Wilcoxon Nonparametric CFAR Scheme for Ship Detection in SAR Image
This addresses the problem of reliable ship detection in SAR imagery for remote sensing applications, offering a more robust alternative to parametric methods, though it is incremental as it builds on existing nonparametric CFAR approaches.
The paper tackles ship detection in SAR images by proposing a Wilcoxon nonparametric CFAR scheme, which maintains robust false alarm performance across varied clutter backgrounds and improves detection of weak ships in rough seas, with demonstrated improvements over parametric methods on datasets like Radarsat-2 and Gaofen-3.
The parametric constant false alarm rate (CFAR) detection algorithms which are based on various statistical distributions, such as Gaussian, Gamma, Weibull, log-normal, G0 distribution, alpha-stable distribution, etc, are most widely used to detect the ship targets in SAR image at present. However, the clutter background in SAR images is complicated and variable. When the actual clutter background deviates from the assumed statistical distribution, the performance of the parametric CFAR detector will deteriorate. In addition to the parametric CFAR schemes, there is another class of nonparametric CFAR detectors which can maintain a constant false alarm rate for the target detection without the assumption of a known clutter distribution. In this work, the Wilcoxon nonparametric CFAR scheme for ship detection in SAR image is proposed and analyzed, and a closed form of the false alarm rate for the Wilcoxon nonparametric detector to determine the decision threshold is presented. By comparison with several typical parametric CFAR schemes on Radarsat-2, ICEYE-X6 and Gaofen-3 SAR images, the robustness of the Wilcoxon nonparametric detector to maintain a good false alarm performance in different detection backgrounds is revealed, and its detection performance for the weak ship in rough sea surface is improved to some extent. Moreover, the Wilcoxon nonparametric detector can suppress the false alarms resulting from the sidelobes at some degree and its detection speed is fast.