User Manual - pancroma

30. SPECTRAL Pan Sharpening Algorithm________________________________________________________All of the methods previously described are designed for pan sharpening colorcomposite images. It may be desirable for to increase the resolution of a singlemultispectral or hyperspectral band if a single band rather than a bandcombination contains the more useful information. This can be done for Landsatand SPOT data using PANCROMA TM SPECTRAL pan sharpening algorithm.The SPECTRAL algorithm does this in two steps. In the first step, themultispectral or hyperspectral band is expanded to match the size of thepanchromatic image. This creates a sparse image with only 25% of the digitalnumbers (DNs) as the panchromatic image. An example of such an image isshown below.In the next step, the missing information is synthesized using both the DNs fromthe multispectral or hyperspectral band and the DNs from the panchromaticband. This is done in a way such that very little spectral distortion is introduced.A comparison between the original Landsat multispectral band image, the pansharpened multispectral band and the panchromatic band is shown in the threeimages below.78