summaryrefslogtreecommitdiffstats
path: root/ast/erfa/fw2xy.c
diff options
context:
space:
mode:
authorWilliam Joye <wjoye@cfa.harvard.edu>2018-01-09 19:28:07 (GMT)
committerWilliam Joye <wjoye@cfa.harvard.edu>2018-01-09 19:28:07 (GMT)
commit3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58 (patch)
treef278119398ae5d67a6a338705a76db420f6b8f7e /ast/erfa/fw2xy.c
parent1332d38f2805d986ea130e43218c0d2e870b4dc1 (diff)
downloadblt-3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58.zip
blt-3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58.tar.gz
blt-3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58.tar.bz2
update ast 8.6.2
Diffstat (limited to 'ast/erfa/fw2xy.c')
-rw-r--r--ast/erfa/fw2xy.c130
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.
+**
+*/