[fitsbits] FITS conventions update

[Lucio Chiappetti]

On Tue, 9 Dec 2014, William Pence wrote:

> This is to announce that a new FITS 'Header Space' convention has been 
> submitted to the Registry of FITS Conventions,

> This convention has been supported by the CFITSIO library since about 
> 1996.

I did not realize such detail ! Of course the convention in itself is a 
fully sound solution and pretty harmless.

I have two (inter-related) comments, a general one, and one concerning the 
last sentence in the submitted text, i.e.

"It should be noted that if a FITS file is processed by software that 
does not support this convention, then new keywords may be written at the 
location of the END keyword (i.e., after the blank keyword records). This 
will make the blank keywords unavailable for future use by software that 
does support this convention"

The general comment is that this is possibly not a true "convention" but 
more a (perfectly legal) "usage feature". I mean, there is no marker or 
univocal signature IN THE FILE which says the file adheres to the 
convention. It is THE MANIPULATING SOFTWARE which adheres to the 
convention !

Concerning the quoted text. knowing the sort of discussions behind this 
issue (I am talking of the Tech Group discussions of which most people of 
fitsbits do not know the details), I wonder whether one might not do an 
update to the Standard, which says that FITS *writers* are allowed to 
write new keywords over any completely blank card image wherever it is 
located in the header (they might even be allowed to "delete" a keyword 
overwriting it with an entirely blank card image). But this might open the 
can of work of order and position of keywords in the header.

Of course (since those blank keywords do not do any harm to any *reader*), 
you could modify just your USAGE RULE to make use of blank card images as 
reserved space wherever located, or rewrite the file shifting them at the 
end (just before END).



> Also, please note that the PSRFITS convention for storing pulsar data has now 
> been under review for many months.   If there are no objections, I will add 
> it to the registry in January.

please proceed


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