User Manual - pancroma

Low numbers mean high discrimination but possibly too narrow a specification.High number mean lower discrimination with the possibility of including unwantedpixels in your mask. I will use Level=3 for my first run. Select ‘OK’.When you do so, the TOA Reflectance Data form will again become visible. Thevalues you used for the Point Spectrum Generator TM and click ‘OK’ and the maskwill be generated as shown below.The color contour plot and the mask show the Euclidean distances between eachpixel reflectance and the spectral signature target reflectance. The mask imagehas zeroed out image pixel values at locations corresponding to the cutoff youspecified with the Level Selection track bar.The analysis has been very successful at discriminating the clouds fromeverything else in the image. In particular, note how the bright cloudy areas areidentified, while the bright snowy areas are not included. To the human eye,these areas are indistinguishable. To the multispectral “eye” of the Landsatsensors, they are quite different. Save the mask for further processing. Select‘File’ | ‘Save Grayscale Image’ | ‘GeoTiff’ from the menu and give the file a namesuch as ‘cloudMask.tif’.Although this example used Landsat, you can make masks using ASTER, EO-1ALI, Landsat Reflectance and WorldView-2 data. This example used theEuclidean Distance analyzer to identify the pixels to include in the mask.262