History of Navigation: Methods of Navigation

Navigation is broken into four sub-disciplines: piloting, dead reckoning, celestial navigation, and electronic navigation.

Chart Detail of Castine

Piloting Piloting is guiding a ship through waters near shore.  Large ships often use professional pilots when entering or leaving port. Piloting a vessel uses visual landmarks and aids to navigation such as lighthouses and buoys to help determine the ship’s position and to plan a course. In addition to a compass for direction and a log to measure speed, the navigator uses a lead line or depth sounder to keep track of water depth.

Charts show navigators water depths, shoals or shallow areas, rocks, islands, points along the shore, lighthouses, landmarks, and other aids to navigation.   Dead Reckoning Dead reckoning or deduced reckoning is keeping track of where the ship has been, both along shore and at sea. By recording course and speed over time, the navigator keeps track of the ship’s position. A navigator essentially adds or draws directions and distances or vector lines to show the vessel’s track and its resulting location. A dead reckoning position is needed to solve some celestial navigation problems.

North Atlantic Chart Showing Ship Track

Pa and Mate Taking the Sun

Celestial Navigation A ship’s position is affected by influences besides its own course and speed, such as leeway and current. To check or verify the ship’s position, the navigator can use “lighthouses of the sky,” the sun, moon, stars, and planets. The angles between the horizon and these celestial bodies can be used to fix the vessel’s location. Electronic Navigation Navigators have used electronics since the first days of radio.  Electronic navigation is now the common satellite-based global positioning system (GPS). Earlier forms like loran relied on special land-based transmitting stations. GPS has become so reliable and easy to use that some navigators use celestial navigation methods only to keep in practice in case of a GPS or electrical failure. GPS has become so universal that it has a wide range of applications, including its use in cars.

Wheelhouse on Dragger