Thresholding of Polarimetric SAR Images of Coastal Zones Based on Three-Component Decomposition and Likelihood Ratio

To address the problem of threshold segmentation of polarimetric images in coastal zones when the intensity is not bimodal under complex coastal environments, a thresholding method based on three-component decomposition and likelihood ratio is proposed in this letter. First, the double-bounce and volume scattering powers are extracted by three-component decomposition. Then, a three-step thresholding diagram is carried out in the two scattering powers. The threshold base point is determined by sampling a typical window region with the minimum or maximum average power and variance first. The threshold interval is then determined by adding or subtracting a fluctuation range from the base point. The threshold point with the maximum likelihood ratio is then searched within the interval. The final two-region or three-region segmentations of coastal images are carried out by segmenting the volume scattering power to obtain the low scattering region and segmenting the double-bounce scattering power to obtain the strong scattering region. The experimental results of RADARSAT-2 Singapore, AirSAR San Francisco, as well as TerraSAR-X Singapore data demonstrate that the proposed method outperforms the traditional thresholding method. It effectively reduces the wrong segmentation in complex coastal scenes, showcasing an average segmentation precision exceeding 85% and an average intersection over union (IoU) rate closing to 0.75. The code is available at
https://github.com/polSAR-lab/polSAR-thresholding
.