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Global Land Cover Characterization

Global Forest Resources Assessment (FRA 2000)

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Methodology

Boreal Forest

The forest cover map, produced at the U.S. Geological Survey (USGS) National Center for Earth Resources Observation and Science (EROS), has five classes: closed forest, open or fragmented forest, other wooded land, other land cover, and water. The classes were delineated based on circa 1995 monthly AVHRR composite images processed using a hybrid maximum-NDVI and minimum-red compositing technique. Modified mixture analysis, geographic stratification, and other classification techniques were used to estimate forest canopy density within 1 square kilometer pixels, which formed the basis for the first two classes: the closed forest (40% - 100% canopy cover), and open or fragmented forest (10 - 40% canopy cover). The remaining three FAO classes were derived using the USGS global land cover characteristics database as a stratification tool. Validated on the basis of existing reference data sets, the map is estimated to be 77 percent accurate for the first four classes (no reference data were available for water), and 86 percent accurate for the forest and nonforest classification.



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