File Coverage

erfasrc/src/pap.c

Criterion	Covered	Total	%
statement	0	17	0.0
branch	0	6	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		double eraPap(double a[3], double b[3])
4			/*
5			** - - - - - - -
6			** e r a P a p
7			** - - - - - - -
8			**
9			** Position-angle from two p-vectors.
10			**
11			** Given:
12			** a double[3] direction of reference point
13			** b double[3] direction of point whose PA is required
14			**
15			** Returned (function value):
16			** double position angle of b with respect to a (radians)
17			**
18			** Notes:
19			**
20			** 1) The result is the position angle, in radians, of direction b with
21			** respect to direction a. It is in the range -pi to +pi. The
22			** sense is such that if b is a small distance "north" of a the
23			** position angle is approximately zero, and if b is a small
24			** distance "east" of a the position angle is approximately +pi/2.
25			**
26			** 2) The vectors a and b need not be of unit length.
27			**
28			** 3) Zero is returned if the two directions are the same or if either
29			** vector is null.
30			**
31			** 4) If vector a is at a pole, the result is ill-defined.
32			**
33			** Called:
34			** eraPn decompose p-vector into modulus and direction
35			** eraPm modulus of p-vector
36			** eraPxp vector product of two p-vectors
37			** eraPmp p-vector minus p-vector
38			** eraPdp scalar product of two p-vectors
39			**
40			** Copyright (C) 2013-2019, NumFOCUS Foundation.
41			** Derived, with permission, from the SOFA library. See notes at end of file.
42			*/
43			{
44			double am, au[3], bm, st, ct, xa, ya, za, eta[3], xi[3], a2b[3], pa;
45
46
47			/* Modulus and direction of the a vector. */
48	0		eraPn(a, &am, au);
49
50			/* Modulus of the b vector. */
51	0		bm = eraPm(b);
52
53			/* Deal with the case of a null vector. */
54	0	0	if ((am == 0.0) \|\| (bm == 0.0)) {
		0
55			st = 0.0;
56			ct = 1.0;
57			} else {
58
59			/* The "north" axis tangential from a (arbitrary length). */
60	0		xa = a[0];
61	0		ya = a[1];
62	0		za = a[2];
63	0		eta[0] = -xa * za;
64	0		eta[1] = -ya * za;
65	0		eta[2] = xaxa + yaya;
66
67			/* The "east" axis tangential from a (same length). */
68	0		eraPxp(eta, au, xi);
69
70			/* The vector from a to b. */
71	0		eraPmp(b, a, a2b);
72
73			/* Resolve into components along the north and east axes. */
74	0		st = eraPdp(a2b, xi);
75	0		ct = eraPdp(a2b, eta);
76
77			/* Deal with degenerate cases. */
78	0	0	if ((st == 0.0) && (ct == 0.0)) ct = 1.0;
79			}
80
81			/* Position angle. */
82	0		pa = atan2(st, ct);
83
84	0		return pa;
85
86			}
87			/*----------------------------------------------------------------------
88			**
89			**
90			** Copyright (C) 2013-2019, NumFOCUS Foundation.
91			** All rights reserved.
92			**
93			** This library is derived, with permission, from the International
94			** Astronomical Union's "Standards of Fundamental Astronomy" library,
95			** available from http://www.iausofa.org.
96			**
97			** The ERFA version is intended to retain identical functionality to
98			** the SOFA library, but made distinct through different function and
99			** file names, as set out in the SOFA license conditions. The SOFA
100			** original has a role as a reference standard for the IAU and IERS,
101			** and consequently redistribution is permitted only in its unaltered
102			** state. The ERFA version is not subject to this restriction and
103			** therefore can be included in distributions which do not support the
104			** concept of "read only" software.
105			**
106			** Although the intent is to replicate the SOFA API (other than
107			** replacement of prefix names) and results (with the exception of
108			** bugs; any that are discovered will be fixed), SOFA is not
109			** responsible for any errors found in this version of the library.
110			**
111			** If you wish to acknowledge the SOFA heritage, please acknowledge
112			** that you are using a library derived from SOFA, rather than SOFA
113			** itself.
114			**
115			**
116			** TERMS AND CONDITIONS
117			**
118			** Redistribution and use in source and binary forms, with or without
119			** modification, are permitted provided that the following conditions
120			** are met:
121			**
122			** 1 Redistributions of source code must retain the above copyright
123			** notice, this list of conditions and the following disclaimer.
124			**
125			** 2 Redistributions in binary form must reproduce the above copyright
126			** notice, this list of conditions and the following disclaimer in
127			** the documentation and/or other materials provided with the
128			** distribution.
129			**
130			** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
131			** the International Astronomical Union nor the names of its
132			** contributors may be used to endorse or promote products derived
133			** from this software without specific prior written permission.
134			**
135			** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
136			** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
137			** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
138			** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
139			** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
140			** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
141			** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
142			** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
143			** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
144			** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
145			** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
146			** POSSIBILITY OF SUCH DAMAGE.
147			**
148			*/