10.07.2015 Views

User Manual - pancroma

User Manual - pancroma

User Manual - pancroma

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carefully. PANCROMA TM is able to process full-size Landsat multispectral bandson most modern systems, but is not able at this time to process the panchromaticband without subsetting it.In order to compute the frequency spectrum of an image, first open a grayscaleband file. Then select ‘FFT’ | ‘Image Fourier Analysis’ | ‘Forward 2D ImageTransform’. A dialog box will appear allowing you to input a scale factor.Because the spectra are often fractional values less than one, it is usuallynecessary to scale them for display. The default value is 1000.The FFT output consists of a number real and an imaginary part. PANCROMA TMwill display the magnitude of the vector consisting of these parts, according to theequation:MAGNITUDE =((REAL 2 + IMAGINARY 2 ) 1/2 ) * scaleFactorSome examples of the magnitude frequency spectra of some images are shownbelow:Sharp squareImage magnitude spectrum286

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