TABLE

 

        CLIC\TABLE Name Status [/RESAMPLE nc ref val inc code  shape  width]
    [/COMPRESS tmax uvmax] [/FREQUENCY name rest-freq] [/DROP  n1 n2] [/FFT]

    This command will create a UV data Table from  the  current  index.  not
    given, the most recently created table will be  extended.   'Status' may
    be  OLD  (default  value  if  not  specified)  to  extend  and  existing
    table, or NEW to create a new table.

    The bands and subbands used are given by command SET SELECTION (See HELP
    SET SELECTION).

    The weighting modes are given by command SET WEIGHTS.

    Option /RESAMPLE enables to resample data on a new  spectral  grid  (for
    line  data).  'nc' is the output number of channels, 'ref' the reference
    channel, 'val' the value of velocity or frequency offset  (with  respect
    to  the  rest frequency) at the reference channel, 'inc' the resolution,
    'code' is "V" if the  value  'val'  and  the  resolution  'inc'  are  in
    velocity  units,  "F"  for  frequency units.  The reference channel thus
    corresponds to the given 'val' velocity, or to the offset 'val'  in  MHz
    from  the  rest  frequency  present  in the header or modified by option
    /FREQUENCY.

    Resampling is done by default  through  linear  interpolation  of  input
    channel data.

    Resampling may also be done (using option  /FFT)  in  Fourier  space  by
    cut-off  or  extrapolation  (by zeroes) of the Fourier components, after
    deconvolution by the channel response of the correlator (due to  on-line
    apodization),   and  followed  by  reconvolution  to  produce  frequency
    channels of the given shape and width. Allowed shapes are:

      TBox = a box in delay space (unapodized  correlator)
      Ppar = a parabola in delay space (apodized correlator) (the default)
      FBox = a box in frequency space (square filter)
      FTri = a triangle in frequency space (Hanning smoothed square filter)

    The width is the channel width in units of channel  separation  (default
    1).

    Option /FFT is not recommended when joining together several subbands to
    produce  a single spectrum, with a limited number of broad channels.  In
    those cases using the FFT could produce a spectrum with "holes"  at  the
    points between subbands with limited overlap.

    Option /FREQUENCY is used to redefine  the  rest  frequency  (and   line
    name) for the output table.  The velocity scale is computed accordingly.
    This rest frequency will correspond to the reference channel  in  option
    RESAMPLE.

    Option /DROP enables to drop the first 'n1' and last 'n2'   channels  in
    each  subband  of  the  OLD  spectral  correlator.  For the NEW spectral
    correlator (data taken  since  summer  1992),  it  is  replaced  by  the
    commands SET GIBBS and SET DROP.

    Option /COMPRESS is used to compress  the  data   before   writing   the
    table.   This  works like the COMPRESS command, but no intermediate file
    is written.

    A UV data Table is a file in the Gildas Data Format,  of   dimension  2.
    Each   column  corresponds  to  a  visibility data point.  Lines contain
    respectively:
  1.  U in meters
  2.  V in meters
  3.  W in meters
  4.  Observation date (integer CLASS Day Number)
  5.  Time in seconds since above date
  6.  Number of start antenna
  7.  Number of end antenna
  8.  First frequency point (real part)
  9.  First frequency point (imaginary part)
  10.  First frequency point (weight = integration  time  x  frequency width
    in  MHz divided by the product of system temperatures of both antennas);
    see SET WEIGHTS to select the weighting modes.
  11.  Same for second frequency point, and so on.  The first  dimension  is
    then  the  3 *  nchan  +  7,  for  nchan  frequency channels; The second
    dimension is the number of UV points measured.  For use with GreG COLUMN
    command,  this  UV  Data  Table  must  be   transposed   by  Gildas Task
    TRANSPOSE.