title: Can Commercial Digital Cameras Be Used as Multispectral Sensors? A Crop Monitoring Test.
abstract: The use of consumer digital cameras or webcams to characterize and monitor different features has become prevalent in various domains, especially in environmental applications. Despite some promising results, such digital camera systems generally suffer from signal aberrations due to the on-board image processing systems and thus offer limited quantitative data acquisition capability. The objective of this study was to test a series of radiometric corrections having the potential to reduce radiometric distortions linked to camera optics and environmental conditions, and to quantify the effects of these corrections on our ability to monitor crop variables. In 2007, we conducted a five-month experiment on sugarcane trial plots using original RGB and modified RGB (Red-Edge and NIR) cameras fitted onto a light aircraft. The camera settings were kept unchanged throughout the acquisition period and the images were recorded in JPEG and RAW formats. These images were corrected to eliminate the vignetting effect, and normalized between acquisition dates. Our results suggest that 1) the use of unprocessed image data did not improve the results of image analyses; 2) vignetting had a significant effect, especially for the modified camera, and 3) normalized vegetation indices calculated with vignetting-corrected images were sufficient to correct for scene illumination conditions. These results are discussed in the light of the experimental protocol and recommendations are made for the use of these versatile systems for quantitative remote sensing of terrestrial surfaces.
authors.affiliation: CIRAD UPR SCA, Station La Bretagne, Saint-Denis, La Réunion, F-97408 France. valentine.lebourgeois@cirad.fr.
authors.forename: Valentine
authors.initials: V
authors.lastname: Lebourgeois
authors.affiliation: CIRAD UMR TETIS, Maison de la Télédétection, Montpellier, F-34093 France. agnes.begue@cirad.fr.
authors.forename: Agnès
authors.initials: A
authors.lastname: Bégué
authors.affiliation: Cemagref UMR TETIS, Maison de la Télédétection, Montpellier, F-34093 France. sylvain.labbe@cemagref.fr.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Labbé
authors.affiliation: CIRAD UMR TETIS, Maison de la Télédétection, Montpellier, F-34093 France. benjamin.mallavan@teledetection.fr.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Mallavan
authors.affiliation: INRA UMR LISAH, SupAgro, Montpellier, F-34060 France. laurent.prevot@supagro.inra.fr.
authors.forename: Laurent
authors.initials: L
authors.lastname: Prévot
authors.affiliation: Avion Jaune, Minéa Incubation, Montpellier, F-34196 France. bruno.roux@lavionjaune.fr.
authors.forename: Bruno
authors.initials: B
authors.lastname: Roux
keywords: Digital camera; airborne images; crop monitoring; radiometric correction; spectral sensitivity; vignetting