earthquake. Therefore,there was a significant background change in the area before the earthquake. The results of the study can provide basic research data for understanding the seismogenic process and mechanism of this earthquake.

Application Study of Climatic Feasibility Demonstration of Airport Project Site Selection

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.

台风期间GNSS-PWV与降雨量的相关性探究——以上海市为例

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。

WSL下基于GAMIT的高精度GPS/BDS基线解算及精度分析

在Windows下的Linux子系统(Windows subsystem for Linux,WSL)下,利用GAMIT 10.70对珠海市北斗连续运行基准站(Zhuhai BeiDou continuously operating reference station,ZHBDCORS)系统的观测数据进行高精度全球定位系统/北斗卫星导航系统(global positioning system/BeiDou navigation satellite system,GPS/BDS)基线解算,从归一化均方根(normalized root mean square,NRMS)值、基线较差、基线重复性等方面对解算成果进行对比分析。结果表明:GPS/BDS基线解NRMS值均在0.2左右,且BDS略优于GPS;GPS/BDS基线较差在各个基线分量上均在合理范围内,基线的长度加权平均值较差满足B级网重复基线长度较差限差要求,证明GPS/BDS的GAMIT基线解算结果具有较强的一致性;GPS在各个基线分量上的基线重复性均优于BDS,垂直方向上GPS优势更大,但BDS仍满足高精度全球导航卫星系统(global navigation satellite system,GNSS)数据处理要求。

Improving the initialization speed for long-range NRTK in network solution mode

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.

手持农田面积测量终端研制

设计开发了一种支持多种GPS定位方式的手持嵌入式一体化农田作业面积测量终端,并针对地块面积、地块形状、GPS定位方式3个影响农田面积测量精度的因素进行了实验。结果表明:面积测量精度随地块面积增大而提高;不同形状的地块中,方形地块的面积测量精度最高,不规则地块面积测量精度的次之,条形地块的面积测量精度最差;当被测地块面积大于等于5 000 m^(2)时,任何GPS定位方式测量误差均小于3%,当被测地块在2 500 m^(2)左右时,GPS差分方式下的测量误差小于5%,可以满足实际应用要求。

ZHBDCORS Multi-GNSS数据质量分析

在北斗导航卫星系统(BeiDou navigation satellite system,BDS)迈进全球服务之际,对珠海市北斗连续运行基准站(Zhuhai BeiDou continuously operating reference station,ZHBDCORS)系统2014年以来积累的全球导航卫星系统(global navigation satellite system,GNSS)连续观测数据进行质量检核,分析其质量变化原因,评估系统的BDS支持度。结果表明,ZHBDCORS站点接收机及解算软件均不可跟踪BDS-3信号,且未完全跟踪BDS-3卫星播发的BDS-2信号;部分基准站受观测环境影响,数据完整性差,多路径误差明显,应考虑迁站升级;同等观测条件下,BDS呈现更强的抗遮挡能力。