distance_sphere_method()

double distance_sphere_method	(	double	lat1,
		double	long1,
		double	lat2,
		double	long2,
		SPHEROID *	sphere
	)

Definition at line 451 of file lwgeom_spheroid.c.

{
        double R,S,X,Y,deltaX,deltaY;
 
        double  distance        = 0.0;
        double  sin_lat         = sin(lat1);
        double  sin2_lat        = sin_lat * sin_lat;
 
        double  Geocent_a       = sphere->a;
        double  Geocent_e2      = sphere->e_sq;
 
        R       = Geocent_a / (sqrt(1.0e0 - Geocent_e2 * sin2_lat));
        /* 90 - lat1, but in radians */
        S       = R * sin(M_PI_2 - lat1) ;
 
        deltaX = long2 - long1;  /* in rads */
        deltaY = lat2 - lat1;    /* in rads */
 
        /* think: a % of 2*pi*S */
        X = deltaX/(2.0*M_PI) * 2 * M_PI * S;
        Y = deltaY/(2.0*M_PI) * 2 * M_PI * R;
 
        distance = sqrt((X * X + Y * Y));
 
        return distance;
}

References SPHEROID::a, distance(), and SPHEROID::e_sq.

Referenced by distance_ellipse().

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