slaDbear -

SYNOPSYS

PARAMETERS

double a1

double b1

double a2

double b2

DESCRIPTION

  Bearing (position angle) of one point on a sphere relative
  to another.

  (double precision)

Given

     a1,b1    double    spherical coordinates of one point
     a2,b2    double    spherical coordinates of the other point

  (The spherical coordinates are RA,Dec, Long,Lat etc, in radians.)

  The result is the bearing (position angle), in radians, of point
  a2,b2 as seen from point a1,b1.  It is in the range +/- pi.  If
  a2,b2 is due east of a1,b1 the bearing is +pi/2.  Zero is returned
  if the two points are coincident.

  P.T.Wallace   Starlink   31 October 1993

SEE ALSO

• slalib.3