Full polarimetric ALOS-2/PALSAR-2 analysis of backscattering characteristics from various types of coasts

Abstract

ABSTRACT Synthetic aperture radar has a clear advantage over optical satellites in being able to monitor the Earth’s surface under any weather condition. The Phased Array type L-band Synthetic Aperture Radar-2 (PALSAR-2) aboard Advanced Land Observing Satellite 2 (ALOS-2) is a unique and highly useful sensor that can acquire high-resolution data using dual-beam receivers. This study aimed at evaluating, both qualitatively and quantitatively, the backscattering characteristics detected via full polarimetric PALSAR-2 data from the shorelines of various types of coasts, using the administrative zone vector data of the National Land Numerical Information (NLNI) database. The four-component scattering images derived from full polarimetric PALSAR-2 data were used to evaluate the characteristics of scattering models that affect shoreline detection. Canny edge detection was applied to the four decomposed datasets (surface, double-bounce, volume and helix scattering power) and the edges of these four datasets were combined by logical conjunction analysis. The results show that a part of the edge line in the surface scattering power image corresponded with the sandy coast shoreline. The boundary between land and sea indicated by the edge line in the surface, double-bounce, volume and helix scattering power image corresponded with the rocky coast and seawalls shoreline, which were analysed using histograms. The relationship between the four-component scattering model and the edges in these components can be explained by an L-band SAR backscattering mechanism.