Data Selection Options
The "Data selection & flag handling" submenu is always the first option in the Runtime Options menu of a Calico script. This submenu has a common structure (although some options may be disabled or missing, depending on context, and which particular script is used):
- "Input MS column" determines which MS column will be read. Typically, this is "DATA" for the original uncalibrated data, or "CORRECTED_DATA" for residuals.
- "Output MS column" determines which MS column will be written to. This is only visible if the tree actually produces some output (such as residuals or corrected visibilities.)
- "Tile size" determines the size of a data chunk, in timeslots. Since most MSs will not fit into memory all at once, they are read in chunks of time called tiles. (During calibration, this also determines the solution interval, but that is not relevant here.) 200 is a sensible tile size for viewing WSRT data. If you find meqserver consuming too much memory (watch the memory meter at the bottom of the browser window), you need to reduce the tile size.
- "Data description ID" is also known as the spectral window number. If your MS contains only one spectral window, this option doesn't show up at all.
- "Field ID" is also known as the pointing number. If your MS contains only one pointing, this option doesn't show up at all.
- The "Channel selection" submenu allows you to select a subset of channels. Channel numbers are 0-based. You can also specify a stepping to select, e.g., every second channel, every third channel, etc. If you unclick the checkbox next to "Channel selection", then the contents of this submenu are ignored, and all channels are read.
"Additional TaQL selection" lets you additionally restrict your input data using TaQL queries. This is powerful, but not for the faint of heart. For example, "sumsqr(UVW[1:2]) > x" will select data where the projected uv length is > sqrt(x).
"Read flags from MS", and "Write flags to MS" (if present) and "Fill legacy FLAG column" (if present) are related to ../FlagHandling. Please see that page for details.