Theory And Methods Of The Earth's Gravity Field Recovery From GOCE Data

The earth's gravity field is always one of a hot study of modern geodesy research and discussion.Nowadays,the satellite gravity gradiometer?SGG?is considered to be one of the most effective ways to restore the earth's gravity field in the word.The recovery of earth gravity field models with high accuracy and high resolution cannot be separated from high-quality gravity gradient data and related calculation models.On basis of tracking the latest GOCE gravity field model released by ESA,the GOCE gravity gradient measurement that are the relevant technology of reference system?time,coordinate?,data preprocessing,the calculation model of restoring gravity field and the application of GOCE gravity field model in high speed railway were systematically studied by combing with the latest research results of GOCE satellite research.The main research work and conclusions of this paper are concluded as follows:1.The research status of gravity gradient measurement both at home and abroad was summarized,and problems existing in the current GOCE gravity field model and its application were also analyzed.2.The expression of the gradient tensor and the singularity formula of Legendre function were derived,and at the same time,the basic principle of the satellite gravity gradient measurement was also introduced.3.In order to discuss the related problems of satellite gravity gradient data preprocessing,the paper briefly introduced the content of the GOCE satellite scientific task plan.Then,this paper discussed the characteristics of the gradient measurement error and the influences of the incident gravity field on the GOCE gravity gradient measurement,and discussed the practicability of the gross error detection.4.After analyzing various methods of recovering the gravity field model,the paper focused on the variance covariance function and the selection of the signal and error weights in gradient data grid by making use of the least squares collocation method.Furthermore,the accuracy of the gravity field model was also explored by the order variance and the external checking method.The computation results indicated that the accuracy of GO_CONS_GCF_2DIR_R4 model and GO_CONS_GCF_2DIR_R5 model of direct solution was obviously higher than that that of the first three generations.In the time-wise method,the GO_CONS_GCF_2TIM_R4 model and GO_CONS_GCF_2TIM_R5 model's accuracy was equal,which were all one order of magnitude higher than that of the first three generations.In the space-wise,the accuracy of GO_CONS_GCF_2SPW_R4 model was the lowest,and the other precision was the same.The accuracy of EIGEN-6C4 model was equivalent to that of the EIGEN-6C2.For the same period,the highest accuracy was the direct solution model,followed by the time-time solution model,and the space-wise solution was the lowest among the three models.5.On basis of model and precision validation by GPS leveling and gravity anomaly data,the application of GOCE gravity field model in high speed railway engineering was discussed.In this paper,the innovative points were summarized as follows:1.Gridding gradient of gravity applied least squares collocation method,the selection method of variance-covariance function was analyzed,and the least square solution equation of least squares collocation method under Tikhonov condition was derived,and the selection of signal to noise ratio was also discussed.2.The five generation gravity field model?direct method,time domain method and space domain method?issued by ESA was compared and analyzed the vertical and horizontal accuracy for the first time,and the internal and external accuracy was discussed.The advantages and disadvantages of each generation of solutions were given in order to facilitate practical application.3.The GOCE gravity field model was verified by the aid of GPS leveling and gravity anomaly data.The accuracy of the model increased with the growth of the order of the GOCE gravity field model.4.Based on the field model and accuracy verification,the application of GOCE gravity field model in high-speed railway engineering was preliminarily discussed.In light of the studies in this paper,we hope to provide help for satellite gravity measurement in data preprocessing and gravity field modeling in future.