Abstract
Synthetic Aperture Radar (SAR) measurements are unique for mapping forest 3D structure and its changes in time. Tomographic SAR (TomoSAR) configurations exploit this potential by reconstructing the 3D radar reflectivity. The frequency of the SAR measurements is one of the main parameters determining the information content of the reconstructed reflectivity in terms of penetration and sensitivity to the individual vegetation elements. This paper attempts to review and characterize the structural information content of L-band TomoSAR reflectivity reconstructions, and their potential to forest structure mapping. First, the challenges in the accurate TomoSAR reflectivity reconstruction of volume scatterers (which are expected to dominate at L-band) and to extract physical structure information from the reconstructed reflectivity is addressed. Then, the L-band penetration capability is directly evaluated by means of the estimation performance of the sub-canopy ground topography. The information content of the reconstructed reflectivity is then evaluated in terms of complementary structure indices. Finally, the dependency of the TomoSAR reconstruction and of its structural information to both the TomoSAR acquisition geometry and the temporal change of the reflectivity that may occur in the time between the TomoSAR measurements in repeat-pass or bistatic configurations is evaluated. The analysis is supported by experimental results obtained by processing airborne acquisitions performed over temperate forest sites close to the city of Traunstein in the south of Germany.
Highlights
The analysis has been carried out by processing airborne L-band Tomographic SAR (TomoSAR) data acquired over the temperate forest of Traunstein
The horizontal and vertical forest structure is described by a pair of complementary indices derived from the distribution of the peaks of the reconstructed reflectivity within a given structure window
L-band structure measurements by means of TomoSAR are not limited to temperate forests and have already been demonstrated in tropical as well as in boreal forest sites [22]
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. A single SAR image does not allow a reconstruction of the 3D distribution of scatterers within the illuminated volume For this a set of SAR images acquired under (slightly) different incidence angles is required in the context of interferometric (InSAR) and/or tomographic SAR (TomoSAR) measurements [14,15]. The capability in deriving physical forest structure indices from L-band TomoSAR reflectivity is discussed within the chosen structure framework. The imaging geometry depends primarily on flight/orbital constraints, and changes across a scene with the incidence angle variation from near- to far-range The impact of such changes on the spatial gradients the retrieved structure descriptors is evaluated. Conventional repeatpass and bistatic TomoSAR implementations are compared in terms of their ability to retrieve physical structure information in presence of temporal reflectivity changes. The analysis is supported by experimental results achieved in the framework of recent airborne SAR (DLR’s F-SAR platform) campaigns over two forest sites close to the city of Traunstein in south Germany
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
