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 cond sub pod time 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] = xa*xa + ya*ya;
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             */