User Manual - pancroma

In addition to Landsat 7, Spectral Analysis is currently implemented for NAIC and SPOTdata as well.IMPORTANT NOTE: Although it is possible to conduct multispectral analysisusing entire Landsat scenes, be advised that the edges of the individual Landsatmultispectral bands do not match exactly. This can produce border regionscontaining invalid Euclidean Distance values because some of the multispectralband values are zero and some are non-zero. This can also influence the minand max value computations that set the color range scale. It is better for mostwork to crop off these regions before conducting multispectral analyses.Creating Masks using Spectral AnalysisVarious methods have been proposed for improving the appearance andusefulness of Landsat images that are obstructed by cloud layers. ThePANCROMA TM utilities for masking clouds use either three or five of the Landsatmultispectral band files. These files are used in a non-linear combinatorialmanner to predict which image pixels correspond to cloud cover and which donot. These methods, particularly the five-file utility based on Luo method can behighly effective.An alternative approach to masking clouds is to use PANCROMA TM multispectralanalysis tools. In addition to being highly discriminating in identifying cloudcover, these tools can also identify cloud shadows, snow, and other features thatyou may wish to remove from your image by pixel substitution from anotherimage. This section describes how this can be done. In the process, it willillustrate how a wide variety of surface features can be identified usingPANCROMA TM spectral analysis tools.The first step in this procedure is to download all of the multispectral bands forboth your target image, and for the image from which you will ‘borrow’ pixels. Iwill call this second image the Reference image. If you are processing Landsatdata you will need all the bands 1,2,3,4,5,6 and 7 for each image. The describedmethod also works for ASTER, EO-1 ALI, Landsat Reflectance and WorldView-2data files.Note that for many Landsat multispectral bundles, the thermal infrared (TIR)band6 image will be half resolution (approximately 60m/pixel) and half the size ofthe multispectral bands. Some band6 data has been processed by expandingthe image and interpolating the gaps. If your data is archived as a 60m image,you can use the PANCROMA TM TIR interpolation utility to expand and interpolateit to match the size and scale of the multispectral files.You must first generate a spectral signature using the PANCROMA TM PointSpectrum Generator TM . You will then use the spectrum and the EuclideanDistance Analyzer to identify targets, in this case clouds, with the masking optionswitched on.260