source: trunk/FACT++/erfa/src/fw2xy.c@ 19098

Last change on this file since 19098 was 18921, checked in by tbretz, 7 years ago
Updated to ERFA 1.4.0
File size: 4.6 KB
Line 
1#include "erfa.h"
2
3void eraFw2xy(double gamb, double phib, double psi, double eps,
4 double *x, double *y)
5/*
6** - - - - - - - - -
7** e r a F w 2 x y
8** - - - - - - - - -
9**
10** CIP X,Y given Fukushima-Williams bias-precession-nutation angles.
11**
12** Given:
13** gamb double F-W angle gamma_bar (radians)
14** phib double F-W angle phi_bar (radians)
15** psi double F-W angle psi (radians)
16** eps double F-W angle epsilon (radians)
17**
18** Returned:
19** x,y double CIP unit vector X,Y
20**
21** Notes:
22**
23** 1) Naming the following points:
24**
25** e = J2000.0 ecliptic pole,
26** p = GCRS pole
27** E = ecliptic pole of date,
28** and P = CIP,
29**
30** the four Fukushima-Williams angles are as follows:
31**
32** gamb = gamma = epE
33** phib = phi = pE
34** psi = psi = pEP
35** eps = epsilon = EP
36**
37** 2) The matrix representing the combined effects of frame bias,
38** precession and nutation is:
39**
40** NxPxB = R_1(-epsA).R_3(-psi).R_1(phib).R_3(gamb)
41**
42** The returned values x,y are elements [2][0] and [2][1] of the
43** matrix. Near J2000.0, they are essentially angles in radians.
44**
45** Called:
46** eraFw2m F-W angles to r-matrix
47** eraBpn2xy extract CIP X,Y coordinates from NPB matrix
48**
49** Reference:
50**
51** Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351
52**
53** Copyright (C) 2013-2017, NumFOCUS Foundation.
54** Derived, with permission, from the SOFA library. See notes at end of file.
55*/
56{
57 double r[3][3];
58
59
60/* Form NxPxB matrix. */
61 eraFw2m(gamb, phib, psi, eps, r);
62
63/* Extract CIP X,Y. */
64 eraBpn2xy(r, x, y);
65
66 return;
67
68}
69/*----------------------------------------------------------------------
70**
71**
72** Copyright (C) 2013-2017, NumFOCUS Foundation.
73** All rights reserved.
74**
75** This library is derived, with permission, from the International
76** Astronomical Union's "Standards of Fundamental Astronomy" library,
77** available from http://www.iausofa.org.
78**
79** The ERFA version is intended to retain identical functionality to
80** the SOFA library, but made distinct through different function and
81** file names, as set out in the SOFA license conditions. The SOFA
82** original has a role as a reference standard for the IAU and IERS,
83** and consequently redistribution is permitted only in its unaltered
84** state. The ERFA version is not subject to this restriction and
85** therefore can be included in distributions which do not support the
86** concept of "read only" software.
87**
88** Although the intent is to replicate the SOFA API (other than
89** replacement of prefix names) and results (with the exception of
90** bugs; any that are discovered will be fixed), SOFA is not
91** responsible for any errors found in this version of the library.
92**
93** If you wish to acknowledge the SOFA heritage, please acknowledge
94** that you are using a library derived from SOFA, rather than SOFA
95** itself.
96**
97**
98** TERMS AND CONDITIONS
99**
100** Redistribution and use in source and binary forms, with or without
101** modification, are permitted provided that the following conditions
102** are met:
103**
104** 1 Redistributions of source code must retain the above copyright
105** notice, this list of conditions and the following disclaimer.
106**
107** 2 Redistributions in binary form must reproduce the above copyright
108** notice, this list of conditions and the following disclaimer in
109** the documentation and/or other materials provided with the
110** distribution.
111**
112** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
113** the International Astronomical Union nor the names of its
114** contributors may be used to endorse or promote products derived
115** from this software without specific prior written permission.
116**
117** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
118** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
119** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
120** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
121** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
122** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
123** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
124** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
125** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
126** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
127** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
128** POSSIBILITY OF SUCH DAMAGE.
129**
130*/
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