UCSB Biogeography Lab

UCSB IBM ERP Related Publications Abstracts

Viewing geometry of AVHRR image composites derived using multiple criteria
David M. Stoms, Michael J. Bueno, and Frank W. Davis

The U. S. Geological Survey currently generates composites of AVHRR imagery based on a single objective--maximizing the Normalized Difference Vegetation Index--as a means of reducing cloud contamination. Our research supports the findings of others that in some cases, NDVI is maximized at the expense of optimal viewing geometry; that is, satellite zenith angles are often further off-nadir than necessary to ensure cloud-free viewing. We explore various compositing methods by systematically varying weights on NDVI, satellite zenith angle, and maximum apparent temperature. A test composite of California from September 1990 appears to be superior to the maximum NDVI and maximum apparent temperature composites in several respects. First, the satellite zenith angle distribution is more closely clustered about nadir, which minimizes atmospheric path length, spatial distortion, and bidirectional reflectance effects. Second, neighboring pixels are more frequently selected with similar viewing geometry and atmospheric conditions.

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	UCSB IBM ERP Related Publications Abstracts Viewing geometry of AVHRR image composites derived using multiple criteria David M. Stoms, Michael J. Bueno, and Frank W. Davis The U. S. Geological Survey currently generates composites of AVHRR imagery based on a single objective--maximizing the Normalized Difference Vegetation Index--as a means of reducing cloud contamination. Our research supports the findings of others that in some cases, NDVI is maximized at the expense of optimal viewing geometry; that is, satellite zenith angles are often further off-nadir than necessary to ensure cloud-free viewing. We explore various compositing methods by systematically varying weights on NDVI, satellite zenith angle, and maximum apparent temperature. A test composite of California from September 1990 appears to be superior to the maximum NDVI and maximum apparent temperature composites in several respects. First, the satellite zenith angle distribution is more closely clustered about nadir, which minimizes atmospheric path length, spatial distortion, and bidirectional reflectance effects. Second, neighboring pixels are more frequently selected with similar viewing geometry and atmospheric conditions. Go to UCSB IBM ERP home page
	Email stoms@bren.ucsb.edu