source: trunk/FACT++/erfa/src/c2ixys.c

Last change on this file was 18921, checked in by tbretz, 7 years ago
Updated to ERFA 1.4.0
File size: 4.8 KB
Line 
1#include "erfa.h"
2
3void eraC2ixys(double x, double y, double s, double rc2i[3][3])
4/*
5** - - - - - - - - - -
6** e r a C 2 i x y s
7** - - - - - - - - - -
8**
9** Form the celestial to intermediate-frame-of-date matrix given the CIP
10** X,Y and the CIO locator s.
11**
12** Given:
13** x,y double Celestial Intermediate Pole (Note 1)
14** s double the CIO locator s (Note 2)
15**
16** Returned:
17** rc2i double[3][3] celestial-to-intermediate matrix (Note 3)
18**
19** Notes:
20**
21** 1) The Celestial Intermediate Pole coordinates are the x,y
22** components of the unit vector in the Geocentric Celestial
23** Reference System.
24**
25** 2) The CIO locator s (in radians) positions the Celestial
26** Intermediate Origin on the equator of the CIP.
27**
28** 3) The matrix rc2i is the first stage in the transformation from
29** celestial to terrestrial coordinates:
30**
31** [TRS] = RPOM * R_3(ERA) * rc2i * [CRS]
32**
33** = RC2T * [CRS]
34**
35** where [CRS] is a vector in the Geocentric Celestial Reference
36** System and [TRS] is a vector in the International Terrestrial
37** Reference System (see IERS Conventions 2003), ERA is the Earth
38** Rotation Angle and RPOM is the polar motion matrix.
39**
40** Called:
41** eraIr initialize r-matrix to identity
42** eraRz rotate around Z-axis
43** eraRy rotate around Y-axis
44**
45** Reference:
46**
47** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
48** IERS Technical Note No. 32, BKG (2004)
49**
50** Copyright (C) 2013-2017, NumFOCUS Foundation.
51** Derived, with permission, from the SOFA library. See notes at end of file.
52*/
53{
54 double r2, e, d;
55
56
57/* Obtain the spherical angles E and d. */
58 r2 = x*x + y*y;
59 e = (r2 > 0.0) ? atan2(y, x) : 0.0;
60 d = atan(sqrt(r2 / (1.0 - r2)));
61
62/* Form the matrix. */
63 eraIr(rc2i);
64 eraRz(e, rc2i);
65 eraRy(d, rc2i);
66 eraRz(-(e+s), rc2i);
67
68 return;
69
70}
71/*----------------------------------------------------------------------
72**
73**
74** Copyright (C) 2013-2017, NumFOCUS Foundation.
75** All rights reserved.
76**
77** This library is derived, with permission, from the International
78** Astronomical Union's "Standards of Fundamental Astronomy" library,
79** available from http://www.iausofa.org.
80**
81** The ERFA version is intended to retain identical functionality to
82** the SOFA library, but made distinct through different function and
83** file names, as set out in the SOFA license conditions. The SOFA
84** original has a role as a reference standard for the IAU and IERS,
85** and consequently redistribution is permitted only in its unaltered
86** state. The ERFA version is not subject to this restriction and
87** therefore can be included in distributions which do not support the
88** concept of "read only" software.
89**
90** Although the intent is to replicate the SOFA API (other than
91** replacement of prefix names) and results (with the exception of
92** bugs; any that are discovered will be fixed), SOFA is not
93** responsible for any errors found in this version of the library.
94**
95** If you wish to acknowledge the SOFA heritage, please acknowledge
96** that you are using a library derived from SOFA, rather than SOFA
97** itself.
98**
99**
100** TERMS AND CONDITIONS
101**
102** Redistribution and use in source and binary forms, with or without
103** modification, are permitted provided that the following conditions
104** are met:
105**
106** 1 Redistributions of source code must retain the above copyright
107** notice, this list of conditions and the following disclaimer.
108**
109** 2 Redistributions in binary form must reproduce the above copyright
110** notice, this list of conditions and the following disclaimer in
111** the documentation and/or other materials provided with the
112** distribution.
113**
114** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
115** the International Astronomical Union nor the names of its
116** contributors may be used to endorse or promote products derived
117** from this software without specific prior written permission.
118**
119** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
120** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
121** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
122** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
123** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
124** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
125** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
126** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
127** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
128** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
129** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
130** POSSIBILITY OF SUCH DAMAGE.
131**
132*/
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