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Minimal Slant Range Resolution for SAR Tomography of Forested Areas

Stefano Tebaldini(1)

(1) Politecnico di Milano, Leonardo da Vinci, 20133, Milan, Italy


In its most basic formulation, the scope of SAR Tomography (T-SAR) is to reconstruct the 3D spatial distribution of the reflectivity of the imaged scene by exploiting the combined information provided by multiple SAR acquisitions with different baselines. The availability of multi-baseline data offers the possibility to gather the backscattered echoes not only along the azimuth direction, but also along the cross-range direction, defined by the axis orthogonal to the Line Of Sight (LOS) and to the orbital track. Accordingly, the backscattered echoes can be focused not only in the slant range, azimuth plane, but in the whole 3D space. Therefore, the exploitation of multi-baseline acquisitions results in a fully 3D imaging system, where the size of the 3D resolution cell is determined by the pulse bandwidth along the slant range direction, and by the lengths of the synthetic apertures in the azimuth and cross range directions. With reference to a forest scenario, it follows that the separation between the ground and the canopy is subjected to the condition that either the ground or the canopy are present in each slant range, cross range resolution cell. Accordingly, the capability of T-SAR to separate the ground and the canopy depends not only on baseline aperture, but also on system bandwidth. This paper is intended to provide a discussion of the implications of this phenomenon, with reference to both a parametric and non parametric formulation of T-SAR of forested areas. The advantages and the drawbacks resulting from pre-processing the data by performing Common Band Filtering will be taken into account as well. Finally, the concepts within this paper will be discussed from an experimental point of view, on the basis of the data-set relative to the Remningstorp forest site acquired by DLR’s E-SAR in the framework of the ESA project BioSAR.



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