SAR tomography of natural environments: Signal processing, applications, and future challenges

Synthetic Aperture Radar (SAR) Tomography (TomoSAR) provides access to the three-dimensional (3D) structure of illuminated media by jointly focusing multiple SAR acquisitions. TomoSAR imaging can be understood in simple terms by considering that multiple SAR flight lines, or orbits, allow forming a bi-dimensional synthetic aperture, resulting in the possibility to resolve the targets not only in the range-azimuth plane, but also in elevation. This simple principle brings along unprecedented possibilities, providing a way to investigate the illuminated media based on a direct observation of their vertical structure. The aim of this paper is to provide the readers with a brief tutorial on the use of TomoSAR imaging in the remote sensing of distributed media, by presenting basic imaging principles, applications, signal processing methods, and identifying challenges for future tomographic SAR systems.