Study Of Determining The Geopotential Using The Time And Frequency Transfer Approach

The conventional approach of determining the geopotential and orthometric height is leveling with additional gravimetry.This method is limited by terrain conditions and the error is accumulated with the increase of the length of the measurement line.Ac-cording to the general theory of relativiy,the gravitational potential difference between two places can be determined by comparing the clock rate of high precision clocks,or by measuring the frequency shift of a microwave signal.With the quick development of high-precision clock manufacturing technology,currently it is possible to apply the relativity methods of gravity survey.In this paper we detailedly elaborate the basic theory,observation method and application field of the relativistic gravity survey,and the highest precision it can achieves at current stage.The main contents are listed as follows:(1)We elaborated the basic theory and formulas of the relativistic gravity sur-vey,including the time transfer method and the frenquency transfer method,and the precision of the formulas is above 10-18.(2)We put forward the methods of determining geopotential difference by cable connection,which can be achieved by frequency signals transfer in optical fibers,or by time pulse signals transfer in coaxial cables.The theoretical precision of the cable connection method can reach 10-18,and relative simulation experiments are carried out,the results show that the precision of the measurements can reach subcentimetre level.(3)According to the tri-frequency combination technique,we put forward the method of determining geopotential using satellite's frequency signal.We detailedly studied the observation equation and improved its precision to 10-18.we provided a series of error estimations and error corrections,including the innovative ionosphere cor-rection and troposphere correction.According to different characters of error sources,we designed and performed a series of simulations experiments include the gravitational potential difference dedermination between a satellite and a ground station,between two ground stations,and direct determination of the gravitational potential of a satellite or a ground station according to a given benchmark.(4)According to the method of determining geopotential using satellite's frequency signal,we proposed a method of unifying the world height datum system,and conducted a simulating experiment.(5)According to the method of determining geopotential using satellite's frequency signal,we proposed two methods to determine the gravitational potential distribution on the surface defined by a low-orbit satellite,which can be realized by ground network datum stations or by high-orbit satellites.And simulating experiments are carried to verify the methods.