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author | William Joye <wjoye@cfa.harvard.edu> | 2017-12-08 18:59:21 (GMT) |
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committer | William Joye <wjoye@cfa.harvard.edu> | 2017-12-08 18:59:21 (GMT) |
commit | 4432c8d7e1ccb371db03e13cdb5378fceaa5ad04 (patch) | |
tree | 52449d211eba99b24d2e4f6e66193f9511c60b59 /ast/erfa/fw2xy.c | |
parent | d8a2dbd825159e4a57ec0c6f4465f62be9e05111 (diff) | |
download | blt-4432c8d7e1ccb371db03e13cdb5378fceaa5ad04.zip blt-4432c8d7e1ccb371db03e13cdb5378fceaa5ad04.tar.gz blt-4432c8d7e1ccb371db03e13cdb5378fceaa5ad04.tar.bz2 |
upgrade AST
Diffstat (limited to 'ast/erfa/fw2xy.c')
-rw-r--r-- | ast/erfa/fw2xy.c | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/ast/erfa/fw2xy.c b/ast/erfa/fw2xy.c new file mode 100644 index 0000000..b4e0693 --- /dev/null +++ b/ast/erfa/fw2xy.c @@ -0,0 +1,130 @@ +#include "erfa.h" + +void eraFw2xy(double gamb, double phib, double psi, double eps, + double *x, double *y) +/* +** - - - - - - - - - +** e r a F w 2 x y +** - - - - - - - - - +** +** CIP X,Y given Fukushima-Williams bias-precession-nutation angles. +** +** Given: +** gamb double F-W angle gamma_bar (radians) +** phib double F-W angle phi_bar (radians) +** psi double F-W angle psi (radians) +** eps double F-W angle epsilon (radians) +** +** Returned: +** x,y double CIP unit vector X,Y +** +** Notes: +** +** 1) Naming the following points: +** +** e = J2000.0 ecliptic pole, +** p = GCRS pole +** E = ecliptic pole of date, +** and P = CIP, +** +** the four Fukushima-Williams angles are as follows: +** +** gamb = gamma = epE +** phib = phi = pE +** psi = psi = pEP +** eps = epsilon = EP +** +** 2) The matrix representing the combined effects of frame bias, +** precession and nutation is: +** +** NxPxB = R_1(-epsA).R_3(-psi).R_1(phib).R_3(gamb) +** +** The returned values x,y are elements [2][0] and [2][1] of the +** matrix. Near J2000.0, they are essentially angles in radians. +** +** Called: +** eraFw2m F-W angles to r-matrix +** eraBpn2xy extract CIP X,Y coordinates from NPB matrix +** +** Reference: +** +** Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351 +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double r[3][3]; + + +/* Form NxPxB matrix. */ + eraFw2m(gamb, phib, psi, eps, r); + +/* Extract CIP X,Y. */ + eraBpn2xy(r, x, y); + + 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. +** +*/ |