Assessing Land Cover Changes Using Standardized Principal Component and Spectral Angle Mapping Techniques

This paper reports a practical application of digitally enhanced Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) data coupled with principal component analysis (PCA) and spectral angle mapping (SAM) techniques to assess changes in vegetation and land condition within the U.S. Army installation at Fort Bliss, Texas. Fort Bliss is located in a semi-arid desert environment where the vegetation is sparse, diverse and highly sensitive to climatic variability. Despite the widespread use of vegetation indices to map vegetation cover in arid and semi-arid environments, we believe that in an area like Fort Bliss, the non-photosynetic plant tissue may be a better indicator of ecosystem health than photosynthetic active vegetation. Results of this study indicate that the main drivers for both temporal and spatial change are climate and various types of disturbance, such as fire, livestock grazing and military training activities.