| Under the action of internal and external forces on the earth's surface,the phenomena such as uplift,depression,tilt,misalignment,etc.and their corresponding changes generally include two aspects.One is the deformation of the earth's internal strata caused by changes in the internal mass of the earth,Or the movement of the crustal plates;the second is the impact of the earth's external conditions on the earth itself,such as the atmosphere surrounded by the earth's surface,the glaciers and snow at high altitudes,the soil water at different depths of the ground,a large number of water bodies and other factors.Non-structural load deformation.With the continuous development of modern geodetic technology and the gradual improvement of theoretical methods,many scholars' studies on the impact of load have shown that the impact of the surface load caused by atmospheric pressure on the earth's gravity field cannot be ignored.This paper takes part of the area as the research area,uses GNSS data,uses periodic reconstruction and other methods to calculate the linear change trend of the site height in the area,and analyzes the changes in the characteristics of each site.Using atmospheric data,using load theory methods,calculated high-precision atmospheric load gravity change point values in the region,and analyzed the relationship and characteristics of atmospheric pressure and gravity changes.Using the Kriging interpolation method,the grid value of the gravity change and its regional change map are obtained,and the characteristics of the maximum value present in the specific area are analyzed.Using the ground height of the GNSS site and the value of the regional gravity change point,the connection and difference between the two are analyzed.The research results of this thesis show that:(1)The change trend of GSGL site's earth height is more obvious than that of other sites,while the change trend of GSML site is the most gentle.The linear change rates of the two are1.26 mm/a and-0.28 mm/a,respectively,and the standard deviations of the periodic reconstruction of the two are 5.24 mm and-0.38 mm,respectively.The peak fluctuations of the GSGL site in 2014,2015 and 2016 were 12.23 mm,8.23 mm and 10.10 mm respectively,and the time of appearance was also different.The largest annual changes in GSGL station,GSGT station and GSML station occurred in 2014.(2)The change trend of the geodetic height of the GNSS site after periodic reconstruction has obvious seasonal characteristics.That is,it increases in spring and summer,and decreases in autumn and winter.Except for the large difference in the time when the characteristic value of the GSGL station appears,the geodetic heights of the GSGT station,GSML station and GSMQ station all have a peak around June each year,and a valley around December.(3)The regional difference of atmospheric load gravity changes is large.Among them,the northeastern region represented by Minqin County and its surrounding areas showed the maximum value,and the northwest region represented by Zhangye showed the minimum value.This regional difference remained basically unchanged in the 6-year time span.While there are differences,the seasonal cycle characteristics are also more obvious,that is,spring and summer show an increasing trend while autumn and winter show a decreasing trend.After further statistics,the results show that the mean values of gravity changes at the 4 stations are: 2.75 u Gal,3.46 u Gal,3.10 u Gal and 3.58 u Gal,respectively.(4)The monthly change of the GNSS site's earth height is positively correlated with the change of atmospheric load gravity.The reflection of this relationship on the GSGL site is slightly different: this site has a negative relationship from June 2014 to mid-December 2017.While GSGT station,GSML station and GSMQ station have a positive correlation,they also show a certain period of lag.Among them,the high peak of the earth at the GSGT station lags behind the change of gravity by one month,and the GSML station and GSMQ station also have a lagging phenomenon in 2013 and 2016. |
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