MARINE & MARITIME 11ATAR

Invention #1 Cross-Staff

The cross-staff made its appearance in Europe in the 1300s and by the mid-seventeenth century it had been developed for use at sea. It was used to measure the altitude of the sun or a star above the horizon to help determine latitude. 

While the cross-staff was an improvement over earlier instruments, it had a few shortcomings. Using the cross-staff required the observer to look in two places at once, but the technique proved to be inaccurate when measuring large angles. The biggest problem was that taking a sight during the day required the navigator to look directly at the sun—a potentially blinding experience! 

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Invention #2 Compass

The first magnetic compass was invented in Venice, Italy, during the Renaissance. It was a device supporting a magnetized needle over a card showing four or eight points of direction.

The compass was a valuable trade secret, and it was not shared with anyone before the year 1311. After 1311, there were many pictures of explorers with compasses.

Before the modern compass was invented, it was very difficult to travel by sea, making exploration of unknown oceans difficult. With a magnetic compass, explorers felt confident to travel the seas to discover new lands.

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Invention #3 Quadrant

The Gunter’s quadrant is a simplified version of the elegant, but complicated, Arabic astrolabe. It is typically a brass or wood instrument with a scale of 0 to 90 degrees. It has two peepholes along one edge for sighting the sun, the moon, stars or the planets. The astrological figures on the quadrant were typically calculated for a specific latitude which limits the instrument's usefulness at sea. 

The principle use of the Gunter quadrant was to tell the time of day. After the observer used the quadrant to determine the altitude of the sun; determined the declination of the sun for that date; and determined his latitude; the scales could be used to determine the time.

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Invention #4 The Backstaff

The back-staff was the first instrument specifically designed for finding latitude at sea. English explorer John Davis conceived the instrument while on a voyage to find the Northwest Passage and in 1595 described it in his book The Seamen’s Secrets.

The back-staff was developed to correct some of the deficiencies of the cross-staff; that is, having to look at two places at once (which with larger angles could produce highly inaccurate measurements) and having to look directly into the sun during the day. By fitting the cross-staff with a small horizon vane, the navigator could sight the horizon and measure the height of the sun at the same time. It was this new method that led to the development of the back-staff.

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Invention #5 The Astrolabe

The Astrolabe is an angle-measuring tool. Its name comes from the Greek, “to take a star. In its earliest uses, the astrolabe was used for astronomy (study of the stars).

The astrolabe was adopted for sea-going use when sailors learned that they could navigate by measuring the longitudes and latitudes while at sea. The first documented use is by Portuguese explorers in 1481, on a voyage down the African coast.

Its one advantage over other early instruments is that it doesn't require a clear horizon. A navigator can take measurements at night, or on foggy days when it might be hard to see the horizon.

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Invention #6 Cartography: The Development of Map-Making

Maps measure distances, provide direction, and depict boundaries. They show how the world is laid out at a particular time.

European maps from the Age of Exploration reflect what was known as well as what people didn't know at the time. Some maps feature well known area such as the regions frequently visited by Europeans.

The overall quality of maps advanced dramatically during the Age of Exploration. Europeans were sailing further from their own shores and returning with accounts of the distant lands they had reached.

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Invention #7 Sextant

A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. This is used to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation.

The estimation of this angle, the altitude, is known as sighting or shooting the object, or taking a sight. The angle, and the time when it was measured, can be used to calculate a position line on a nautical or aeronautical chart.

A sextant can also be used to measure the lunar distance between the moon and another celestial object (such as a star or planet) in order to determine Greenwich Mean Time and hence longitude.

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Invention #8 Chronometer

James Cook led one of the first major sea voyages with the ability to determine longitude. He carried aboard a chronometer - a special clock invented for use at sea.

Sailors had long been able to determine their latitude, by using the stars. However, without the ability to determine longitude, they could only guess how far east or west they were. They knew longitude could be determined by comparing Greenwich mean time to the local time.

Prior to 1735, however, clocks didn't run accurately on ships. Waves and rocking affected the clock mechanisms. In 1735, John Harrison, a working class cabinet maker, solved the problem. Cook used Harrison's H4 chronometer on his voyage: the original pocket watch.

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Invention #9 Nautical Charts

Map scale refers to the size of the object on the map as compared to the size of the object on the ground. The standard scale in architectural drawings, for example, is 1/4 inch to one foot. This means 1/4 of an inch on the drawing equals one foot on the object.

Nautical charts use different scales and can be generally classified as follows: ocean sailing charts are small-scale charts, 1:5,000,000 or smaller, used for planning long voyages or marking the daily progress of a ship. Sailing charts, used for offshore navigation, show a generalized shoreline, only offshore soundings, and are at a scale between 1:600,000 and 1:5,000,000. As an illustration, a 10-knot ship covers about 29 inches (74 centimetres) at 1:600,000 scale in a day.

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