The double Brewster angle effect

Thirion-Lefevre, Laetitia; Guinvarc'H, Régis

doi:10.1016/j.crhy.2018.02.003

Cited by 23 publications

(16 citation statements)

References 7 publications

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“…Since the CPD we observed in our data was predominantly less than 90°, we attributed the anomalous decomposition results to the small CPD values we observed. In the course of our investigation, we also found several papers that suggested that these low values of CPD might be a consequence of the physics of microwave reflection by water and vegetation [7]- [10]. Thirion-Lefevre and Guinvarc'h [10] introduce the terminology "Double Brewster Effect" and show that this effect can result in a high ratio of HH to VV backscatter over a large range of incidence angles.…”

Section: Introductionmentioning

confidence: 61%

“…Ulaby and El-Rayes [21] present mathematical models to calculate the dielectric constants of water and vegetation that have been widely used by the remote sensing community. We have used their equations (2) and (10) to calculate the dielectric constants of fresh water and vegetation for the RADARSAT-2 frequency of 5.4 GHz, followed by (1) to calculate the corresponding indices of refraction. The indices of refraction used to produce the curves in Fig.…”

Section: Fresnel Reflection From Single Planes Of Glass Water Anmentioning

confidence: 99%

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Insights Into Polarimetric Processing for Wetlands From Backscatter Modeling and Multi-Incidence Radarsat-2 Data

Ahern¹,

Brisco

Murnaghan

et al. 2018

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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We have observed unexpected results using the Freeman-Durden (FD) and other polarimetric decompositions in Radarsat-2 quad-pol data from many swamps in Eastern Ontario. In particular, the decompositions reported minimal backscatter from the double-bounce mechanism in a situation where there was compelling evidence that double-bounce backscatter contributed substantially to the return. This led to a hypothesis that the FD and similar models give erroneous results because of the physics of Fresnel reflection of wood, a lossy dielectric material, that makes up the vertical reflecting surfaces in swamps. We found some support for this hypothesis in the literature, and now report on an extensive theoretical and observational investigation. This work has shown that the Freeman-Durden decomposition, and other decompositions that use the same logic, will often mistake doublebounce backscatter as single-bounce backscatter in wetlands. This is a consequence of the fundamental physics of Fresnel reflection. It is important for users to be aware of this pitfall. Double-bounce backscatter from natural surfaces can be identified without recourse to polarimetric decomposition. The simplest, and most reliable, indicator of double-bounce backscatter is a high return in HH polarization. Double-bounce backscatter will generally produce higher return in HH than any other scattering mechanism. If both HH and VV polarizations are available, a high HH/VV intensity ratio is also a strong indicator of double-bounce backscatter. Additional modeling efforts are expected to provide further insights that can lead to improved applications of polarimetric data.

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Section: Introductionmentioning

confidence: 61%

Section: Fresnel Reflection From Single Planes Of Glass Water Anmentioning

confidence: 99%

Insights Into Polarimetric Processing for Wetlands From Backscatter Modeling and Multi-Incidence Radarsat-2 Data

Ahern¹,

Brisco

Murnaghan

et al. 2018

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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“…When a dielectric dihedral is well aligned with the radar line of sight, its response is maximum. In this case, we have shown that the double-bounce scattering mechanism can be approximated using two successive specular reflections over the two parts of the dihedral [11], as illustrated in Figure 3. When there is a specular mechanism, a particular incidence angle φ exists-known as Brewster's angle (BA) or Pseudo Brewster's Angle (PBA)-for which the VV reflected field is either null or minimum whether the dielectric material has losses or not.…”

Section: The Dielectric Dihedral and The Double Brewster's Angle Effectmentioning

confidence: 90%

“…Finally, we can also question the way this orientation is compensated, as there is not a strict equivalence between the orientation of the target and the rotation angle estimated for this compensation [10]. In [11], Thirion-Lefevre and Guinvarc'h have investigated the phenomenology of the polarimetric backscattering by a dielectric dihedral structure with no orientation angle. In particular, they show the existence of a strong attenuation effect, called the DBE for Double Brewster's angle Effect, that affects differently VV and HH intensities.…”

Section: Introductionmentioning

confidence: 99%

The Combined Effect of Orientation Angle and Material on PolSAR Images of Urban Areas

2020

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Polarimetric Synthetic Aperture Radar (PolSAR) images containing cities may exhibit misclassified areas when using polarimetric decompositions. Several articles relate this problem to the effects of orientation between the facades of buildings and the acquisition trajectory. Materials also play a role in polarimetric behavior. This paper deals with this combined effect of material and orientation. It analyzes different sets of data, airborne or space-borne, at L-, C- and X-bands, and for different orientation angles. It shows that considering dielectric dihedral rather than metallic in the polarimetric mechanism of double-bounce has a very important impact on the differences of intensities between the channels HH and VV. This difference is very important for small angles of orientation, and then decreases for large angles. Furthermore, the curves of the ratios between polarimetric intensities as a function of the orientation angle vary little with the materials and the frequencies encountered in all the scenarios envisaged. The signal of the ratio VV/HH raises a plateau around −1 dB for orientations higher than 30°. We also observe a plateau for HV/HH, but with a value around −5 dB.

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“…Ref. [14] considers the effect of the double Brewster angle on dihedrals which strongly affects the V V amplitude. Finally [15] studies the backscatter response from rotated dihedrals for which the signature is often very confusing.…”

Section: Introductionmentioning

confidence: 99%

Novel Techniques for Built-Up Area Extraction From Polarimetric SAR Images

Ratha

Gamba

Bhattacharya

et al. 2020

IEEE Geosci. Remote Sensing Lett.

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Built-up area extraction from remote sensing images is important to monitor and manage urbanization and industrialization. In this work, we propose two built-up area extraction techniques based on the analysis of fully PolSAR data. Both methods exploit the geodesic distance on the unit sphere in the space of Kennaugh matrices. The first method is based on the three dominant scattering types in the scene and compares them with scattering models; if any of them matches with built-up type elementary scattering models, then the pixel is said to belong to a built-up area. The second method is based on a novel PolSAR built-up index (RBUI) composed by considering scattering mechanisms from built-up structures. The two proposed techniques are validated on two different urban scenes, one acquired at C-band by RADARSAT-2 and other at L-band by ALOS-2 SAR sensors.

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The double Brewster angle effect

Cited by 23 publications

References 7 publications

Insights Into Polarimetric Processing for Wetlands From Backscatter Modeling and Multi-Incidence Radarsat-2 Data

Insights Into Polarimetric Processing for Wetlands From Backscatter Modeling and Multi-Incidence Radarsat-2 Data

The Combined Effect of Orientation Angle and Material on PolSAR Images of Urban Areas

Novel Techniques for Built-Up Area Extraction From Polarimetric SAR Images

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