Using Thematic Mapper Imagery to Examine - Forest Understory


Most recent research in remote sensing has focused on the canopy vegetation characteristics with little attention given to the associated understory. The objective of this study was to examine the feasibility of detecting the presence or absence of vegetated understory for varying canopy closures within the Sierran mixed conifer zone using the high spectral and spatial resolution of Landsat Thematic Mapper (TM) data. Canopy and understory density and composition were measured in the field for 60 plots within a USGS 7.5 minute quadrangle map. The TM image was classified using an unsupervised classification approach. The TM band combinations evaluated include (A) 2,3,4; (B) 2,3,4,7; (C) 1,3,4,5; (D) 2,3,4,5,7; (E) 2,4,5; and (G) 4,5,7. The forested areas were stratified into three categories of canopy closure: sparse (<30percent), moderate (30 to 70 percent) and dense (>70percent). In each of the canopy classes, presence or absence of vegetated understory was then determined using spectral response pattern analysis. All of the ground data were then used to assess the accuracy of the classification for each of the seven band combinations. Any TM band combination including band 5 produced equally accurate canopy and understory classification results. Overall, the accuracy of understory presence or absence ranged from 55 to 69 percent.


Natural Resources and the Environment

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Journal Title

Photogrammetric Engineering and Remote Sensing


American Society for Photogrammetry and Remote Sensing

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©1990 American Society for Photogrammetry and Remote Sensing