source: trunk/FACT++/sofa/src/c2t00b.c@ 18355

Last change on this file since 18355 was 18346, checked in by tbretz, 11 years ago
File size: 7.8 KB
Line 
1#include "sofa.h"
2
3void iauC2t00b(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 b
8** - - - - - - - - - -
9**
10** Form the celestial to terrestrial matrix given the date, the UT1 and
11** the polar motion, using the IAU 2000B 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) The present function is faster, but slightly less accurate (about
68** 1 mas), than the iauC2t00a function.
69**
70** Called:
71** iauC2i00b celestial-to-intermediate matrix, IAU 2000B
72** iauEra00 Earth rotation angle, IAU 2000
73** iauPom00 polar motion matrix
74** iauC2tcio form CIO-based celestial-to-terrestrial matrix
75**
76** Reference:
77**
78** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
79** IERS Technical Note No. 32, BKG (2004)
80**
81** This revision: 2013 June 18
82**
83** SOFA release 2015-02-09
84**
85** Copyright (C) 2015 IAU SOFA Board. See notes at end.
86*/
87{
88 double rc2i[3][3], era, rpom[3][3];
89
90/* Form the celestial-to-intermediate matrix for this TT (IAU 2000B). */
91 iauC2i00b(tta, ttb, rc2i);
92
93/* Predict the Earth rotation angle for this UT1. */
94 era = iauEra00(uta, utb);
95
96/* Form the polar motion matrix (neglecting s'). */
97 iauPom00(xp, yp, 0.0, rpom);
98
99/* Combine to form the celestial-to-terrestrial matrix. */
100 iauC2tcio(rc2i, era, rpom, rc2t);
101
102 return;
103
104/*----------------------------------------------------------------------
105**
106** Copyright (C) 2015
107** Standards Of Fundamental Astronomy Board
108** of the International Astronomical Union.
109**
110** =====================
111** SOFA Software License
112** =====================
113**
114** NOTICE TO USER:
115**
116** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
117** CONDITIONS WHICH APPLY TO ITS USE.
118**
119** 1. The Software is owned by the IAU SOFA Board ("SOFA").
120**
121** 2. Permission is granted to anyone to use the SOFA software for any
122** purpose, including commercial applications, free of charge and
123** without payment of royalties, subject to the conditions and
124** restrictions listed below.
125**
126** 3. You (the user) may copy and distribute SOFA source code to others,
127** and use and adapt its code and algorithms in your own software,
128** on a world-wide, royalty-free basis. That portion of your
129** distribution that does not consist of intact and unchanged copies
130** of SOFA source code files is a "derived work" that must comply
131** with the following requirements:
132**
133** a) Your work shall be marked or carry a statement that it
134** (i) uses routines and computations derived by you from
135** software provided by SOFA under license to you; and
136** (ii) does not itself constitute software provided by and/or
137** endorsed by SOFA.
138**
139** b) The source code of your derived work must contain descriptions
140** of how the derived work is based upon, contains and/or differs
141** from the original SOFA software.
142**
143** c) The names of all routines in your derived work shall not
144** include the prefix "iau" or "sofa" or trivial modifications
145** thereof such as changes of case.
146**
147** d) The origin of the SOFA components of your derived work must
148** not be misrepresented; you must not claim that you wrote the
149** original software, nor file a patent application for SOFA
150** software or algorithms embedded in the SOFA software.
151**
152** e) These requirements must be reproduced intact in any source
153** distribution and shall apply to anyone to whom you have
154** granted a further right to modify the source code of your
155** derived work.
156**
157** Note that, as originally distributed, the SOFA software is
158** intended to be a definitive implementation of the IAU standards,
159** and consequently third-party modifications are discouraged. All
160** variations, no matter how minor, must be explicitly marked as
161** such, as explained above.
162**
163** 4. You shall not cause the SOFA software to be brought into
164** disrepute, either by misuse, or use for inappropriate tasks, or
165** by inappropriate modification.
166**
167** 5. The SOFA software is provided "as is" and SOFA makes no warranty
168** as to its use or performance. SOFA does not and cannot warrant
169** the performance or results which the user may obtain by using the
170** SOFA software. SOFA makes no warranties, express or implied, as
171** to non-infringement of third party rights, merchantability, or
172** fitness for any particular purpose. In no event will SOFA be
173** liable to the user for any consequential, incidental, or special
174** damages, including any lost profits or lost savings, even if a
175** SOFA representative has been advised of such damages, or for any
176** claim by any third party.
177**
178** 6. The provision of any version of the SOFA software under the terms
179** and conditions specified herein does not imply that future
180** versions will also be made available under the same terms and
181** conditions.
182*
183** In any published work or commercial product which uses the SOFA
184** software directly, acknowledgement (see www.iausofa.org) is
185** appreciated.
186**
187** Correspondence concerning SOFA software should be addressed as
188** follows:
189**
190** By email: sofa@ukho.gov.uk
191** By post: IAU SOFA Center
192** HM Nautical Almanac Office
193** UK Hydrographic Office
194** Admiralty Way, Taunton
195** Somerset, TA1 2DN
196** United Kingdom
197**
198**--------------------------------------------------------------------*/
199}
Note: See TracBrowser for help on using the repository browser.