POWRSPEC3(1)

NAME

     powrspec3 -  calculate a 3-d power spectrum of  a  3-d  data
     set

SYNOPSIS

     powrspec3
      [-v] [argument= value ...]

DESCRIPTION

     powrspec3 is designed to calculate  the  full  3-dimensional
     power  spectrum  of  a  time series of 2-dimensional images.
     The input data are optionally apodized by a (1-x^2)^2  taper
     operating  between  specified  inner  and outer radii of the
     images and a similar taper  operating  on  the  time  (image
     number).    The   input  data  series  must  consist  of  3-
     dimensional  data  cubes  (such   as   those   produced   by
     track_region),  each  treated  as  a separate data set.  The
     module is designed to work with a  series  of  2-dimensional
     images  as well, with the entire data series is treated as a
     single data set.  This is not yet implemented however.

     The Fast Fourier Transform used is the parallelized SGI math
     library single-precision function sfft3du().

OPTIONS

     in=Dataset_Name     NO DEFAULT

     out=Dataset_Name    NO DEFAULT

     mask_in=real        The inner radius  of  the  annulus  over
                         which  image  apodization is applied, in
                         units of  the  image  halfwidth  in  its
                         minimum  dimension.  If the inner radius
                         exceeds the outer radius, sharp (boxcar)
                         apodization  is  imposed  at the "outer"
                         radius.  (Default: 0.9375)

     mask_out=real       The outer radius  of  the  annulus  over
                         which  image apodization is applied.  If
                         the outer radius is 0, no image apodiza-
                         tion will be applied.  (Default: 1.0)

     apodize=real        The fractional distance from the  series
                         endpoints  over which symmetric temporal
                         apodization  is  applied.   If   it   is
                         greater  than  or  equal  to 1, temporal
                         apodization  is  suppressed.   (Default:
                         0.96875)

EXAMPLES

FILES

SEE ALSO

     track_region (1), sfft3du (3F)

DIAGNOSTICS

     soi_errno is returned to the driver, but no results keys are
     set.

BUGS

     Calculating the power  spectrum  of  a  collection  of  two-
     dimensional images is not yet implemented.

     The workspace size initialized  by  sfft3dui()  exceeds  the
     amount  stated  in  the man page by an amount of roughly 2 +
     log_4 (planes); the extra workspace allocated should suffice
     for  values  of  the  number  of  planes up to at least 64K;
     unfortunately sfft3dui does not return an error  status  and
     merrily  writes  beyond its bounds, so unpredictable results
     are possible when the workspace is insufficient.

     The module has not been tested with non-square images.

     It might be better to output the (scaled) log of  the  power
     spectrum  or  the  magnitude spectrum rather the power spec-
     trum.

AUTHOR

     Rick Bogart

HISTORY

     1997-03-12     SOI Version 2.2