Speaker
Description
The increasing request for accurate maps of ground elevation in many fields of human activity strongly pushed forward this research field. Commercial uses include infrastructure administration, regional planning and risk management; scientific uses range from subsidence analysis to vegetation characterization. Tropical forests represent the most challenging environments for this kind of task: trees can reach up to 50m and the vegetation is dense and heterogeneous. LiDAR systems rely on the few echoes that are not intercepted by leaves or branches and reach the ground. SAR systems working at frequencies lower than 1GHz collect returns coming from the upper crown down to the ground level, however the echoes associated with different elevations get mixed at the receiver as they fall in the same resolution cell. According to the InSAR principles, the exploitation of a couple of SAR images gives access to the interferometric coherence whose phase is linearly dependent on the elevation of the scattering target. However, this elevation is associated with the phase center of the target; for a forest the phase center is a point placed somewhere between ground level and tree top depending on scene geometry and wave extinction. As opposed to InSAR, TomoSAR allows to focus the signal in the 3D space by jointly exploiting several interferometric SAR images. By doing so, SAR tomography provides an estimation of the whole vertical profile of the target, thus pinpointing the ground location. The aim of this talk is to provide a careful evaluation of the capabilities of P-Band tomographic data in the retrieval of terrain topography in tropical forests. The analysis is carried out based on experimental data acquired in the frame of the ESA campaign AfriSAR, flown in 2015 in equatorial Africa. Results demonstrate that tomography can be used to produce high quality digital models of the terrain below a tropical forests, to within an accuracy comparable to that of high-resolution Lidar systems.
