12.2 uv data plots

A procedure is available to do various plots from a continuum or line table. Its name is UVALL and it is called by clicking on ``Interferometric UV operations'' in the GRAPHIC standard menu. One has to select the first and last channel to be plotted (0 0 to get all channels) and the name of the parameters to be plotted in abscissa and ordinate. The following examples are the most useful plots:

uv coverage:

to get an idea of the imaging quality that may be obtained, to check if one configuration has been forgotten, ...

  

Figure 12.2: Example of a uv coverage plot

weight vs. number:

check if some data got strange weights (e.g., zero) for any reason

  

Figure 12.3: Weight versus visibility number plot

Amplitude vs. antenna spacing:

quite useful if a source is strong to see if it looks resolved. Also check for spurious high amplitude points.

  

Figure 12.4: Amplitude versus antenna spacing plot

Amplitude vs. weight:

another useful check: spurious high-amplitude points with non-negligible weight can cause a lot of harm in a map.

These plotting facilities are also implemented in the MAPPING program as a command (SHOW UV).