Navigating At Sea

Navigating At Sea. U.S.S. North Carolina. In the age before global positioning system (GPS), ships used celestial navigation in the open sea. An art and science it is navigating by the stars, sun, moon, and planets. The Quartermasters and Navigator used a sextant, chronometer, and nautical almanacs to determine the Ship's latitude and longitude. , , Keeping Time , The Quartermasters maintained the Ship's three chronometers, a clock for keeping accurate time at sea. Knowing the exact time of day at the Prime Meridian (Greenwich Mean Time, Greenwich, England) was essential for determining the Ship's longitude by celestial navigation. GMT was compared with local time, where one hour of difference is equivalent to 15° longitude. Once a week the Ship received a time check from Washington D.C. and the Quartermasters compared it to the chronometers. They also checked and wound all of the Ship's clocks and made sure they were in synch with the chronometers. , , Weather Reporting , A Quartermaster's duties included weather observations. He recorded data on temperature, relative humidity, atmospheric pressure, wind, clouds, sea condition and other phenomena and sent the data by radio to shore-based weather stations. On larger ships, such as the Battleship, an Aerographer's Mate drew complete weather charts. , , Crew Memories , We were coming out of Majuro one afternoon while Captain Thomas was commanding. This was quite a narrow entrance or exit from the harbor with a strong current. Consequently, we needed speed to maintain our course, An LST was patrolling outside the entrance and was on a collision course with us. The captain had to stop engines much to his distress to let the LST clear. He indignantly sent a message to the LST saying, 'Are you familiar with the rules of the road?' The answer came back, 'NEGATIVE.'" , , Commander T.J. Van Metre, Navigator , (captions) , Commander Tolley, Navigator, is using a sextant which measures the angle between two objects such as the sun or a star and the visible horizon. It can be extremely accurate in determining the ship's location. While Tolley is "shooting the sun," Chief Quartermaster Joe Ringhoffer records the time and sights. , , The sailor, far left, is holding a stadimeter. It is a device for estimating the range to an object of known height such as a mast of another ship. It was used to keep ships at the proper distance from each other when steaming in formation.