  Synthetic aperture radar (SAR) is considered being a good option for earth
observation with its unique advantages. In this paper, we proposed an adaptive
ship detector using full-polarization SAR images. First, by thoroughly
investigating the scattering characteristics between ships and their
background, and the wave polarization anisotropy, a novel ship detector is
proposed by jointing the two characteristics, named Scattering-Anisotropy joint
(joint-SA). Based on the theoretical analysis, we showed that the joint-SA is
an effective physical quantity to show the difference between the ship and its
background, and thus joint-SA can be used for ship detection of
full-polarization image data. Second, the generalized Gamma distribution was
used to characterize the joint-SA statistics of sea clutter with a large range
of homogeneity. As a result, an adaptive constant false alarm rate (CFAR)
method was implemented based on the joint-SA. Finally, RADARSAT-2 and GF-3 data
in C-band and ALOS data in L-band are used for verification. We tested on five
datasets, and the experimental results verify the correctness and superiority
of the constant false alarm rate (CFAR) method based on the joint-SA. In
addition, the experimental results also showed that the signal-clutter ratio
(SCR) of the proposed ship detector joint-SA (33.17 dB, 35.98 dB, 57.25 dB) is
better than that of DBSP (8.92 dB, 3.43 dB, 25.40 dB) and RsDVH (17.28 dB,
11.17 dB, 54.55 dB). More importantly, the proposed detector joint-SA has
higher detection accuracy and a lower false alarm rate.
