#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 routine. ** ** 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: 2015 January 20 ** ** SOFA release 2015-02-09 ** ** Copyright (C) 2015 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 longitude of the ascending node of the Galactic ** plane 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) 2015 ** 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 ** **--------------------------------------------------------------------*/ }