Study on Ship Detection Using SAR Dual-polarization Data:ENVISAT ASAR AP Mode

Abstract

Preliminary results are reported on ship detection using coherence images computed fromcross-correlating images of multi-look-processed dual-polarization data (HH and HV) of ENVISAT ASAR.The traditional techniques of ship detection by radars such as CFAR (Constant False Alarm Rate) rely on theamplitude data, and therefore the detection tends to become difficult when the amplitudes of ships imagesare at similar level as the mean amplitude of surrounding sea clutter. The proposed method utilizes theproperty that the multi-look images of ships are correlated with each other. Because the inter-look imagesof sea surface are covered by uncorrelated speckle, cross-correlation of multi-look images yields the differentdegrees of coherence between the images and water. In this paper, the polarimetric information of ships,land and intertidal zone are first compared based on the cross-correlation between HH and HV images. Inthe next step, we examine the technique when the dual-polarization data are split into two multi-lookimages. It was shown that the inter-look cross-correlation method could be applicable in the performanceimprovement of small ship detection and the land masking. It was also found that a simple combination ofcoherence images from each co-polarised (HH) inter-look and cross-polarised (HV) inter-look data canprovide much higher target-detection possibilities.