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slalib/dsep.f

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+      DOUBLE PRECISION FUNCTION sla_DSEP (A1, B1, A2, B2)
+*+
+*     - - - - -
+*      D S E P
+*     - - - - -
+*
+*  Angle between two points on a sphere.
+*
+*  (double precision)
+*
+*  Given:
+*     A1,B1    d     spherical coordinates of one point
+*     A2,B2    d     spherical coordinates of the other point
+*
+*  (The spherical coordinates are [RA,Dec], [Long,Lat] etc, in radians.)
+*
+*  The result is the angle, in radians, between the two points.  It
+*  is always positive.
+*
+*  Called:  sla_DCS2C, sla_DSEPV
+*
+*  Last revision:   7 May 2000
+*
+*  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., 59 Temple Place, Suite 330, 
+*    Boston, MA  02111-1307  USA
+*
+*-
+
+      IMPLICIT NONE
+
+      DOUBLE PRECISION A1,B1,A2,B2
+
+      DOUBLE PRECISION V1(3),V2(3)
+      DOUBLE PRECISION sla_DSEPV
+
+
+
+*  Convert coordinates from spherical to Cartesian.
+      CALL sla_DCS2C(A1,B1,V1)
+      CALL sla_DCS2C(A2,B2,V2)
+
+*  Angle between the vectors.
+      sla_DSEP = sla_DSEPV(V1,V2)
+
+      END