The Extended Bragg Scattering Model-Based Method for Ship and Oil-Spill Observation Using Compact Polarimetric SAR

Abstract

Ocean surveillance is one of the important applications in synthetic aperture radar (SAR) imagery. Polarimetric SAR provides multichannel information and shows great potential for ocean target observation. Oil-spills and ships possess different polarimetric features from the ocean surface, whose physical backscattering property is generally admitted as being dominated by the Bragg resonant scattering. In this study, we focus on the oil-spill and ship observation based on the polarimetric features. Oil-spills present a non-Bragg scattering property. While backscatter from ships is predominated by the double-bounce scattering and the multiple reflections between the ship and sea surface. Ships exhibit very different scattering characteristics from the ocean Bragg scattering. Based on the extended Bragg (X-Bragg) model, a new method is proposed for observing oil-spills and ships. This method allows distinguishing oil-spills from two kinds of important look-alikes, i.e., biogenic slicks and the low-wind region (LWR), and also shows good performance for ship enhancement. Experiments are performed on the C-band fully polarimetric SAR data acquired by both SIR-C/X-SAR and RADARSAT-2. The other issue concerned is the application potential of the hybrid dual-polarimetric (i.e., compact polarimetry (CP)) SAR mode, which has the advantage of providing larger imaging coverage compared to the full polarimetry. Based on the X-Bragg model, where the backscatter reflection symmetry is assumed, an equivalent method is proposed with the circularly polarized transmission CP mode. Experimental results show that similar results can be obtained between the CP and full polarimetry for ocean target observation.