Abstract
Focusing on scattering from natural media, dihedral (double bounce) scattering is often characterized as a soil-trunk double Fresnel reflection, like for instance, in most model-based decompositions. As soils are predominantly rough in agriculture, the classical Rank 1 dihedral scattering component has to be extended to account for soil roughness-induced depolarization. Therefore, an azimuthal Line of Sight (LoS) rotation is applied solely on the soil plane of the double-bounce reflection to generate a depolarized dihedral scattering signal in agriculture. The results of the sensitivity analysis are shown for a distributed target in coherency matrix representation. It reveals that the combination of coherency matrix elements T22XD + T33XD is quasi-independent of the roughness-induced depolarization, while (T22XD − T33XD)/(T22XD + T33XD) is quasi-independent of the dielectric properties of the reflecting media. Therefore, a depolarization-independent retrieval of soil moisture or a direct roughness retrieval from the extended dihedral scattering component might be possible in stalk-dominated agriculture under certain conditions (e.g., the influence of a differential phase stays at a low level: ϕ < 15°). The first analyses with L-band airborne-SAR data of DLR’s E-SAR and F-SAR systems in agricultural regions during the AgriSAR, OPAQUE, SARTEO and TERENO project campaigns state the existence and potential of the extended Fresnel scattering mechanism to represent dihedral scattering between a rough (tilled) soil and the stalks of the agricultural plants.
Highlights
The increasing availability of fully-polarimetric datasets from space-borne SAR systems likeALOS-1/-2, Radarsat-2, TerraSAR-X and TanDEM-X motivates the investigation of polarimetric scattering mechanisms for natural media [1,2,3,4,5,6,7]
The analysis indicates that αXD from the X-Fresnel model generally decreases until about 50◦ local incidence and strongly rises until ω l = 70◦
The classical Rank 1 dihedral scattering, often included in model-based decompositions, was extended to account for soil roughness-induced depolarization appearing in the scattering of natural media
Summary
The increasing availability of fully-polarimetric datasets from space-borne SAR systems like. The Eigen-based methods represent a mathematical approach for decomposition, which result in a set of eigenvalues and eigenvectors [9,10]. These parameters are not straightforward to interpret in their physical sense. Hajnsek et al [14] showed how to incorporate Rank 3 extended Bragg surface scattering into the surface component in order to account for roughness-induced depolarization on agricultural ground. This is of special importance for agricultural areas, where the soil roughness is distinct and cannot be neglected.
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