PLOTTING VISIBILITIES

The Miriad task uvplt can plot a variety of quantities from visibility data for each baseline, which is a useful application tool for users to identify bad data points. A feature of color-coded for sources has been added to the task smauvplt. For polarization data, color index used for polarization components in the original code uvplt conflicts with the color index for source in some cases. For non-polarization data, smauvplt has an advantage to identify bad data points in a multiple source file. Here is an example to plot the visibilities versus time by selecting the baselines related to antenna 4:

 Task:   smauvplt
  vis      = gc_rx1.lsb.tsys
  select   = ant(4)
  axis     = time,ampl
  yrange   = -10,250
  device   = /xs 
  nxy      = 2,4

The beginning visibility points in each of scans appear to be bad (Fig.2.8).

Figure: This plot shows the amplitude of the visibility as a function of time on the baselines related to antenna 4. The scans on different sources can be separated by the color. The problematic visibilities, such as the low gain in the beginning of each scan, can be easily identified.