source: trunk/FACT++/sofa/src/c2i00a.c@ 18368

Last change on this file since 18368 was 18346, checked in by tbretz, 11 years ago
File size: 7.2 KB
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1#include "sofa.h"
2
3void iauC2i00a(double date1, double date2, double rc2i[3][3])
4/*
5** - - - - - - - - - -
6** i a u C 2 i 0 0 a
7** - - - - - - - - - -
8**
9** Form the celestial-to-intermediate matrix for a given date using the
10** IAU 2000A precession-nutation model.
11**
12** This function is part of the International Astronomical Union's
13** SOFA (Standards Of Fundamental Astronomy) software collection.
14**
15** Status: support function.
16**
17** Given:
18** date1,date2 double TT as a 2-part Julian Date (Note 1)
19**
20** Returned:
21** rc2i double[3][3] celestial-to-intermediate matrix (Note 2)
22**
23** Notes:
24**
25** 1) The TT date date1+date2 is a Julian Date, apportioned in any
26** convenient way between the two arguments. For example,
27** JD(TT)=2450123.7 could be expressed in any of these ways,
28** among others:
29**
30** date1 date2
31**
32** 2450123.7 0.0 (JD method)
33** 2451545.0 -1421.3 (J2000 method)
34** 2400000.5 50123.2 (MJD method)
35** 2450123.5 0.2 (date & time method)
36**
37** The JD method is the most natural and convenient to use in
38** cases where the loss of several decimal digits of resolution
39** is acceptable. The J2000 method is best matched to the way
40** the argument is handled internally and will deliver the
41** optimum resolution. The MJD method and the date & time methods
42** are both good compromises between resolution and convenience.
43**
44** 2) The matrix rc2i is the first stage in the transformation from
45** celestial to terrestrial coordinates:
46**
47** [TRS] = RPOM * R_3(ERA) * rc2i * [CRS]
48**
49** = rc2t * [CRS]
50**
51** where [CRS] is a vector in the Geocentric Celestial Reference
52** System and [TRS] is a vector in the International Terrestrial
53** Reference System (see IERS Conventions 2003), ERA is the Earth
54** Rotation Angle and RPOM is the polar motion matrix.
55**
56** 3) A faster, but slightly less accurate result (about 1 mas), can be
57** obtained by using instead the iauC2i00b function.
58**
59** Called:
60** iauPnm00a classical NPB matrix, IAU 2000A
61** iauC2ibpn celestial-to-intermediate matrix, given NPB matrix
62**
63** References:
64**
65** "Expressions for the Celestial Intermediate Pole and Celestial
66** Ephemeris Origin consistent with the IAU 2000A precession-
67** nutation model", Astron.Astrophys. 400, 1145-1154
68** (2003)
69**
70** n.b. The celestial ephemeris origin (CEO) was renamed "celestial
71** intermediate origin" (CIO) by IAU 2006 Resolution 2.
72**
73** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
74** IERS Technical Note No. 32, BKG (2004)
75**
76** This revision: 2013 June 18
77**
78** SOFA release 2015-02-09
79**
80** Copyright (C) 2015 IAU SOFA Board. See notes at end.
81*/
82{
83 double rbpn[3][3];
84
85/* Obtain the celestial-to-true matrix (IAU 2000A). */
86 iauPnm00a(date1, date2, rbpn);
87
88/* Form the celestial-to-intermediate matrix. */
89 iauC2ibpn(date1, date2, rbpn, rc2i);
90
91 return;
92
93/*----------------------------------------------------------------------
94**
95** Copyright (C) 2015
96** Standards Of Fundamental Astronomy Board
97** of the International Astronomical Union.
98**
99** =====================
100** SOFA Software License
101** =====================
102**
103** NOTICE TO USER:
104**
105** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
106** CONDITIONS WHICH APPLY TO ITS USE.
107**
108** 1. The Software is owned by the IAU SOFA Board ("SOFA").
109**
110** 2. Permission is granted to anyone to use the SOFA software for any
111** purpose, including commercial applications, free of charge and
112** without payment of royalties, subject to the conditions and
113** restrictions listed below.
114**
115** 3. You (the user) may copy and distribute SOFA source code to others,
116** and use and adapt its code and algorithms in your own software,
117** on a world-wide, royalty-free basis. That portion of your
118** distribution that does not consist of intact and unchanged copies
119** of SOFA source code files is a "derived work" that must comply
120** with the following requirements:
121**
122** a) Your work shall be marked or carry a statement that it
123** (i) uses routines and computations derived by you from
124** software provided by SOFA under license to you; and
125** (ii) does not itself constitute software provided by and/or
126** endorsed by SOFA.
127**
128** b) The source code of your derived work must contain descriptions
129** of how the derived work is based upon, contains and/or differs
130** from the original SOFA software.
131**
132** c) The names of all routines in your derived work shall not
133** include the prefix "iau" or "sofa" or trivial modifications
134** thereof such as changes of case.
135**
136** d) The origin of the SOFA components of your derived work must
137** not be misrepresented; you must not claim that you wrote the
138** original software, nor file a patent application for SOFA
139** software or algorithms embedded in the SOFA software.
140**
141** e) These requirements must be reproduced intact in any source
142** distribution and shall apply to anyone to whom you have
143** granted a further right to modify the source code of your
144** derived work.
145**
146** Note that, as originally distributed, the SOFA software is
147** intended to be a definitive implementation of the IAU standards,
148** and consequently third-party modifications are discouraged. All
149** variations, no matter how minor, must be explicitly marked as
150** such, as explained above.
151**
152** 4. You shall not cause the SOFA software to be brought into
153** disrepute, either by misuse, or use for inappropriate tasks, or
154** by inappropriate modification.
155**
156** 5. The SOFA software is provided "as is" and SOFA makes no warranty
157** as to its use or performance. SOFA does not and cannot warrant
158** the performance or results which the user may obtain by using the
159** SOFA software. SOFA makes no warranties, express or implied, as
160** to non-infringement of third party rights, merchantability, or
161** fitness for any particular purpose. In no event will SOFA be
162** liable to the user for any consequential, incidental, or special
163** damages, including any lost profits or lost savings, even if a
164** SOFA representative has been advised of such damages, or for any
165** claim by any third party.
166**
167** 6. The provision of any version of the SOFA software under the terms
168** and conditions specified herein does not imply that future
169** versions will also be made available under the same terms and
170** conditions.
171*
172** In any published work or commercial product which uses the SOFA
173** software directly, acknowledgement (see www.iausofa.org) is
174** appreciated.
175**
176** Correspondence concerning SOFA software should be addressed as
177** follows:
178**
179** By email: sofa@ukho.gov.uk
180** By post: IAU SOFA Center
181** HM Nautical Almanac Office
182** UK Hydrographic Office
183** Admiralty Way, Taunton
184** Somerset, TA1 2DN
185** United Kingdom
186**
187**--------------------------------------------------------------------*/
188}
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