# Introduction

WCSLIB is a C library, supplied with a full set of Fortran wrappers, that implements the "World Coordinate System" (WCS) standard in FITS (Flexible Image Transport System). It also includes a PGPLOT-based routine, PGSBOX, for drawing general curvilinear coordinate graticules and a number of utility programs.

The FITS data format is widely used within the international astronomical community, from the radio to gamma-ray regimes, for data interchange and archive, and also increasingly as an online format. It is described in

- "Definition of The Flexible Image Transport System (FITS)", FITS Standard, Version 3.0, 2008 July 10.

available from the FITS Support Office at http://fits.gsfc.nasa.gov.

The FITS WCS standard is described in

- "Representations of world coordinates in FITS" (Paper I), Greisen, E.W., & Calabretta, M.R. 2002, A&A, 395, 1061-1075

- "Representations of celestial coordinates in FITS" (Paper II), Calabretta, M.R., & Greisen, E.W. 2002, A&A, 395, 1077-1122

- "Representations of spectral coordinates in FITS" (Paper III), Greisen, E.W., Calabretta, M.R., Valdes, F.G., & Allen, S.L. 2006, A&A, 446, 747

- "Mapping on the HEALPix Grid" (HPX), Calabretta, M.R., & Roukema, B.F. 2007, MNRAS, 381, 865

Reprints of all published papers may be obtained from NASA's Astrophysics Data System (ADS), http://adsabs.harvard.edu/. Reprints of Papers I, II (+HPX) and III are available from http://www.atnf.csiro.au/people/Mark.Calabretta. This site also includes errata and supplementary material for Papers I, II and III.

Additional information on all aspects of FITS and its various software implementations may be found at the FITS Support Office http://fits.gsfc.nasa.gov.