10 european navigation tools and methods

From ancient times, ships usually went along the coast in Europe. As a result, there were heavy traffic as well as many navigation obstructions such as reefs and shoals in coastal waters. To help sailors to locate their ships and ensure smooth voyages, many facilities and waterway marks, such as lighthouses and beacon lights, were built up. In La Coruña, Spain, a lighthouse built three thousand years ago survives to this day.

In the High Middle Ages, most merchant ships in the Mediterranean went along the coast. Usually the merchant ships from western Mediterranean shore first sailed southwards along the Italian Peninsula (Apennine peninsula), passed through the Strait of Messina, went around the Greek peninsula, headed for Rhodes and Cyprus along the northern shore of Candia (modern Heraklion), then went straight to Syrian coast and sailed southwards to Tyre, Lebanon. After passing through the Strait of Gibraltar and entered the Mediterranean, instead of going straight eastwards, the ships from northwestern Europe went along the coast of Spain, France and Italy. In a word, no captain dared to go deeper into the ocean where sailors could not see the continents, because they believed the vast ocean was much more horrible than reefs and shoals. There were three reasons why sailors did not dare to go straight across the ocean: disorientation, the storms at the sea, and the pirate attacks. But the first reason was the primary one. Because, in the following era where the navigation technology was improved, ships dared to go straight across the ocean regardless of the second and third reasons.

Jacob’s staff

Therefore, orientation was the first thing to do in voyages. There were many relevant empirical approaches in the western Europe. Arabs invented the “Kamal”, Chinese invented the “star drawing operation”, similarly Europeans had long known the principle of positioning by measuring the angles of celestial bodies. Ancient Greeks referred to it as “dioptra”. In the Early Middle Ages, Vikings used that principle too. During the voyage, they used any available rough tool, even an arm, a thumb or a segmented stick, to maintain the angle they observed, so as to hold the course. Around 1342, this principle was adopted in the navigation in Mediterranean. Navigators here used a simple instrument named “Jacob’s staff” to measure the angle of celestial body. The observer could measure the drift angle by jointing two poles together at the top ends, with the lower one in parallel with the horizon and the upper one pointing at the target celestial body (star or sun). Then the latitude and voyage range could be calculated based on the difference of drift angles

The cross staff

The cross staff was more advanced than the “Jacob’s staff”, but it was not applied until the late Middle Ages. The observer put the top of pole before his eyes, pulled the cross-bar (or cross-plank, usually more than one) placed on the pole, aimed one end of the cross-bar at the sun and the other at the horizon, and thus got the angle of sun.

Astrolabe

Another more advanced observation instrument was astrolabe. It was said to be used by Columbus in his explorations. Astrolabe was a copper disc with a small ring for hanging it. A rotatable pointer, which was called alidade rule and going around the disc, was fixed on the astrolabe. There was a small hole on each end of the alidade rule. When the disc was hung vertically, the observer must slowly rotate the alidade rule. When the sunlight or starlight could be seen through both holes, the angle indicated by alidade rule on the disc was that of the star (or the sun). Although the astrolabe was not widely used until the late Middle Ages, but actually the famous 8th-century Frankish litterateur St. Louis had described it in his prayer.

This method of determining latitude was quite successful, but it still was very difficult to determine the longitude. Therefore, “latitude sailing” was widely adopted in the western Europe. The early Vikings did not have any concept of latitude, but they had learnt to use the principle of celestial deflection: put themselves on the same latitude line as their destination, held this course and went straight to the destination. This method had been used till the 15th century without major changes. Even Columbus used this method in his exploration of the New World. He first went southwards to the latitude line which he considered to be the same as India, then sailed straight westwards.

wind roses cards

Apart from navigating with celestial bodies such sun, moon and stars, wind direction was also an important mark that helped to determine the course. In ancient Greek, “wind” and “direction” was the same word. They named the main four wind directions (east, south, west, north), and marked another four secondary ones. The Tower of the Winds, which exists now in Athens, was built in the 2nd century BC. Today it can still point out each of the eight wind directions. Greeks also knew how to make use of the monsoons on the Indian Ocean during the voyage. The well-known southwest monsoon on the Indian Ocean between June and October was referred to as the “Hippalus wind”, because Greek navigator Hippalus in 1st century BC had proved that it was possible to sail from the Red Sea to Indian coast with this monsoon.

Before the compass was invented, almost all the European navigators believed the “direction” was the “wind direction”. Although the Germanic people only named four main wind directions, it was common in the western Europe to use “wind roses” cards, which indicated four, eight or even twelve wind directions, to navigate. Similarly, the European worship of wind was no less than Easterners, even the Virgin Mary was called the “Notre Dame des Vents”.

physiographic data

In the North Sea and the Baltic, sailors used more physiographic data to navigate. Among early Vikings, captains knew much about the natural objects at sea, including birds, fishes, currents, driftwood, seaplants, colors of water, iceblink, clouds and winds. In the 9th century, famous Nordic navigator Flóki Vilgerðarson released a raven which guided him to Iceland.

measuring the depth of the water

The coastal shelf in northwestern Europe was very wide, so sailors pinpointed the course mainly by measuring the depth of the water and investigating the condition under the sea. They dropped a lead block coated with animal oil and bound to a rope to measure the depth of water, and fetched samples of sand and mud from the sea. Even after the invention of compass, sailors in the northwestern Europe still used this traditional measuring method. The oldest surviving English sailing directions (written in the mid-15th century) directed English sailors to return to English harbor city Bristol from Spain as below: “When you leave Cape Finisterre (in Spain), keep going northeast. If you estimate that two thirds of the voyage had been completed, you should go north by east till you enter the shallow water. If you measure a water depth of 90 to 100 fathoms, keep going north till you arrived at a light grey sand bed about 72 fathoms under the water. That was the foreland between the Cape Clear Island (Ireland) and the Isles of Scilly (England). After that, you head north till you collect mud from the sea, then turn northeast or east by north.”

compass

What really changed the European navigation was the application of compass. Compass was introduced into Europe around the 12th century. Joseph Needham thought that the Chinese magnetic compass was brought to the West overland, and then was reformed by European navigators to “indicate the north”. Compass was first mentioned in European records by Alexander Neckam, a scholar from the University of Paris. In an article written around 1180, he said: “Under dull weather or in the evening, when sailors could neither see the sun nor learn where they were heading to, they would put a needle on the magnet, and the needle tip would rotate and stop when pointing at the north.” But the first time European used compass should be earlier than this. It was generally believed that Italian sailors began to use compass around 1150.

The earliest compass in Europe was the Compass Rose, which was similar to the previous “wind roses”, but it marked 16 or 32 direction points. The original compass card was circular, where there carved the pattern of “wind roses”. It was placed flat on the table when being used. A small plate of water was put aside, with a simple magnetic needle placed on a wood chip floating on the water. The navigator kept turning the chip according to the direction indicated by the needle. Later, the needle was attached under the chip, which rotated following the floating needle, so as to indicate the right direction at all time. Around 1250, magnetic compass had been developed to be able to continuously measure all the horizontal directions, with the error less than 3°.

But it took a long time before magnetic compass was widely accepted by Europeans. As people could not scientifically explain why the needle tip could “find” the north, magnetic compass remained mysterious and sailors did not dare to use it. Even those bold and cautious captains only secretly used it, and put it in a small box to keep it out of sight. Therefore, compass was not widely used until the late 13th century.

Before the application of compass, navigation in the Mediterranean was greatly limited by weather. The weather was clear between May and October of each year, and there were north wind and northwest wind on the sea, which helped ships to sail from Italy in the northwest to Egypt in the southeast, but also made it difficult for the ships returned from Egypt. Ships must make a detour from Cyprus and then go westwards. In the so-called “rough weather” season, which was between the October and the March in the next year, the winds were fair but it was gloomy and cloudy on the sea. So it was difficult for sailors to determine the direction and ships could only stay in harbor. In many Italian cities, there was a large number of records regarding the shipping suspension in winter. The fleet heading for the eastern Mediterranean usually could take a round trip only once a year. They either left Venice before the Easter and returned in September before the cloudy season; or left Venice in August, arrived in the destination in September, spent the winter there and returned to Venice in the next May. Actually, these merchant ships were suspended in half of the year.

The application of compass greatly changed the situation for navigation in the Mediterranean. The gloomy and cloudy weather was no longer the obstacles to navigators. All-weather navigation became possible, so did the cross-sea navigation. In addition, sailing on the right course significantly shortened the voyage range and saved much time. In the last 25 years of the 13th century, a ship could go around the Mediterranean twice a year and even sail in winter. In 1300, Italian ships could be on the sea at any time of the year.

waterclock

Meanwhile, some other navigational instruments were also put into use. For example, the sailing distance could be calculated after the “waterclock” for measuring the ship speed was put into use. There were systematic records of course, the trigonometric table specially written for navigation, and the new technology of directional control by the stern rudder installed on the center line of the hull. These new devices and technologies enabled navigators and particularly Italian merchant ships to determine their bearings in time.

range quadrant

In the 15th century, Portuguese made some contributions to the development of navigational technology. Portuguese began to take explorations in the West Africa after 1420. Compared with previous navigation activities, Portuguese were faced with two new problems. The first problem was that the central and southern Atlantic were completely unknown to them. The second one was that the celestial bodies significantly changed when sailing southwards. The changes of Atlantic Ocean currents and magnetic field often made navigators misoriented. Navigators and astronomers tried to find solutions. From 1450, they measured the meridian altitude of a celestial body with range quadrant. After the ship passed the equator and the Polaris could not be seen, they measured the meridian altitude of the sun to check the calculated orientation. Meanwhile, hydrology department also provided navigators with sufficient materials such as nautical charts, nautical instruments, star catalogues and course charts. In this way, their voyage southward could be made successfully.

nautical chart

European navigators had been collecting navigational information since a very early age. Around the 6th and 5th century BC, some sailors began to record some waypoints and coastal features in the Mediterranean as well as useful experience. Such records was referred to as the “circumnavigation”, and was called “coastal navigation” in later times. The earliest “coastal navigation” was written by Scylax of Caryanda in the 6th century BC. In the deck log, he detailedly described the dangerous waters and fairways in the Mediterranean, recorded the time for every trip in good wind direction and weather. For instance, he recorded: “It takes 12 days to sail from the Pillars of Hercules (Gibraltar) to the Syrnos island all the way along the coast. There are shoals, mud and seaplants in the waters around the Syrnos island, and therefore it is no longer passable for ships there. The seaplant there is as wide as a palm, with sharp tip end that hurts people.” However, these ancient sailing directions were mainly written records. As the drawing technique was underdeveloped and the routes must be kept secret due to the requirement for business competition, no nautical chart written before the 14th century was passed down to this day in Europe.

Around 1300, “the first real maps”, the nautical charts of the Mediterranean, appeared in Europe. These charts, which were often referred to as “port guideline” or “guidebook” in Italy, provided many detailed nautical materials. These materials remained to be reliable data source for cartologists till the 16th century, and was even used by Dutch sailors as sailing directions.

Among these 14th-century maps, the most famous one was the Catalan Atlas. It was drawn by a Jew named Abraham Cresques for the king of Aragon, and was now preserved in the Bibliothèque Nationale at Paris. He drew the central part of the world (from India to Spain) from east to west into 12 maps, bound them on wood planks. These maps could be folded and expanded, and were basically an atlas for coastal navigation. He referred to numerous materials recorded by previous navigators, and accurately showed the coast of the Black Sea, the Mediterranean and the western Europe. Also, in the east, for the first time he depicted India as a huge peninsula; and in the west, he drew the “west ocean” (the Atlantic) which was little known at that time.

The feature of typical accurate coastal charts in medieval Europe lay in the geometric figures that represented the relationship between wind directions and climate.

Its shape was like a rose. There was usually a central point on the nautical chart, with a circle around it; there were also 8 to 16 points in the circle, and each of them emitted many lines at all directions. These lines indicated the wind directions, and many of them also indicated the courses. Although these charts had practical value on the macro level, but it was still difficult to determine the specific orientation during the voyage. Also, these charts were hand drawn and not identical at all. Therefore, in the 15th century, as Ptolemy’s Cartographic theory was re-recognized by Europeans, navigators soon began to use latitude lines and meridian coordinate system to draw nautical charts. And following the application of printing, the geometric nautical charts where directional lines and distance were marked began to be popularized in Europe.

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