%0 Journal Article %J International Journal of Remote Sensing %D 2000 %T Potential NDVI as a baseline for monitoring ecosystem functioning %A Stoms, D. M. %A Hargrove, W. W. %K AVHRR %K California %K GAP %K managed areas %K NDVI %K net primary production %K NPP %K Oregon %K regression tree analysis %K time integrated NDVI %K Washington %X Baseline data are needed to determine the overall magnitude and direction of change in ecosystem functioning. This letter presents an approach to estimate potential NDVI from environmental variables and training data of actual NDVI in nature reserves. Patterns of deviations of actual NDVI from the baseline generally correspond with land-use types in the western United States. %B International Journal of Remote Sensing %V 21 %P 401-407 %8 2000 %G eng %U ://000084681200014 %0 Journal Article %J Photogrammetric Engineering and Remote Sensing %D 1998 %T Map-guided classification of regional land-cover with multi-temporal AVHRR data %A Stoms, D. M. %A Bueno, M. J. %A Davis, F. W. %A Cassidy, K. M. %A Driese, K. L. %A Kagan, J. S. %K accuracy assessment %K AVHRR %K gap analysis %K Intermountain Semidesert ecoregion %K map-guided classification %K National Vegetation Classification Standards %K NVCS %K remote sensing %X Cartographers often need to use information in existing land-cover maps when compiling regional or global maps, but there are no standardized techniques for using such data effectively. An iterative, map-guided classification approach was developed to compile a spatially and thematically consistent, seamless land-cover map of the entire Intermountain Semi-Desert ecoregion from a set of semi-independent subregional maps derived by various methods. A multi-temporal dataset derived from AVHRR data was classified using the subregional maps as training data. The resulting regional map attempted to meet the guidelines of the proposed National Vegetation Classification Standards for classification at the alliance level. The approach generally improved the spatial properties of the regional mapping, while maintaining the thematic detail of the source maps. The methods described may be useful in many situations where mapped information exists but is incomplete, compiled by different methods, or is based on inconsistent classification systems. %B Photogrammetric Engineering and Remote Sensing %V 64 %P 831-838 %8 1998 %G eng %U ://000075109200012 %0 Journal Article %J Photogrammetric Engineering and Remote Sensing %D 1997 %T Viewing geometry of AVHRR image composites derived using multiple criteria %A Stoms, D. M. %A Bueno, M. J. %A Davis, F. W. %K AVHRR %K cloud removal %K compositing %K NDVI %K Normalized Difference Vegetation Index %K satellite zenith angle %X 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. %B Photogrammetric Engineering and Remote Sensing %V 63 %P 681-689 %8 1997 %G eng %U ://A1997XC40700004