14.3 Data editing

Editing the interferometer data is not very flexible when done in the $uv$ tables. If a problem occurs, is is not easily diagnosed since many of the parameters associated with the data acquisition are not present: atmospheric data, total powers, ... It is however useful when something strange occurs in the mapping process to do $uv$ plots of the input table to look for the faulty data. Using time or scan number as X coordinate is recommended. One then may go back to the CLIC program and flag the faulty data, tag the corresponding scans, and keep a log of these problems so that they are not encountered again when the $uv$ tables are reconstructed for any reason.

Two tasks have been written that may directly edit the data in $uv$ tables:

UV_CLIP flags all visibilities larger than a given flux: this deletes visibility points with totally wrong numbers, if any.

UV_FLAG deletes visibility points in a given time interval for a given baseline.

Both tasks work by setting the corresponding weight to zero: their action is irreversible (you will have to reconstruct the $uv$ table to go back).

The MAPPING program provides a more efficient, simpler and reversible interactive tool to flag parts of a $uv$ data set (command UV_FLAG).