source: trunk/FACT++/erfa/src/c2i06a.c@ 18711

Last change on this file since 18711 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: 5.6 KB
Line 
1#include "erfa.h"
2
3void eraC2i06a(double date1, double date2, double rc2i[3][3])
4/*
5** - - - - - - - - - -
6** e r a C 2 i 0 6 a
7** - - - - - - - - - -
8**
9** Form the celestial-to-intermediate matrix for a given date using the
10** IAU 2006 precession and IAU 2000A nutation models.
11**
12** Given:
13** date1,date2 double TT as a 2-part Julian Date (Note 1)
14**
15** Returned:
16** rc2i double[3][3] celestial-to-intermediate matrix (Note 2)
17**
18** Notes:
19**
20** 1) The TT date date1+date2 is a Julian Date, apportioned in any
21** convenient way between the two arguments. For example,
22** JD(TT)=2450123.7 could be expressed in any of these ways,
23** among others:
24**
25** date1 date2
26**
27** 2450123.7 0.0 (JD method)
28** 2451545.0 -1421.3 (J2000 method)
29** 2400000.5 50123.2 (MJD method)
30** 2450123.5 0.2 (date & time method)
31**
32** The JD method is the most natural and convenient to use in
33** cases where the loss of several decimal digits of resolution
34** is acceptable. The J2000 method is best matched to the way
35** the argument is handled internally and will deliver the
36** optimum resolution. The MJD method and the date & time methods
37** are both good compromises between resolution and convenience.
38**
39** 2) The matrix rc2i is the first stage in the transformation from
40** celestial to terrestrial coordinates:
41**
42** [TRS] = RPOM * R_3(ERA) * rc2i * [CRS]
43**
44** = RC2T * [CRS]
45**
46** where [CRS] is a vector in the Geocentric Celestial Reference
47** System and [TRS] is a vector in the International Terrestrial
48** Reference System (see IERS Conventions 2003), ERA is the Earth
49** Rotation Angle and RPOM is the polar motion matrix.
50**
51** Called:
52** eraPnm06a classical NPB matrix, IAU 2006/2000A
53** eraBpn2xy extract CIP X,Y coordinates from NPB matrix
54** eraS06 the CIO locator s, given X,Y, IAU 2006
55** eraC2ixys celestial-to-intermediate matrix, given X,Y and s
56**
57** References:
58**
59** McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
60** IERS Technical Note No. 32, BKG
61**
62** Copyright (C) 2013-2016, NumFOCUS Foundation.
63** Derived, with permission, from the SOFA library. See notes at end of file.
64*/
65{
66 double rbpn[3][3], x, y, s;
67
68
69/* Obtain the celestial-to-true matrix (IAU 2006/2000A). */
70 eraPnm06a(date1, date2, rbpn);
71
72/* Extract the X,Y coordinates. */
73 eraBpn2xy(rbpn, &x, &y);
74
75/* Obtain the CIO locator. */
76 s = eraS06(date1, date2, x, y);
77
78/* Form the celestial-to-intermediate matrix. */
79 eraC2ixys(x, y, s, rc2i);
80
81 return;
82
83}
84/*----------------------------------------------------------------------
85**
86**
87** Copyright (C) 2013-2016, NumFOCUS Foundation.
88** All rights reserved.
89**
90** This library is derived, with permission, from the International
91** Astronomical Union's "Standards of Fundamental Astronomy" library,
92** available from http://www.iausofa.org.
93**
94** The ERFA version is intended to retain identical functionality to
95** the SOFA library, but made distinct through different function and
96** file names, as set out in the SOFA license conditions. The SOFA
97** original has a role as a reference standard for the IAU and IERS,
98** and consequently redistribution is permitted only in its unaltered
99** state. The ERFA version is not subject to this restriction and
100** therefore can be included in distributions which do not support the
101** concept of "read only" software.
102**
103** Although the intent is to replicate the SOFA API (other than
104** replacement of prefix names) and results (with the exception of
105** bugs; any that are discovered will be fixed), SOFA is not
106** responsible for any errors found in this version of the library.
107**
108** If you wish to acknowledge the SOFA heritage, please acknowledge
109** that you are using a library derived from SOFA, rather than SOFA
110** itself.
111**
112**
113** TERMS AND CONDITIONS
114**
115** Redistribution and use in source and binary forms, with or without
116** modification, are permitted provided that the following conditions
117** are met:
118**
119** 1 Redistributions of source code must retain the above copyright
120** notice, this list of conditions and the following disclaimer.
121**
122** 2 Redistributions in binary form must reproduce the above copyright
123** notice, this list of conditions and the following disclaimer in
124** the documentation and/or other materials provided with the
125** distribution.
126**
127** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
128** the International Astronomical Union nor the names of its
129** contributors may be used to endorse or promote products derived
130** from this software without specific prior written permission.
131**
132** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
133** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
134** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
135** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
136** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
137** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
138** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
139** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
140** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
141** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
142** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
143** POSSIBILITY OF SUCH DAMAGE.
144**
145*/
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