In this band combination, vegetation appeared in color ranges from orange to brown. The images were overlaid with a grid representing the limits of the USGS 7.5 minute Quadrangle series to provide a quick visual reference to a particular map. Thirty-six of the Quadrangles covered by the images were selected as areas for specific focus of change detection activities. Three different image processing approaches were tested for the identification of water bodies on both images. The most effective was to classify water separately on each image date.
Water is present in the early date, but absent in the late date.
The water files for each of the image dates were overlaid, and the pixel values compared. Vector polygon files were also generated for 36 7.5 minute USGS Quadrangles for production of transparent map overlays. The National Dam Inventory was overlaid to the water change data layer to relate case results to this given data base. Included in this analysis was a separate list of NDI dams known to have failed. A logical operation was established based upon the best estimate of the significance of each case in the total assessment of a polygon.