Stability Analysis Of Regional CORS

Continuous Operation Reference Station System(CORS)is an important infrastructure for national and regional modern mapping reference systems and geographic frameworks.It provides users with high-precision navigation and positioning services,and plays an important role in establishing and maintaining the stability of regional coordinate reference frames.Due to the influence of crustal plate movement and ground subsidence,the position of the base stations will also change to varying degrees,and the accur,acy and reliability of the benchmark will be affected.Therefore,the analysis of the stability of regional CORS has important scientific and application value:This paper takes Hong Kong CORS as an example,to process and evaluate the original observation data,and analyze the noise characteristics of the base stations coordinates time series.The specific research contents and achievements mainly include:(1)Study the effects of VMF1,GMF,NMF tropospheric mapping functions and FES2004,NAO99b,CSR4 ocean tide models on high-precision GNSS positioning in Hong Kong.The results show that the root mean square error and baseline repetition rate of the solution using VMF1 function are lower than GMF and NMF functions,and the accuracy is higher.The influence of the tide model on the baseline has nothing to do with the length,and it is related to the position of the base stations.The influence in the horizontal direction is about 2～3mm,and the influence in the elevation direction is 2～3 times in the horizontal direction.The accuracy of the FES2004 model is slightly better than the other two kinds of models.(2)Analyzing the quality of the original observation data of the reference stations,calculating the baseline and adjusting the network,obtaining the time series of the coordinates of the stations.The results show that except for HKMW station,the multipath effect of other stations is less than 0.5,the data efficiency of all stations is more than 95%,the CSR value is less than 10,and the observation data quality is good.The repetition rates of the longest baseline and the shortest baseline are 4.4 mm and 3.6 mm,and the relative repetition rates are 1.27×10-9 and 2.23 ×10-7.Stations coordinates show obvious linear trend in N and E directions,but the rule of U direction is not obvious.(3)The maximum likelihood estimation method is used to determine the optimal noise model of base stations coordinates time series in Hong Kong as WN+FN.Based on the optimal noise model,estimating the speed and analyzing the stability of the base stations.The results show that the base stations move in the southeast direction with an average velocity of +31.72 mm/a in the east-west direction and-10.73/mm in the North-South direction.In vertical direction,the uplift rates of HKLT,HKST and HKWS are 2.81 mm/a,1.46 mm/a and 0.43 mm/a,respectively.The subsidence rates of HKOH and HKTK stations are-3.23 mm/a and-2.33 mm/a.The overall stability of reference stations is good.