Les images multispectrales incluant une bande rouge et une bande infrarouge ont prouve leur efficacite pour la discrimination entre sol et vegetation et le suivi cultural en teledetection. Mais elles restent rarement utilisees pour l'imagerie au sol ou par drone, du fait de la non disponibilite de capteurs adaptes. Nous proposons ici une solution originale pour obtenir simultanement les bandes rouge et infrarouge a partir d'un appareil photographique couleur ordinaire, apres avoir retire le filtre interne bloquant l'infrarouge. Nous decrivons d'abord l'approche theorique, ainsi que des resultats simules sur un jeu de donnees spectrales, pour deux types d'appareils. Des exemples d'acquisition sur le terrain en conditions reelles sont ensuite presentes, et compares a une acquisition couleur standard pour la discrimination sol/plantes. Dans la plupart des cas notre approche apporte une amelioration significative, ouvrant de nouvelles opportunites pour les applications de suivi de culture. / Multispectral images including red and near-infrared bands have proved their efficiency for vegetation-soil discrimination and agricultural monitoring in remote sensing applications. But they remain rarely used in ground and UAV imagery, due to a limited availability of adequate 2D imaging devices. In this paper, we propose and evaluate an original solution to obtain simultaneously the near-infrared and red bands from a standard RGB camera, after having removed the near-infrared blocking filter inside. First, the theoretical approach is described, as well as simulated results on a set of soil and vegetation luminance spectra with two different still cameras (Canon 500D and Sigma SD14). Then examples of images obtained in real field conditions are given, and compared with standard colour image acquisition for pixel-based plant/soil discrimination, using an automatic thresholding method. It appears that in most cases our new acquisition procedure brings a significative improvement, opening new opportunities for crop monitoring applications.
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