Analysis Of Influence Of Tide Load On Accuracy Of GPS Observation Data In Shanghai

In recent years,GPS technology has become the most widely used navigation and positioning system.Due to its all-weather,continuous,global coverage and high precision,it has become the main technical means to observe the crustal changes.However,using GPS technology to observe crustal changes is susceptible to environmental,tidal,noise and other factors,affecting the accuracy of observation data.The Shanghai area is close to the East China Sea and is susceptible to ocean tides.According to previous studies,coastal areas are greatly affected by sea tides,and some of them have reached the order of centimeter in vertical deformation under the influence of sea tides.Based on the above problems,this paper uses the global ocean tide model and the East China Sea tide model to analyze the GPS observation data in the Shanghai CORS network for the first time.And revised the global tide model to get a composite model.Then analyze the crustal displacement of the Shanghai crust in 2013-2015 under the composite model.The specific research contents and research results are as follows:(1)Using GPS pre-processing software TEQC to format and quality the data of Shanghai CORS station.Then using GAMIT/GLOBK10.60 software to solve the data of Chongming Station(DCMD),Baoshan Station(SHBS),Jinshan Station(SHJS)and Shaoshan Station(SHAO)and to obtain the time series of each site.The results show that the observation data of the four stations in Shanghai area are of good quality and the solution results are in line with the standard.(2)Using the global tide model FES2004 and NAO99b to calculate the difference in horizontal and vertical components of the ocean tide load displacement generated byS₂?M₂?K₁?O₁ four tidal waves in Shanghai.The results show that there are obvious differences between the two models in Shanghai,and the difference decreases with increasing distance from the ocean.The difference of the horizontal components in the four tidal waves does not exceed 1 mm,and the maximum difference of the vertical components is 4 mm.(3)Due to the complexity of the coastline of the East China Sea and the seabed topography,the accuracy of the global tide model may be reduced in Shanghai.In response to this problem,based on the Farrell theory,this paper uses the Chinese East China Sea tide model osu.chinasea.2010 to modify the East China Sea region in the FES2004 global tide model to obtain a composite model,and use it to calculate the displacement generated by the tide.The experimental results show that the displacement accuracy calculated by the composite model is significantly improved,and the influence of the tidal effect of the East China Sea on the GPS observation data in Shanghai is up to 5 mm.The influences on the vertical components of the four stations are DCMD station(5.1mm),SHBS station(4.9mm),SHJS(4.2mm),and SHAO(3.6mm).(4)Using the least squares method to analyze the movement trends of Chongming Station(DCMD),Baoshan Station(SHBS)and Jinshan Station(SHJS)under the influence of ocean tide load.The experimental data show that the three stations have a linear trend of moving eastward and southward.The cumulative movement in the east-west direction is 100mm in three years,and the cumulative movement in the north-south direction is 60mm.The vertical component fluctuates cyclically with a maximum amplitude of 20mm.The peaks of the anniversary of the three stations in the elevation direction are mainly on April 1 and July 1.The peaks of the half-anniversary are concentrated around May 15 and November 15,and the tides fluctuate greatly from 2013 to 2015.The August 15th tide occurred on September 19th,September 8th and September 27th.Combined with data analysis,the ocean tide load is not only the only influencing factor of the cyclical fluctuation of GPS time series,but also other influencing factors,such as periodic rainfall.(5)Using the power spectrum analysis method and the maximum likelihood estimation method from the frequency domain and the time domain to analyze the noise characteristics in the GPS observation data in Shanghai.The experimental results show that the GPS station in Shanghai not only includes white noise,but also flicker noise.If the existence of flicker noise is neglected,the speed estimation and error of the GPS station will be reduced,and the error is about 4?8 times.The Shanghai area is adjacent to the East China Sea.The GPS observation data is affected by the tides in the East China Sea.The maximum displacement of the vertical component is 5mm,and the horizontal component displacement is about 1mm.Under the influence of the tides in the East China Sea,the Shanghai GPS station has a horizontal displacement of 60 to 100 mm and a vertical fluctuation of 20 mm for three years.The overall trend is eastward and southward.The research data in this paper provides a reference for the analysis of crustal movement in Shanghai.