source: branches/FACT++_part_filenames/erfa/src/pmat76.c@ 18732

Last change on this file since 18732 was 18711, checked in by tbretz, 8 years ago
Updated to ERFA 1.3.0 (no relevant code change except the leap second at the beginning of 2017)
File size: 5.9 KB
Line 
1#include "erfa.h"
2
3void eraPmat76(double date1, double date2, double rmatp[3][3])
4/*
5** - - - - - - - - - -
6** e r a P m a t 7 6
7** - - - - - - - - - -
8**
9** Precession matrix from J2000.0 to a specified date, IAU 1976 model.
10**
11** Given:
12** date1,date2 double ending date, TT (Note 1)
13**
14** Returned:
15** rmatp double[3][3] precession matrix, J2000.0 -> date1+date2
16**
17** Notes:
18**
19** 1) The TT date date1+date2 is a Julian Date, apportioned in any
20** convenient way between the two arguments. For example,
21** JD(TT)=2450123.7 could be expressed in any of these ways,
22** among others:
23**
24** date1 date2
25**
26** 2450123.7 0.0 (JD method)
27** 2451545.0 -1421.3 (J2000 method)
28** 2400000.5 50123.2 (MJD method)
29** 2450123.5 0.2 (date & time method)
30**
31** The JD method is the most natural and convenient to use in
32** cases where the loss of several decimal digits of resolution
33** is acceptable. The J2000 method is best matched to the way
34** the argument is handled internally and will deliver the
35** optimum resolution. The MJD method and the date & time methods
36** are both good compromises between resolution and convenience.
37**
38** 2) The matrix operates in the sense V(date) = RMATP * V(J2000),
39** where the p-vector V(J2000) is with respect to the mean
40** equatorial triad of epoch J2000.0 and the p-vector V(date)
41** is with respect to the mean equatorial triad of the given
42** date.
43**
44** 3) Though the matrix method itself is rigorous, the precession
45** angles are expressed through canonical polynomials which are
46** valid only for a limited time span. In addition, the IAU 1976
47** precession rate is known to be imperfect. The absolute accuracy
48** of the present formulation is better than 0.1 arcsec from
49** 1960AD to 2040AD, better than 1 arcsec from 1640AD to 2360AD,
50** and remains below 3 arcsec for the whole of the period
51** 500BC to 3000AD. The errors exceed 10 arcsec outside the
52** range 1200BC to 3900AD, exceed 100 arcsec outside 4200BC to
53** 5600AD and exceed 1000 arcsec outside 6800BC to 8200AD.
54**
55** Called:
56** eraPrec76 accumulated precession angles, IAU 1976
57** eraIr initialize r-matrix to identity
58** eraRz rotate around Z-axis
59** eraRy rotate around Y-axis
60** eraCr copy r-matrix
61**
62** References:
63**
64** Lieske, J.H., 1979, Astron.Astrophys. 73, 282.
65** equations (6) & (7), p283.
66**
67** Kaplan,G.H., 1981. USNO circular no. 163, pA2.
68**
69** Copyright (C) 2013-2016, NumFOCUS Foundation.
70** Derived, with permission, from the SOFA library. See notes at end of file.
71*/
72{
73 double zeta, z, theta, wmat[3][3];
74
75
76/* Precession Euler angles, J2000.0 to specified date. */
77 eraPrec76(ERFA_DJ00, 0.0, date1, date2, &zeta, &z, &theta);
78
79/* Form the rotation matrix. */
80 eraIr( wmat);
81 eraRz( -zeta, wmat);
82 eraRy( theta, wmat);
83 eraRz( -z, wmat);
84 eraCr( wmat, rmatp);
85
86 return;
87
88}
89/*----------------------------------------------------------------------
90**
91**
92** Copyright (C) 2013-2016, NumFOCUS Foundation.
93** All rights reserved.
94**
95** This library is derived, with permission, from the International
96** Astronomical Union's "Standards of Fundamental Astronomy" library,
97** available from http://www.iausofa.org.
98**
99** The ERFA version is intended to retain identical functionality to
100** the SOFA library, but made distinct through different function and
101** file names, as set out in the SOFA license conditions. The SOFA
102** original has a role as a reference standard for the IAU and IERS,
103** and consequently redistribution is permitted only in its unaltered
104** state. The ERFA version is not subject to this restriction and
105** therefore can be included in distributions which do not support the
106** concept of "read only" software.
107**
108** Although the intent is to replicate the SOFA API (other than
109** replacement of prefix names) and results (with the exception of
110** bugs; any that are discovered will be fixed), SOFA is not
111** responsible for any errors found in this version of the library.
112**
113** If you wish to acknowledge the SOFA heritage, please acknowledge
114** that you are using a library derived from SOFA, rather than SOFA
115** itself.
116**
117**
118** TERMS AND CONDITIONS
119**
120** Redistribution and use in source and binary forms, with or without
121** modification, are permitted provided that the following conditions
122** are met:
123**
124** 1 Redistributions of source code must retain the above copyright
125** notice, this list of conditions and the following disclaimer.
126**
127** 2 Redistributions in binary form must reproduce the above copyright
128** notice, this list of conditions and the following disclaimer in
129** the documentation and/or other materials provided with the
130** distribution.
131**
132** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
133** the International Astronomical Union nor the names of its
134** contributors may be used to endorse or promote products derived
135** from this software without specific prior written permission.
136**
137** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
138** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
139** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
140** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
141** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
142** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
143** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
144** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
145** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
146** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
147** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
148** POSSIBILITY OF SUCH DAMAGE.
149**
150*/
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