3DPOWER(1)

NAME

     3dpower - strategy module to calculate the power spectrum of
     a three-dimensional data set

SYNOPSIS

     3dpower
      [argument= value ...]

DESCRIPTION

     3dpower performs a  Fourier  transform  on  a  3-dimensional
     dataset  and calculates a magnitude (sqrt (power)) spectrum,
     scaled by a power of k, the  two-dimensional  wavenumber  in
     the  first two dimensions.  The output is placed in a single
     3-dimensional FITS file.

ARGUMENTS

     in=name             The  input  dataset  name.   The   input
                         dataset  must be three-dimensional.  The
                         length of each axis should be a power of
                         two.

     out=name            The output dataset name.

     Zeit=int            Not used.

     power=float         The exponent in k by which the magnitude
                         is scaled.  Default: 2.0

FILES

SEE ALSO

     fft2d(3), rowfft(3)

DIAGNOSTICS

BUGS

     The name is both awkward (because it starts  with  a  digit)
     and  misleading,  because  it is the magnitude spectrum, not
     the power spectrum, that is calculated.  The default normal-
     ization  by k^2 is inappropriate; for typical noise spectra,
     the background magnitude spectrum  is  more  nearly  propor-
     tional to 1/k.

     It might be better to calculate the log of the  power  spec-
     trum, scaling the results on output.

AUTHOR

     Lyle Bacon

HISTORY

     1994-11-11     SOI Version 0.9