Abstract
Synthetic Aperture Radar (SAR) Tomography (TomoSAR) allows extending the 2-D focusing capabilities of SAR to the elevation direction, orthogonal to the azimuth and range. The multi-dimensional extension (along the time) also enables the monitoring of possible scatterer displacements. A key aspect of TomoSAR is the identification, in the presence of noise, of multiple persistent scatterers interfering within the same 2-D (azimuth range plane) pixel. To this aim, the use of multi-look has been shown to provide tangible improvements in the detection of single and double interfering persistent scatterers at the expense of a minor spatial resolution loss. Depending on the system acquisition characteristics, this operation may require also the detection of multiple scatterers interfering at distances lower than the Rayleigh resolution (super-resolution). In this work we further investigated the use of multi-look in TomoSAR for the detection of multiple scatterers located also below the Rayleigh resolution. A solution relying on the Capon filtering was first analyzed, due to its improved capabilities in the separation of the responses of multiple scatterers and sidelobe suppression. Moreover, in the framework of the Generalized Likelihood Ratio Test (GLRT), the single-look support based detection strategy recently proposed in the literature was extended to the multi-look case. Experimental results of tests carried out on two datasets acquired by TerraSAR-X and COSMO-SkyMED sensors are provided to show the performances of the proposed solution as well as the effects of the baseline span of the dataset for the detection capabilities of interfering scatterers.
Highlights
Synthetic Aperture Radar (SAR) provides high resolution 2-D microwaves images of the illuminated scene at night and day and in all-weather conditions
Before starting with the analysis of the detection performances, a comparison of the elevation estimates achieved by Capon and BF was first performed with reference to the Bucharest dataset, which is characterized by a poor vertical resolution
Depending on the system resolution along the elevation direction and the scene height distribution, the identification of multiple scatterers may be affected by the limitations in the detection of interfering scatterers below the Rayleigh resolution as well as by the effects of leakage
Summary
Synthetic Aperture Radar (SAR) provides high resolution 2-D (azimuth and range) microwaves images of the illuminated scene at night and day and in all-weather conditions This results in a systematic acquisition capability, which is an essential feature with reference to the environmental risk monitoring applications. The class of Persistent Scatterer Interferometry (PSI) methods, typically operating at full resolution [2], relies on the assumption that the scattering response is spatially concentrated and persistent over the observation time interval, the name of Permanent Scatterer (PS) This scattering assumption, along with the use of a multi-acquisition model, allows accurately estimating the scatterers parameters, which are the residual topography (RT) and the related deformation parameters, typically given by the mean deformation velocity (MDV) and the thermal dilation (TD). Upon extension to the time and more dimensions (Multi-D imaging) [4], similar to PSI, TomoSAR allows the estimation of the scatterers parameters related to possible deformations (i.e., MDV and TD) as well
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