User Manual - pancroma

determine if one number is different from another, in multispectral signaturematching for example. The signal to noise ratio is expected to be much better forLandsat 8 as well.This increased resolving power comes with a price. Landsat 8 scenes areconsiderably larger than Landsat 7 scenes Landsat 8 scenes on the other handwill be in the neighborhood of 1.5GB (unzipped), more than twice as large asLandsat 7 scenes.Another reason for the large difference in size between Landsat 8 and Landsat 7scenes is the number of spectral bands. Landsat 7 has 8 or 9, depending onwhether the scene contains one or two versions of the thermal infrared (TIR)band (high gain/low gain). Landsat 8 has two additional multispectral bands, twonarrower TIR bands in place of the single Landsat 7 TIR band and apanchromatic band for a total of 11 bands. The two additional bands are anarrow Coastal Aerosol band at a slightly shorter wavelength than the blue bandand a Cirrus band sensitive to radiation wavelengths between 1.36 and 1.38microns.Another difference between Landsat 8 and its predecessor is the character of thepanchromatic band. The Landsat 7 panchromatic band is sensitive toelectromagnetic radiation between wavelengths 0.52 to 0.90 microns. This rangeexcludes visible blue but includes the NIR band. It was probably chosen in orderto produce a clearer image, since the blue band is most susceptible to Rayleighscattering than any other. The result however is severe color distortion when theband was used for pan sharpening. It takes a lot of computational effort to correctthis and few do it very well. (The PANCROMA ELIN algorithm is one of thebest for removing such distortions).The Landsat 8 panchromatic band covers a range of 0.50 to 0.68 microns. Thisstill excludes the blue band but also excludes the NIR band, spanning the visiblegreen and red bands. As a result we can still expect color distortions resultingfrom pan sharpening, but perhaps not quite so severe as Landsat 7. The bandspecifications are shown in the table and graphic below.Finally, the passbands for Landsat 8 bands 5, 6 and 7 are narrower (morediscriminating) than the corresponding Landsat 7 bands. This will benefit spectralsignature matching and other target discrimination techniques.17