/*  
 *  - - - - - - - - - - -  
 *   g a l _ b p n 2 x y  
 *  - - - - - - - - - - -  
 *  
 *  This routine is part of the General Astrodynamics Library  
 *  
 *  Description: 
 *  
 *  Extract from the bias-precession-nutation matrix the X,Y coordinates  
 *  of the Celestial Intermediate Pole.  
 *  
 *  This routine is an independent translation of a FORTRAN routine  
 *  that is part of IAU's SOFA software collection.  
 *  
 *  Status:
 *  
 *     support routine.  
 *  
 *  Given:
 *  
 *     rbpn             d[3][3]     celestial-to-true matrix (Note 1)  
 *  
 *  Returned:
 *  
 *     *x,*y               d        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) x,y are components of the Celestial Intermediate Pole unit vector  
 *     in the Geocentric Celestial Reference System.  
 *  
 *  References:  
 *  
 *     Capitaine, N., Chapront, J., Lambert, S. and Wallace, P.,  
 *     "Expressions for the Celestial Intermediate Pole and Celestial  
 *     Ephemeris Origin consistent with the IAU 2000A precession-nutation  
 *     model", Astronomy & Astrophysics, 400, 1145-1154 (2003)  
 *  
 *     n.b. The celestial ephemeris origin (CEO) was renamed "celestial  
 *          intermediate origin" (CIO) by IAU 2006 Resolution 2.  
 *  
 *  This revision:
 *  
 *     2007 April 11 ( c version 2008 June 8 )  
 *  
 *  
 *  Copyright (C) 2008 Paul C. L. Willmott. See notes at end.  
 *  
 *-----------------------------------------------------------------------  
 */  
  
#ifndef _GAL_BPN2XY_H_  
#define _GAL_BPN2XY_H_ 1  

#undef __BEGIN_DECLS  
#undef __END_DECLS  
#ifdef __cplusplus  
#define __BEGIN_DECLS extern "C" {  
#define __END_DECLS }  
#else  
#define __BEGIN_DECLS /* empty */  
#define __END_DECLS /* empty */  
#endif
  
__BEGIN_DECLS  
  
void  
gal_bpn2xy  
 (  
    double rbpn[3][3],  
    double *x,  
    double *y  
 ) ;  
  
__END_DECLS  
  
#endif /* !_GAL_BPN2XY_H_ */  

/*  
 *  gal - General Astrodynamics Library  
 *  Copyright (C) 2008 Paul C. L. Willmott  
 *  
 *  This program is free software; you can redistribute it and/or modify  
 *  it under the terms of the GNU General Public License as published by  
 *  the Free Software Foundation; either version 2 of the License, or  
 *  (at your option) any later version.  
 *  
 *  This program is distributed in the hope that it will be useful,  
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of  
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the  
 *  GNU General Public License for more details.  
 *  
 *  You should have received a copy of the GNU General Public License along  
 *  with this program; if not, write to the Free Software Foundation, Inc.,  
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.  
 *  
 *  Contact:  
 *  
 *  Paul Willmott  
 *  vp9mu@amsat.org  
 */  
