SUBROUTINE iau_C2TEQX ( RBPN, GST, RPOM, RC2T ) *+ * - - - - - - - - - - - * i a u _ C 2 T E Q X * - - - - - - - - - - - * * Assemble the celestial to terrestrial matrix from equinox-based * components (the celestial-to-true matrix, the Greenwich Apparent * Sidereal Time and the polar motion matrix). * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: support routine. * * Given: * RBPN d(3,3) celestial-to-true matrix * GST d Greenwich (apparent) Sidereal Time * RPOM d(3,3) polar-motion matrix * * Returned: * RC2T d(3,3) celestial-to-terrestrial matrix (Note 2) * * Notes: * * 1) This routine constructs the rotation matrix that transforms * vectors in the celestial system into vectors in the terrestrial * system. It does so starting from precomputed components, namely * the matrix which rotates from celestial coordinates to the * true equator and equinox of date, the Greenwich Apparent Sidereal * Time and the polar motion matrix. One use of the present routine * is when generating a series of celestial-to-terrestrial matrices * where only the Sidereal Time changes, avoiding the considerable * overhead of recomputing the precession-nutation more often than * necessary to achieve given accuracy objectives. * * 2) The relationship between the arguments is as follows: * * [TRS] = RPOM * R_3(GST) * RBPN * [CRS] * * = RC2T * [CRS] * * where [CRS] is a vector in the Geocentric Celestial Reference * System and [TRS] is a vector in the International Terrestrial * Reference System (see IERS Conventions 2000). * * Called: * iau_CR copy r-matrix * iau_RZ rotate around Z-axis * iau_RXR r-matrix product * * Reference: * * McCarthy, D.D., IERS Conventions 2000, Chapter 5 (2002). * * This revision: 2003 March 17 * * Copyright (C) 2003 IAU SOFA Review Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION RBPN(3,3), GST, RPOM(3,3), RC2T(3,3) DOUBLE PRECISION R(3,3) * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Construct the matrix. CALL iau_CR ( RBPN, R ) CALL iau_RZ ( GST, R ) CALL iau_RXR ( RPOM, R, RC2T ) * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2003 * Standards Of Fundamental Astronomy Review Board * of the International Astronomical Union. * * ===================== * SOFA Software License * ===================== * * NOTICE TO USER: * * BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING TERMS AND CONDITIONS * WHICH APPLY TO ITS USE. * * 1. The Software is owned by the IAU SOFA Review Board ("the Board"). * * 2. The Software is made available free of charge for use by: * * a) private individuals for non-profit research; and * * b) non-profit educational, academic and research institutions. * * 3. Commercial use of the Software is specifically excluded from the * terms and conditions of this license. Commercial use of the * Software is subject to the prior written agreement of the Board on * terms to be agreed. * * 4. The provision of any version of the 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. * * 5. The user may modify the Software for his/her own purposes. The * user may distribute the modified software provided that the Board * is informed and that a copy of the modified software is made * available to the Board on request. All modifications made by the * user shall be clearly identified to show how the modified software * differs from the original Software, and the name(s) of the * affected routine(s) shall be changed. The original SOFA Software * License text must be present. * * 6. In any published work produced by the user and which includes * results achieved by using the Software, the user shall acknowledge * that the Software was used in producing the information contained * in such publication. * * 7. The user may incorporate or embed the Software into other software * products which he/she may then give away free of charge but not * sell provided the user makes due acknowledgement of the use which * he/she has made of the Software in creating such software * products. Any redistribution of the Software in this way shall be * made under the same terms and conditions under which the user * received it from the SOFA Center. * * 8. The user shall not cause the Software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or by * inappropriate modification. * * 9. The Software is provided to the user "as is" and the Board makes * no warranty as to its use or performance. The Board does not and * cannot warrant the performance or results which the user may * obtain by using the Software. The Board 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 the Board be liable to the user for any consequential, * incidental, or special damages, including any lost profits or lost * savings, even if a Board representative has been advised of such * damages, or for any claim by any third party. * * Correspondence concerning SOFA software should be addressed as * follows: * * Internet email: sofa@rl.ac.uk * Postal address: IAU SOFA Center * Rutherford Appleton Laboratory * Chilton, Didcot, Oxon OX11 0QX * United Kingdom * * *----------------------------------------------------------------------- END