Research On The Refining Methods Of Gravity Anomaly

Mean gravity anomaly is the basic data for the gravity field of the Earth. It is the foundation in calculating height anomaly and disturbing gravity. It is also widely used in the spatial grid mean calculation technique, geodetic survey and geophysics and so on.A detailed investigation was made on the basic theory of the earth's exterior gravity field and the methods of establishing the gravity anomaly model. There exists impressive demand for the high precision and high resolution grid gravity anomaly model. To solve the above problems, the main work and innovative points of the author are listed as follows:1. The Toeplitz characteristic of the discrete convolution integral was used to extend it as cyclic Toeplitz matrix multiplied by the surveying vector data, and the Fourier transformation was used to express the Toeplitz matrix, and then the fast algorithm which was equivalent to the discrete convolution integral was realized.2. The method of establishing the local gravity anomaly reference field using the isostatic theory on the basis of global integral was studied. In the practical calculation, the integral includes two parts: the interior integral (such as the 30' radius) and the exterior integral (excluding the inside part), and then two parts were computed respectively. The rigorous prism integral method and the sphere discrete sum method were used to calculate the interior part, and the discrete sum method or the FFT method instead of the rigorous prism integral method were used to calculate the exterior integral. Then the results were constrained by some surveying gravity points and corrected through the special interpolation method. At last, an examination was made in some area showing that the precision is about±4.46mgal using this method.3. The technique of calculating the land gravity anomaly using the inverse Vening-Meinesz formula was studied, and then a remove-restore method was put forward using terrain information, the isostatic compensation theory and EGM96 to calculate the land gravity anomaly. Then the results were also corrected by some surveying gravity values and the interpolation method was used to get the final results. At last, an examination was made in some area showing that the precision is about±2.40mgaI using the method.