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 $uv$ 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 $uv$ 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

$uv$ distance ( $\sqrt{U^2+V^2}$) [m];

angle

$uv$ position angle (atan2(V,U)) [deg];

time

UT time of observation [hrs];

date

Date of observation [days];

scan

Scan number;

number

Visibility number in $uv$ 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 $uv$ 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.