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] CDELTn



 
 
Thread Tools Display Modes
  #1  
Old September 18th 07, 12:26 PM posted to sci.astro.fits
David Berry
external usenet poster
 
Posts: 4
Default [fitsbits] CDELTn

Section 2.1.2 of FITS-WCS paper 1 says "Furthermore, all CDELTi must
be non-zero." Even if NAXISn is 1, that one pixel should still have
some width. If any CDELT is zero then the transformation from pixel to
WCS cannot be inverted.

David


On 18/09/2007, Francois Ochsenbein wrote:

Hello,

I just found a curiosity: FITS files having CDELTn axis set to zero.
This may look strange, but when the corresponding NAXISn is 1, this
should be harmless. Is the value zero actually forbidden in the
FITS definition ? (I did not find this restriction in the FITS definition).

It seems that fv does not like such FITS file, it generates an error.

--Francois
================================================== ==============================
Francois Ochsenbein ------ Observatoire Astronomique de Strasbourg
11, rue de l'Universite F-67000 STRASBOURG Phone: +33-(0)390 24 24 29
Email: (France) Fax: +33-(0)390 24 24 17
================================================== ==============================
_______________________________________________
fitsbits mailing list

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



--
Note my change of e-mail address. Please send e-mail to
from now on.
  #2  
Old September 18th 07, 04:43 PM posted to sci.astro.fits
LC's NoSpam Newsreading account[_2_]
external usenet poster
 
Posts: 23
Default [fitsbits] CDELTn

On Tue, 18 Sep 2007, David Berry wrote:

Section 2.1.2 of FITS-WCS paper 1 says "Furthermore, all CDELTi must
be non-zero."


And the WCS paper is "incorporated by reference" in the draft FITS
standard 3.0. So it looks like Francois has spotted something which is
best to spell out clearly and explicitly also in the standard (and we in
the technical panel have missed).

.... oh, wait a moment ... if this wasn't stated before WCS came out,
FITS file created before then would be exempt from the "new"
requirement, wont't they ? How do these go together ?

--
----------------------------------------------------------------------
is a newsreading account used by more persons to
avoid unwanted spam. Any mail returning to this address will be rejected.
Users can disclose their e-mail address in the article if they wish so.
 




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] CDELTn Phil Hodge FITS 0 September 18th 07 01:44 PM
[fitsbits] CDELTn Francois Ochsenbein FITS 0 September 18th 07 12:17 PM
[fitsbits] fitsbits--sci.astro.fits gateway fully operationalagain Don Wells FITS 0 September 29th 06 05:17 PM
[fitsbits] sci.astro.fits link to FITSBITS is still broken William Pence FITS 0 May 31st 06 07:21 PM
[fitsbits] fitsbits and spam (test) Lucio Chiappetti FITS 1 March 22nd 04 06:52 PM


All times are GMT +1. The time now is 07:42 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.