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			       P2

      This subroutine computes a one or two-dimensional Fourier transform
 and/or the corresponding power spectrum of a SAD file, and writes
 them to a new file or files.  The power spectrum is equal to the sum
 of the squares of the real and the imaginary parts of the (complex) 
 Fourier transform, and may be output in a symmetric form
 (positive and negative frequencies) or a nonsymmetric form (only positive
 frequencies).  The Fourier transform may be output in two different 
 formats, either complex or in an encapsulated format where the odd 
 columns contain the real part, and the even columns contain the imaginary 
 part.  For a file of M columns and N rows for which a two-dimensional
 transform is computed, the output Fourier transform will will have a size 
 equal to (INT(M/2)+1) columns by N rows for the complex format, or 
 2(INT(M/2)+1) columns by N rows for the encapsulated format.  The 
 output frequencies range from 0 to 0.5 pixel pairs per pixel (0 to pi)
 along rows and 0 to 0.5 pixel pairs per pixel to the lowest nonzero 
 negative frequency along columns.  The power spectrum file will be 
 INT(M/2)+1 columns by INT(N/2)+1 rows in the nonsymmetric case and 
 2*INT(M)/2)+1 columns by 2*INT(N/2)+1 rows in the symmetric case.

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 Enter an option:                               2-APR-1995 16:30:02.12
 OPTION=P2                                                                
 PWRSPEC, Version 2
 Open the file whose Fourier transform and/or power spectrum is to be computed
 Enter the filename:  (<CR> for default)
 FILE_IN=CE
 There is one map in the file
 Reading from the file
  100 rows of  100 pixels in R4 format
 Enter the area to be transformed:
 Enter start-column end-column start-row end-row:  (default = entire map)
 BOUNDARIES=
          1
        100
          1
        100
 Enter the dimension of the fourier transform/power spectrum:  (default = 2)
 DIMENSION=
          2
 Enter a command:  A = Writes only the fourier transform
                   B = Writes only the power spectrum (default)
                   C = Writes the power spectrum and the fourier transform
  
 COMMAND=A
 Enter a choice for the Fourier transform format:
               C = Complex (default)
               E = Encapsulated (odd columns real;  even columns imaginary
  
 FOURIER_TRANSFORM_FORMAT=E
 Do you wish to make the image to be transformed approximately continuous
 at the edges?  (default = Y)
 CONTINUOUS=
  T
 Enter the number of pixels to be used in the cosbell
 smoothing on each side:  (default = 4)
 NUMBER=
          4
 Enter the name of the file to contain the fourier transform:
 (default = TCE)
 FILE_FOURIER=
 TCE                                     
 Creating new file
 For the Fourier transform output file
 Enter the ouput map number(s):  (default = 1)
 MAPS_OUT=
          1

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