Research on method of flat earth effect removal based on refined local fringe frequency

As is well known, interferometric synthetic aperture radar (InSAR) has been widely used in remote sensing field, which can reflect actual topographic trend or surface deformation. The precision of interferometric phase is crucial to the final measurement. Due to the orbit attitude influence, the flat-earth phase usually causes the interferogram dense and difficult to be used in further procedures. So before phase unwrapping, interferogram must be flattened accurately. Nevertheless, some flat-earth phase is still left in the flattened interferogram with the traditional methods. In this paper, two refined algorithms of flat earth effect removal are proposed which are based on precise local fringe frequency. They are respectively the algorithm of Fast Fourier Transform (FFT) and cubic spline interpolation as well as that of FFT and Chirp-Z transform (CZT). Finally, both simulated and actual data are presented to validate the feasibility and practicality of the refined flattening algorithms proposed in this paper.