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dc.contributor.advisorBonn, Ferdinandfr
dc.contributor.authorBeaulieu, Nathaliefr
dc.date.accessioned2014-05-15T18:09:06Z
dc.date.available2014-05-15T18:09:06Z
dc.date.created1998fr
dc.date.issued1998fr
dc.identifier.isbn0612357562fr
dc.identifier.urihttp://savoirs.usherbrooke.ca/handle/11143/2692
dc.description.abstractThis study aims at determining how images from an airborne Synthetic Aperture Radar System, in C-band and with two polarisation configurations, can help evaluate the degree of protection offered to soils by vegetation against erosion in tropical areas. With the objective of supplying information to improve the planning of images from the RADARSAT satellite for soil conservation projects, the study aims at establishing which incident angles and which climatic conditions improve contrasts between bare and protected soils. The study encompasses three sites in Costa Rica. Two of them are located in the central cordillera, in mountainous terrain: the Tierra Blanca site where root crops dominate, and the Juan Viänas site where sugar cane is cultivated. The images have been prepared to allow the quantitative analysis of radar backscattering. The first stage of the analysis compares the discriminating capacities of images acquired on each site with different incident angles and polarisations. In general, the backscattering coefficient of crops has shown a lower tendency to diminish in function of local incident angle than that of bare soil. Results suggest that for sugar cane in relatively dry conditions, it is possible to distinguish plots of bare soil from vegetated ones on the basis of their average backscattering coefficient, except for very high incident angles (higher than 73[degree]). The second part of the analysis treats of the complementarity of the HH and VV polarisations and of images acquired with different incident angles. From the results of this study, we can draw recommendations for the acquisition of RADARSAT images even if the images studied here present a higher spatial resolution and higher incident angles, in many cases. Higher incident angles are recommended because they enhance contrasts between bare soil plots and vegetated ones. The very high incident angles at which we observed the opposite effect are not attainable with satellite radars. Relief causes important radiometric variations that must be corrected in order to appreciate the variations caused by changes in land cover. The correction method developed here can also be applied to satellite radar images. Its approach is to calculate the backscattering coefficient for a reference terrain that is flat, perfectly rough (producing isotropic backscattering) with the elevation considered for calibration, supposing that the studied terrain is also perfectly rough."--Résumé abrégé par UMIfr
dc.language.isofrefr
dc.publisherUniversité de Sherbrookefr
dc.rights© Nathalie Beaulieufr
dc.titleUtilité des images de radar aéroporté en bande C pour l'évaluation du stade de croissance de la canne à sucre et des cultures maraîchères en milieu tropical, dans une optique de conservation des solsfr
dc.typeThèsefr
tme.degree.disciplineTélédétectionfr
tme.degree.grantorFaculté des lettres et sciences humainesfr
tme.degree.levelDoctoratfr
tme.degree.namePh.D.fr


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