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+      SUBROUTINE slDC2S (V, A, B)
+*+
+*     - - - - - -
+*      D C 2 S
+*     - - - - - -
+*
+*  Cartesian to spherical coordinates (double precision)
+*
+*  Given:
+*     V     d(3)   x,y,z vector
+*
+*  Returned:
+*     A,B   d      spherical coordinates in radians
+*
+*  The spherical coordinates are longitude (+ve anticlockwise looking
+*  from the +ve latitude pole) and latitude.  The Cartesian coordinates
+*  are right handed, with the x axis at zero longitude and latitude, and
+*  the z axis at the +ve latitude pole.
+*
+*  If V is null, zero A and B are returned.  At either pole, zero A is
+*  returned.
+*
+*  Last revision:   22 July 2004
+*
+*  Copyright P.T.Wallace.  All rights reserved.
+*
+*  License:
+*    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 (see SLA_CONDITIONS); if not, write to the
+*    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+*    Boston, MA  02110-1301  USA
+*
+*  Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
+*-
+
+      IMPLICIT NONE
+
+      DOUBLE PRECISION V(3),A,B
+
+      DOUBLE PRECISION X,Y,Z,R
+
+
+      X = V(1)
+      Y = V(2)
+      Z = V(3)
+      R = SQRT(X*X+Y*Y)
+
+      IF (R.EQ.0D0) THEN
+         A = 0D0
+      ELSE
+         A = ATAN2(Y,X)
+      END IF
+
+      IF (Z.EQ.0D0) THEN
+         B = 0D0
+      ELSE
+         B = ATAN2(Z,R)
+      END IF
+
+      END