vector_angle()

double vector_angle	(	const POINT3D *	v1,
		const POINT3D *	v2
	)

Angle between two unit vectors.

Definition at line 501 of file lwgeodetic.c.

References cross_product(), dot_product(), normalize(), pixval::x, and pixval::y.

Referenced by test_vector_angle().

{
        POINT3D v3, normal;
        double angle, x, y;

        cross_product(v1, v2, &normal);
        normalize(&normal);
        cross_product(&normal, v1, &v3);

        x = dot_product(v1, v2);
        y = dot_product(v2, &v3);

        angle = atan2(y, x);
        return angle;
}

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