The Standard for Documentation of Astronomical Catalogues is a set of conventions for archiving astronomical data. As well as path, filename and data format conventions, it also specifies how to construct a plain text description file for documenting the data files. It was developed as an alternative to FITS that would be more suited to archives, permit human inspection, and allow manipulation via standard Unix command-line tools.
SDAC was developed by CDS (Centre de Données astronomiques de Strasbourg). Version 2.0 is the most recent; it was released in February 2000.
A set of four tools for working with SDAC-compliant archives: acut can be used to edit text files in a columnar fashion; trcol removes or transforms columns from a text file; anafile verifies that data files conform to their description; tofits converts SDAC tables to FITS tables.
CDS (Centre de Données astronomiques de Strasbourg/Strasbourg astronomical Data Centre) is a member of the ICSU World Data System, specializing in astronomical data and related information. Its VizieR catalogue system uses SDAC to organize data and metadata holdings.