Dual-Polarized L-Band SAR Imagery for Temporal Monitoring of Marine Oil Slick Concentration

Abstract

SAR sensors are usually used in the offshore domain to detect marine oil slicks which allows the authorities to guide cleanup operations or prosecute polluters. As radar imagery can be used any time of day or year and in almost any weather conditions, the use and programming of such remote sensing data is usually favored over optical imagery. Nevertheless, images collected in the optical domain provide access to key information not accessible today by SAR instruments, such as the thickness or the amount of pollutant. To address this knowledge gap, a methodology based on the joint use of a scattering model (U-WCA) and remote sensing data collected by a low frequency (e.g., L-band) imaging radar over controlled release of mineral oil spill is reported in this paper. The proposed method allows estimation of the concentration of pollutant within an oil-in-water mixture as well as the temporal variation of this quantity due to weathering processes.

Health security and environment capability of slick detection, characterization, and quantification in the offshore domain thanks to radar or optical imagery

“…Finally, SAR imagery collected at low frequency (e.g. L-band) as proven to allow an estimation of the oil concentration within and oil and seawater mixture [8] [9].…”

“…It is based on the pixel by pixel numerical inversion of the surface properties from the polarization ratio (PR) inferred by the Universal Weighted Curvature Approximation (U-WCA) scattering model [15]. A simplification of the original method is reported on in [9], which makes it less time-consuming and no longer dependent on a reference clean sea image. This simplification, however, is made at the expense of the accuracy of the oil concentration estimate, especially for low percentages values of oil.…”

“…The bibliography stressed the potential of radar and optical imagery for spill detection [1][2] and optical imagery ( [3]- [6]) for hydrocarbons characterization and quantification. In the frame of NAOMI project, work has been performed to extend the radar detection capability toward characterization [7] and quantification [8] [9] and to test and enhance optics capability in these fields. Choice has been made to associate laboratory, pool, airborne, and (when available) space-borne measurements, modelling and physically based image processing to progress on signal understanding and reach the project objectives.…”

Mineral Oil Slicks Identification Using Dual Co-polarized Radarsat-2 and TerraSAR-X SAR Imagery

“…This is the first limitation of our method. However, the other dual co-pol methods based on NRCS models also impose a similar restriction [14,28] to remove unnecessary uncertainties in the form of reflections from slopes of long waves. According to the definition of the NRCS model [34], the following expressions for the resonant and non-resonant parts of the backscattered signal are obtained:…”

“…where ε is the seawater relative dielectric constant. Equations (A3) and (A4) reflect the fact that the resonant (Bragg) scattering depends on the polarization [28,31]. The ratio of σ H B to σ V B is called the co-polarization ratio P B :…”