def rotation_coefs(self):
        """ get the rotation coefficents in radians

        Returns
        -------
        rotation_coefs : list
            the rotation coefficients implied by Vario2d.bearing


        """
        return [np.cos(self.bearing_rads),
                np.sin(self.bearing_rads),
                -1.0*np.sin(self.bearing_rads),
                np.cos(self.bearing_rads)]
get the rotation coefficents in radians

        Returns
        -------
        rotation_coefs : list
            the rotation coefficients implied by Vario2d.bearing