source: branches/FACT++_lidctrl_new_eth/erfa/src/pb06.c@ 20041

Last change on this file since 20041 was 18711, checked in by tbretz, 9 years ago
Updated to ERFA 1.3.0 (no relevant code change except the leap second at the beginning of 2017)
File size: 6.1 KB
Line 
1#include "erfa.h"
2
3void eraPb06(double date1, double date2,
4 double *bzeta, double *bz, double *btheta)
5/*
6** - - - - - - - -
7** e r a P b 0 6
8** - - - - - - - -
9**
10** This function forms three Euler angles which implement general
11** precession from epoch J2000.0, using the IAU 2006 model. Frame
12** bias (the offset between ICRS and mean J2000.0) is included.
13**
14** Given:
15** date1,date2 double TT as a 2-part Julian Date (Note 1)
16**
17** Returned:
18** bzeta double 1st rotation: radians cw around z
19** bz double 3rd rotation: radians cw around z
20** btheta double 2nd rotation: radians ccw around y
21**
22** Notes:
23**
24** 1) The TT date date1+date2 is a Julian Date, apportioned in any
25** convenient way between the two arguments. For example,
26** JD(TT)=2450123.7 could be expressed in any of these ways,
27** among others:
28**
29** date1 date2
30**
31** 2450123.7 0.0 (JD method)
32** 2451545.0 -1421.3 (J2000 method)
33** 2400000.5 50123.2 (MJD method)
34** 2450123.5 0.2 (date & time method)
35**
36** The JD method is the most natural and convenient to use in
37** cases where the loss of several decimal digits of resolution
38** is acceptable. The J2000 method is best matched to the way
39** the argument is handled internally and will deliver the
40** optimum resolution. The MJD method and the date & time methods
41** are both good compromises between resolution and convenience.
42**
43** 2) The traditional accumulated precession angles zeta_A, z_A,
44** theta_A cannot be obtained in the usual way, namely through
45** polynomial expressions, because of the frame bias. The latter
46** means that two of the angles undergo rapid changes near this
47** date. They are instead the results of decomposing the
48** precession-bias matrix obtained by using the Fukushima-Williams
49** method, which does not suffer from the problem. The
50** decomposition returns values which can be used in the
51** conventional formulation and which include frame bias.
52**
53** 3) The three angles are returned in the conventional order, which
54** is not the same as the order of the corresponding Euler
55** rotations. The precession-bias matrix is
56** R_3(-z) x R_2(+theta) x R_3(-zeta).
57**
58** 4) Should zeta_A, z_A, theta_A angles be required that do not
59** contain frame bias, they are available by calling the ERFA
60** function eraP06e.
61**
62** Called:
63** eraPmat06 PB matrix, IAU 2006
64** eraRz rotate around Z-axis
65**
66** Copyright (C) 2013-2016, NumFOCUS Foundation.
67** Derived, with permission, from the SOFA library. See notes at end of file.
68*/
69{
70 double r[3][3], r31, r32;
71
72
73/* Precession matrix via Fukushima-Williams angles. */
74 eraPmat06(date1, date2, r);
75
76/* Solve for z. */
77 *bz = atan2(r[1][2], r[0][2]);
78
79/* Remove it from the matrix. */
80 eraRz(*bz, r);
81
82/* Solve for the remaining two angles. */
83 *bzeta = atan2 (r[1][0], r[1][1]);
84 r31 = r[2][0];
85 r32 = r[2][1];
86 *btheta = atan2(-ERFA_DSIGN(sqrt(r31 * r31 + r32 * r32), r[0][2]),
87 r[2][2]);
88
89 return;
90
91}
92/*----------------------------------------------------------------------
93**
94**
95** Copyright (C) 2013-2016, NumFOCUS Foundation.
96** All rights reserved.
97**
98** This library is derived, with permission, from the International
99** Astronomical Union's "Standards of Fundamental Astronomy" library,
100** available from http://www.iausofa.org.
101**
102** The ERFA version is intended to retain identical functionality to
103** the SOFA library, but made distinct through different function and
104** file names, as set out in the SOFA license conditions. The SOFA
105** original has a role as a reference standard for the IAU and IERS,
106** and consequently redistribution is permitted only in its unaltered
107** state. The ERFA version is not subject to this restriction and
108** therefore can be included in distributions which do not support the
109** concept of "read only" software.
110**
111** Although the intent is to replicate the SOFA API (other than
112** replacement of prefix names) and results (with the exception of
113** bugs; any that are discovered will be fixed), SOFA is not
114** responsible for any errors found in this version of the library.
115**
116** If you wish to acknowledge the SOFA heritage, please acknowledge
117** that you are using a library derived from SOFA, rather than SOFA
118** itself.
119**
120**
121** TERMS AND CONDITIONS
122**
123** Redistribution and use in source and binary forms, with or without
124** modification, are permitted provided that the following conditions
125** are met:
126**
127** 1 Redistributions of source code must retain the above copyright
128** notice, this list of conditions and the following disclaimer.
129**
130** 2 Redistributions in binary form must reproduce the above copyright
131** notice, this list of conditions and the following disclaimer in
132** the documentation and/or other materials provided with the
133** distribution.
134**
135** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
136** the International Astronomical Union nor the names of its
137** contributors may be used to endorse or promote products derived
138** from this software without specific prior written permission.
139**
140** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
141** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
142** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
143** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
144** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
145** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
146** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
147** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
148** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
149** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
150** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
151** POSSIBILITY OF SUCH DAMAGE.
152**
153*/
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