FACT++  1.0
c2ixys.c
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1 #include "erfa.h"
2 
3 void 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) 2013-2015, 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) 2013-2015, 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 */
eraIr
void eraIr(double r[3][3])
Definition: ir.c:3
eraRy
void eraRy(double theta, double r[3][3])
Definition: ry.c:3
eraRz
void eraRz(double psi, double r[3][3])
Definition: rz.c:3
eraC2ixys
void eraC2ixys(double x, double y, double s, double rc2i[3][3])
Definition: c2ixys.c:3