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        MAP\XY_MAP [FilenamePrefix] [/NOGRID] [/TYPE LMV|VLM|...]

    Build  an LMV spectra cube and an associated weight image from an XY ta-
    ble. The LMV cube (.lmv), WEI image (.wei) and XY table (.tab) share the
    same file name, given without extension. By default, data is grided with
    a convolution (general case), unless /NOGRID option is invoked (typical-
    ly when the data is already regularly placed).

    By default, the spatial grid of the LMV cube will be large enough to use
    all the spectra of the XY table. The pixel size will ensure Nyquist sam-
    pling (i.e. at least 2 pixels per beam). The grid position reference and
    position angle will be taken from the XY table header.  The  convolution
    kernel is a Gaussian of size one-third the telescope beamwidth, the con-
    volution being computed on a limited support (large enough to ensure ex-
    cellent accuracy).

    However,  the  griding  process may be finely tuned through user defined
    values of the MAP structure. The header of an existing LMV cube  may  be
    used  as  a  template for the grid definition. To do this, the user must
    set the MAP%LIKE variable to the template filename. When MAP%LIKE is set
    to  an  empty  string,  the user may define the grid by hand through the
    following parameters

    MAP%CELL     [arcsec    ]   X and Y pixel size
    MAP%SIZE     [pixel     ]   X and Y map   size
    MAP%ANGLE    [degree    ]   Grid position angle
    MAP%RA       [  HH:MM:SS]   Grid reference position
    MAP%DEC      [+DDD:MM:SS]   Grid reference position
    MAP%SHIFT    [logical   ]   Shift and/or Rotate grid?

    The natural beamwidth of the telescope is set in order of precedence by

    TAB%MAJOR    [radian    ]   The resolution in the table header, if defined
    MAP%TELE     [string    ]   The telescope name
    MAP%DIAM     [m         ]   The telescope diameter (if MAP%DIAM = 0)
    MAP%BEAM     [arcsec    ]   The beam size (if MAP%TELE = "" and MAP%DIAM = 0

    Because of the convolution, the spatial resolution of  the  grided  data
    will by default be 5.4% wider than the telescope beamwidth at the obser-
    vation frequency. It is however possible to grid the data with  a  wider
    Gaussian  in  order  to smooth the data (e.g. to increase the signal-to-
    noise ratio of extended emission). The user have to define the  required
    resolution of the grided data through

    MAP%RESO     [arcsec    ]   Final resolution of the grided data (default is

    the  command  will  deduce the size of the griding kernel from the tele-
    scope beamwidth and the required resolution.

    It is advised to avoid changing the following more technical parameters.
    However those parameters are tunable through

    MAP%COL      [integer   ]   Range of columns to grid
    MAP%WCOL     [integer   ]   Column of weights
    MAP%CTYPE    [integer   ]   Convolution kernel type
    MAP%SUPPORT  [arcsec    ]   Convolution kernel support size

    For  ease  of use, a sensible value of each griding parameter will auto-
    matically be computed from the context if the value of the corresponding
    MAP structure component is set to its default value, i.e. zero value and
    empty string. The only exception is the position reference and/or  posi-
    tion  angle  of  the  grid:  Changing  them  requires in addition to set

    The output LMV cube can be then analysed with the  standard  GreG  tools
    like GO VIEW. However, it is also possible to reimport the cube in Class
    as a set of spectra thanks to the command ANALYSE\LMV (see HELP for  de-


Gildas manager 2014-07-01