source: trunk/FACT++/erfa/src/pv2s.c@ 20000

Last change on this file since 20000 was 18921, checked in by tbretz, 8 years ago
Updated to ERFA 1.4.0
File size: 5.3 KB
Line 
1#include "erfa.h"
2
3void eraPv2s(double pv[2][3],
4 double *theta, double *phi, double *r,
5 double *td, double *pd, double *rd)
6/*
7** - - - - - - - -
8** e r a P v 2 s
9** - - - - - - - -
10**
11** Convert position/velocity from Cartesian to spherical coordinates.
12**
13** Given:
14** pv double[2][3] pv-vector
15**
16** Returned:
17** theta double longitude angle (radians)
18** phi double latitude angle (radians)
19** r double radial distance
20** td double rate of change of theta
21** pd double rate of change of phi
22** rd double rate of change of r
23**
24** Notes:
25**
26** 1) If the position part of pv is null, theta, phi, td and pd
27** are indeterminate. This is handled by extrapolating the
28** position through unit time by using the velocity part of
29** pv. This moves the origin without changing the direction
30** of the velocity component. If the position and velocity
31** components of pv are both null, zeroes are returned for all
32** six results.
33**
34** 2) If the position is a pole, theta, td and pd are indeterminate.
35** In such cases zeroes are returned for all three.
36**
37** Copyright (C) 2013-2017, NumFOCUS Foundation.
38** Derived, with permission, from the SOFA library. See notes at end of file.
39*/
40{
41 double x, y, z, xd, yd, zd, rxy2, rxy, r2, rtrue, rw, xyp;
42
43
44/* Components of position/velocity vector. */
45 x = pv[0][0];
46 y = pv[0][1];
47 z = pv[0][2];
48 xd = pv[1][0];
49 yd = pv[1][1];
50 zd = pv[1][2];
51
52/* Component of r in XY plane squared. */
53 rxy2 = x*x + y*y;
54
55/* Modulus squared. */
56 r2 = rxy2 + z*z;
57
58/* Modulus. */
59 rtrue = sqrt(r2);
60
61/* If null vector, move the origin along the direction of movement. */
62 rw = rtrue;
63 if (rtrue == 0.0) {
64 x = xd;
65 y = yd;
66 z = zd;
67 rxy2 = x*x + y*y;
68 r2 = rxy2 + z*z;
69 rw = sqrt(r2);
70 }
71
72/* Position and velocity in spherical coordinates. */
73 rxy = sqrt(rxy2);
74 xyp = x*xd + y*yd;
75 if (rxy2 != 0.0) {
76 *theta = atan2(y, x);
77 *phi = atan2(z, rxy);
78 *td = (x*yd - y*xd) / rxy2;
79 *pd = (zd*rxy2 - z*xyp) / (r2*rxy);
80 } else {
81 *theta = 0.0;
82 *phi = (z != 0.0) ? atan2(z, rxy) : 0.0;
83 *td = 0.0;
84 *pd = 0.0;
85 }
86 *r = rtrue;
87 *rd = (rw != 0.0) ? (xyp + z*zd) / rw : 0.0;
88
89 return;
90
91}
92/*----------------------------------------------------------------------
93**
94**
95** Copyright (C) 2013-2017, 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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