In this paper

an efficient implementation of the topography adaptive filter based on local frequency estimation is proposed.This filter tunes its central frequency according to the local topography to preserve the tight fringes of the interferometric phase map as well as reduce the phase noise.We describe the structure and the implementation of this topography adaptive filter in detail.The 2D chirp-Z transform is applied to improve the efficiency and accuracy of the frequency estimation.X-SAR data of Mt.Etna is employed to show the effectiveness of this filter in comparison with the traditional multilook filter in term of fringe preservation.