A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Astronomy and Astrophysics » FITS
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

[fitsbits] Proposed Changes to the FITS Standard



 
 
Thread Tools Display Modes
  #1  
Old August 18th 07, 04:15 AM posted to sci.astro.fits
Doug Tody
external usenet poster
 
Posts: 19
Default [fitsbits] Proposed Changes to the FITS Standard

I'll just second this. I have seen many cases where a FITS header gets
multiple keyword instances after it has been modified by different
programs. This is awful of course as the header is then ambiguous,
but it happens. Software may or may not use the last instance as
a runtime value; for example, if the software does a linear search
through the header it is possible that it will take the first value
encountered (for either reading or writing) as this is more efficient,
and there are not supposed to be multiple keyword instances. If the
software does this on a write, then it is the *first* value in the
header which will have the correct value.

We should strongly recommend that software which writes to a header not
create multiple values. If there already *are* multiple values, frankly
it is not often clear what to do, as one does not like to delete
information from a header.

If we ever do a FITS 2.0 we should revisit this, but it is hard to
do more at this point for standard FITS than recommend that multiple
values not be allowed in the first place. Once they are there you have
a problem. - Doug



On Fri, 17 Aug 2007, Jonathan McDowell wrote:

I agree with Thierry that there are many files which have repeated keywords,
but I agree with another poster that there are existing implementations which
assume it's the first instance, not the last instance, which prevails.
So I think we should just strongly deprecate (not ban, and not impose
an interpretation).
- Jonathan McDowell
_______________________________________________
fitsbits mailing list

http://listmgr.cv.nrao.edu/mailman/listinfo/fitsbits

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
[fitsbits] Proposed Changes to the FITS Standard Preben Grosbol FITS 0 August 16th 07 04:11 PM
[fitsbits] Proposed Changes to the FITS Standard Mark Calabretta FITS 0 August 1st 07 09:01 AM
[fitsbits] Proposed Changes to the FITS Standard William Pence FITS 0 July 27th 07 07:38 PM
[fitsbits] Proposed Changes to the FITS Standard Rob Seaman FITS 0 July 24th 07 07:21 PM
[fitsbits] Proposed Changes to the FITS Standard William Pence FITS 2 July 24th 07 04:57 AM


All times are GMT +1. The time now is 05:55 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.