Any nautical chart, fair sheet or any other navigational chart or bathymetric sheet prepared in accordance with any other written law, purporting to be a true copy of such a nautical chart or fair sheet and purporting to be signed by the National Hydrographer or any officer acting on his behalf shall be admissible in evidence in all cases and for all purposes and may be taken as prima facie evidence of the truth of the facts stated therein and it shall not be necessary to prove that such copy was in fact signed or authenticated by the