Reflection Asymmetric Target Detection Based on Correlation Coefficients Ken Yoong LEE, Soo Chin LIEW, Santo V. SALINAS and Kim Hwa LIM
Centre for Remote Imaging, Sensing and Processing, National University of Singapore
Abstract
Nghiem et al. (1992) presented an in-depth investigation on symmetric properties of geophysical media encountered in polarimetric remote sensing. Recently, Connetable et al. (2022) made use of statistical test for independence in evaluating the reflection symmetry in multi-look PolSAR data. They derived the so-called block-diagonality test statistic, where its asymptotic distribution is a chi-squared distribution. In this paper, the mathematical relationship between the block-diagonality test statistic and multiple correlation R was first investigated. The former can actually be expressed in form of the latter, which arises from multiple linear regression. Moreover, the exact distribution of the squared multiple correlation R^2 for a 3x3 polarimetric covariance matrix is a beta distribution, which depends only on the number of looks L. As the number of looks tends to infinity, the limiting distribution of LR^2 is a gamma distribution with unit scale parameter and a shape parameter of two. In this study, the reflection asymmetric target detection was carried out using multi-look ALOS-2 PALSAR-2 quad-polarisation data, which covered two separate test sites in Southeast Asia, namely, Singapore and Penang (Malaysia). Meanwhile, quantitative assessment was reported by using simulated PolSAR data through Monte-Carlo method following the procedure suggested by Lee et al. (1994). The experimental results confirmed the usefulness of reflection symmetry property of geophysical media, particularly in detecting man-made objects, such as bridge, slightly oriented buildings, vessels, aquaculture farms, etc.
