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#include "erfa.h"
void eraPmat76(double date1, double date2, double rmatp[3][3])
/*
** - - - - - - - - - -
** e r a P m a t 7 6
** - - - - - - - - - -
**
** Precession matrix from J2000.0 to a specified date, IAU 1976 model.
**
** Given:
** date1,date2 double ending date, TT (Note 1)
**
** Returned:
** rmatp double[3][3] precession matrix, J2000.0 -> date1+date2
**
** Notes:
**
** 1) The TT date date1+date2 is a Julian Date, apportioned in any
** convenient way between the two arguments. For example,
** JD(TT)=2450123.7 could be expressed in any of these ways,
** among others:
**
** date1 date2
**
** 2450123.7 0.0 (JD method)
** 2451545.0 -1421.3 (J2000 method)
** 2400000.5 50123.2 (MJD method)
** 2450123.5 0.2 (date & time method)
**
** The JD method is the most natural and convenient to use in
** cases where the loss of several decimal digits of resolution
** is acceptable. The J2000 method is best matched to the way
** the argument is handled internally and will deliver the
** optimum resolution. The MJD method and the date & time methods
** are both good compromises between resolution and convenience.
**
** 2) The matrix operates in the sense V(date) = RMATP * V(J2000),
** where the p-vector V(J2000) is with respect to the mean
** equatorial triad of epoch J2000.0 and the p-vector V(date)
** is with respect to the mean equatorial triad of the given
** date.
**
** 3) Though the matrix method itself is rigorous, the precession
** angles are expressed through canonical polynomials which are
** valid only for a limited time span. In addition, the IAU 1976
** precession rate is known to be imperfect. The absolute accuracy
** of the present formulation is better than 0.1 arcsec from
** 1960AD to 2040AD, better than 1 arcsec from 1640AD to 2360AD,
** and remains below 3 arcsec for the whole of the period
** 500BC to 3000AD. The errors exceed 10 arcsec outside the
** range 1200BC to 3900AD, exceed 100 arcsec outside 4200BC to
** 5600AD and exceed 1000 arcsec outside 6800BC to 8200AD.
**
** Called:
** eraPrec76 accumulated precession angles, IAU 1976
** eraIr initialize r-matrix to identity
** eraRz rotate around Z-axis
** eraRy rotate around Y-axis
** eraCr copy r-matrix
**
** References:
**
** Lieske, J.H., 1979, Astron.Astrophys. 73, 282.
** equations (6) & (7), p283.
**
** Kaplan,G.H., 1981. USNO circular no. 163, pA2.
**
** Copyright (C) 2013-2014, NumFOCUS Foundation.
** Derived, with permission, from the SOFA library. See notes at end of file.
*/
{
double zeta, z, theta, wmat[3][3];
/* Precession Euler angles, J2000.0 to specified date. */
eraPrec76(ERFA_DJ00, 0.0, date1, date2, &zeta, &z, &theta);
/* Form the rotation matrix. */
eraIr( wmat);
eraRz( -zeta, wmat);
eraRy( theta, wmat);
eraRz( -z, wmat);
eraCr( wmat, rmatp);
return;
}
/*----------------------------------------------------------------------
**
**
** 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.
**
*/
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