File Coverage

erfasrc/src/pb06.c

Criterion	Covered	Total	%
statement	0	15	0.0
branch	0	8	0.0
condition			n/a
subroutine			n/a
pod			n/a
total	0	23	0.0

line	stmt	bran	code
1			#include "erfa.h"
2
3	0		void 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) 2013-2020, NumFOCUS Foundation.
67			** Derived, with permission, from the SOFA library. See notes at end of file.
68			*/
69			{
70			double r[3][3], y, x;
71
72
73			/* Precession matrix via Fukushima-Williams angles. */
74	0		eraPmat06(date1, date2, r);
75
76			/* Solve for z, choosing the +/- pi alternative. */
77	0		y = r[1][2];
78	0		x = -r[0][2];
79	0	0	if ( x < 0.0 ) {
80	0		y = -y;
81			x = -x;
82			}
83	0	0	*bz = ( x != 0.0 \|\| y != 0.0 ) ? - atan2(y,x) : 0.0;
84
85			/* Derotate it out of the matrix. */
86	0		eraRz ( *bz, r );
87
88			/* Solve for the remaining two angles. */
89	0		y = r[0][2];
90	0		x = r[2][2];
91	0	0	*btheta = ( x != 0.0 \|\| y != 0.0 ) ? - atan2(y,x) : 0.0;
92
93	0		y = -r[1][0];
94	0		x = r[1][1];
95	0	0	*bzeta = ( x != 0.0 \|\| y != 0.0 ) ? - atan2(y,x) : 0.0;
96
97	0		}
98			/*----------------------------------------------------------------------
99			**
100			**
101			** Copyright (C) 2013-2020, NumFOCUS Foundation.
102			** All rights reserved.
103			**
104			** This library is derived, with permission, from the International
105			** Astronomical Union's "Standards of Fundamental Astronomy" library,
106			** available from http://www.iausofa.org.
107			**
108			** The ERFA version is intended to retain identical functionality to
109			** the SOFA library, but made distinct through different function and
110			** file names, as set out in the SOFA license conditions. The SOFA
111			** original has a role as a reference standard for the IAU and IERS,
112			** and consequently redistribution is permitted only in its unaltered
113			** state. The ERFA version is not subject to this restriction and
114			** therefore can be included in distributions which do not support the
115			** concept of "read only" software.
116			**
117			** Although the intent is to replicate the SOFA API (other than
118			** replacement of prefix names) and results (with the exception of
119			** bugs; any that are discovered will be fixed), SOFA is not
120			** responsible for any errors found in this version of the library.
121			**
122			** If you wish to acknowledge the SOFA heritage, please acknowledge
123			** that you are using a library derived from SOFA, rather than SOFA
124			** itself.
125			**
126			**
127			** TERMS AND CONDITIONS
128			**
129			** Redistribution and use in source and binary forms, with or without
130			** modification, are permitted provided that the following conditions
131			** are met:
132			**
133			** 1 Redistributions of source code must retain the above copyright
134			** notice, this list of conditions and the following disclaimer.
135			**
136			** 2 Redistributions in binary form must reproduce the above copyright
137			** notice, this list of conditions and the following disclaimer in
138			** the documentation and/or other materials provided with the
139			** distribution.
140			**
141			** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
142			** the International Astronomical Union nor the names of its
143			** contributors may be used to endorse or promote products derived
144			** from this software without specific prior written permission.
145			**
146			** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
147			** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
148			** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
149			** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
150			** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
151			** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
152			** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
153			** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
154			** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
155			** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
156			** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
157			** POSSIBILITY OF SUCH DAMAGE.
158			**
159			*/