Abstract
Synthetic aperture radar (SAR) tomography has shown great potential in multi-dimensional monitoring of urban infrastructures and detection of their possible slow deformations. Along this line, undeniable improvements in SAR tomography (TomoSAR) detection framework of multiple permanent scatterers (PSs) have been observed by the use of a multi-looking operation that is the necessity for data’s covariance matrix estimation. This paper attempts to further analyze the impact of a robust multi-looking operation in TomoSAR PS detection framework and assess the challenging issues that exist in the estimation of the covariance matrix of large stack data obtained from long interferometric time series acquisition. The analyses evaluate the performance of non-local covariance matrix estimation approaches in PS detection framework using the super-resolution multi-looked Generalized Likelihood Ratio Test (GLRT). Experimental results of multi-looking impact assessment are provided using two datasets acquired by COSMO-SkyMED (CSK) and TerraSAR-X (TSX) over Tehran, Iran, and Toulouse, France, respectively. The results highlight that non-local estimation of the sample covariance matrix allows revealing the presence of the scatterers, that may not be detectable using the conventional local-based framework.
Highlights
The differential synthetic aperture radar (SAR) interferometric techniques are today well assessed and widely exploited in remote sensing of complex urban scenarios to measure the Earth’s surface displacement [1,2,3]
The first dataset was acquired by COSMO-SkyMED sensor over Tehran metropolitan, and it consists of 75 single look complex images acquired between June 2011 and December 2014 with the system operating in the strip-map mode and HH polarization
It has been shown that under the same TomoSAR configuration parameters and the same system resolutions, the detection of multiple scatterers can be affected by the non-robust estimation of the sample covariance matrix
Summary
The differential synthetic aperture radar (SAR) interferometric techniques are today well assessed and widely exploited in remote sensing of complex urban scenarios to measure the Earth’s surface displacement [1,2,3]. The approach mainly operates at the full spatial resolution and allows improved information extraction of coherent scatterers. It should be reminded that the term coherent scatterer mainly refers to the spatially concentrated backscattering responses, such as those obtained from the anthropic structures in the urban area that are persistent over the data acquisition time interval. Due to the side-looking intrinsic properties of SAR systems, the vertical structures of an urban environment can represent a challenging scenario for interferometric data-processing and limit the PS-InSAR application for inspection of man-made constructions. In such a scenario, an alternative approach is SAR tomography (TomoSAR). TomoSAR completes and extends the application of PS-InSAR and it allows estimation of the scatterer’s parameters related to possible deformation that may be given by the mean deformation velocity and the thermal dilation [8,9,10]
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