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/*
*+
* Name:
* palDtp2s
* Purpose:
* Tangent plane to spherical coordinates
* Language:
* Starlink ANSI C
* Type of Module:
* Library routine
* Invocation:
* palDtp2s( double xi, double eta, double raz, double decz,
* double *ra, double *dec);
* Arguments:
* xi = double (Given)
* First rectangular coordinate on tangent plane (radians)
* eta = double (Given)
* Second rectangular coordinate on tangent plane (radians)
* raz = double (Given)
* RA spherical coordinate of tangent point (radians)
* decz = double (Given)
* Dec spherical coordinate of tangent point (radians)
* ra = double * (Returned)
* RA spherical coordinate of point to be projected (radians)
* dec = double * (Returned)
* Dec spherical coordinate of point to be projected (radians)
* Description:
* Transform tangent plane coordinates into spherical.
* Authors:
* PTW: Pat Wallace (STFC)
* TIMJ: Tim Jenness (JAC, Hawaii)
* {enter_new_authors_here}
* History:
* 2012-02-08 (TIMJ):
* Initial version with documentation taken from Fortran SLA
* Adapted with permission from the Fortran SLALIB library.
* {enter_further_changes_here}
* Copyright:
* Copyright (C) 1995 Rutherford Appleton Laboratory
* Copyright (C) 2012 Science and Technology Facilities Council.
* All Rights Reserved.
* Licence:
* This program is free software: you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation, either
* version 3 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* License along with this program. If not, see
* <http://www.gnu.org/licenses/>.
* Bugs:
* {note_any_bugs_here}
*-
*/
#include "pal.h"
#include "pal1sofa.h"
#include <math.h>
void
palDtp2s ( double xi, double eta, double raz, double decz,
double *ra, double *dec ) {
double cdecz;
double denom;
double sdecz;
double d;
sdecz = sin(decz);
cdecz = cos(decz);
denom = cdecz - eta * sdecz;
d = atan2(xi, denom) + raz;
*ra = eraAnp(d);
*dec = atan2(sdecz + eta * cdecz, sqrt(xi * xi + denom * denom));
return;
}
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