Thematic Mapper Analysis of Tree Cover in Semiarid Woodlands Using a Model of Canopy Shadowing
نویسندگان
چکیده
T h e effect of variable tree canopy cover, shadows, and topography on Thematic Mapper (TM) data was examined for blue oak (Quercus douglasii) woodland and wooded grassland on rugged terrain in central California. Thematic Mapper data were analyzed from September 1986 (trees in leaf, grass understory senescent) and December 1984 (trees leafless, grasses emerging. Tree cover measured in 84 60 m x 60 m field plots was strongly negatively correlated with TM radiances (excluding Band 6) on both dates, and was positively correlated with the Normalized Difference Vegetation Index (NDVI) in September. TM Band 3 was most highly correlated with canopy cover. The Li-Strahler geometric-optical canopy reflectance model was used to predict the projected cover of shadow cast by the trees based on crown and illumination geometry. The spectral model was ag-
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