直接读入实测数据，以grd网格化格式，然后给定延拓高度，利用了快速傅里叶变换，快速得到延拓后的grd数据，直接用surfer画图即可。(Directly read the measured data, GRD grid format, and then given the height of the extension, the use of fast Fourier transform, quickly obtained after the extension of the GRD data,