Summary
International Symposium on Antennas and Propagation
2010
Session Number:3TD1
Session:
Number:3TD1-3
Extraction of Underwater Laver Cultivation Area by SAR Polarimetric Entropy
E.S. Won, K. Ouchi,
pp.-
Publication Date:2010/11/23
Online ISSN:2188-5079
Summary:
In January 2006, Advanced Land Observing Satellite (ALOS) was launched by Japan Aerospace Exploration Agency (JAXA), carrying Phased Array L-band Synthetic Aperture Radar (PALSAR). Although ALOS-PALSAR is aimed mainly on land observation, it can play a major role in the field of oceanography such as ocean surveillance, maritime meteorology and pollution. Especially, using polarimetric data of ALOS-PALSAR, it can obtain more information than single-polarization data. Thus, radar remote sensing using polarimetric information comes to the forefront of the current research. This paper describes a technique of extracting underwater laver cultivation nets by using entropy analysis from ALOS-PALSAR polarimetric data in the water around the Futtsu Horn, Chiba, Japan. The method is based on the difference in the backscattered fields from the almost specular surface above the laver nets and slightly rough surface in open water. Under weak to moderate wind conditions, the backscattered field from open water is dominated by the surface (Bragg) scattering. While the laver nets are placed at a few centimeters below the sea surface, so that waves are damped, resulting in the specular surface causing little radar backscatter. This difference in radar cross section (RCS) can be detected by X-band TerraSAR-X, but the difference is too small to detect by PALSAR because both the surfaces are effectively smooth for L-band microwave. However, since the radar backscatter from the specular surface is at the system noise level, the image can be considered as arising from a random process of various scattering contributions. The polarimetric entropy should then be higher than the single-bounce surface scattering from the open water. We will show, in this paper, that the polarimetric entropy is an effective means of identifying the underwater laver nets compared with the RCS-based method from PALSAR L-band data.