FACT++  1.0
bpn2xy.c
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1 #include "erfa.h"
2 
3 void eraBpn2xy(double rbpn[3][3], double *x, double *y)
4 /*
5 ** - - - - - - - - - -
6 ** e r a B p n 2 x y
7 ** - - - - - - - - - -
8 **
9 ** Extract from the bias-precession-nutation matrix the X,Y coordinates
10 ** of the Celestial Intermediate Pole.
11 **
12 ** Given:
13 ** rbpn double[3][3] celestial-to-true matrix (Note 1)
14 **
15 ** Returned:
16 ** x,y double Celestial Intermediate Pole (Note 2)
17 **
18 ** Notes:
19 **
20 ** 1) The matrix rbpn transforms vectors from GCRS to true equator (and
21 ** CIO or equinox) of date, and therefore the Celestial Intermediate
22 ** Pole unit vector is the bottom row of the matrix.
23 **
24 ** 2) The arguments x,y are components of the Celestial Intermediate
25 ** Pole unit vector in the Geocentric Celestial Reference System.
26 **
27 ** Reference:
28 **
29 ** "Expressions for the Celestial Intermediate Pole and Celestial
30 ** Ephemeris Origin consistent with the IAU 2000A precession-
31 ** nutation model", Astron.Astrophys. 400, 1145-1154
32 ** (2003)
33 **
34 ** n.b. The celestial ephemeris origin (CEO) was renamed "celestial
35 ** intermediate origin" (CIO) by IAU 2006 Resolution 2.
36 **
37 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
38 ** Derived, with permission, from the SOFA library. See notes at end of file.
39 */
40 {
41 /* Extract the X,Y coordinates. */
42  *x = rbpn[2][0];
43  *y = rbpn[2][1];
44 
45  return;
46 
47 }
48 /*----------------------------------------------------------------------
49 **
50 **
51 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
52 ** All rights reserved.
53 **
54 ** This library is derived, with permission, from the International
55 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
56 ** available from http://www.iausofa.org.
57 **
58 ** The ERFA version is intended to retain identical functionality to
59 ** the SOFA library, but made distinct through different function and
60 ** file names, as set out in the SOFA license conditions. The SOFA
61 ** original has a role as a reference standard for the IAU and IERS,
62 ** and consequently redistribution is permitted only in its unaltered
63 ** state. The ERFA version is not subject to this restriction and
64 ** therefore can be included in distributions which do not support the
65 ** concept of "read only" software.
66 **
67 ** Although the intent is to replicate the SOFA API (other than
68 ** replacement of prefix names) and results (with the exception of
69 ** bugs; any that are discovered will be fixed), SOFA is not
70 ** responsible for any errors found in this version of the library.
71 **
72 ** If you wish to acknowledge the SOFA heritage, please acknowledge
73 ** that you are using a library derived from SOFA, rather than SOFA
74 ** itself.
75 **
76 **
77 ** TERMS AND CONDITIONS
78 **
79 ** Redistribution and use in source and binary forms, with or without
80 ** modification, are permitted provided that the following conditions
81 ** are met:
82 **
83 ** 1 Redistributions of source code must retain the above copyright
84 ** notice, this list of conditions and the following disclaimer.
85 **
86 ** 2 Redistributions in binary form must reproduce the above copyright
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88 ** the documentation and/or other materials provided with the
89 ** distribution.
90 **
91 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
92 ** the International Astronomical Union nor the names of its
93 ** contributors may be used to endorse or promote products derived
94 ** from this software without specific prior written permission.
95 **
96 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
97 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
98 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
99 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
100 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
101 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
102 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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109 */
eraBpn2xy
void eraBpn2xy(double rbpn[3][3], double *x, double *y)
Definition: bpn2xy.c:3