173 lines
6.5 KiB
C
173 lines
6.5 KiB
C
#include "sofa.h"
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double iauEe06a(double date1, double date2)
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/*
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** - - - - - - - - -
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** i a u E e 0 6 a
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** - - - - - - - - -
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**
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** Equation of the equinoxes, compatible with IAU 2000 resolutions and
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** IAU 2006/2000A precession-nutation.
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**
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** This function is part of the International Astronomical Union's
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** SOFA (Standards Of Fundamental Astronomy) software collection.
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**
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** Status: support function.
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**
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** Given:
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** date1,date2 double TT as a 2-part Julian Date (Note 1)
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**
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** Returned (function value):
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** double equation of the equinoxes (Note 2)
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**
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** Notes:
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**
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** 1) The TT date date1+date2 is a Julian Date, apportioned in any
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** convenient way between the two arguments. For example,
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** JD(TT)=2450123.7 could be expressed in any of these ways,
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** among others:
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**
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** date1 date2
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**
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** 2450123.7 0.0 (JD method)
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** 2451545.0 -1421.3 (J2000 method)
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** 2400000.5 50123.2 (MJD method)
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** 2450123.5 0.2 (date & time method)
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**
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** The JD method is the most natural and convenient to use in
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** cases where the loss of several decimal digits of resolution
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** is acceptable. The J2000 method is best matched to the way
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** the argument is handled internally and will deliver the
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** optimum resolution. The MJD method and the date & time methods
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** are both good compromises between resolution and convenience.
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**
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** 2) The result, which is in radians, operates in the following sense:
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**
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** Greenwich apparent ST = GMST + equation of the equinoxes
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**
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** Called:
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** iauAnpm normalize angle into range +/- pi
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** iauGst06a Greenwich apparent sidereal time, IAU 2006/2000A
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** iauGmst06 Greenwich mean sidereal time, IAU 2006
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**
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** Reference:
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**
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** McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
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** IERS Technical Note No. 32, BKG
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**
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** This revision: 2008 May 18
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**
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** SOFA release 2020-07-21
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**
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** Copyright (C) 2020 IAU SOFA Board. See notes at end.
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*/
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{
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double gst06a, gmst06, ee;
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/* Apparent and mean sidereal times. */
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gst06a = iauGst06a(0.0, 0.0, date1, date2);
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gmst06 = iauGmst06(0.0, 0.0, date1, date2);
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/* Equation of the equinoxes. */
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ee = iauAnpm(gst06a - gmst06);
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return ee;
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/*----------------------------------------------------------------------
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**
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** Copyright (C) 2020
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** Standards Of Fundamental Astronomy Board
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** of the International Astronomical Union.
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**
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** =====================
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** SOFA Software License
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** =====================
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**
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** NOTICE TO USER:
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**
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** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
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** CONDITIONS WHICH APPLY TO ITS USE.
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**
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** 1. The Software is owned by the IAU SOFA Board ("SOFA").
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**
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** 2. Permission is granted to anyone to use the SOFA software for any
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** purpose, including commercial applications, free of charge and
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** without payment of royalties, subject to the conditions and
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** restrictions listed below.
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**
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** 3. You (the user) may copy and distribute SOFA source code to others,
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** and use and adapt its code and algorithms in your own software,
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** on a world-wide, royalty-free basis. That portion of your
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** distribution that does not consist of intact and unchanged copies
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** of SOFA source code files is a "derived work" that must comply
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** with the following requirements:
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**
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** a) Your work shall be marked or carry a statement that it
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** (i) uses routines and computations derived by you from
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** software provided by SOFA under license to you; and
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** (ii) does not itself constitute software provided by and/or
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** endorsed by SOFA.
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**
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** b) The source code of your derived work must contain descriptions
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** of how the derived work is based upon, contains and/or differs
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** from the original SOFA software.
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**
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** c) The names of all routines in your derived work shall not
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** include the prefix "iau" or "sofa" or trivial modifications
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** thereof such as changes of case.
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**
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** d) The origin of the SOFA components of your derived work must
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** not be misrepresented; you must not claim that you wrote the
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** original software, nor file a patent application for SOFA
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** software or algorithms embedded in the SOFA software.
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**
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** e) These requirements must be reproduced intact in any source
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** distribution and shall apply to anyone to whom you have
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** granted a further right to modify the source code of your
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** derived work.
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**
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** Note that, as originally distributed, the SOFA software is
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** intended to be a definitive implementation of the IAU standards,
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** and consequently third-party modifications are discouraged. All
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** variations, no matter how minor, must be explicitly marked as
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** such, as explained above.
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**
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** 4. You shall not cause the SOFA software to be brought into
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** disrepute, either by misuse, or use for inappropriate tasks, or
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** by inappropriate modification.
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**
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** 5. The SOFA software is provided "as is" and SOFA makes no warranty
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** as to its use or performance. SOFA does not and cannot warrant
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** the performance or results which the user may obtain by using the
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** SOFA software. SOFA makes no warranties, express or implied, as
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** to non-infringement of third party rights, merchantability, or
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** fitness for any particular purpose. In no event will SOFA be
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** liable to the user for any consequential, incidental, or special
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** damages, including any lost profits or lost savings, even if a
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** SOFA representative has been advised of such damages, or for any
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** claim by any third party.
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**
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** 6. The provision of any version of the SOFA software under the terms
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** and conditions specified herein does not imply that future
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** versions will also be made available under the same terms and
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** conditions.
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*
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** In any published work or commercial product which uses the SOFA
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** software directly, acknowledgement (see www.iausofa.org) is
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** appreciated.
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**
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** Correspondence concerning SOFA software should be addressed as
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** follows:
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**
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** By email: sofa@ukho.gov.uk
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** By post: IAU SOFA Center
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** HM Nautical Almanac Office
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** UK Hydrographic Office
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** Admiralty Way, Taunton
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** Somerset, TA1 2DN
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** United Kingdom
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**
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**--------------------------------------------------------------------*/
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}
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