SUBROUTINE iau_TPSTS ( XI, ETA, A0, B0, A, B ) * * - - - - - - - - - - * i a u _ T P S T S * - - - - - - - - - - * * In the tangent plane projection, given the star's rectangular * coordinates and the spherical coordinates of the tangent point, * solve for the spherical coordinates of the star. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: support routine. * * Given: * XI,ETA d rectangular coordinates of star image (Note 2) * A0,B0 d tangent point's spherical coordinates * * Returned: * A,B d star's spherical coordinates * * 1) The tangent plane projection is also called the "gnomonic * projection" and the "central projection". * * 2) The eta axis points due north in the adopted coordinate system. * If the spherical coordinates are observed (RA,Dec), the tangent * plane coordinates (xi,eta) are conventionally called the "standard * coordinates". If the direction cosines are with respect to a * right-handed triad, (xi,eta) are also right-handed. The units of * (xi,eta) are, effectively, radians at the tangent point. * * 3) All angular arguments are in radians. * * 4) This routine is a member of the following set: * * spherical vector solve for * * iau_TPXES iau_TPXEV xi,eta * > iau_TPSTS < iau_TPSTV star * iau_TPORS iau_TPORV origin * * Called: * iau_ANP normalize angle into range 0 to 2pi * * References: * * Calabretta M.R. & Greisen, E.W., 2002, "Representations of * celestial coordinates in FITS", Astron.Astrophys. 395, 1077 * * Green, R.M., "Spherical Astronomy", Cambridge University Press, * 1987, Chapter 13. * * This revision: 2018 January 2 * * SOFA release 2023-10-11 * * Copyright (C) 2023 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION XI, ETA, A0, B0, A, B DOUBLE PRECISION SB0, CB0, D DOUBLE PRECISION iau_ANP * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - SB0 = SIN(B0) CB0 = COS(B0) D = CB0 - ETA*SB0 A = iau_ANP(ATAN2(XI,D)+A0) B = ATAN2(SB0+ETA*CB0,SQRT(XI*XI+D*D)) * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2023 * 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. 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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 * *----------------------------------------------------------------------- END