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Title: FIELD AND LANDSCAPE BRDF OPTICAL WAVELENGTH MEASUREMENTS: EXPERIENCE TECHNIQUES AND THE FUTURE

Author
item Walthall, Charles
item ROUJEAN, JEAN-LOUIS - METEO FRANCE
item MORISETH, JEFF - UNIVERSITY OF MARYLAND

Submitted to: Remote Sensing Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2000
Publication Date: 5/8/2000
Citation: N/A

Interpretive Summary: Measurements of the directional reflectance properties of vegetation and soils at various scales are needed to further advance remote sensing. Landscape measurements are especially needed to address effects of mixed imagery pixels. This is forcing experimenters to review measurement protocols for ground-based and airborne instruments. Researchers are gaining insights on view angle choices, atmospheric corrections, and spectral variability. Although seemingly unconnected, measurement on plots from different ecosystems have contributed to our understanding of processes which led to the development of reflectance simulation models. The accuracy of most measurements is now considered consistent with the simulation models employed for global applications. There is an evolution towards measurements that consider requirements of the earth science communities and satellite algorithm validation issues. Once data archiving demands are met, an emphasis on validation efforts within the context of the new generation sensor systems is needed. It is recommended future directional measurements address compromises between angular and spectral, spatial, and temporal limitations. Thereby, providing better remote sensing tools for resource managers and producers.

Technical Abstract: Measurements of the bidirectional reflectance distribution function (BRDF) from surfaces at various scales are needed to further advance remote sensing science. Landscape BRDF measurements of vegetation are, in particular, needed to address effects of heterogeneity. This is forcing experimenters to review measurement protocols for ground-based and airborne instruments. This benefits investigators via insights on angular sampling, atmospheric correction, and spectral variability. While isolated and often disconnected, BRDF measurements collected on plots of different ecosystems have contributed to our understanding of mechanisms which led to the development of reflectance models. It now appears that accuracy assessment of most measurements is consistent with the models employed for global applications. There is an evolution towards demands for measurements which consider user requirements of the earth science communities and satellite validation issues. Once data archiving demands are met, an emphasis on validation efforts within the context of the new generation sensor systems is needed. It is recommended that future investigations acquire BRDF measurements which account for the compromises between angular and spectral, spatial, and temporal limitations, thereby, better answering to the needs of end users.