#include "erfa.h"
double eraEors(double rnpb[3][3], double s)
/*
** - - - - - - - -
** e r a E o r s
** - - - - - - - -
**
** Equation of the origins, given the classical NPB matrix and the
** quantity s.
**
** Given:
** rnpb double[3][3] classical nutation x precession x bias matrix
** s double the quantity s (the CIO locator)
**
** Returned (function value):
** double the equation of the origins in radians.
**
** Notes:
**
** 1) The equation of the origins is the distance between the true
** equinox and the celestial intermediate origin and, equivalently,
** the difference between Earth rotation angle and Greenwich
** apparent sidereal time (ERA-GST). It comprises the precession
** (since J2000.0) in right ascension plus the equation of the
** equinoxes (including the small correction terms).
**
** 2) The algorithm is from Wallace & Capitaine (2006).
**
** References:
**
** Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
**
** Wallace, P. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
**
** Copyright (C) 2013-2014, NumFOCUS Foundation.
** Derived, with permission, from the SOFA library. See notes at end of file.
*/
{
double x, ax, xs, ys, zs, p, q, eo;
/* Evaluate Wallace & Capitaine (2006) expression (16). */
x = rnpb[2][0];
ax = x / (1.0 + rnpb[2][2]);
xs = 1.0 - ax * x;
ys = -ax * rnpb[2][1];
zs = -x;
p = rnpb[0][0] * xs + rnpb[0][1] * ys + rnpb[0][2] * zs;
q = rnpb[1][0] * xs + rnpb[1][1] * ys + rnpb[1][2] * zs;
eo = ((p != 0) || (q != 0)) ? s - atan2(q, p) : s;
return eo;
}
/*----------------------------------------------------------------------
**
**
** Copyright (C) 2013-2014, NumFOCUS Foundation.
** All rights reserved.
**
** This library is derived, with permission, from the International
** Astronomical Union's "Standards of Fundamental Astronomy" library,
** available from http://www.iausofa.org.
**
** The ERFA version is intended to retain identical functionality to
** the SOFA library, but made distinct through different function and
** file names, as set out in the SOFA license conditions. The SOFA
** original has a role as a reference standard for the IAU and IERS,
** and consequently redistribution is permitted only in its unaltered
** state. The ERFA version is not subject to this restriction and
** therefore can be included in distributions which do not support the
** concept of "read only" software.
**
** Although the intent is to replicate the SOFA API (other than
** replacement of prefix names) and results (with the exception of
** bugs; any that are discovered will be fixed), SOFA is not
** responsible for any errors found in this version of the library.
**
** If you wish to acknowledge the SOFA heritage, please acknowledge
** that you are using a library derived from SOFA, rather than SOFA
** itself.
**
**
** TERMS AND CONDITIONS
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions
** are met:
**
** 1 Redistributions of source code must retain the above copyright
** notice, this list of conditions and the following disclaimer.
**
** 2 Redistributions in binary form must reproduce the above copyright
** notice, this list of conditions and the following disclaimer in
** the documentation and/or other materials provided with the
** distribution.
**
** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
** the International Astronomical Union nor the names of its
** contributors may be used to endorse or promote products derived
** from this software without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
** POSSIBILITY OF SUCH DAMAGE.
**
*/