Forest SAR Tomography: Principles and Applications

Aghababaei, Hossein; Ferraioli, Giampaolo; Ferro-Famil, Laurent; Huang, Yué; d’Alessandro, Mauro Mariotti; Pascazio, Vito; Schirinzi, Gilda; Tebaldini, Stefano

doi:10.1109/mgrs.2019.2963093

Cited by 67 publications

(26 citation statements)

References 55 publications

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“…The fast-time simulation resolution (which is different than range resolution or ADC sampling resolution) should be considerably smaller than time difference corresponding to pixel spacing; however, smaller time resolution leads to slower simulation run. As shown in (14), range ambiguities can occur if the distance corresponding to PRF ( ) is large compared to the extent of targets. Although range ambiguities are not included in (18), we include them in the 2D simulations.…”

Section: Raw Data Generation In 2dmentioning

confidence: 99%

“…Several works on TomoSAR have been published since the first demonstrations and signal data models appeared in the literature [6,7,[9][10][11][12][13]. Over the past two decades, SAR tomography has been applied with increasingly promising results to forests [12][13][14][15][16][17][18][19][20][21][22], croplands [23], urban environment [24][25][26][27][28][29], and, more recently, ice [30] and snow [31][32][33][34][35]. All these natural media share a volumetric structure causing multiple scatterers to lie within the same radar resolution cell, which TomoSAR can identify and disentangle, providing opportunities for resolving the internal components of the media.…”

Section: Introductionmentioning

confidence: 99%

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Tomographic Performance of Multi-Static Radar Formations: Theory and Simulations

Şeker

Lavalle

2021

Remote Sensing

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3D imaging of Earth’s surface layers (such as canopy, sub-surface, or ice) requires not just the penetration of radar signal into the medium, but also the ability to discriminate multiple scatterers within a slant-range and azimuth resolution cell. The latter requires having multiple radar channels distributed in across-track direction. Here, we describe the theory of multi-static radar tomography with emphasis on resolution, SNR, sidelobes, and nearest ambiguity location vs. platform distribution, observation geometry, and different multi-static modes. Signal-based 1D and 2D simulations are developed and results for various observation geometries, target distributions, acquisition modes, and radar parameters are shown and compared with the theory. Pros and cons of multi-static modes are compared and discussed. Results for various platform formations are shown, revealing that unequal spacing is useful to suppress ambiguities at the cost of increased multiplicative noise. In particular, we demonstrate that the multiple-input multiple-output (MIMO) mode, in combination with nonlinear spacing, outperforms the other modes in terms of ambiguity, sidelobe levels, and noise suppression. These findings are key to guiding the design of tomographic SAR formations for accurate surface topography and vegetation mapping.

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Section: Raw Data Generation In 2dmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tomographic Performance of Multi-Static Radar Formations: Theory and Simulations

Şeker

Lavalle

2021

Remote Sensing

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“…The complex, diverse, and dynamic nature of tropical forests demands a new approach to surveying and examining the three-dimensional (3D) distribution of the ecosystem. Remote sensing imaging techniques from active sensors such as multi-baseline synthetic aperture radar (SAR) systems have been shown to be a promising approach for monitoring forest 3D structures [12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of P-Band SAR Tomography for Mapping Tropical Forest Vertical Backscatter and Tree Height

et al. 2021

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Low-frequency tomographic synthetic aperture radar (TomoSAR) techniques provide an opportunity for quantifying the dynamics of dense tropical forest vertical structures. Here, we compare the performance of different TomoSAR processing, Back-projection (BP), Capon beamforming (CB), and MUltiple SIgnal Classification (MUSIC), and compensation techniques for estimating forest height (FH) and forest vertical profile from the backscattered echoes. The study also examines how polarimetric measurements in linear, compact, hybrid, and dual circular modes influence parameter estimation. The tomographic analysis was carried out using P-band data acquired over the Paracou study site in French Guiana, and the quantitative evaluation was performed using LiDAR-based canopy height measurements taken during the 2009 TropiSAR campaign. Our results show that the relative root mean squared error (RMSE) of height was less than 10%, with negligible systematic errors across the range, with Capon and MUSIC performing better for height estimates. Radiometric compensation, such as slope correction, does not improve tree height estimation. Further, we compare and analyze the impact of the compensation approach on forest vertical profiles and tomographic metrics and the integrated backscattered power. It is observed that radiometric compensation increases the backscatter values of the vertical profile with a slight shift in local maxima of the canopy layer for both the Capon and the MUSIC estimators. Our results suggest that applying the proper processing and compensation techniques on P-band TomoSAR observations from space will allow the monitoring of forest vertical structure and biomass dynamics.

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“…This paper focuses on the characterization of the Ground/Volume (GV) Double-Bounce (DB) scattering mechanism occurring during the measurement of a volumetric scattering medium lying over the ground. Volume imaging using Polarimetric SAR Tomography (PolTomSAR) has been widely applied to the study of natural environments like forests [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Such scenes consist of a ground surface and a vegetated medium that is composed of trunks and randomly oriented particles considered as a volume.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, even if it may be used to improve the description of complex volumetric scenes, 3D imaging may still be affected by ambiguous behaviors, related to a finite resolution of analysis or to high-order scattering terms. Most of the studies [1][2][3][6][7][8][9][10]13,15] conducted in order to characterize vegetated 3D environments concentrated on the analysis of the observed volume. Only a few of them [4,5,11,12,14] addressed the underlying ground response too.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Double-Bounce Interaction between a Random Volume and an Underlying Ground, Using a Controlled High-Resolution PolTomoSAR Experiment

et al. 2021

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The radar response of vegetated environments, and forested areas in particular, are usually modeled using a very simple structure made of a random volume, representing a cloud of vegetation particles, lying over a semi-infinite medium with a rough interface, associated with the underlying ground. This Random Volume over Ground model can efficiently handle double-bounce scattering mechanisms, or arbitrary volume reflectivity profiles. This paper proposes to analyze a specific component of the Random Volume over Ground simplified scattering model, which concerns the double-bounce interaction between the ground and the volume. This specific contribution is not considered by classical characterization techniques and is studied in this work using a controlled experiment involving a Synthetic Aperture Radar operated in a Polarimetric and Tomographic configuration in order to image in 3D a controlled miniaturized scene composed of volume lying over a ground. It is shown that ground/volume double-bounce scattering, which remains focused at the ground level even in 3D imaging mode, and has polarimetric patterns that differ largely from those usually expected from double-bounce reflections, with volume-like features, such as a strong cross-polarized reflectivity or decorrelation between co-polarized channels. Moreover, it is shown that the full rank polarimetric patterns of the ground-volume mechanism are tightly linked to the reflectivity of the volume and may mask the ground response. As a consequence, isolating the ground response using 3D imaging does not permit to avoid a generally very strong distortion of the soil response by the double-bounce reflection, and the estimation of different geophysical parameters of the ground, such as its humidity or roughness are significantly altered.

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Forest SAR Tomography: Principles and Applications

Cited by 67 publications

References 55 publications

Tomographic Performance of Multi-Static Radar Formations: Theory and Simulations

Tomographic Performance of Multi-Static Radar Formations: Theory and Simulations

Evaluation of P-Band SAR Tomography for Mapping Tropical Forest Vertical Backscatter and Tree Height

Analysis of the Double-Bounce Interaction between a Random Volume and an Underlying Ground, Using a Controlled High-Resolution PolTomoSAR Experiment

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