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Improvement of Bare Soil Semi-Empirical radar Backscattering Models (Oh and Dubois) with SAr Multi-Spectral Satellite Data (X-, C- and L-Bands)

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Advances in remote Sensing 2016年第4期5卷 296-314页

作者： rémy fieuzal Frédéric Baup Centre d’études de la BIOsphère (CESBIO) Université de Toulouse CNES/CNRS/IRD/UPS Toulouse France

The objective of this study is to improve the performance of semi-empirical radar backscatter models, which are mainly used in microwave remote sensing (Oh 1992, Oh 2004 and Dubois). The study is based on satellite and ground data collected on bare soil surfaces during the Multispectral Crop Monitoring experimental campaign of the CESBIO laboratory in 2010 over an agricultural region in southwestern France. The dataset covers a wide range of soil (viewing top soil moisture, surface roughness and texture) and satellite (at different frequencies: X-, C- and L-bands, and different incidence angles: 24.3° to 53.3°) configurations. The proposed methodology consists in identifying and correcting the residues of the models, depending on the surface properties (roughness, moisture, texture) and/or sensor characteristics (frequency, incidence angle). Finally, one model has been retained for each frequency domain. results show that the enhancements of the models significantly increase the simulation performances. The coefficient of correlation increases of 23% in mean and the simulation errors (rMSE) are reduced to below 2 dB (at the X and C-bands) and to 1 dB at the L-band, compared to the initial models. At the X- and C-bands, the best performances of the modified models are provided by Dubois, whereas Oh 2004 is more suitable for the L-band (r is equal to 0.69, 0.65 and 0.85). Moreover, the modified models of Oh 1992 and 2004 and Dubois, developed in this study, offer a wider domain of validity than the initial formalism and increase the capabilities of retrieving the backscattering signal in view of applications of such approaches to stronglycontrasted agricultural surface states.

关键词： Semi-Empirical Backscatters Model Oh Model Dubois Model Multi-Frequency (X- C- L-Band) Microwave TerraSAr-X radarsat-2 Alos-PALSAr

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Monitoring Wheat and rapeseed by Using Synchronous Optical and radar Satellite Data—From Temporal Signatures to Crop Parameters Estimation

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Advances in remote Sensing 2013年第2期2卷 162-180页

作者： rémy fieuzal Frédéric Baup Claire Marais-Sicre Centre d’Etudes Spatiales de la Biosphère (CESBIO) Université de Toulouse Toulouse France

This paper investigates the sensitivity of multi-temporal SAr data acquired at different frequencies (X-, C-and L-bands), polarizations (HH, VV, VH and HV) and incidence angles (from 24° to 53°) during the growing season of two winter crops (rapeseed and wheat). This study was part of a multi-sensor crop-monitoring experiment that was performed from February to November 2010 (MCM’10). During the experiment, dense series of satellite data were acquired in microwave, optical and thermal domains (more than 150 images were provided by TerraSAr-X, radarsat-2 Alos, Formosat-2, Spot-4/5 and Landsat-5/7) were synchronous with ground measurements over an agricultural area located in southwestern France, near Toulouse. An angular normalization of radar signals is first performed for each crop type at X-and C-bands by using a dense temporal satellite series and the complementarity provided by microwave and optical data. The results show that the angular sensitivity of radar backscatter decreases with the increase of the vegetation index (from 0.4 dB.°ˉ1 over bare soils to 0.05 dB.°ˉ1 for fully vegetated fields). Lower angular sensitivity is observed at X-band (compared to C-band), and for the cross-polarized signal. Analyses of the temporal signatures of the radar backscatter show a well-marked signal dynamic at X-, C-and L-bands, depending on the crops and theirs associated phenological stages. During the stems elongation of wheat while the NDVI increases of 0.2, a dynamic of 10 dB is observed at X-band and at C-band with VV polarization. Interesting behaviors are also observed during the crop senescence with an increase of several dB (depending on the sensor configuration), while the NDVI decreases of 0.5. Over rapeseed, cross-polarized backscatters offer promising dynamic of 6 dB during the seed development, while the NDVI saturates at maximum values. The use of radar signals, in complement of optical, for crop parameters monitoring is achieved in terms of leaf area index a

关键词： TerraSAr-X radarsat-2 Alos X-Band C-Band L-Band SAr Formosat-2 Spot-4/5 Optical Wheat rapeseed Crop Height Leaf Area Index

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Sensitivity of X-Band (σ⁰, γ) and Optical (NDVI) Satellite Data to Corn Biophysical Parameters

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Advances in remote Sensing 2016年第2期5卷 103-117页

作者： Frédéric Baup Lucio Villa rémy fieuzal Maël Ameline Centre d’Etudes de la BIOsphère (CESBIO) Université de Toulouse CNES/CNRS/IRD/UPS Toulouse France Asociación para la Investigación y el Desarrollo Integral (AIDEr) Lima Perú

The objective of this work was to evaluate the sensitivity of three different satellite signals (interferometric coherence (γ), backscattering coefficient (σ0) and NDVI) to corn biophysical parameters (leaf area index, height, biomass and water content) throughout its entire vegetation cycle. All of the satellite and in situ data were collected during the Multi-spectral Crop Monitoring (MCM’10) experiment conducted in 2010 by the CESBIO Laboratory over eight different agricultural sites located in southwestern France. The results demonstrated that the NDVI is well adapted for leaf area index monitoring, whereas γ27.3° is much more suited to the estimation of the three other Biophysical Parameters throughout the entire crop cycle, with a coefficient of determination ranging from 0.83 to 0.99, using non-linear relationships. Moreover, contrary to the use of the NDVI or backscattering coefficients, the use of coherence exhibited a low sensitivity to the changes in vegetation and soil moisture occurring during senescence, offering interesting perspectives in the domain of applied remote sensing

关键词： Corn Biophysical Parameters Interferometric Coherence Backscattering Coefficients NDVI

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