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Diffstat (limited to 'ast/erfa/bpn2xy.c')
-rw-r--r-- | ast/erfa/bpn2xy.c | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/ast/erfa/bpn2xy.c b/ast/erfa/bpn2xy.c new file mode 100644 index 0000000..769bd33 --- /dev/null +++ b/ast/erfa/bpn2xy.c @@ -0,0 +1,109 @@ +#include "erfa.h" + +void eraBpn2xy(double rbpn[3][3], double *x, double *y) +/* +** - - - - - - - - - - +** e r a B p n 2 x y +** - - - - - - - - - - +** +** Extract from the bias-precession-nutation matrix the X,Y coordinates +** of the Celestial Intermediate Pole. +** +** Given: +** rbpn double[3][3] celestial-to-true matrix (Note 1) +** +** Returned: +** x,y double Celestial Intermediate Pole (Note 2) +** +** Notes: +** +** 1) The matrix rbpn transforms vectors from GCRS to true equator (and +** CIO or equinox) of date, and therefore the Celestial Intermediate +** Pole unit vector is the bottom row of the matrix. +** +** 2) The arguments x,y are components of the Celestial Intermediate +** Pole unit vector in the Geocentric Celestial Reference System. +** +** Reference: +** +** "Expressions for the Celestial Intermediate Pole and Celestial +** Ephemeris Origin consistent with the IAU 2000A precession- +** nutation model", Astron.Astrophys. 400, 1145-1154 +** (2003) +** +** n.b. The celestial ephemeris origin (CEO) was renamed "celestial +** intermediate origin" (CIO) by IAU 2006 Resolution 2. +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ +/* Extract the X,Y coordinates. */ + *x = rbpn[2][0]; + *y = rbpn[2][1]; + + return; + +} +/*---------------------------------------------------------------------- +** +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** All rights reserved. +** +** This library is derived, with permission, from the International +** Astronomical Union's "Standards of Fundamental Astronomy" library, +** available from http://www.iausofa.org. +** +** The ERFA version is intended to retain identical functionality to +** the SOFA library, but made distinct through different function and +** file names, as set out in the SOFA license conditions. The SOFA +** original has a role as a reference standard for the IAU and IERS, +** and consequently redistribution is permitted only in its unaltered +** state. The ERFA version is not subject to this restriction and +** therefore can be included in distributions which do not support the +** concept of "read only" software. +** +** Although the intent is to replicate the SOFA API (other than +** replacement of prefix names) and results (with the exception of +** bugs; any that are discovered will be fixed), SOFA is not +** responsible for any errors found in this version of the library. +** +** If you wish to acknowledge the SOFA heritage, please acknowledge +** that you are using a library derived from SOFA, rather than SOFA +** itself. +** +** +** TERMS AND CONDITIONS +** +** Redistribution and use in source and binary forms, with or without +** modification, are permitted provided that the following conditions +** are met: +** +** 1 Redistributions of source code must retain the above copyright +** notice, this list of conditions and the following disclaimer. +** +** 2 Redistributions in binary form must reproduce the above copyright +** notice, this list of conditions and the following disclaimer in +** the documentation and/or other materials provided with the +** distribution. +** +** 3 Neither the name of the Standards Of Fundamental Astronomy Board, +** the International Astronomical Union nor the names of its +** contributors may be used to endorse or promote products derived +** from this software without specific prior written permission. +** +** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS +** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE +** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, +** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, +** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; +** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER +** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN +** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +** POSSIBILITY OF SUCH DAMAGE. +** +*/ |