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slalib/pav.f

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+      REAL FUNCTION sla_PAV ( V1, V2 )
+*+
+*     - - - -
+*      P A V
+*     - - - -
+*
+*  Position angle of one celestial direction with respect to another.
+*
+*  (single precision)
+*
+*  Given:
+*     V1    r(3)    direction cosines of one point
+*     V2    r(3)    direction cosines of the other point
+*
+*  (The coordinate frames correspond to RA,Dec, Long,Lat etc.)
+*
+*  The result is the bearing (position angle), in radians, of point
+*  V2 with respect to point V1.  It is in the range +/- pi.  The
+*  sense is such that if V2 is a small distance east of V1, the
+*  bearing is about +pi/2.  Zero is returned if the two points
+*  are coincident.
+*
+*  V1 and V2 do not have to be unit vectors.
+*
+*  The routine sla_BEAR performs an equivalent function except
+*  that the points are specified in the form of spherical
+*  coordinates.
+*
+*  Called:  sla_DPAV
+*
+*  Last revision:   11 September 2005
+*
+*  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
+
+      REAL V1(3), V2(3)
+
+      INTEGER I
+      DOUBLE PRECISION D1(3), D2(3)
+
+      DOUBLE PRECISION sla_DPAV
+
+
+*  Call the double precision version.
+      DO I=1,3
+         D1(I) = V1(I)
+         D2(I) = V2(I)
+      END DO
+      sla_PAV = REAL(sla_DPAV(D1,D2))
+
+      END