Research on the Method of Gravity Data Edge Expanding Based on Step By Step Iterative Interpolation

In order to study the edge expanding interpolation method considering the variation characteristics of gravity anomaly, we used 1∶50000 gravity data obtained from theoretical gravity anomaly simulation for research. Through the comparison of 7 interpolation methods in surfer software, it is considered that the radial basis function method can obtain better results in data expanding. On this basis, the idea of step by step iterative interpolation is proposed and the expanding parameters are optimized as follows: ① The kernel function is multiquadric function, ② The number of sectors to research is 4, ③ The maximum number of data to use from all sectors is 64, ④ The search radius R₁/R₂=6/18, and the radius R₂ parallels to the main strike of the anomaly, ⑤ The search angle was selected when the search radius R₂ is parallels to the main strike of the anomaly, ⑥ The R² parameter is generally between 0 and 1, among them, R² parameter is selected according to the residual error comparison results of boundary points when expanding for the first time, and 0.1 parameter can be selected for other levels of expanding. In the application of actual data edge expanding of LY block in west of Yin’e basin, the “three–step method” can be used for interpolation to jointly consider the external expanding and internal interpolation parameters. The expanding results show that the gravity anomaly at the junction of the expanding area and the measured area is continuous and smooth, and the expanding area better reflects the main strike and local variation characteristics of the anomaly.