def rotation_matrix(self):
        """Get the 3x3 rotation matrix equivalent of the quaternion rotation.

        Returns:
            A 3x3 orthogonal rotation matrix as a 3x3 Numpy array

        Note:
            This feature only makes sense when referring to a unit quaternion. Calling this method will implicitly normalise the Quaternion object to a unit quaternion if it is not already one.

        """
        self._normalise()
        product_matrix = np.dot(self._q_matrix(), self._q_bar_matrix().conj().transpose())
        return product_matrix[1:][:,1:]