source: branches/FACT++_part_filenames/erfa/src/c2ixy.c@ 19365

Last change on this file since 19365 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 eraC2ixy(double date1, double date2, double x, double y,
4 double rc2i[3][3])
5/*
6** - - - - - - - - -
7** e r a C 2 i x y
8** - - - - - - - - -
9**
10** Form the celestial to intermediate-frame-of-date matrix for a given
11** date when the CIP X,Y coordinates are known. IAU 2000.
12**
13** Given:
14** date1,date2 double TT as a 2-part Julian Date (Note 1)
15** x,y double Celestial Intermediate Pole (Note 2)
16**
17** Returned:
18** rc2i double[3][3] celestial-to-intermediate matrix (Note 3)
19**
20** Notes:
21**
22** 1) The TT date date1+date2 is a Julian Date, apportioned in any
23** convenient way between the two arguments. For example,
24** JD(TT)=2450123.7 could be expressed in any of these ways,
25** among others:
26**
27** date1 date2
28**
29** 2450123.7 0.0 (JD method)
30** 2451545.0 -1421.3 (J2000 method)
31** 2400000.5 50123.2 (MJD method)
32** 2450123.5 0.2 (date & time method)
33**
34** The JD method is the most natural and convenient to use in
35** cases where the loss of several decimal digits of resolution
36** is acceptable. The J2000 method is best matched to the way
37** the argument is handled internally and will deliver the
38** optimum resolution. The MJD method and the date & time methods
39** are both good compromises between resolution and convenience.
40**
41** 2) The Celestial Intermediate Pole coordinates are the x,y components
42** of the unit vector in the Geocentric Celestial Reference System.
43**
44** 3) The matrix rc2i is the first stage in the transformation from
45** celestial to terrestrial coordinates:
46**
47** [TRS] = RPOM * R_3(ERA) * rc2i * [CRS]
48**
49** = RC2T * [CRS]
50**
51** where [CRS] is a vector in the Geocentric Celestial Reference
52** System and [TRS] is a vector in the International Terrestrial
53** Reference System (see IERS Conventions 2003), ERA is the Earth
54** Rotation Angle and RPOM is the polar motion matrix.
55**
56** 4) Although its name does not include "00", This function is in fact
57** specific to the IAU 2000 models.
58**
59** Called:
60** eraC2ixys celestial-to-intermediate matrix, given X,Y and s
61** eraS00 the CIO locator s, given X,Y, IAU 2000A
62**
63** Reference:
64**
65** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
66** IERS Technical Note No. 32, BKG (2004)
67**
68** Copyright (C) 2013-2016, NumFOCUS Foundation.
69** Derived, with permission, from the SOFA library. See notes at end of file.
70*/
71
72{
73/* Compute s and then the matrix. */
74 eraC2ixys(x, y, eraS00(date1, date2, x, y), rc2i);
75
76 return;
77
78}
79/*----------------------------------------------------------------------
80**
81**
82** Copyright (C) 2013-2016, NumFOCUS Foundation.
83** All rights reserved.
84**
85** This library is derived, with permission, from the International
86** Astronomical Union's "Standards of Fundamental Astronomy" library,
87** available from http://www.iausofa.org.
88**
89** The ERFA version is intended to retain identical functionality to
90** the SOFA library, but made distinct through different function and
91** file names, as set out in the SOFA license conditions. The SOFA
92** original has a role as a reference standard for the IAU and IERS,
93** and consequently redistribution is permitted only in its unaltered
94** state. The ERFA version is not subject to this restriction and
95** therefore can be included in distributions which do not support the
96** concept of "read only" software.
97**
98** Although the intent is to replicate the SOFA API (other than
99** replacement of prefix names) and results (with the exception of
100** bugs; any that are discovered will be fixed), SOFA is not
101** responsible for any errors found in this version of the library.
102**
103** If you wish to acknowledge the SOFA heritage, please acknowledge
104** that you are using a library derived from SOFA, rather than SOFA
105** itself.
106**
107**
108** TERMS AND CONDITIONS
109**
110** Redistribution and use in source and binary forms, with or without
111** modification, are permitted provided that the following conditions
112** are met:
113**
114** 1 Redistributions of source code must retain the above copyright
115** notice, this list of conditions and the following disclaimer.
116**
117** 2 Redistributions in binary form must reproduce the above copyright
118** notice, this list of conditions and the following disclaimer in
119** the documentation and/or other materials provided with the
120** distribution.
121**
122** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
123** the International Astronomical Union nor the names of its
124** contributors may be used to endorse or promote products derived
125** from this software without specific prior written permission.
126**
127** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
128** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
129** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
130** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
131** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
132** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
133** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
134** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
135** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
136** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
137** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
138** POSSIBILITY OF SUCH DAMAGE.
139**
140*/
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