Subject: Re: hierarchical keywords

From: gtr at mail.ast.cam.ac.uk (Guy Rixon)
Date: 10 Jun 1994 08:14:13 GMT

Unless you are preparing FITS files for a specific audience, all of whom 
use customized FITS readers, hierarchical FITS is best avoided: it causes more problems
than it solves.

A variant of hierarchical keywords has been used at the Isaac Newton Group of Telescopes
for many years now, and over that time RGO and ING have had a steady stream of complaints
that "your FITS headers are unreadable".  The problem is that most readers lose the
hierarchical keywords when copying FITS to some other format.  We tried to get round this
by distributing specialized readers (some INT FITS tapes have the FORTRAN source for the
FITS reader encoded in the header of the first file!), but the community wasn't satisfied
with this.

Hierarchical FITS will become extinct at ING sometime over the next two to three years.  I
recommend that you stay clear of it.

Guy Rixon