source: trunk/FACT++/sofa/src/c2t00a.c@ 18355

Last change on this file since 18355 was 18346, checked in by tbretz, 11 years ago
File size: 7.9 KB
Line 
1#include "sofa.h"
2
3void iauC2t00a(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 0 a
8** - - - - - - - - - -
9**
10** Form the celestial to terrestrial matrix given the date, the UT1 and
11** the polar motion, using the IAU 2000A nutation model.
12**
13** This function is part of the International Astronomical Union's
14** SOFA (Standards Of Fundamental Astronomy) software collection.
15**
16** Status: support function.
17**
18** Given:
19** tta,ttb double TT as a 2-part Julian Date (Note 1)
20** uta,utb double UT1 as a 2-part Julian Date (Note 1)
21** xp,yp double coordinates of the pole (radians, Note 2)
22**
23** Returned:
24** rc2t double[3][3] celestial-to-terrestrial matrix (Note 3)
25**
26** Notes:
27**
28** 1) The TT and UT1 dates tta+ttb and uta+utb are Julian Dates,
29** apportioned in any convenient way between the arguments uta and
30** utb. For example, JD(UT1)=2450123.7 could be expressed in any of
31** these ways, among others:
32**
33** uta utb
34**
35** 2450123.7 0.0 (JD method)
36** 2451545.0 -1421.3 (J2000 method)
37** 2400000.5 50123.2 (MJD method)
38** 2450123.5 0.2 (date & time method)
39**
40** The JD method is the most natural and convenient to use in
41** cases where the loss of several decimal digits of resolution is
42** acceptable. The J2000 and MJD methods are good compromises
43** between resolution and convenience. In the case of uta,utb, the
44** date & time method is best matched to the Earth rotation angle
45** algorithm used: maximum precision is delivered when the uta
46** argument is for 0hrs UT1 on the day in question and the utb
47** argument lies in the range 0 to 1, or vice versa.
48**
49** 2) The arguments xp and yp are the coordinates (in radians) of the
50** Celestial Intermediate Pole with respect to the International
51** Terrestrial Reference System (see IERS Conventions 2003),
52** measured along the meridians to 0 and 90 deg west respectively.
53**
54** 3) The matrix rc2t transforms from celestial to terrestrial
55** coordinates:
56**
57** [TRS] = RPOM * R_3(ERA) * RC2I * [CRS]
58**
59** = rc2t * [CRS]
60**
61** where [CRS] is a vector in the Geocentric Celestial Reference
62** System and [TRS] is a vector in the International Terrestrial
63** Reference System (see IERS Conventions 2003), RC2I is the
64** celestial-to-intermediate matrix, ERA is the Earth rotation
65** angle and RPOM is the polar motion matrix.
66**
67** 4) A faster, but slightly less accurate result (about 1 mas), can
68** be obtained by using instead the iauC2t00b function.
69**
70** Called:
71** iauC2i00a celestial-to-intermediate matrix, IAU 2000A
72** iauEra00 Earth rotation angle, IAU 2000
73** iauSp00 the TIO locator s', IERS 2000
74** iauPom00 polar motion matrix
75** iauC2tcio form CIO-based celestial-to-terrestrial matrix
76**
77** Reference:
78**
79** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
80** IERS Technical Note No. 32, BKG (2004)
81**
82** This revision: 2013 June 18
83**
84** SOFA release 2015-02-09
85**
86** Copyright (C) 2015 IAU SOFA Board. See notes at end.
87*/
88{
89 double rc2i[3][3], era, sp, rpom[3][3];
90
91/* Form the celestial-to-intermediate matrix for this TT (IAU 2000A). */
92 iauC2i00a(tta, ttb, rc2i );
93
94/* Predict the Earth rotation angle for this UT1. */
95 era = iauEra00(uta, utb);
96
97/* Estimate s'. */
98 sp = iauSp00(tta, ttb);
99
100/* Form the polar motion matrix. */
101 iauPom00(xp, yp, sp, rpom);
102
103/* Combine to form the celestial-to-terrestrial matrix. */
104 iauC2tcio(rc2i, era, rpom, rc2t);
105
106 return;
107
108/*----------------------------------------------------------------------
109**
110** Copyright (C) 2015
111** Standards Of Fundamental Astronomy Board
112** of the International Astronomical Union.
113**
114** =====================
115** SOFA Software License
116** =====================
117**
118** NOTICE TO USER:
119**
120** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
121** CONDITIONS WHICH APPLY TO ITS USE.
122**
123** 1. The Software is owned by the IAU SOFA Board ("SOFA").
124**
125** 2. Permission is granted to anyone to use the SOFA software for any
126** purpose, including commercial applications, free of charge and
127** without payment of royalties, subject to the conditions and
128** restrictions listed below.
129**
130** 3. You (the user) may copy and distribute SOFA source code to others,
131** and use and adapt its code and algorithms in your own software,
132** on a world-wide, royalty-free basis. That portion of your
133** distribution that does not consist of intact and unchanged copies
134** of SOFA source code files is a "derived work" that must comply
135** with the following requirements:
136**
137** a) Your work shall be marked or carry a statement that it
138** (i) uses routines and computations derived by you from
139** software provided by SOFA under license to you; and
140** (ii) does not itself constitute software provided by and/or
141** endorsed by SOFA.
142**
143** b) The source code of your derived work must contain descriptions
144** of how the derived work is based upon, contains and/or differs
145** from the original SOFA software.
146**
147** c) The names of all routines in your derived work shall not
148** include the prefix "iau" or "sofa" or trivial modifications
149** thereof such as changes of case.
150**
151** d) The origin of the SOFA components of your derived work must
152** not be misrepresented; you must not claim that you wrote the
153** original software, nor file a patent application for SOFA
154** software or algorithms embedded in the SOFA software.
155**
156** e) These requirements must be reproduced intact in any source
157** distribution and shall apply to anyone to whom you have
158** granted a further right to modify the source code of your
159** derived work.
160**
161** Note that, as originally distributed, the SOFA software is
162** intended to be a definitive implementation of the IAU standards,
163** and consequently third-party modifications are discouraged. All
164** variations, no matter how minor, must be explicitly marked as
165** such, as explained above.
166**
167** 4. You shall not cause the SOFA software to be brought into
168** disrepute, either by misuse, or use for inappropriate tasks, or
169** by inappropriate modification.
170**
171** 5. The SOFA software is provided "as is" and SOFA makes no warranty
172** as to its use or performance. SOFA does not and cannot warrant
173** the performance or results which the user may obtain by using the
174** SOFA software. SOFA makes no warranties, express or implied, as
175** to non-infringement of third party rights, merchantability, or
176** fitness for any particular purpose. In no event will SOFA be
177** liable to the user for any consequential, incidental, or special
178** damages, including any lost profits or lost savings, even if a
179** SOFA representative has been advised of such damages, or for any
180** claim by any third party.
181**
182** 6. The provision of any version of the SOFA software under the terms
183** and conditions specified herein does not imply that future
184** versions will also be made available under the same terms and
185** conditions.
186*
187** In any published work or commercial product which uses the SOFA
188** software directly, acknowledgement (see www.iausofa.org) is
189** appreciated.
190**
191** Correspondence concerning SOFA software should be addressed as
192** follows:
193**
194** By email: sofa@ukho.gov.uk
195** By post: IAU SOFA Center
196** HM Nautical Almanac Office
197** UK Hydrographic Office
198** Admiralty Way, Taunton
199** Somerset, TA1 2DN
200** United Kingdom
201**
202**--------------------------------------------------------------------*/
203}
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