Sea oil slick observation by means of fully-polarimetric ALOS PalSAR data
Mauricio Migliaccio(1), Attilio Gambardella(1), Ferdinando Nunziata(1), Masanobu Shimada(2) and Osamu Isoguchi(2)
(1) Università degli Studi di Napoli, Centro Direzionale, Isola C4, 80143, Napoli, Italy
(2) Japan Aerospace Exploration Agency, Earth Observation Research Centre, Sengen 2-1-1 Tsukuba Ibaraki, Japan
In this study an electromagnetic approach has been firstly proposed for exploiting polarimetric information for sea oil slick observation in PALSAR data.
The presence of a surface slick, reducing the signal backscattered to the radar antenna, generates a low-backscattering area which, in SAR images, appears as a dark area. Following this rationale image processing techniques are commonly employed on single-polarimetric SAR data to detect dark areas. Since other natural phenomena generate dark areas in SAR images semi-automatic approaches, based on the extraction of some radiometric, texture or geometric related features, allow classifying the detected dark areas as oil slick or look-alikes.
The approach proposed in this study is based on the different sea surface scattering expected with and without surface slicks. In particular, it has been demonstrated in - that though the sea surface scattering follow a Bragg or tilted Bragg scattering mechanism, the presence of a surface slick, depending on its damping properties, may lead to a completely different non-Bragg scattering mechanism. In this study, following this theoretical rationale, polarimetric information are exploited for sea oil slick observation. In detail, the phase difference between the HH and VV complex channel (co-polarize phase difference) and the alpha-entropy parameters, obtained decomposing the 3x3 coherence matrix according to the Cloude&Pottier decomposition, are read in terms of sea surface scattering mechanism with and without surface slicks and a simple and very effective filtering technique has been developed for sea oil slick observation.
Experiments accomplished on full-polarimetric ALOS PalSAR SAR data show the effectiveness of the proposed approach for sea oil slick observation. The experimental results allow underlining the importance of fully polarimetric L-band SAR data for oil slick observation.
M. Migliaccio, F. Nunziata, A. Gambardella, “On The Copolarised Phase Difference for Oil Spill Observation”, International Journal of Remote Sensing, in print.
F. Nunziata, A. Gambardella and M. Migliaccio, “On the Mueller scattering matrix for SAR sea oil slick observation ”. IEEE Geoscience and Remote Sensing Letters, vol. 5, n. 4, 2008.