begin data gag_scratch:imager.hlp

1 IMAGER 

     IMAGER is a interferometric imaging package, tailored for usage 
  simplicity and efficiency for multi-spectral data sets.

     The basic concept of IMAGER is the use of a simple
         READ data  - ACTION(s) - [SHOW or VIEW] - WRITE
  sequence of commands, minimizing the data I/O as much as possible.
  Automatic guesses of appropriate default values for the ACTIONs 
  parameters is implemented whenever possible.

2 Actions

     The main IMAGER Actions are
     
     UV_MAP    Basic dirty image construction
     CLEAN     Deconvolution (Cleaning) tools
     SELFCAL   Self calibration
     UV_SHORT  Short spacings inclusion in UV data

     Input parameters for each Action is obtained by
         ACTION ?  
     where ACTION is the appropriate command name.
     
2 BEAM_Handling

  BEAM_STEP is an integer variable that controls how the natural
  Frequency dependence of the spatial resolution (1/Frequency) is 
  handled in the dirty beam.
  
  BEAM_STEP = 0   forces IMAGER to produce a single beam for all channels.
    This is only possible if all channels have the same weight, and only
    makes sense if the relative bandwidth is limited.
    
  BEAM_STEP = N   instructs IMAGER to change the dirty beam every N channels,
    so that the Frequency dependence is minimized
    
  BEAM_STEP = -1  instructs IMAGER to select N such as to keep a specified
    precision in the beam accuracy.
    
  BEAM_STEP = 1   may be the only way to handle channel dependent weights
    in complex cases (but it doubles the data size...)
  
  Note that IMAGER always produce a single Clean beam, even if the Dirty
  beam is frequency dependent.  See help UV_MAP BEAM_STEP, and the IMAGER 
  documentation for further details.
     
2 MAP_Handling

     IMAGER contains a number of Image-oriented commands to resample 
  (in frequency), compress (by channels), compute integrated intensity 
  maps, etc..
     
     These commands typically start with MAP_
      
2 UV_Handling

     IMAGER contains a number of UV-oriented commands to handle UV data. 
  This includes time averaging, spectral resampling, line / continuum 
  identification and separation, flagging, re-weighting, azimutal 
  averaging, etc...  
     
     These commands typically start with UV_
     
2 WebPage
    IMAGER WebPage is available at 
    
    https:://imager.oasu.u-bordeaux.fr

2 HOW_TO

     IMAGE has an "HOW to" facility, where simple questions can be
  typed, and answers are searched for in a (small) database. See
  HELP HOW_TO for details.
  
2 MAPPING
     Caution:  IMAGER is *** NOT *** MAPPING
    
     Although the underlying algorithms are the same as in the
  MAPPING program, the concepts are quite different.  
    
    The user interface to MAPPING is file-oriented. The user interacts
  with MAPPING generally by a script, packaging a complex sequence of 
  commands, tasks, reads and writes to intermediate files. Fine control 
  of the script parameters are in general done through widgets.
    
    The basic concept of IMAGER is opposite: a single READ of data, a 
  few simple processing commands with built-in intelligent parameter 
  guesses, a visual user control, and a single WRITE of the results 
  once the user is satisfied of it. 
    
1 ENDOFHELP
end data 
!
define command IMAGER "@ welcome.ima" gag_scratch:imager.hlp
