spheroid_distance()

double spheroid_distance	(	const GEOGRAPHIC_POINT *	a,
		const GEOGRAPHIC_POINT *	b,
		const SPHEROID *	spheroid
	)

Computes the shortest distance along the surface of the spheroid between two points, using the inverse geodesic problem from GeographicLib (Karney 2013).

Parameters

a	- location of first point
b	- location of second point
s	- spheroid to calculate on

Returns

spheroidal distance between a and b in spheroid units

Definition at line 79 of file lwspheroid.c.

{
        struct geod_geodesic gd;
 
        /* Same point => zero distance */
        if ( geographic_point_equals(a, b) )
                return 0.0;
 
        geod_init(&gd, spheroid->a, spheroid->f);
        double lat1 = a->lat * 180.0 / M_PI;
        double lon1 = a->lon * 180.0 / M_PI;
        double lat2 = b->lat * 180.0 / M_PI;
        double lon2 = b->lon * 180.0 / M_PI;
        double s12 = 0.0; /* return distance */
        geod_inverse(&gd, lat1, lon1, lat2, lon2, &s12, 0, 0);
        return s12;
}

References SPHEROID::a, SPHEROID::f, geographic_point_equals(), GEOGRAPHIC_POINT::lat, and GEOGRAPHIC_POINT::lon.

Referenced by circ_tree_distance_tree(), ptarray_distance_spheroid(), ptarray_length_spheroid(), and test_spheroid_distance().

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