An Azimuth Ambiguity Identification Method for Ship Detection in Multilook PolSAR Imagery

Azimuth ambiguity is a common issue in polarimetric synthetic aperture radar (PolSAR) imagery, particularly on calm and windless maritime surfaces, which causes numerous false alarms in ship detection. Numerous methods have been applied in single look complex (SLC) PolSAR imagery to suppress ambiguities. Nevertheless, identifying and removing azimuth ambiguities in multilook complex (MLC) PolSAR imagery remains an open problem. This letter proposes an azimuth ambiguity identification method for ship detection in multilook PolSAR imagery. The process is divided into two steps: potential target detection and ambiguity identification. First, the four-component scattering model (Y4O) proposed by Yamaguchi is utilized to decompose the multilook PolSAR image into four dominant scattering categories. Then, the constant false alarm rate (CFAR) detection is conducted based on the total scattering power to detect all potential targets. Azimuth ambiguities are identified according to the correlation coefficient between the measured and standard scattering power vectors. Eventually, the detection map is formed by removing azimuth ambiguities from the CFAR detection result. The proposed method is validated on RadarSAT-2 and Airborne SAR (AIRSAR) images.