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Diffstat (limited to 'ast/erfa/pmat76.c')
-rw-r--r-- | ast/erfa/pmat76.c | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/ast/erfa/pmat76.c b/ast/erfa/pmat76.c new file mode 100644 index 0000000..c38e6c4 --- /dev/null +++ b/ast/erfa/pmat76.c @@ -0,0 +1,150 @@ +#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) 2013-2016, 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) 2013-2016, 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. +** +*/ |