Subject: WCSLIB 2.1

From: Mark Calabretta <mcalabre at atnf.CSIRO.AU>
Date: Fri, 17 Nov 1995 19:41:44 +1100

Version 2.1 of WCSLIB is now available for collection from either of the
following sites

   ftp.atnf.csiro.au:/pub/software/wcslib/wcslib-2.1.tar.gz
   fits.cv.nrao.edu:/fits/src/wcs/wcslib-2.1.tar.gz

The change log file is appended below.

WCSLIB consists of independent C and FORTRAN implementations of the algorithms
described in the draft paper "Representations of Celestial Coordinates in
FITS" by Eric Greisen and Mark Calabretta.  The latest version of this paper,
dated 1995/10/30, may be obtained from

   fits.cv.nrao.edu:/fits/documents/wcs/wcs.all.ps.Z

Mark Calabretta
ATNF

WCSLIB version 2.1
------------------

The main change of interest to programmers is that of changed call sequences
for WCSFWD and WCSREV as described below.

* The WCS linear transformations are now implemented in WCSLIB, complete with
  matrix inverter.  The new files are lin.f and test program tlin.f.

* Given either the celestial longitude or latitude plus an element of the
  pixel coordinate a new routine, WCSMIX, solves for the remaining elements
  by iterating on the unknown celestial coordinate element using WCSFWD.

* The high level driver routines WCSFWD, WCSREV, and WCSMIX now apply the full
  WCS algorithm chain (except for pixel regularization table), including
  parsing the CTYPEn header cards and computing non-celestial elements of the
  world coordinate.  This required a change to their call sequences which now
  more closely reflect the sequence of algorithms applied.  A new routine,
  WCSSET, parses the CTYPEn.

* The high level driver routines of WCSLIB 1.0 are available as intermediate
  level drivers CELSET, CELFWD, and CELREV, but note that their call sequences
  have been extended to return native coordinates.  The related parameter
  array is now called CEL instead of WCS.

* The reference point for conic projections is now at the midpoint of the
  standard parallels.  The FITS header cards PROJP1 and PROJP2 now give the
  half-sum (midpoint) and half-difference of the latitudes of the standard
  parallels; previously they gave the latitudes of the standard parallels
  themselves.  The change is reflected in this release of WCSLIB.

* A bug in CELSET (formerly WCSSET) which misapplied WCS draft equations 7
  has been fixed (thanks to Rick Ebert IPAC/JPL and Lindsey Davis, NOAO for
  reporting this).  This affected the computation of Euler angles for the
  celestial coordinate transformation for those projections which have their
  reference point away from the native pole.  In investigating this a
  deficiency with the formalism was discovered which led to the introduction
  of a LATPOLE FITS header card which may be used to disambiguate where
  CRVAL1, CRVAL2, and LONGPOLE do not uniquely determine the latitude of the
  native pole.  The CEL parameter array (formerly WCS) has been extended to
  accomodate LATPOLE as CEL(4), and the flag variable is now CEL(5) (formerly
  WCS(4)).

* Default values of LONGPOLE and LATPOLE are now supported and their use is
  recommended where appropriate.

* Numerical precision was being lost near the native poles in the SIN, AIR,
  and QSC projections and this has been recovered (reported by Lindsey Davis,
  NOAO).  Floating underflows in CSC are now avoided.

* Numerical precision was also lost in certain circumstances in the spherical
  coordinate transformation routines and this has been fixed.

* The test programs have been enhanced in various ways and the library has
  been validated on an SGI machine using both 32-bit and 64-bit compilers.

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$Id: CHANGES,v 2.3 1995/11/16 07:07:05 mcalabre Exp $