Visualization (GO UVALL and GO UVCOV)
Keywords: map

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Visualization (`GO UVALL` and `GO UVCOV`)

Although images are a wonderful way to display results, problems may be more obvious in scatter plots of visibilities. For instance, large strips in the dirty image often originates from a single outlier visibility. `GO UVALL` is a procedure to explore the content of a table through visualization of scatter plots. This procedure is controlled by several input parameters, in particular the following global variables

`NAME`
  The filename without extension of the input table;
`XTYPE` and `YTYPE`
  The types of data to be plotted along the X and Y axes. These two variables can take the following values
  `u` or `v`
    Fourier coordinates [m];
  `radius`
    distance (`` ) [m];
  `angle`
    position angle (`atan2(V,U)`) [deg];
  `time`
    UT time of observation [hrs];
  `date`
    Date of observation [days];
  `scan`
    Scan number;
  `number`
    Visibility number in table;
  `amp`
    Amplitude of visibility [Jy];
  `phase`
    Phase of visibility [deg];
  `real`
    Real part of visibility [Jy];
  `image`
    Imaginary part of visibility [Jy];
  `weight`
    Weights of visibility [*** ? JP ***].
  The default is to plot the amplitude vs the radius of the visibilities.
`FIRST` and `LAST`,
  i.e. the first and last channel to plot. By default, all channels are plotted.

Other input parameters are available. Please type `input uvall` to obtain the most recent available help. For instance, to obtain the scatter plots of amplitude vs weight of the visibility (which should look like an hyperbole), you would type:

           1 let name 12cs21
           2 let xtype weight
           3 let ytype radius
           4 go uvall

The plot of the coverage of the data is such an important subset of the `GO UVALL` possibility that we created a dedicated procedure for it, namely `GO UVCOV`.

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