This exercise will introduce a second aspect which deals with the enhancement of the spectral component of an image. Convolution filtering deals with the spatial component by mathematically manipulating pixels that fall within a defined area of the image.
Spectral enhancement deals with the non-spatial nature of an image, the spectral component.
Your Logan image consists of 6 of the 7 available bands of the Landsat Thematic Mapper. Depending on the band combinations, different features have different colors. This is because there are different values in each of the 6 bands provided to you and any combination of three of these to the three color guns of the screen will give you different colors. Spectral enhancement takes advantage of the fact that different features on the surface have different reflectance characteristics in different bands of the electromagnetic spectrum. Others, such as principal components analysis and band ratios we will be experimenting with.