[fitsbits] CDELTn

[David Berry]

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 <francois at vizir.u-strasbg.fr> 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: francois at astro.u-strasbg.fr   (France)         Fax: +33-(0)390 24 24 17
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