A Slope Adaptive Filtering Method for Multi-frequency InSAR

The noise in the interferogram directly affects the accuracy and speed of phase unwrapping. Therefore, interferometric phase filtering is performed to suppress phase noise, thereby reducing difficulty on subsequent phase unwrapping. The slope adaptive filtering is widely applied because of its ability to maintain interferometric fringes well. But the ability of existing slope adaptive filtering methods are limited because a smaller window have to be used for fringe estimation in dense fringe areas. In this paper, a multi-frequency slope adaptive filtering method is proposed to enlarge the filter window size in dense fringe. It converts the low-frequency interferometric phase to the high-frequency reference terrain phase, uses a larger window to perform noise suppression on the residual phase after removing the reference terrain phase from high-frequency phase. So a better noise suppression effect is obtained in dense fringe area. Experimental results with simulated and real data demonstrate the effectiveness of the proposed method.