source: trunk/FACT++/sofa/src/c2t06a.c@ 18365

Last change on this file since 18365 was 18346, checked in by tbretz, 10 years ago
File size: 7.8 KB
Line 
1#include "sofa.h"
2
3void iauC2t06a(double tta, double ttb, double uta, double utb,
4 double xp, double yp, double rc2t[3][3])
5/*
6** - - - - - - - - - -
7** i a u C 2 t 0 6 a
8** - - - - - - - - - -
9**
10** Form the celestial to terrestrial matrix given the date, the UT1 and
11** the polar motion, using the IAU 2006 precession and IAU 2000A
12** nutation models.
13**
14** This function is part of the International Astronomical Union's
15** SOFA (Standards Of Fundamental Astronomy) software collection.
16**
17** Status: support function.
18**
19** Given:
20** tta,ttb double TT as a 2-part Julian Date (Note 1)
21** uta,utb double UT1 as a 2-part Julian Date (Note 1)
22** xp,yp double coordinates of the pole (radians, Note 2)
23**
24** Returned:
25** rc2t double[3][3] celestial-to-terrestrial matrix (Note 3)
26**
27** Notes:
28**
29** 1) The TT and UT1 dates tta+ttb and uta+utb are Julian Dates,
30** apportioned in any convenient way between the arguments uta and
31** utb. For example, JD(UT1)=2450123.7 could be expressed in any of
32** these ways, among others:
33**
34** uta utb
35**
36** 2450123.7 0.0 (JD method)
37** 2451545.0 -1421.3 (J2000 method)
38** 2400000.5 50123.2 (MJD method)
39** 2450123.5 0.2 (date & time method)
40**
41** The JD method is the most natural and convenient to use in
42** cases where the loss of several decimal digits of resolution is
43** acceptable. The J2000 and MJD methods are good compromises
44** between resolution and convenience. In the case of uta,utb, the
45** date & time method is best matched to the Earth rotation angle
46** algorithm used: maximum precision is delivered when the uta
47** argument is for 0hrs UT1 on the day in question and the utb
48** argument lies in the range 0 to 1, or vice versa.
49**
50** 2) The arguments xp and yp are the coordinates (in radians) of the
51** Celestial Intermediate Pole with respect to the International
52** Terrestrial Reference System (see IERS Conventions 2003),
53** measured along the meridians to 0 and 90 deg west respectively.
54**
55** 3) The matrix rc2t transforms from celestial to terrestrial
56** coordinates:
57**
58** [TRS] = RPOM * R_3(ERA) * RC2I * [CRS]
59**
60** = rc2t * [CRS]
61**
62** where [CRS] is a vector in the Geocentric Celestial Reference
63** System and [TRS] is a vector in the International Terrestrial
64** Reference System (see IERS Conventions 2003), RC2I is the
65** celestial-to-intermediate matrix, ERA is the Earth rotation
66** angle and RPOM is the polar motion matrix.
67**
68** Called:
69** iauC2i06a celestial-to-intermediate matrix, IAU 2006/2000A
70** iauEra00 Earth rotation angle, IAU 2000
71** iauSp00 the TIO locator s', IERS 2000
72** iauPom00 polar motion matrix
73** iauC2tcio form CIO-based celestial-to-terrestrial matrix
74**
75** Reference:
76**
77** McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
78** IERS Technical Note No. 32, BKG
79**
80** This revision: 2013 June 18
81**
82** SOFA release 2015-02-09
83**
84** Copyright (C) 2015 IAU SOFA Board. See notes at end.
85*/
86{
87 double rc2i[3][3], era, sp, rpom[3][3];
88
89/* Form the celestial-to-intermediate matrix for this TT. */
90 iauC2i06a(tta, ttb, rc2i);
91
92/* Predict the Earth rotation angle for this UT1. */
93 era = iauEra00(uta, utb);
94
95/* Estimate s'. */
96 sp = iauSp00(tta, ttb);
97
98/* Form the polar motion matrix. */
99 iauPom00(xp, yp, sp, rpom);
100
101/* Combine to form the celestial-to-terrestrial matrix. */
102 iauC2tcio(rc2i, era, rpom, rc2t);
103
104 return;
105
106/*----------------------------------------------------------------------
107**
108** Copyright (C) 2015
109** Standards Of Fundamental Astronomy Board
110** of the International Astronomical Union.
111**
112** =====================
113** SOFA Software License
114** =====================
115**
116** NOTICE TO USER:
117**
118** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
119** CONDITIONS WHICH APPLY TO ITS USE.
120**
121** 1. The Software is owned by the IAU SOFA Board ("SOFA").
122**
123** 2. Permission is granted to anyone to use the SOFA software for any
124** purpose, including commercial applications, free of charge and
125** without payment of royalties, subject to the conditions and
126** restrictions listed below.
127**
128** 3. You (the user) may copy and distribute SOFA source code to others,
129** and use and adapt its code and algorithms in your own software,
130** on a world-wide, royalty-free basis. That portion of your
131** distribution that does not consist of intact and unchanged copies
132** of SOFA source code files is a "derived work" that must comply
133** with the following requirements:
134**
135** a) Your work shall be marked or carry a statement that it
136** (i) uses routines and computations derived by you from
137** software provided by SOFA under license to you; and
138** (ii) does not itself constitute software provided by and/or
139** endorsed by SOFA.
140**
141** b) The source code of your derived work must contain descriptions
142** of how the derived work is based upon, contains and/or differs
143** from the original SOFA software.
144**
145** c) The names of all routines in your derived work shall not
146** include the prefix "iau" or "sofa" or trivial modifications
147** thereof such as changes of case.
148**
149** d) The origin of the SOFA components of your derived work must
150** not be misrepresented; you must not claim that you wrote the
151** original software, nor file a patent application for SOFA
152** software or algorithms embedded in the SOFA software.
153**
154** e) These requirements must be reproduced intact in any source
155** distribution and shall apply to anyone to whom you have
156** granted a further right to modify the source code of your
157** derived work.
158**
159** Note that, as originally distributed, the SOFA software is
160** intended to be a definitive implementation of the IAU standards,
161** and consequently third-party modifications are discouraged. All
162** variations, no matter how minor, must be explicitly marked as
163** such, as explained above.
164**
165** 4. You shall not cause the SOFA software to be brought into
166** disrepute, either by misuse, or use for inappropriate tasks, or
167** by inappropriate modification.
168**
169** 5. The SOFA software is provided "as is" and SOFA makes no warranty
170** as to its use or performance. SOFA does not and cannot warrant
171** the performance or results which the user may obtain by using the
172** SOFA software. SOFA makes no warranties, express or implied, as
173** to non-infringement of third party rights, merchantability, or
174** fitness for any particular purpose. In no event will SOFA be
175** liable to the user for any consequential, incidental, or special
176** damages, including any lost profits or lost savings, even if a
177** SOFA representative has been advised of such damages, or for any
178** claim by any third party.
179**
180** 6. The provision of any version of the SOFA software under the terms
181** and conditions specified herein does not imply that future
182** versions will also be made available under the same terms and
183** conditions.
184*
185** In any published work or commercial product which uses the SOFA
186** software directly, acknowledgement (see www.iausofa.org) is
187** appreciated.
188**
189** Correspondence concerning SOFA software should be addressed as
190** follows:
191**
192** By email: sofa@ukho.gov.uk
193** By post: IAU SOFA Center
194** HM Nautical Almanac Office
195** UK Hydrographic Office
196** Admiralty Way, Taunton
197** Somerset, TA1 2DN
198** United Kingdom
199**
200**--------------------------------------------------------------------*/
201}
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