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Issue A&A Volume 395, Number 3, December I 2002 Page(s) 1061 - 1075 Section Instruments, observational techniques and data processing DOI 10.1051/0004-6361:20021326

A&A 395, 1061-1075 (2002)
DOI: 10.1051/0004-6361:20021326

Representations of world coordinates in FITS

E. W. Greisen¹ and M. R. Calabretta<sup>2

1</sup>  National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801-0387, USA
²  Australia Telescope National Facility, PO Box 76, Epping, NSW 1710, Australia

(Received 24 July 2002 / Accepted 9 September 2002)

Abstract
The initial descriptions of the FITS format provided a simplified method for describing the physical coordinate values of the image pixels, but deliberately did not specify any of the detailed conventions required to convey the complexities of actual image coordinates. Building on conventions in wide use within astronomy, this paper proposes general extensions to the original methods for describing the world coordinates of FITS data. In subsequent papers, we apply these general conventions to the methods by which spherical coordinates may be projected onto a two-dimensional plane and to frequency/wavelength/velocity coordinates.

Key words: methods: data analysis -- techniques: image processing -- astronomical data bases: miscellaneous

Offprint request: E. W. Greisen, egreisen@nrao.edu

© ESO 2002

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