Speckle Filtering and Physical Scattering Decomposition for ALOS-2 PALSAR-2 Polarimetric Mosaic

Abstract

This paper presents the speckle filtering and physical scattering decomposition for the ALOS-2 PALSAR-2 fully polarimetric mosaic. The processing steps include 1) multi-looking, 2) speckle filtering, 3) geocoding, 4) mosaicking, and 5) model-based polarimetric decomposition. Another variant of iterative bilateral filter, called gravitational filter, was assessed for polarimetric speckle filtering. Benchmarking against the refined Lee filter and the boxcar filter, the experimental results on the ALOS-2 PALSAR-2 polarimetric data confirmed the effectiveness of the gravitational filter in speckle reduction and image feature retention. Prior to the mosaicking, the geodetic coordinates of selected control points, which were given based on the Geodetic Reference System 1980, were first converted into the Universal Transverse Mercator map coordinates. Subsequently, the ALOS-2 PALSAR-2 speckle filtered data were geocoded by using second-order polynomial equation and least squares method. For the polarimetric scattering decomposition, an iterative multistage four-component decomposition was applied to the ALOS-2 PALSAR-2 polarimetric mosaic. From the decomposition result, a large amount of negative power pixels over vegetated areas were reduced. The total number of the remaining negative power pixels was only 0.006%.