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3.6.2 FITS-plus

A variant form of FITS file is written by the FitsPlusTableWriter handler. This is the same as the basic form, except that the primary HDU (HDU#0) contains a 1-d array of characters which form the text of a DATA-less VOTable. The FITS table in the first extension (HDU#1) is understood to contain the data. The point of this is that the VOTable can contain all the rich metadata about the table, but the bulk data are in a form which can be read efficiently. Crucially, the resulting FITS file is a perfectly good FITS table on its own, so non-VOTable-aware readers can read it in just the usual way, though of course they do not benefit from the additional metadata stored in the VOTable header.

While the normal VOTable/FITS encoding has some of these advantages, it is inconvenient in that either (for in-line data) the FITS file is base64-encoded and so hard to read efficiently, in particular for random access or (for referenced data) the table is split across two files.


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STIL - Starlink Tables Infrastructure Library
Starlink User Note 252
STIL web page: http://www.starlink.ac.uk/stil/
Author email: m.b.taylor@bristol.ac.uk
Starlink: http://www.starlink.ac.uk/