Abstract: To eliminate the pervasive geometric distortion and improve the application value of SAR images,orthorectification taking topography into account must be performed to generate orthoimages in a certain map projection.This process is known as SAR geocoding.To solve the problems of traditional methods for SAR geocoding in efficiency and accuracy,here a modified 3D grid interpolation method is proposed.Experimental results with ENVISAT ASAR data show that significant improvements in geometric location accuracy can be achieved by using the modified method when compared with the original one,while the increases in computation time cost are limited.Therefore,the modified 3D grid interpolation method can be used to perform fast SAR image geocoding with high accuracy.