#include "sofa.h" double iauGst06a(double uta, double utb, double tta, double ttb) /* ** - - - - - - - - - - ** i a u G s t 0 6 a ** - - - - - - - - - - ** ** Greenwich apparent sidereal time (consistent with IAU 2000 and 2006 ** resolutions). ** ** This function is part of the International Astronomical Union's ** SOFA (Standards Of Fundamental Astronomy) software collection. ** ** Status: canonical model. ** ** Given: ** uta,utb double UT1 as a 2-part Julian Date (Notes 1,2) ** tta,ttb double TT as a 2-part Julian Date (Notes 1,2) ** ** Returned (function value): ** double Greenwich apparent sidereal time (radians) ** ** Notes: ** ** 1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both ** Julian Dates, apportioned in any convenient way between the ** argument pairs. For example, JD=2450123.7 could be expressed in ** any of these ways, among others: ** ** Part A Part B ** ** 2450123.7 0.0 (JD method) ** 2451545.0 -1421.3 (J2000 method) ** 2400000.5 50123.2 (MJD method) ** 2450123.5 0.2 (date & time method) ** ** The JD method is the most natural and convenient to use in ** cases where the loss of several decimal digits of resolution ** is acceptable (in the case of UT; the TT is not at all critical ** in this respect). The J2000 and MJD methods are good compromises ** between resolution and convenience. For UT, the date & time ** method is best matched to the algorithm that is used by the Earth ** rotation angle function, called internally: maximum precision is ** delivered when the uta argument is for 0hrs UT1 on the day in ** question and the utb argument lies in the range 0 to 1, or vice ** versa. ** ** 2) Both UT1 and TT are required, UT1 to predict the Earth rotation ** and TT to predict the effects of precession-nutation. If UT1 is ** used for both purposes, errors of order 100 microarcseconds ** result. ** ** 3) This GAST is compatible with the IAU 2000/2006 resolutions and ** must be used only in conjunction with IAU 2006 precession and ** IAU 2000A nutation. ** ** 4) The result is returned in the range 0 to 2pi. ** ** Called: ** iauPnm06a classical NPB matrix, IAU 2006/2000A ** iauGst06 Greenwich apparent ST, IAU 2006, given NPB matrix ** ** Reference: ** ** Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981 ** ** This revision: 2013 June 18 ** ** SOFA release 2016-05-03 ** ** Copyright (C) 2016 IAU SOFA Board. See notes at end. */ { double rnpb[3][3], gst; /* Classical nutation x precession x bias matrix, IAU 2000A. */ iauPnm06a(tta, ttb, rnpb); /* Greenwich apparent sidereal time. */ gst = iauGst06(uta, utb, tta, ttb, rnpb); return gst; /*---------------------------------------------------------------------- ** ** Copyright (C) 2016 ** Standards Of Fundamental Astronomy Board ** of the International Astronomical Union. ** ** ===================== ** SOFA Software License ** ===================== ** ** NOTICE TO USER: ** ** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND ** CONDITIONS WHICH APPLY TO ITS USE. ** ** 1. The Software is owned by the IAU SOFA Board ("SOFA"). ** ** 2. Permission is granted to anyone to use the SOFA software for any ** purpose, including commercial applications, free of charge and ** without payment of royalties, subject to the conditions and ** restrictions listed below. ** ** 3. You (the user) may copy and distribute SOFA source code to others, ** and use and adapt its code and algorithms in your own software, ** on a world-wide, royalty-free basis. That portion of your ** distribution that does not consist of intact and unchanged copies ** of SOFA source code files is a "derived work" that must comply ** with the following requirements: ** ** a) Your work shall be marked or carry a statement that it ** (i) uses routines and computations derived by you from ** software provided by SOFA under license to you; and ** (ii) does not itself constitute software provided by and/or ** endorsed by SOFA. ** ** b) The source code of your derived work must contain descriptions ** of how the derived work is based upon, contains and/or differs ** from the original SOFA software. ** ** c) The names of all routines in your derived work shall not ** include the prefix "iau" or "sofa" or trivial modifications ** thereof such as changes of case. ** ** d) The origin of the SOFA components of your derived work must ** not be misrepresented; you must not claim that you wrote the ** original software, nor file a patent application for SOFA ** software or algorithms embedded in the SOFA software. ** ** e) These requirements must be reproduced intact in any source ** distribution and shall apply to anyone to whom you have ** granted a further right to modify the source code of your ** derived work. ** ** Note that, as originally distributed, the SOFA software is ** intended to be a definitive implementation of the IAU standards, ** and consequently third-party modifications are discouraged. All ** variations, no matter how minor, must be explicitly marked as ** such, as explained above. ** ** 4. You shall not cause the SOFA software to be brought into ** disrepute, either by misuse, or use for inappropriate tasks, or ** by inappropriate modification. ** ** 5. The SOFA software is provided "as is" and SOFA makes no warranty ** as to its use or performance. SOFA does not and cannot warrant ** the performance or results which the user may obtain by using the ** SOFA software. SOFA makes no warranties, express or implied, as ** to non-infringement of third party rights, merchantability, or ** fitness for any particular purpose. In no event will SOFA be ** liable to the user for any consequential, incidental, or special ** damages, including any lost profits or lost savings, even if a ** SOFA representative has been advised of such damages, or for any ** claim by any third party. ** ** 6. The provision of any version of the SOFA software under the terms ** and conditions specified herein does not imply that future ** versions will also be made available under the same terms and ** conditions. * ** In any published work or commercial product which uses the SOFA ** software directly, acknowledgement (see www.iausofa.org) is ** appreciated. ** ** Correspondence concerning SOFA software should be addressed as ** follows: ** ** By email: sofa@ukho.gov.uk ** By post: IAU SOFA Center ** HM Nautical Almanac Office ** UK Hydrographic Office ** Admiralty Way, Taunton ** Somerset, TA1 2DN ** United Kingdom ** **--------------------------------------------------------------------*/ }