Ship Positioning in Navigation in the Olden Days:

Dead Reckoning

This ancient form of navigation known as dead reckoning begins with a known position, or fix, which is then advanced, mathematically or directly on the chart, by means of recorded heading, speed, and time.

The navigator finds a position by measuring the course and distance they have sailed from some known point. Starting from a port, the navigator measures the distance from that point on a chart. Each day’s end position would be the starting point for the next day’s course and distance-measurement.

 
The navigator plots his 9am position, indicated by the triangle, and, using his course and speed, estimates his position at 9:30am and 10am.

Without an accurate way to tell time, dead reckoning was notoriously inaccurate in the open ocean, making Columbus’s feats all the more remarkable.

Compass

 

A compass is a navigational instrument that shows directions in a frame of reference that is stationary relative to the surface of the Earth. The frame of reference defines the four cardinal directions (or points) – north, south, east, and west. Intermediate directions are also defined. Usually, a diagram called a compass rose, which shows the directions (with their names usually abbreviated to initials), is marked on the compass.

One of their first contributions of China was the invention of the magnetic compass. The first definitive reports that the Chinese were aware of magnetism date to 240 B.C.

Chinese scientists knew as early as the third century AD that iron ore, called magnetite, aligned itself in North/South position. They learned that by heating pieces of ore and then placing the pieces in a North/South position, they could make a magnet. The magnet was then placed on a piece of reed and floated in bowl of water marked with directional bearings.

Admiral Zheng He is China's most famous maritime explorer. His extraordinary ability and vision found brilliant expression in the great achievements of his life, including maritime exploration, foreign diplomacy, and military affairs.

Records show that Zheng He of Yunnan (1371-1435) used the device during his voyages. Based on the history of the compass, these voyages took place between 1405 to 1433.

To navigate throughout the Indian Ocean, Zheng He would have made use of the magnetic compass, invented in China during the Song dynasty. Photo credit: © WGBH Educational Foundation

Marine Chronometer 

 A marine chronometer designed by at sea by Yorkshire-born John Harrison was critical to success of Captain Cook.

Until the 28th century, there were no clocks that could accurately keep time at sea – the rolling waves, changes in temperature and humidity played havoc with the delicate, inner workings of any mechanical timepiece. The quest for an accurate way to calculate longitude reached fever pitch by the end of the 1700s. In England, Parliament offered a prize to anyone who could solve the riddle.

Using a combination of different metals, ingenious design and painstaking trial and error, Harrison took four years to build his first spring-driven friction-free device.

 Drawings of Harrison's H4 chronometer of 1761, published in The principles of Mr Harrison's time-keeper, 1767