TomoSAR Mapping of 3D Forest Structure: Contributions of L-Band Configurations

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.

Numerical Full Inversion of Two Dielectric Cylinders Upon a Metallic Plane: A First Step Toward Forest Parameters Retrieval From VHF to P-Band Radar Data

“…supp and for each scattering mechanism: [17,12,12,17]. [17,12,12,17]. Notice that CRB remains always lower than the variance, as expected.…”

“…Figure 6 indicates different shapes but similar MSE trends with an acceptable minimum for the sixth size configuration for both vertical (Figure 6(a)) and tilted (Figure 6(b)) cylinders. That is:• Vertical cylinder: [K SB supp , K DBa supp , K DBb supp , K T B supp ] =[17,12,12,17].• Tilted cylinder: [K SB supp , K DBa supp , K DBb supp , K T B supp ] =[17,12,12,17]. Notice that CRB remains always lower than the variance, as expected.…”

“…There are different target subspaces for each scattering mechanisms (single, double and triple bounces). The size K of each of them is chosen according to the results obtained in Section 4.4: The target subspace size for target localization, namely the support: [17,12,12,17]. [17,12,12,17].…”

“…The size K of each of them is chosen according to the results obtained in Section 4.4: The target subspace size for target localization, namely the support: [17,12,12,17]. [17,12,12,17]. The target subspace size for target scattering coefficient linearization: [14,14,14,14].…”

“…On one hand, several measurement techniques have been investigated from Polarimetric [5] and/or interferometric sensors [6,7] to data fusion such as RADAR/LIDAR data [8], from high resolution SAR imaging [9] to tomography [10][11][12]. All of them consist in top-down approaches, aiming to extract biophysical information from real data acquired on real forest at large geographic scale: from forest stand scale [13] to the continental scale [14].…”