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Measuring the directional variations of land surface reflectance from MODIS / François-Marie Bréon in IEEE Transactions on geoscience and remote sensing, vol 53 n° 8 (August 2015)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 53 n° 8 (August 2015) . - pp 4638 - 4649 Titre : Measuring the directional variations of land surface reflectance from MODIS Type de document : Article/Communication Auteurs : François-Marie Bréon, Auteur ; Eric F. Vermote, Auteur ; Emilie Fedele Murphy, Auteur ; Belen Franch, Auteur Année de publication : 2015 Article en page(s) : pp 4638 - 4649 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] distribution du coefficient de réflexion bidirectionnelle BRDF [Termes IGN] filtrage du bruit [Termes IGN] image Aqua-MODIS [Termes IGN] image Terra-MODIS [Termes IGN] réflectance de surface [Termes IGN] série temporelle Résumé : (Auteur) The directional variation of land surface reflectance generates an apparent noise in the time series acquired from satellites with variable observation geometries, which can be corrected through appropriate modeling of the bidirectional reflectance distribution function (BRDF). In a previous paper, we described and validated the VJB method that estimates a target BRDF shape and corrects for directional effects and yet retains the high temporal resolution of the measurement. Here, we analyze its potential to measure the BRDF of targets at the 0.5-km resolution of Moderate Resolution Imaging Spectroradiometer (MODIS). The description of the BRDF in the NASA MCD43A1 product shows very large temporal variations that are unrealistic. However, the reflectance time series, normalized to a standard observation geometry using this modeling, have a similar quality as those derived using VJB. Conversely, the MCD43A1 modeled reflectances for a nonstandard geometry are unrealistically variable. These results indicate that the standard BRDF model inversion used to derive the MCD43A1 product is underconstrained due to the limited directional sampling of the 16-day composite period. The apparent noise in the corrected reflectance time series is significantly larger than the one obtained at lower spatial resolution, and is very much a function of the spatial heterogeneity of the area surrounding the target. These results strongly indicate that the multitemporal MODIS measurement at high spatial resolution (0.5 km) is affected by a change in the effective resolution for off-nadir observation and by inaccurate registration. The resulting noise in the measurements precludes an accurate measurement of the BRDF at such a scale. Numéro de notice : A2015-369 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2015.2405344 En ligne : https://doi.org/10.1109/TGRS.2015.2405344 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76806 [article]

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Continental scale hotspot observations of Australia at sub-degree angular resolution from POLDER / F. Grant in International Journal of Remote Sensing IJRS, vol 25 n° 18 (September 2004)  

Public [article]  inInternational Journal of Remote Sensing IJRS > vol 25 n° 18 (September 2004) . - pp 3625 - 3636 Titre : Continental scale hotspot observations of Australia at sub-degree angular resolution from POLDER Type de document : Article/Communication Auteurs : F. Grant, Auteur ; C. Heyraud, Auteur ; François-Marie Bréon, Auteur Année de publication : 2004 Article en page(s) : pp 3625 - 3636 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] analyse comparative [Termes IGN] Australie [Termes IGN] bande spectrale [Termes IGN] carte de la végétation [Termes IGN] image ADEOS-POLDER [Termes IGN] réflectance végétale [Termes IGN] tâche claire Résumé : (Auteur) Angular signatures of the innermost few degrees of the hotspot are retrieved on Australian land surfaces with an angular resolution better than 0.5° and a spatial resolution of around 150 km, using data from the Polarization and Directionality of the Earth's Reflectances (POLDER) instrument on the Advanced Earth Observing Satellite (ADEOS). These constitute the first comprehensive hotspot measurements at the scale of a continent. The retrieval technique requires that the hotspot characteristics at small angular scales are approximately invariant over a region of about 50km in extent, but accommodates pixel-to-pixel variations in the other characteristics, of the angular signature. Continental maps of the amplitude and half-width of the hotspot, in two spectral bands, are presented for two 41-day orbit cycles in different seasons and compared with a vegetation map. The half-widths are predominantly in the range 0.5°-1.5°, with no systematic difference between the 670 nm and 865 nm bands, and show little spatial structure. The maps of hotspot amplitude display significant spatial structure that corresponds closely to the vegetation map. Generally, areas of trees and tall shrubs are characterized by low hotspot amplitudes, while cropland, grassland and areas of low shrubs have high hotspot amplitudes. The evergreen broadleaf eucalypt forests are notable in that the amplitude is low at 670 nm and high at 865 nm. Numéro de notice : A2004-354 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/01431160310001648000 En ligne : https://doi.org/10.1080/01431160310001648000 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26881 [article]

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Bidirectional reflectance of Earth targets: evaluation of analytical models using a large set of spaceborne measurements with emphasis on the Hot Spot / F. Maignan in Remote sensing of environment, vol 90 n° 2 (30/03/2004)  

Public [article]  inRemote sensing of environment > vol 90 n° 2 (30/03/2004) . - pp 210 - 220 Titre : Bidirectional reflectance of Earth targets: evaluation of analytical models using a large set of spaceborne measurements with emphasis on the Hot Spot Type de document : Article/Communication Auteurs : F. Maignan, Auteur ; François-Marie Bréon, Auteur ; R. Lacaze, Auteur Année de publication : 2004 Article en page(s) : pp 210 - 220 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Rayonnement électromagnétique [Termes IGN] albedo [Termes IGN] distribution du coefficient de réflexion bidirectionnelle BRDF [Termes IGN] image ADEOS-POLDER [Termes IGN] réflectance [Termes IGN] rétrodiffusion [Termes IGN] tâche claire [Termes IGN] transfert radiatif Résumé : (Auteur) Multidirectional observation from the spacebome POLDER (Polarization and Directionality of the Earth Reflectance) instrument makes it possible to measure the bidirectional reflectance of a large variety of Earth targets. A careful selection of cloud-free measurements with a large directional coverage lead to about 22,000 sets of measured Bidirectional Reflectance Distribution Functions (BRDFs). This data set is used to evaluate the ability of analytical models to reproduce the observed directional signatures. Among those evaluated, the best models appear to be the three-parameter linear Ross-Li model, and the nonlinear Rahman-Pinty-Verstraete (RPV) model. On the other hand, all models fail to accurately reproduce the sharp reflectance increase (hot spot) close to the backscattering direction. Based on physical considerations, we suggest a modification of the Ross-Li model, without adding a free parameter, to account for the complex radiative transfer within the canopy that leads to the hot spot signature. The modified linear model performs better than all others, including the RPV nonlinear model. Although the correction modifies the retrieved directional signature parameters, it does not change significantly the surface albedo estimates. Numéro de notice : A2004-142 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2003.12.006 En ligne : https://doi.org/10.1016/j.rse.2003.12.006 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26669 [article]

Airborne measurement of hot spot reflectance signatures / F. Camacho-De Coca in Remote sensing of environment, vol 90 n° 1 (15/03/2004)  

Public [article]  inRemote sensing of environment > vol 90 n° 1 (15/03/2004) . - pp 63 - 75 Titre : Airborne measurement of hot spot reflectance signatures Type de document : Article/Communication Auteurs : F. Camacho-De Coca, Auteur ; François-Marie Bréon, Auteur ; M. Leroy, Auteur ; F.J. Garcia-Haro, Auteur Année de publication : 2004 Article en page(s) : pp 63 - 75 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] ARAT [Termes IGN] composition colorée [Termes IGN] couvert végétal [Termes IGN] cultures [Termes IGN] distribution du coefficient de réflexion bidirectionnelle BRDF [Termes IGN] Espagne [Termes IGN] image DAIS [Termes IGN] image en couleur composée [Termes IGN] image HYMAP [Termes IGN] image POLDER [Termes IGN] Leaf Area Index [Termes IGN] réflectance végétale [Termes IGN] tâche claire [Termes IGN] transfert radiatif Résumé : (Auteur) The so-called hot spot is a fine directional signature of the surface reflectance observed for phase angles close to zero. In this paper, we analyze and discuss several such signatures acquired from the airborne POLDER and HyMap instruments during the DAISEX'99 campaign over agricultural crops. The observed signatures are very similar to those acquired from space at a resolution of several tens of kilometers [J. Geophys. Res. 107 (2002)], which provides further evidence that the hot spot is a scale-free feature. The hot spots can be fitted by a twoparameter function (amplitude and width) of the phase angle derived from canopy radiative transfer modeling. The model predicts that the amplitude is directly related to the leaf reflectance, while the width is a function of the canopy structure. The retrieved leaf reflectance values over a wide spectral range are in very good agreement with noncoincident laboratory measurement. The retrieved half widths are on the order of 1° with no significant variability between the analyzed targets. There is an apparent spectral variability in the half width, a feature in contradiction with the modeling, although the variations are not larger than the uncertainties. Numéro de notice : A2004-128 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2003.11.019 En ligne : https://doi.org/10.1016/j.rse.2003.11.019 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26655 [article]