4.2 Gildas data format

Internally, IMAGER works on data represented in the Gildas data format.

The Gildas data format handles images, a generic term to indicate \(N\) -Dimensional data cubes (typically up to \(N=4\) in most cases). Data is stored in direct access files that contain a compact header, followed by the data array values in binary form.

The header contains the number of dimensions, their sizes, a conversion formula between axis pixels and user coordinates, sky projection information, velocity and frequency information, min and max of the data, etc...

The Gildas data format also includes special handling for 2-D arrays, called Tables, in contains list of values organized like in a tabler (columns and rows). In general, axis coordinates have no meaning for these Gildas tables.

An exception is the specific variant of these Gildas Tables called uv Tables, which contain visibilities coming from interferometric measurements.