Investigagtions on Space-borne Sar Tomography for Structural Analysis of Forested Areas

Remote sensing systems are of great interest to gain geospatial information in forest environment. In particular, Synthetic Aperture Radar (SAR) which is an active and coherent imaging technique is commonly used from aerial and satellite platforms. Microwave pulses are emitted by a transmitter and their echos reflected from objects on ground are coherently recorded and processed in such a way, that the resulting 2D data matrix is showing the specific reflectance of the sensed ground objects in form of an intensity image. Since SAR is a coherent technique, not only the measured intensity of the illuminated objects is available, but also the phase information. Depending on the application different kind of SAR processing strategies can be used, like Interferometric SAR (InSAR), Persistant Scatterer InSAR (PSI), and the recently developed SAR tomography. SAR tomography inherits its name from the well-known principle of tomography in medicine. While medical tomography is a 3D sensing technique for estimating the volume scattering of a human body, the SAR analogon does the same for remote sensed natural objects. To reconstruct the 3D scattering distribution of the objects, a series of space-borne SAR images each image capturing the same objects but sensed from a slightly different orbits are coherently combined in such a way, that the resulting function gives an estimate of the objects volume scattering or the number of prominent scatterers inside one resolution cell.