User Manual - pancroma

PANCROMA TM has an image processing algorithm for removing them. It isdisabled as the default condition. (This algorithm is not needed for all images,and there is a possibility that the correction algorithm itself could introduce otherunwanted side effects.) The algorithm can be enabled by checking the ‘RemoveHighlights’ check box in the Histogram data group within the Image ProcessingData Input box. When you do so, two Combo Boxes will become visible. Theseare used to set the lower and upper limits of the transformation function levels towhich the correction will be applied.The levels are defined in terms of fractions and multiples of sigma, the standarddeviation of the output histogram. The lower level is equal to the histogrammean plus sigma plus the standard deviation divided by the lower level integer.The upper level is defined by the histogram mean plus sigma multiplied by theupper level multiple. (The algorithm will decrease the value of all channels withinits span in its attempt to correct the highlights, so it is important to exclude brightcloud, snow and surf pixels on the upper end and vegetation and ocean pixels onthe lower end.)lowerLevel = xBar + (sigma/lower Integer)upperLevel = xBar + (sigma * upper Integer)58