Documentation on velplot

Task: velplot
Purpose: Interactive task to plot spectra and slices from Miriad Images.
Categories: image analysis

        VELPLOT is an interactive task to analyse spectra, position-velocity
        slices, and integrated velocity maps from Miriad Images.
        There are three basic display options:

         - Velocity-averaged x-y images over selected velocity intervals.
        	Also makes velocity and velocity dispersion images.
         - Spectra at selected x-y positions. The data can be convolved
        	in the x-y or velocity. Gaussian fitting routine.
         - Position-velocity maps along user selected position angles,
        	or plots of intensity versus position for selected velocity
        	channels. The data can be convolved in the x-y plane.

        (x,y) positions are (HA,DEC) in arcsec relative to map center.
        Position angles are measured from the north towards the east.

        The output from each option can be plotted, printed, or written out
        as Miriad images of velocity-averaged maps, position-velocity maps,
        or ascii spectra respectively. Gaussian fits are written into the log.

        The task saves user-defined lists of velocity-averaged maps, position-
        velocity cuts, and spectra positions. These lists can be created and 
        edited within the task, and can be passed between the three options. 
        For example, a list of spectra or position-velocity cuts can be created 
        with the cursor whilst displaying a velocity-averaged map. These lists
        are used to display the spectra and position-velocity cuts, and can be
        written out and read in as ascii files.

        A menu option provides a choice of display style, contour levels,
        and units. Further interactive help is available within the task.

Key: in
        Input image name. No default.

Key: device
        The PGPLOT plotting device. 

Key: region
        Region of image to be plotted. E.g.
          % image region=relpix,box(-30,-30,20,90)(16,57)
        reads in 50 x 120 pixels of image planes 16 to 57.
        The default is the whole Image. The current size limit is 128 in
        any dimension.

Key: log
        The output log file. The default filename is velplot.log
        Results from image analysis are written into the log file.