#include "sofa.h"
void iauG2icrs ( double dl, double db, double *dr, double *dd )
/*
** - - - - - - - - - -
** i a u G 2 i c r s
** - - - - - - - - - -
**
** Transformation from Galactic Coordinates to ICRS.
**
** This function is part of the International Astronomical Union's
** SOFA (Standards of Fundamental Astronomy) software collection.
**
** Status: support function.
**
** Given:
** dl double galactic longitude (radians)
** db double galactic latitude (radians)
**
** Returned:
** dr double ICRS right ascension (radians)
** dd double ICRS declination (radians)
**
** Notes:
**
** 1) The IAU 1958 system of Galactic coordinates was defined with
** respect to the now obsolete reference system FK4 B1950.0. When
** interpreting the system in a modern context, several factors have
** to be taken into account:
**
** . The inclusion in FK4 positions of the E-terms of aberration.
**
** . The distortion of the FK4 proper motion system by differential
** Galactic rotation.
**
** . The use of the B1950.0 equinox rather than the now-standard
** J2000.0.
**
** . The frame bias between ICRS and the J2000.0 mean place system.
**
** The Hipparcos Catalogue (Perryman & ESA 1997) provides a rotation
** matrix that transforms directly between ICRS and Galactic
** coordinates with the above factors taken into account. The
** matrix is derived from three angles, namely the ICRS coordinates
** of the Galactic pole and the longitude of the ascending node of
** the galactic equator on the ICRS equator. They are given in
** degrees to five decimal places and for canonical purposes are
** regarded as exact. In the Hipparcos Catalogue the matrix
** elements are given to 10 decimal places (about 20 microarcsec).
** In the present SOFA function the matrix elements have been
** recomputed from the canonical three angles and are given to 30
** decimal places.
**
** 2) The inverse transformation is performed by the function iauIcrs2g.
**
** Called:
** iauAnp normalize angle into range 0 to 2pi
** iauAnpm normalize angle into range +/- pi
** iauS2c spherical coordinates to unit vector
** iauTrxp product of transpose of r-matrix and p-vector
** iauC2s p-vector to spherical
**
** Reference:
** Perryman M.A.C. & ESA, 1997, ESA SP-1200, The Hipparcos and Tycho
** catalogues. Astrometric and photometric star catalogues
** derived from the ESA Hipparcos Space Astrometry Mission. ESA
** Publications Division, Noordwijk, Netherlands.
**
** This revision: 2021 January 25
**
** SOFA release 2021-05-12
**
** Copyright (C) 2021 IAU SOFA Board. See notes at end.
*/
{
double v1[3], v2[3];
/*
** L2,B2 system of galactic coordinates in the form presented in the
** Hipparcos Catalogue. In degrees:
**
** P = 192.85948 right ascension of the Galactic north pole in ICRS
** Q = 27.12825 declination of the Galactic north pole in ICRS
** R = 32.93192 Galactic longitude of the ascending node of
** the Galactic equator on the ICRS equator
**
** ICRS to galactic rotation matrix, obtained by computing
** R_3(-R) R_1(pi/2-Q) R_3(pi/2+P) to the full precision shown:
*/
double r[3][3] = { { -0.054875560416215368492398900454,
-0.873437090234885048760383168409,
-0.483835015548713226831774175116 },
{ +0.494109427875583673525222371358,
-0.444829629960011178146614061616,
+0.746982244497218890527388004556 },
{ -0.867666149019004701181616534570,
-0.198076373431201528180486091412,
+0.455983776175066922272100478348 } };
/* Spherical to Cartesian. */
iauS2c(dl, db, v1);
/* Galactic to ICRS. */
iauTrxp(r, v1, v2);
/* Cartesian to spherical. */
iauC2s(v2, dr, dd);
/* Express in conventional ranges. */
*dr = iauAnp(*dr);
*dd = iauAnpm(*dd);
/* Finished. */
/*----------------------------------------------------------------------
**
** Copyright (C) 2021
** 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
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** 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
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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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** conditions.
*
** In any published work or commercial product which uses the SOFA
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** appreciated.
**
** Correspondence concerning SOFA software should be addressed as
** follows:
**
** By email: sofa@ukho.gov.uk
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**
**--------------------------------------------------------------------*/
}