Developments in Navigation

Earlier in the pathway, we explored some of the early advancements in tools for navigation: the astrolabe, the compass, and “dead reckoning”.

These would form the backbone of navigation up to the 18th century.

But that doesn’t mean that no important progress was made during the height of the age of exploration.

This orb details some of the innovations and challenges that dominated the 17th and 18th centuries.

A new invention of vital importance to navigation was the telescope, usually credited to Dutch eyeglass maker Hans Lippershey in 1608.

Before the telescope, sailors were limited in their ability to navigate by the naked eye alone. They could only estimate their position based on the stars and other natural landmarks, by which ships could easily go off course or run aground.

With a telescope, sailors see land masses and other ships on the horizon in much greater detail, allowing them to chart their course with accuracy, and avoiding hazards.

The telescope was later aided by the 'reflecting quadrant', also known as Octant, invented by John Hadley in the 1730s, used for accurately measuring the angle between the horizon and a celestial object such as the sun, moon, or stars.

Some of the most significant technological developments both leading up to and during the Age of Exploration occurred in cartography.

One such invention was the portolan chart (from the italian ‘portolano’ or 'pilot's book'), used by European sailors beginning in the thirteenth century.

These charts depicted coastlines, landmarks, and ports of call, along with rhumb lines, as lines corresponding to a constant compass direction, allowed navigation along coastlines and between ports with a degree of precision that was not previously possible.

Another significant development was the creation of the Mercator projection by Gerardus Mercator in the sixteenth century.

The Mercator projection is a type of map that shows the world on a flat surface while preserving the shape and angle of lines of longitude and latitude.

This would allow sailors to plot a straight-line course between two points on the map, which was particularly useful for long-distance navigation.

Although a major breakthrough in cartography, the Mercator Projection could not be used in practice for many years to come, due to the difficulties in calculating longitude at sea.

While latitude (ones’ position north or south) could be determined by measuring the angle of the sun or stars relative to the horizon, longitude (one’s position east or west) presented far more of a challenge, and finding an accurate method would take centuries.

This was in part due to limitations in timekeeping, since longitude was eventually reliably established by comparing the time across distances.

For example, consider that the earth is divided into 24 time zones, each separated by 15 degrees of longitude.

If it's noon in London and the local time on a ship at sea is 1 p.m. the ship is one hour ahead of London time, which corresponds to a difference in longitude of 15 degrees. Therefore, the ship's longitude can be calculated as the longitude of London plus 15 degrees.

While the first to propose the method of comparing clocks at sea was Gemma Frisius in 1530, timekeeping technology was far too inaccurate to make this method practical - particularly true at sea, when the temperatures, salt, and motion of the ship easily interfered with mechanisms.

Christiaan Huygens patented the pendulum clock in 1657, which revolutionized timekeeping. However, the motion of the pendulum was still susceptible to interference from the motion of the ship, rendering it useless for timekeeping at sea.

As such, maps suitable for the 'dead reckoning', along with maps suitable to this technique, remained in use beyond the invention of the Mercator Projection.

So too did other methods of calculating longitude, such as the method of lunar measurement first proposed by Amerigo Vespucci in 1499 - a serviceable, though imperfect solution that required complex measurements and charts.

With the complexity of calculations required for accurate navigation, the Age of Exploration gave rise to a practical interest in mathematical education.

For example, a Mathematical School at Christ’s Hospital in London was founded by King Edward VI in 1673 in order to teach potential sailors, selected around age 11, preparing them for careers in the Royal Navy.

To this end, the school provided instruction on topics such as geometry, trigonometry and astronomy - all essential skills for undertaking long voyages across unknown waters.

This was a savvy investment during a time of fierce competition in navigation. Many, including Isaac Newton, suspected that longitude would be solved through mathematics.

And whichever state was to succeed in calculating longitude could expect a significant global advantage.

In 1714, the British government established the Board of Longitude, with the aim of encouraging invention and competition among scientists and navigators.

The board offered rewards for anyone who could devise an accurate method for determining longitude at sea, offering up to £20,000 - a huge sum at that time - as incentive.

The eventual victor was a humble carpenter named John Harrison.

His 1759 marine chronometer - his fourth prototype - used a novel system of counterbalanced springs, rather than gravity, and was therefore unaffected by motion.

It was accepted as sufficiently accurate by the Board of Longitude in 1762 after rigorous testing. The Board, however, withheld the prize until 1773, offering less than half promised, and only two years prior to Harrison’s death.

Nevertheless, Harrison has been remembered in history for revolutionizing the art of navigation.