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Proceedings Paper

Vegetation change monitoring with spectral indices: the importance of view and sun angle standardized data
Author(s): Willem J. D. van Leeuwen; Alfredo R. Huete; Trevor W. Laing; Kamel Didan
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Paper Abstract

Remotely sensed reflectance data are often acquired at variable view and solar geometric configurations. Vegetation change monitoring with the NDVI (Normalized Difference Vegetation Index) is sensitive to the effects of solar and view angle geometry. However, by using a BRDF (Bidirectional Reflectance Distribution Function) model, the view and sun angle variability in the NDVI can be standardized. If multi- sun angle data are not available, a second method allows us to extrapolate (nadir) satellite observations to a standard sun angle by using predetermined linear regression relationships between sun angle and ground-based nadir NDVI values for a range of vegetation types. Both methods were applied to one month of daily, atmospherically corrected, multi-angle SeaWiFS (Sea viewing Wide Field-of-view Spectroradiometer) land reflectance data, with promising results. The difference in NDVI due to a sun angle change from 20 degrees to 70 degrees can be up to 50%. The NDVI values for very dense vegetated and bare soil surface areas are less affected by changes in solar zenith angles. This research shows that the sun and view angle effects on the widely used spectral indices could be standardized to improve the accuracy of regional and global vegetation and crop monitoring efforts.

Paper Details

Date Published: 17 December 1999
PDF: 10 pages
Proc. SPIE 3868, Remote Sensing for Earth Science, Ocean, and Sea Ice Applications, (17 December 1999); doi: 10.1117/12.373099
Show Author Affiliations
Willem J. D. van Leeuwen, Univ. of Arizona (United States)
Alfredo R. Huete, Univ. of Arizona (United States)
Trevor W. Laing, Univ. of Arizona (United States)
Kamel Didan, Univ. of Arizona (United States)

Published in SPIE Proceedings Vol. 3868:
Remote Sensing for Earth Science, Ocean, and Sea Ice Applications
Giovanna Cecchi; Edwin T. Engman; Eugenio Zilioli, Editor(s)

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