#include "slalib.h" #include "slamac.h" float slaBear ( float a1, float b1, float a2, float b2 ) /* ** - - - - - - - - ** s l a B e a r ** - - - - - - - - ** ** Bearing (position angle) of one point on a sphere relative ** to another. ** ** (single precision) ** ** Given: ** a1,b1 float spherical coordinates of one point ** a2,b2 float 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. The ** sense is such that if a2,b2 is a small distance east of a1,b1, ** the bearing is about +pi/2. Zero is returned if the two points ** are coincident. ** ** If either b-coordinate is outside the range +/- pi/2, the ** result may correspond to "the long way round". ** ** The routine slaPav performs an equivalent function except ** that the points are specified in the form of Cartesian unit ** vectors. ** ** Called: slaDbear ** ** Last revision: 8 December 1996 ** ** Copyright P.T.Wallace. All rights reserved. */ { return (float) slaDbear ( (double) a1, (double) b1, (double) a2, (double) b2 ); }