17 research outputs found
Performance of change detection using remotely sensed data and evidential fusion: Comparison of three cases of application.
International audienc
Canopy Bidirectional Reflectance Calculation based on adding method and SAIL formalism
International audienc
Suivi de lâĂ©tat hydrique du sol par tĂ©lĂ©dĂ©tection radar
National audienceDepuis 25 ans, le site de lâOrgeval est le lieu dâune riche activitĂ© de dĂ©veloppements mĂ©thodologiques, afin dâestimer lâhumiditĂ© de surface du sol par tĂ©lĂ©dĂ©tection microondes active. La rĂ©solution spatiale Ă©tait un point dĂ©terminant pour le choix des hypothĂšses considĂ©rĂ©es dans les mĂ©thodes dâinversion. Ce chapitre prĂ©sente les principaux travaux qui ont Ă©tĂ© menĂ©s pour lâestimation et le suivi de lâĂ©tat hydrique. Ils sont classĂ©s en fonction de lâĂ©chelle spatiale des approches dâinversion. Il prĂ©sente lâeffort expĂ©rimental rĂ©alisĂ© sur le site de lâOrgeval pour la validation des mĂ©thodologies satellite, ainsi que le suivi de lâĂ©tat hydrique Ă lâĂ©chelle de la parcelle. Lâapport des nouveaux capteurs mĂ©triques permettant une analyse fine Ă une Ă©chelle intraparcellaire est ensuite prĂ©sentĂ© et les mĂ©thodologies permettant des estimations Ă basse rĂ©solution spatiale sont dĂ©taillĂ©es, Ă travers des agrĂ©gations des donnĂ©es ROS ou lâutilisation des diffusiomĂštres radar
Canopy bidirectional reflectance calculation based on Adding method and SAIL formalism: AddingS / AddingSD
The SAIL model (proposed by Verhoef) is largely used in the remote sensing community to calculate the canopy Bidirectional Reflectance Distribution Function. The simulation results appear acceptable compared to observations especially for not very dense planophile vegetation. However, for erectophile dense crops (e.g. corn) the simulations appear less accurate. This inadequacy is due to the assumption that the multiple scattered fluxes are isotropically distributed. The SAIL parameters are interpretable at the level of elementary layer components. Now, the Adding method (initially proposed by Van de Hulst) provides a good framework to model the radiative transfer inside a vegetation layer, but its parameter estimation lies on very simple geometric modeling of the canopy. In this paper, we first propose an adaptation of the Adding method using the SAIL model canopy representation in the turbid case: it is called AddingS model. Such an approach allows to overcome the isotropy assumption. Second, AddingS is extended to the Discrete case: defining the AddingSDmodel. It allows to take into account the multi hot spot effect. Moreover, the AddingS and AddingSD models allow to check the energy conservation in respectively turbid and discrete cases. Finally, in order to keep reasonable time performance, a fast computation method was developed
Backscattering over bare soils : measurements and simulations using SIRC-XSAR and ERASME 1994 data over Orgeval
The comparison between radar data and numerical simulations from a theoretical model (IEM) and a semi-empirical algorithm shows adequacies and limits. The IEM model reproduces well radar scatter over smooth surfaces. The algorithm agrees with the backscatter response over rough surfaces at medium incidence angle. / La comparaison entre des données radar et des simulations numériques obtenues à partir d'un modÚle théorique (IEM) et un algorithme semi-empirique présente des convergences et des limites. Le modÚle IEM reproduit bien la diffusion radar sur les surfaces non rugueuses. L'algorithme est en harmonie avec la rétrodiffusion radar sur les surfaces rugueuses pour une valeur moyenne de l'angle d'incidence
AIMWATER Analysis, investigation and monitoring of water resources for the management of multi-purpose reservoirs. Final report
AIMWATER : Contract n" ENV4-CT98-0740 (DG 12-ESCY)SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : GR 1996 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc