source: branches/FACT++_lidctrl_usb/erfa/src/gst06.c@ 19875

Last change on this file since 19875 was 18711, checked in by tbretz, 10 years ago
Updated to ERFA 1.3.0 (no relevant code change except the leap second at the beginning of 2017)
File size: 5.9 KB
Line 
1#include "erfa.h"
2
3double eraGst06(double uta, double utb, double tta, double ttb,
4 double rnpb[3][3])
5/*
6** - - - - - - - - -
7** e r a G s t 0 6
8** - - - - - - - - -
9**
10** Greenwich apparent sidereal time, IAU 2006, given the NPB matrix.
11**
12** Given:
13** uta,utb double UT1 as a 2-part Julian Date (Notes 1,2)
14** tta,ttb double TT as a 2-part Julian Date (Notes 1,2)
15** rnpb double[3][3] nutation x precession x bias matrix
16**
17** Returned (function value):
18** double Greenwich apparent sidereal time (radians)
19**
20** Notes:
21**
22** 1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both
23** Julian Dates, apportioned in any convenient way between the
24** argument pairs. For example, JD=2450123.7 could be expressed in
25** any of these ways, among others:
26**
27** Part A Part B
28**
29** 2450123.7 0.0 (JD method)
30** 2451545.0 -1421.3 (J2000 method)
31** 2400000.5 50123.2 (MJD method)
32** 2450123.5 0.2 (date & time method)
33**
34** The JD method is the most natural and convenient to use in
35** cases where the loss of several decimal digits of resolution
36** is acceptable (in the case of UT; the TT is not at all critical
37** in this respect). The J2000 and MJD methods are good compromises
38** between resolution and convenience. For UT, the date & time
39** method is best matched to the algorithm that is used by the Earth
40** rotation angle function, called internally: maximum precision is
41** delivered when the uta argument is for 0hrs UT1 on the day in
42** question and the utb argument lies in the range 0 to 1, or vice
43** versa.
44**
45** 2) Both UT1 and TT are required, UT1 to predict the Earth rotation
46** and TT to predict the effects of precession-nutation. If UT1 is
47** used for both purposes, errors of order 100 microarcseconds
48** result.
49**
50** 3) Although the function uses the IAU 2006 series for s+XY/2, it is
51** otherwise independent of the precession-nutation model and can in
52** practice be used with any equinox-based NPB matrix.
53**
54** 4) The result is returned in the range 0 to 2pi.
55**
56** Called:
57** eraBpn2xy extract CIP X,Y coordinates from NPB matrix
58** eraS06 the CIO locator s, given X,Y, IAU 2006
59** eraAnp normalize angle into range 0 to 2pi
60** eraEra00 Earth rotation angle, IAU 2000
61** eraEors equation of the origins, given NPB matrix and s
62**
63** Reference:
64**
65** Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
66**
67** Copyright (C) 2013-2016, NumFOCUS Foundation.
68** Derived, with permission, from the SOFA library. See notes at end of file.
69*/
70{
71 double x, y, s, era, eors, gst;
72
73
74/* Extract CIP coordinates. */
75 eraBpn2xy(rnpb, &x, &y);
76
77/* The CIO locator, s. */
78 s = eraS06(tta, ttb, x, y);
79
80/* Greenwich apparent sidereal time. */
81 era = eraEra00(uta, utb);
82 eors = eraEors(rnpb, s);
83 gst = eraAnp(era - eors);
84
85 return gst;
86
87}
88/*----------------------------------------------------------------------
89**
90**
91** Copyright (C) 2013-2016, NumFOCUS Foundation.
92** All rights reserved.
93**
94** This library is derived, with permission, from the International
95** Astronomical Union's "Standards of Fundamental Astronomy" library,
96** available from http://www.iausofa.org.
97**
98** The ERFA version is intended to retain identical functionality to
99** the SOFA library, but made distinct through different function and
100** file names, as set out in the SOFA license conditions. The SOFA
101** original has a role as a reference standard for the IAU and IERS,
102** and consequently redistribution is permitted only in its unaltered
103** state. The ERFA version is not subject to this restriction and
104** therefore can be included in distributions which do not support the
105** concept of "read only" software.
106**
107** Although the intent is to replicate the SOFA API (other than
108** replacement of prefix names) and results (with the exception of
109** bugs; any that are discovered will be fixed), SOFA is not
110** responsible for any errors found in this version of the library.
111**
112** If you wish to acknowledge the SOFA heritage, please acknowledge
113** that you are using a library derived from SOFA, rather than SOFA
114** itself.
115**
116**
117** TERMS AND CONDITIONS
118**
119** Redistribution and use in source and binary forms, with or without
120** modification, are permitted provided that the following conditions
121** are met:
122**
123** 1 Redistributions of source code must retain the above copyright
124** notice, this list of conditions and the following disclaimer.
125**
126** 2 Redistributions in binary form must reproduce the above copyright
127** notice, this list of conditions and the following disclaimer in
128** the documentation and/or other materials provided with the
129** distribution.
130**
131** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
132** the International Astronomical Union nor the names of its
133** contributors may be used to endorse or promote products derived
134** from this software without specific prior written permission.
135**
136** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
137** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
138** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
139** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
140** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
141** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
142** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
143** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
144** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
145** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
146** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
147** POSSIBILITY OF SUCH DAMAGE.
148**
149*/
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