source: trunk/FACT++/erfa/src/fw2xy.c@ 18679

Last change on this file since 18679 was 18348, checked in by tbretz, 9 years ago
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) 2013-2015, 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/* Form NxPxB matrix. */
60 eraFw2m(gamb, phib, psi, eps, r);
61
62/* Extract CIP X,Y. */
63 eraBpn2xy(r, x, y);
64
65 return;
66
67}
68/*----------------------------------------------------------------------
69**
70**
71** Copyright (C) 2013-2015, NumFOCUS Foundation.
72** All rights reserved.
73**
74** This library is derived, with permission, from the International
75** Astronomical Union's "Standards of Fundamental Astronomy" library,
76** available from http://www.iausofa.org.
77**
78** The ERFA version is intended to retain identical functionality to
79** the SOFA library, but made distinct through different function and
80** file names, as set out in the SOFA license conditions. The SOFA
81** original has a role as a reference standard for the IAU and IERS,
82** and consequently redistribution is permitted only in its unaltered
83** state. The ERFA version is not subject to this restriction and
84** therefore can be included in distributions which do not support the
85** concept of "read only" software.
86**
87** Although the intent is to replicate the SOFA API (other than
88** replacement of prefix names) and results (with the exception of
89** bugs; any that are discovered will be fixed), SOFA is not
90** responsible for any errors found in this version of the library.
91**
92** If you wish to acknowledge the SOFA heritage, please acknowledge
93** that you are using a library derived from SOFA, rather than SOFA
94** itself.
95**
96**
97** TERMS AND CONDITIONS
98**
99** Redistribution and use in source and binary forms, with or without
100** modification, are permitted provided that the following conditions
101** are met:
102**
103** 1 Redistributions of source code must retain the above copyright
104** notice, this list of conditions and the following disclaimer.
105**
106** 2 Redistributions in binary form must reproduce the above copyright
107** notice, this list of conditions and the following disclaimer in
108** the documentation and/or other materials provided with the
109** distribution.
110**
111** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
112** the International Astronomical Union nor the names of its
113** contributors may be used to endorse or promote products derived
114** from this software without specific prior written permission.
115**
116** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
117** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
118** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
119** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
120** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
121** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
122** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
123** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
124** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
125** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
126** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
127** POSSIBILITY OF SUCH DAMAGE.
128**
129*/
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