The term 'Guidance System at Sea' can be summarized as a system that uses the LORAN (Long Range Navigation) system to provide navigational guidance for ships and other vessels. LORAN is a radio navigation system that uses low frequency radio signals transmitted from multiple land-based stations to determine the position of a vessel. This system has been used since the 1940s and is still in use today, providing an important navigational aid for ships and other vessels.