Detection of Multiple Scatterers in Sar Tomography
نویسندگان
چکیده
Due to the capability to provide direct physical measurements, interferometry is among the remote sensing techniques that have most pushed the applications of SAR to a wide range of scientific areas and have provided direct returns for our society in terms of improved security. Repeat pass DInSAR and, more specifically, its evolution to Persistent Scatterers Interferometry (PSI), which allows the accurate localization of ground targets and the monitoring of possible displacements up to a mm/year order accuracy, has been the breakthrough for the application of SAR in the risk monitoring. Multipass/multiview SAR data are today available for most of the Earth surface by means of existing sensor acquisitions carried out over repeated orbits. Such amount of data demands for the development of new processing techniques aimed, similarly to multiple pass DInSAR and PSI, at jointly processing, in a coherent way, the available information lying in the complex data cube (associated to the Single Look Complex (SLC) image stack) to produce accurate physical measures. SAR tomography, also referred to as 3D SAR imaging, is a further example along this line. It is based on the principle that the acquisitions, corresponding to different passes, can be assimilated to the data collected at the different elements of an antenna array parallel to the elevation direction. Hence, as in the classic azimuth antenna synthesis process, digitally performed offline on the acquired signal, an (synthetic) aperture in elevation direction can be synthesized to profile the scattering distribution along that direction and, hence, to image the scene in full 3D. DInSAR and SAR tomography have been recently fused to identify a new framework, i.e. the differential SAR tomography processing, also known as 4D (space velocity) SAR imaging [1], [2]. Such technique has shown the potentiality to overcome the spatial resolution limits of the classic PSI, allowing the separation of multiple interfering scatterers within the same pixel. The analysis of long-term multiview/multitemporal data requires the development of techniques able to distinguish the useful signal from noise and clutter in order to identify, locate, and monitor the huge number of ground structures. At the same time, it is also necessary to keep as low as possible the occurrence of signal misinterpretation, even in relatively low Signal-to-Noise Ratio (SNR) conditions. Standard PSI techniques carry out the detection of single scatterers via a threshold comparison of a decision variable, obtained by matching the observed phase values to a multibaseline/multitemporal linear model. On the contrary, 3D/4D based analysis detects single targets by comparing the focused scattering distribution along the elevation/elevation-velocity directions and the ideal response of a scatterer located at the given elevation/elevation velocity position. In [3], the problem of detecting single and stationary scatterers in multidimensional SAR imaging has been investigated, resorting to detection schemes based on the Generalized Likelihood Ratio Test (GLRT); however, such a detector is unable to accommodate multiple signal models, that can be describe a situation with multiple scatterers. In this work we follow an alternative approach, proposed in [4], based on the multifamily likelihood ratio test; such approach extends the GLRT and alleviates its limitation in the detection of multiple scatterers within the same pixel. [1] F. Lombardini, “Differential Tomography: a New Framework for SAR Interferometry”, IEEE Trans. Geosci. Remote Sens., Vol.43, pp.~7-44, 2005. [2] G. Fornaro, F. Lombardini, and F. Serafino, “Multidimensional Imaging with ERS Data”, Fringe 2005 Workshop, Frascati (Italy), 28 November 2 December 2005, (http://earth.esa.int/workshops /fringe2005/ programme.html). [3] A. De Maio, G. Fornaro, A. Pauciullo, “Detection of Single Scatterers in Multi-Dimensional SAR Imaging”, in print on IEEE Trans. on Geosci. and Remote Sens. [4] S. M. Kay, “The Multifamily Likelihood Ratio Test for Multiple Signal Model Detection”, IEEE Signal Processing Letters, Vol. 12, No. 5, May 2005.
منابع مشابه
Radiometric Issues in Adaptive Polarimetric Sar Tomography
Multibaseline (MB) SAR tomography (Tomo-SAR) is an advanced mode of SAR interferometry, allowing full 3D imaging of volumetric and layover scatterers along the azimuth, range and height dimensions. Recently, this technique has also been extended in a polarimetric sense (PolTomo-SAR), exploiting MB SAR data acquired with different polarization channels. In this way, the joint estimation is possi...
متن کاملExtension of a Fast GLRT Algorithm to 5D SAR Tomography of Urban Areas
This paper analyzes a method for Synthetic Aperture Radar (SAR) Tomographic (TomoSAR) imaging, allowing the detection of multiple scatterers that can exhibit time deformation and thermal dilation by using a CFAR (Constant False Alarm Rate) approach. In the last decade, several methods for TomoSAR have been proposed. The objective of this paper is to present the results obtained on high resoluti...
متن کاملDetermination of height of urban buildings based on non-parametric estimation of signal spectrum in SAR data tomography
Nowadays, the TomoSAR technique has been able to overcome the limitations of radar interferometry techniques in separating multiple scatterers of pixels. By extending the principles of virtual aperture in the elevation direction, these techniques pay much attention in the analysis of urban challenging areas. Despite the expectation of interference of the distribution of buildings with different...
متن کاملSupport Detection for SAR Tomographic Reconstructions from Compressive Measurements
The problem of detecting and locating multiple scatterers in multibaseline Synthetic Aperture Radar (SAR) tomography, starting from compressive measurements and applying support detection techniques, is addressed. Different approaches based on the detection of the support set of the unknown sparse vector, that is, of the position of the nonzero elements in the unknown sparse vector, are analyze...
متن کاملBayesian Inference, Applications in Persistent Scatterer Interferometric Synthetic Aperture Radar
Coherent Synthetic Aperture Radar (SAR) imagery and its potential in interferometric analysis widened the horizon of earth observation and geodetic measurements in the past decades. Overcoming the error sources in conventional Interferometric SAR (InSAR) techniques, the advanced methods of Persistent Scatterer Interferometry (PSI) and differential SAR Tomography (TomoSAR) have been able to retr...
متن کامل