[ Basic Info | User Guide ]
Basic Information on tvclip
Purpose: Interactive editing of a UV data set on a TV device.
Categories: calibration, uv-data, tv, plotting, display
TVCLIP is a MIRIAD task which allows interactive baseline
editing of a UV data set. The user should make sure,
if the display device is capable of creating menus that
the menu program has been loaded ``before'' running this
routine (eg. xpanel for the XMTV) - see the User's Guide
or Cookbook under TV Devices for details.
When this program is run, each baseline is displayed,
one at a time, with the x-axis representing channel
number (increasing to the right), the y-axis representing
the change in time (increasing upward), and the color
intensity representing the amplitude or phase (depending
on the value of the keyword ``mode'') of the visibility.
The current antenna that constitute the baseline are
labeled at the bottom of the plot (if room permits).
In addition, if room permits, a color wedge is displayed
to the right side of the visibility data and is the sum
of the data over all displayed channels. Also, a wedge
of the sum of the data over all displayed times will
appear above (or below) the data as room permits.
The user may edit the data in one of two ways: 1) By
entering commands at the keyboard; or 2) by selecting
commands from the listed menu items. Which method is
determined by the presence of a menu program (such as
``XPANEL'' for the Sun systems).
If no menu program is currently active, then a message
is issued to the user and all commands are prompted from
the keyboard. Commands are entered followed by a carriage
return (<CR>). Single letter abbreviations are used for
all commands. The current command list, each corresponding
abbreviation, and a brief description of each command is
available by entering a question mark (``?'') as a command.
Commands requiring further interaction (eg. ``select'' and
``value'') will prompt the user when they are invoked.
If a menu program is active, then TVCLIP will attempt
to construct an assortment of menu buttons and other
items that will perform the equivalent of entering commands
at the keyboard. Certain commands (eg. ``select'' and
``value'') require further cursor input and will prompt
the user for a particular action (for example: ``select''
will request the user to select the region to box for
further flagging commands).
The current technique of editing is to load the baseline
to be edited, zoom and pan to the desired location, and
then, select the region to be edited followed by an
editing command. To identify a region to edit, chose
the ``select'' command (or ``channel'' or ``time'' select
options) and then use the cursor to box the desired points.
To select a desired region, move the cursor (mouse) to a
corner of the region to select; identify, to the program,
the corner (usually by pushing and holding the left mouse
button); move the pointer to the other corner (by dragging
the mouse), and then identify, again to the program, the
other corner (usually by releasing the left mouse button).
After the region to edit has been identified, the selected
region may be flagged as good or bad using the appropriate
editting command (or button). If data is flagged improperly,
the ``undo'' command will reverse the last editing operation.
NOTE: If the device does not support this type of ``rubber-
band'' selection (Eg. XMTV does; MXAS does not), then the
user will be asked to use the cursor to identify two opposite
corners to delimit the selected region.
To save the editing done to a particular baseline, use
the ``exit'' command (or select the ``exit'' button).
The flagging changes will be immediately applied to the
data. To NOT save the changes made to a particular
baseline, use the ``quit'' command (or button). After
a ``quit'' or ``exit'' operation, the data for the next
baseline is loaded onto the display and the user may continue
editing. Selecting the ``abort'' command (button) at any
time will perform the same operation as ``quit'', but
will also terminate the program.
You can use the 'batch-mode' of tvclip if you have a lot of
similar flagging to do. Use tvclip in interactive mode to
determine a good clip level and a sequence of DIFF and CLIP
commands that is appropriate for your data. Then set the
clip level and enter the commands in the 'commands' keyword.
You can then either watch the automatic flagging on the tv,
or switch off the display (options=notv) to speed things up.
The name of the input UV data set. A visibility file name
must be supplied. Only one file may be edited at a time.
Standard keyword server. See the help on server for more information.
An integer specifying which TV channel the data is
displayed. The default is channel 1.
The minimum and maximum range used in scaling the data
on the TV. Default is to autoscale to the first image.
If this keyword is used, TWO parameters must be input.
The integer device coordinate of the lower left corner
of the image. The default is to center the image on the
display. If this keyword is used and only the x coordinate
value is input, the y coordinate value is set to the x value.
Standard keyword line. See the help on line for more information.
NOTE: Here ``type'' must be `channel' or ``wide'' and the maximum
of both ``width'' and ``step'' must be 1. The default is
to display all channels.
Display ``amplitude'', ``phase'', ``real'', ``imaginary''.
By default, ``amplitude'' is selected. For mode=phase, the
phase is in degrees.
The length of time (in minutes) used to average the data when
determining the running mean. This is used with the "DIFF"
command, where the running mean of the data are subtraced off.
Two values can be given for taver, being TTOT and TGAP
respectively. If the time interval between any
two successive data points is greater than TGAP, or if the
total time between the first data point in an average
and any succeeding data point exceeds TTOT, then a new
average is started. The default for TTOT is 5 minutes, whereas
the default TGAP is the value of TTOT.
The clip level (in average absolute deviations, a parameter
similar to rms, but less sensitive to outliers)
This is used with the "CLIP" command. All data more than clip
times the av. abs. dev. from the median will be clipped.
This clip operation is repeated until no more points are clipped.
Common values are 4,5,6. Flagging on stokes V data with clip=4
usually gets rid of most interference. The default is 5.
Extra processing options. Several are possible:
'nochannel', 'notime' and 'nopixel' are clip options.
By default the "CLIP" command will flag channels, times
and individual pixels with an rms that is too far from
the median. These options allow you to exclude some
forms of clipping.
'notv' display option, do not show anything on the tv.
Speeds up non-interactive clipping. This can only be
used if you also fill in the commands keyword. Because
with 'notv' the data does not have to fit on the screen,
less time averaging is needed. Usually the data will be
flagged at full time resolution.
'nosrc' Do not cause a break in the display when the source
changes. Normally TVFLAG puts a gap in the display
whenever the source changes.
This allows non-interactive flagging using the "CLIP" command.
Use this to specify a sequence of flagging commands to be applied
for each baseline, e.g., commands=diff,clip.
The "EXIT" command is implicitly added at the end of the list.
You will not be able to interact with tvclip using mouse or
keyboard if "commands" is set.
Standard keyword select. See the help on select for more information.
NOTE: The default is to use all visibilities.
Revision: 1.10, 2013/08/30 01:49:21 UTC
Generated by firstname.lastname@example.org on 21 Jun 2016