source: branches/FACT++_lidctrl_usb/erfa/src/pv2s.c@ 19875

Last change on this file since 19875 was 18711, checked in by tbretz, 10 years ago
Updated to ERFA 1.3.0 (no relevant code change except the leap second at the beginning of 2017)
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) 2013-2016, 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) 2013-2016, 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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