After calibration with CLIC, the calibrated data may be stored in a particular file called a `uv table'. This is useful because much of the data in the CLIC data file are not needed any more: atmospheric parameters, total powers, image side band visibilities, data from other receivers may be discarded at this stage. All that counts is: the data that are needed to describe the source itself, the sky frequency that was observed, ... One may for instance create a uv table for the continuum and one for each line that was observed.
These uv tables are just special GILDAS tables suited for uv data handling that are created by CLIC. Mapping consists of transforming these tables into something more meaningful for the astronomer, either images or numbers like positions, flux densities, sizes, etc. However a good part of the data evaluation and analysis can be directly performed on the uv data itself, before performing any of the complex operations involved in creating an image (Fourier transform and deconvolution). Direct analysis of the uv data is the subject of this Lecture.