%N spaxsw %F $MIR/src/subs/spaxsw.for
%D Switch (freq/velo) the spectral axis descriptors of an image
%P nebk/rjs
%: utilities
%B
      subroutine spaxsw (lh, switch, ctype, cdelt, crval)
      implicit none

      integer lh
      double precision cdelt, crval
      character*(*) switch, ctype

   Switch the reference value, pixel increment and axis type for the
   spectral axis of image to those describing the axis in one of 
   frequency or velocity (radio or optical definition)

  Input
    lh         Input handle
    switch     The requested type of the spectral axis.  Choose from
                 ' '        meaning  freq    -> radio
                                     radio   -> frequency
                                     optical -> frequency
                 'radio'    meaning          -> radio
                 'optical'  meaning          -> optical
  Input/output
    ctype      Axis type. Should start with one of FREQ, FELO (optical 
               velocity and  VELO (radio velocity)
    cdelt      Pixel increment (GHz or km/s)
    crval      Reference value (GHs or km/s)
