[fitsbits] Start of the TPV and ZPX FITS Convention Comment Periods

[David Berry]

Two points:

1) I think the description of the convention should also say that If
FITS reading software encounters a TPV header, then the standard
meanings attached to PV1_0 to PV1_4 (where i is the index of the
longitude axis) are suspended in favour of the meanings attached to
these keywords by the TPV convention. In the published standard these
PV values record information about the native coords of the fiducial
point and celestial pole (see section 2.6 of FITS-WCS paper II), but
in the TPV convention, they record polynomial distortion coefficients.
So in the TPV convention, the native coords of the celestial pole need
to be obtained from the LONPOLE and LATPOLE keywords, and the native
coords of the fiducial point are assumed to take their default values
for a TAN projection.

2) Version 5.7-3 of the starlink AST library also supports the TPV convention

David Berry


On 6 October 2011 22:34, William Pence <William.Pence at nasa.gov> wrote:
> This is to announce the start of the Public Comment Period on the
> TPV and ZPX FITS world coordinate system conventions developed at
> NOAO.  These 2 conventions have been submitted to the Registry of
> FITS Conventions which is maintained by the IAU FITS Working Group.
>
> The TPV and ZPX conventions build on the standard TAN and ZPN WCS
> projections, respectively, with the addition of a general polynomial
> distortion correction.
>
> Detailed information about these conventions and sample FITS files
> that use them are available for public review and comment from the
> FITS registry web page at
>
>               http://fits.gsfc.nasa.gov/fits_registry.html
>
> Comments about these conventions may be posted here on the FITSBITS
> email exploder.  Minor typographical issues may be sent directly to
> the author of the convention.
>
> Bill Pence
> (on behalf of the IAU FITS Working Group)
> --
> ____________________________________________________________________
> Dr. William Pence                       William.Pence at nasa.gov
> NASA/GSFC Code 662       HEASARC        +1-301-286-4599 (voice)
> Greenbelt MD 20771                      +1-301-286-1684 (fax)
>
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