This article contains a list of the main navigational tools and their description.
Navigation instruments and instruments
To ensure the safety of navigation, control over the movement of the vessel and its location relative to the shore, various technical navigation aids (TCN), navigation instruments and tools are used in navigational practice:
- to determine direction- compasses;
- to determine the speed of the vessel and the distance traveled- logs;
- to determine the depth under the keel- hand lots and echo sounders;
- goniometer instruments (sextants), watches and stopwatches, optical rangefinders, binoculars, tiltmeters, etc.;
- traditional tools for working on a map- navigational protractor, parallel ruler, measuring compass, compass, protractor, weights for maps;
- hydrometeorological instruments- barometer, barograph, anemometer, SMO circle, external thermometer, inclinometer.
Compasses.
These are navigation instruments designed to determine the course of the vessel and directions to coastal landmarks and floating objects that are in the field of view of the navigator. On small vessels there may be various types of compasses and their modifications. The most common heading indicator is a magnetic compass.
Speed meters - logs
Lags various types have firmly taken their place along with other modern TSS. Of all the types of logs (hydrodynamic, induction, Doppler hydroacoustic, correlation, radio Doppler), the most acceptable for boats and yachts are hydroacoustic and induction logs; for hovercraft, the radio Doppler log is the most acceptable.
Depth meters.
Lot is a device used to measure depths under the bottom of a ship. Navigation lots of various types are designed to measure depths up to 500 m. There are hand-held and hydroacoustic echo sounders. On small vessels, hand lots are used predominantly,
Hand lot designed for measuring depths up to 50 m. The lot consists of a weight and a line.
Echo sounder. Although rare, modern depth meters - echo sounders - are also used on small vessels
The operating principle of an echo sounder is based on measuring the time it takes for a sound pulse to reach the bottom and, after being reflected, to return. After the necessary transformations (almost this happens instantly), the depth value and bottom topography are displayed on a special board or display.
Distance meters.
Binoculars. Binoculars are used by navigators to monitor their surroundings (other ships, coastal landmarks, navigational signs, etc.)
Sextan– a reflective-type goniometric instrument for measuring the heights of celestial bodies and angles (vertical and horizontal) on the earth’s surface. To measure the vertical angle, the sextant is taken in the right hand and, in a vertical position, is directed with a pipe to the base of an object (lighthouse, ship, factory chimney, sign, etc.). Then the stopper moves the alidade so as to bring the twice-reflected image of the upper part of the object to its base. After that, the countdown in degrees is taken according to the alidade index in accordance with the division of the dial, and the minutes and their tenths are taken from the counting drum. The taken reading is corrected by adjusting the sextant index and the result obtained will correspond to the value of the vertical angle to the given object.
Time meters.
Marine chronometer.
This device is used to determine fairly accurate Greenwich time; it is often called the keeper of universal time. High precision of movement and its uniformity are ensured by special regulators. The large dial is divided into 12 hour divisions and has an hour and minute hand. On one of the two small dials, the hand counts down the seconds, on the other, the time elapsed since the last winding of the chronometer. The chronometer is stored in a special box on a cardan suspension, which ensures a state of rest for the clock mechanism during swinging. The chronometer is wound up every day at the same time (usually at 8 o'clock).
The chronometer correction (the difference between Tgr and the chronometer reading) is determined by radio signals of the exact time and is recorded every day in a special journal. Fig.15 Chronometer
Deck clock. They are set according to Greenwich time, and if there is no chronometer on the ship, they perform its function. The watch mechanism has increased accuracy.
The dial is divided into 12 divisions and has hour, minute and central seconds hands.
Ship or marine watches. The purpose of a ship's clock is to show the ship's time, according to which service and daily life on board the ship are organized. They are installed in cabins and service areas. The watch has a round dial divided into 12 or 24 hour divisions, hour, minute and central seconds hands. As a rule, watches are wound for a week.
Stopwatch- used for precise measurement of short periods of time. On small boats, a hand or pocket watch with a large central second hand can easily replace a stopwatch. The same watch can be used to determine the distance traveled, the moment of taking bearings, the time of course change and other points that need to be plotted on the map.
Gasketsinstruments
When working on a map, an amateur navigator must use a laying tool, the set of which includes a parallel ruler, a protractor, a measuring compass, and weights for maps.
Parallel ruler(Fig. 16) is used to draw straight lines and parallel to a given direction on the map. The ruler consists of two halves connected by two equal rods on hinges. The cuts of the rulers should not have nicks, bends, or burrs, and the rods should easily rotate around the axes, but without free play. When working with a ruler, it is necessary to monitor the parallelism of movement so as not to disrupt the given direction of the line. The lines are drawn with a sharpened pencil without noticeable effort.
Navigational protractor(Fig. 16) is used to plot and measure angles, courses and bearings on the map. It is a semicircle with a ruler; there are several varieties). The center of the semicircle is marked by a cutout on the ruler. The upper cut of the arc is graded along the top row from point 1 to point 2 to the left - from 0 to 90°, from point 2 to point 3 to the left - from 270 to 360°, along the bottom row from point 1 to point 2 to the left - from 180 to 270 ° and from point 2 to point 3 - from 90° to 180°. The top row of numbers is used to plot the directions of the northern half of the compass card, and the bottom row is used to plot the southern half.
It should be remembered that the angles increase from 0 to 360° from the northern part of the meridian to the right.
Compass meter used to measure distances and plot them on a map. It is more convenient to work with a compass with one hand. Large distances are laid aside in parts. It is not recommended to spread the legs of the compass more than 90°. The distance is measured on the side frame of the map at the same latitude where the voyage occurs or the distance being measured is located. Having set aside the distance, you should check it by repeating the reverse measurement.
Weights for cards are designed to hold cards in the workplace. On small vessels where there is no deckhouse, the weights can be replaced with buttons that secure the map to a flat wooden portable tablet.
Hydrometeorological instruments.
Atmospheric pressure (air pressure, barometric pressure) is determined by the weight of a column of air that presses on a unit area of a horizontal surface. Instrument for measuring atmospheric pressure is called a barometer. The instrument scale is graduated in millimeters of mercury and has a built-in thermometer.
The history of navigation, and therefore piracy, is closely connected with the history of navigation and cartography. The history of navigation, and therefore piracy, is closely connected with the history of navigation and cartography. When were nautical maps invented? How did people in ancient times navigate the sea? Answering these questions is not as simple as it might seem at first.
Of course, sailing along the coast does not require maps or any special ways orientation. It is enough to study the coastline. Most ancient sailors did just that; by the way, this greatly simplified the equipment of the ship: it was not necessary to have a significant supply of provisions and fresh water. And if so, then it would seem that devices for navigation should have appeared quite recently. But the thing is that long voyages took place thousands of years ago, while the first information about any navigational instruments dates back to a rather late time.
Modern science believes that the Indians of both American continents, as well as the Papuans of the islands of Oceania, descend from Siberian tribes that migrated across the ocean. Siberians left their “mark” in the places where the Mayans, Incas, Aztecs and other tribes lived. However, there are other hypotheses in this regard. For example, scientists do not exclude the migration of the Phoenicians or other peoples who inhabited the Mediterranean across the Atlantic Ocean. The famous traveler and scientist Thor Heyerdahl undertook several successful expeditions to the Kon-Tiki and Ra in order to confirm this assumption.
Be that as it may, we are certainly talking about sailing across the ocean, far from the shores, where the only reference point could be the starry sky, the sun and the moon. Today it is believed that the first navigators used entrete orientation (that is, by eye) using the celestial bodies. East and west were determined by sunrise and sunset, and north and south by the position of the North Star or stars from the Southern Cross constellation.
Ancient sailors often took bird cages with them.. If a ship was lost at sea, the sailors would periodically release a bird (often a black raven). If the bird returned back, then there was no land nearby, and if it flew away in a certain direction, then the ship followed it, completely trusting the bird: that means the bird was flying to land. This technique was especially popular among the Scandinavians.
Ptolemy's map (2nd century AD) Thanks to a survey of merchants and sailors, as well as reading all the reports of ancient travelers, he managed to draw a map of the world in a conical projection, with parallels and meridians
This probably gave impetus to the appearance of portolans, although exact time I would not dare to name the origin of these cards even approximately. What are portolans?
Mediterranean sailors felt the need to have accurate guides that would help them conduct trade over very long distances from their home ports. Due to the fickleness of the winds, it was not always possible to move away from the shores of the Mediterranean Sea, since the capricious weather of the Mediterranean made these trips very dangerous. Even in the Middle Ages, most movement in the region still took place within sight of the coast.
During the times of the Cretan, Phoenician and Egyptian navigators, many ships plied the Mediterranean, but due to the need to stay on shore, only one trip from east to west could be made per year. From October to March, trade practically ceased, and some routes from north to south (Greece - Egypt, Gaul - North Africa), with a headwind, took entire months.
Thus, in ancient times and the early Middle Ages, the first maps became guides for moving from port to port rather than accurate descriptions of the coast. The pilots were more interested in an accurate knowledge of the topography of the coast, the presence of shoals, the constancy of winds, and the location of port cities, rather than in a scientific understanding of the surface of the Earth. Without a compass to steer the ship, without any means of determining latitude (especially when clouds covered the sky), the only option left for the pilot - be he Egyptian, Greek, Venetian or Catalan - was to draw a map! He needed a portolan (from the Italian “portolano”, that is, “a guide to ports”). In other words, a guidebook was required that would combine information about coasts, ports, winds, depths and currents collected by navigation professionals since antiquity, information with the help of which trade was carried out in Mediterranean ports in the Middle Ages.
The first information about the direct nautical maps of Marin of Tyre dates back to the 2nd century BC. e., although maps generally existed already among the ancient Polynesians in the 5th century BC. e. and were mats woven from plants depicting islands and reefs.
Maps of that period differed little from very schematic plans, and the larger the territories depicted, the less accurate the maps were: after all, the Earth is round, and large areas of its surface cannot be shown on a plane without distortion!
One of the solutions to this problem was found two thousand years ago by Eratosthenes (276–196 BC), who began to use a square equidistant cylindrical projection when creating maps. By the way, it was Erastophenes, observing the midday height of the sun in Alexandria and Aswan, who determined the radius of the Earth (6366.7 km) with such high accuracy that people are still amazed at this! And the camel “acted” as a measuring instrument! Erastofen determined the distance between two points by calculating the average number of steps, and, knowing the difference in the length of the sun's shadow, carried out simple calculations. Now this is an elementary geometry problem about the similarity of two triangles, but in those days it was a miracle.
To read a map better, you need a navigational guide. Pilot (from the Dutch loodsen - to lead a ship) - a guide for swimming in a certain water basin with detailed description its navigational features. The oldest surviving sailing guide is that of the Greek Skilakas (VI century BC), which described in detail the distances between ports, their equipment, anchorages, navigational hazards...
In general, long before medieval cosmographers, people made attempts to depict the Earth in the shape of a globe. The already mentioned Eratosthenes and Marinus of Tire were like this, and so was Ptolemy: they boldly drew maps based on their own calculations. When Palla Strozzi brought a complete copy of Ptolemy’s “Geography” to Constantinople, its translation into Latin became, as they would say today, one of the “bestsellers” of the nascent printing industry! Ptolemy was a Greek scholar from Alexandria who lived from approximately 90 to 160 AD. Thanks to a survey of merchants and sailors, as well as reading all the reports of ancient travelers, he managed to draw a map of the world in a conical projection, with parallels and meridians, that is, a grid of coordinates calculated in degrees, where latitudes were measured from the equator, and longitudes from the westernmost point the then known world. Partially erroneous, very inaccurate in many of its places, “Geography” nevertheless represented a tangible stage in the mathematical understanding of the world.
The quadrant is a primitive instrument for measuring the altitude of stars and determining latitude.
As has already become clear, the concepts of geographic latitude and longitude for unambiguously determining a location on the Earth’s surface first arose in Ancient Greece. During the day (at noon) latitude was determined by the length of the sun's shadow, at night - by the height of certain stars above the horizon. Today, the palm in the use of latitude and longitude is awarded to Hipparchus of Nicaea (c. 190–125 BC), who proposed a method for determining the longitude of different points by measuring local time when observing a lunar eclipse. In addition, Hipparchus invented the astrolabe (Greek astron - “star”, and labe - “grasping”) - a goniometric instrument that served from ancient times until the beginning of the 18th century to determine the position of celestial bodies. Previously, a quadrant was used for the same purposes.
In 1342, the mathematician Levi Ben Gershon first described a device later called the “Levi stick”. Also called a “crossbow,” it was a simple but ingenious device that could be used to measure the relative height of the sun at its zenith in relation to the horizon. Thanks to the tables of Zacuto and Visigno (1465), used simultaneously, it was possible to determine one's location to within one or two degrees of latitude.
Levi's wand is a medieval tool for determining the latitude of a location.
The evolution of European cartography up to the 16th century reflects a gigantic collective effort to create an understanding of the world, drawing information from the crude empiricism of the portolans. Thus, sailors little by little gain the opportunity to enjoy all the fruits of scientific knowledge of the Earth. In place of descriptions, even quite accurate, but always incomplete, are maps that can give a geometrically correct idea of our planet. But for this it was necessary to get rid of the prejudices of the mythologized consciousness, and at the same time acquire some navigational and topographical tools.
One of the first navigational “instruments” can be considered solarstein (translated from Old Norse - “sun stone”). With its help it was possible to determine the position of the sun in foggy weather. It is mentioned several times in ancient Viking texts. It is assumed that we are talking about a crystal of Icelandic feldspar (cordierite), which had magnetic properties.
The phenomenon of magnetism was noticed by people in ancient times. The history of magnetism is rich in observations and facts, different views and ideas.
Today it is believed that the properties of magnetic iron ore were first described by Thales of Miletus in the 6th century BC. e. These were purely theoretical calculations, not confirmed by experiments. Thales gave an incomprehensible explanation for the properties of the magnet, attributing to it “animation.” A century after him, Empedocles explained the attraction of iron by a magnet by certain “outflows” of some immaterial substance from it. Later, a similar explanation in a more definite form was presented in the book of Lucretius “On the Nature of Things.” There were also statements about magnetic phenomena in the works of Plato, where he described them in poetic form. Representations of the creature magnetic actions were among scientists of a later time - Descartes, Huygens and Euler, and these ideas in some respects were not too different from the ideas of ancient philosophers.
Magnetic phenomena have been used in maritime navigation since the early Middle Ages. At the end of the 12th century, in the works of the Englishman Nekam and the Frenchman Guio de Provence, the simplest compass (French boussole) was first described - a device that allows you to determine the magnetic azimuth in the sea. Although in China the compass was used for navigation even before our era. In Europe, it became widespread only in the 13th century.
The first experimenter to study magnets was Peter Peregrin from Maricourt (13th century). He experimentally established the existence of magnetic poles, the attraction of unlike poles and the repulsion of like poles. While cutting the magnet, he discovered that it was impossible to isolate one pole from the other. He carved a spheroid from magnetic iron ore and tried to experimentally show the analogy in the magnetic relationship between this spheroid and the earth. This experience was later (in 1600) reproduced even more clearly by Gilbert.
The first compasses, invented independently of each other in Asia and Scandinavia around the 11th century, came to the Mediterranean coast of Europe in the 12th century and were a board floating in a shell filled with water. Attached to one of its ends was a piece of calamite, a stone with natural magnetic properties, imported from Magnesia in Greece, where it is very common. Such a compass worked well only with slight rocking on the ship.
A). One of the first compasses, which was a board floating in a shell filled with water. A piece of lodestone was attached to one of its ends;
b). The common compass, consisting of a steel magnetic needle rotating on a point located in the center of a small round or quadrangular box ("bossola" in Italian), was most common on board early caravels.
V). A compass or dry compass with an arrow, improved in the Sagra school, was made from a cardboard disk on which a compass rose was drawn. A small magnetized steel strip was fixed under the northern point of the compass rose. This is a more accurate tool to keep you on the right course.
So was the information contained in the portolans reliable? I think it depended on the tasks assigned to them. They were quite suitable for solving “local” applied problems - getting from point A to point B. Navigation in the Mediterranean Sea was quite well studied, since it was constantly supported by large pilotage schools, such as the Genoese, Venetian or Lagos. Portolans were completely unsuitable for understanding the whole world, confusing researchers more than helping them.
It was only from the end of the 13th century that the first attempts at ocean navigation, as well as the wider use of the compass, revealed the need to actually display the coastal topography on a flat sheet of paper, indicating the winds and the main coordinates.
After the 14th century, portolans are often accompanied by rough outline drawings of the Mediterranean coast and the Atlantic coasts of Western Europe. Gradually, ships leaving for ocean voyages begin to get involved in the work of drawing up more accurate portolans and drawings.
Somewhere around the beginning of the 15th century, real navigation maps appeared. They already represent a complete set of information for the pilot: coastal topography, a list of distances, indications of latitude and longitude, landmarks, names of ports and local inhabitants, winds, currents and sea depths are indicated.
The map, the heir to the mathematical knowledge acquired by the ancients, increasingly accurate information about astronomy and thousands of years of experience in navigation from port to port, becomes one of the main fruits of the scientific thought of the discoverers: from now on, during long voyages it is necessary to compile reports necessary for a complete display of knowledge about the world. And what’s more, the first ship’s logs appeared! Of course, sea voyages have been described before, but now this is beginning to become a regular occurrence. Infante Henry was the first to introduce a mandatory ship's log for the captains of his caravels. Captains had to write down information about the shores daily, indicating coordinates - an extremely useful task for drawing up reliable maps.
Despite the desire to clarify and verify that motivated the most famous cartographers (Fra Mauro in 1457 claimed that he was unable to fit into his map all the information that he managed to collect), fantasies, legends, and fiction surrounded any cartographic work with a kind of “folklore” aura : on most maps dating before the 17th century, we see how, in place of little-known or insufficiently explored regions, images of various monsters, drawn from ancient and early Christian mythologies, appear.
Quite often, the compiler, when describing the inhabitants of remote corners, resorted to speculation. Areas explored and brought under the rule of European kings were marked with coats of arms and flags. However, magnificently painted vast compass roses could not be of any use if they were incorrectly oriented or marked in erroneous lines of “diamonds” (a primitive orientation system that predated the system of meridians and parallels). Often the cartographer's work became a real work of art. At the courts of the kings, planispheres were looked at like canvases, sailors who had embarked on long journeys could be seen behind them, monsters caused trembling, the distances traveled and intriguing names fascinated. It took a long time before the custom of making a decorative map gave way to truly useful cartography, devoid of all fiction.
This explains the distrust with which the great navigators, and first of all Christopher Columbus, treated the painted maps of the 15th century. Most sailors preferred to rely on their knowledge of winds, bottom topography, currents and observations of the celestial sphere, or tracking the movement of schools of fish or flocks of birds, in order to navigate the vast expanses of the ocean.
Undoubtedly, it was in the 15th century, thanks to the Portuguese navigators, and then the voyage of Columbus and, finally, the round-the-world voyage of Magellan in 1522, that humanity was able to test in practice the calculations of the ancient Greeks and the idea of the sphericity of the Earth. Many navigators now received concrete knowledge in practice indicating the sphericity of our planet. The curved line of the horizon, the movement of the relative height of the stars, the increase in temperature as one approaches the equator, the change of constellations in the southern hemisphere - all this made obvious a truth that contradicted Christian dogma: the Earth is a sphere! All that remained was to measure the distances that had to be covered on the open sea to get to India, in a southern direction, as the Portuguese did in 1498, or in a western direction, as Columbus seemed to do when he encountered an insurmountable obstacle on his way in 1492. the face of both Americas.
Columbus was well acquainted with the cosmographic literature of that time. His brother was a cartographer in Lisbon, and he himself tried to build a globe based on the available atlases, modern and ancient treatises on cosmography. He, however, made, following Pierre Ailly and his “Imago Mundi” (1410), a gross mistake in assessing the distance between Portugal and Asia, underestimating it (there is a hypothesis that he did this deliberately). However, he heeded the advice of eminent cartographers such as Toscanelli (who believed in a sea route to the west), Piccolomini (the future Pope Pius II) and Martin Behaim (later the author of a fairly accurate globe).
Beginning in 1435, Portuguese and Italian sailors made it a rule to sail at a distance from the African coast to avoid dangerous zones and changeable winds. The coastal area, replete with reefs and shoals, indeed presented an obvious danger of shipwreck.
However, such a significant distance from the coast that it is lost from sight presupposes the ability to navigate the open sea on a flat, monotonous space without lighthouses, limited only by the horizon line. And 15th-century sailors lacked the theoretical knowledge of mathematics and geometry necessary to accurately determine their location. As for measuring instruments, things were even worse with them. Until the 16th and 17th centuries, none of them were truly good at it. The maps, although constantly updated, had significant gaps.
To appreciate the extraordinary courage of the sailors who mastered the near and then the far Atlantic, one must remember what pitiful means they had to determine their location on the open sea. The list will be short: the sailors of the 15th century, including Christopher Columbus, had practically nothing that would help them solve the three main tasks of any navigator setting off on a long voyage: to keep a course, to measure the distance traveled, to know with accuracy their current location.
The 15th century sailor had at his disposal only a primitive compass (in various variations), a crude hourglass, error-infested maps, approximate tables of the declination of the stars and, in most cases, erroneous ideas about the size and shape of the Earth! In those days, any expedition across the oceans became a dangerous adventure, often with fatal consequences.
In 1569, Mercator compiled the first map in a conformal cylindrical projection, and the Dutchman Luca Wagener introduced the atlas. This was a major step in the science of navigation and cartography, because even today, in the twenty-first century, modern nautical maps are compiled into atlases and made in Mercator projection!
In 1530, the Dutch astronomer Gemma Frisius (1508-1555), in his work “Principles of Astronomical Cosmography,” proposed a method for determining longitude using a chronometer, but the lack of sufficiently accurate and compact clocks left this method purely theoretical for a long time. This method was called chronometric. Why did the method remain theoretical, since watches appeared much earlier?
The fact is that clocks in those days could rarely run continuously for 24 hours, and their accuracy did not exceed 12–15 minutes per day. And the watch mechanisms of that time were not adapted to work in conditions of sea motion, high humidity and sudden temperature changes. Of course, in addition to mechanical ones, in maritime practice for a long time hourglasses and sundials were used, but the accuracy of the sundial and the time to “wind” the hourglass were completely insufficient to implement the chronometric method of determining longitude.
Today it is believed that the first accurate clocks were assembled in 1735 by the Englishman John Harrison (1693-1776). Their accuracy was 4–6 seconds per day! At that time, this was simply fantastic accuracy! And what’s more, the watch was adapted for sea travel!
Ancestors naively believed that the Earth rotates evenly, lunar tables had inaccuracies, quadrants and astrolabes introduced their own errors, so the final errors in coordinate calculations amounted to up to 2.5 degrees, which is about 150 nautical miles, i.e. almost 250 km!
In 1731, the English optician John Hadley improved the astrolabe. The new device, called the octant, made it possible to solve the problem of measuring latitude on a moving ship, since now two mirrors made it possible to simultaneously see both the horizon and the sun. But the octant did not get the glory of the astrolabe: a year earlier, Hadley had designed a sextant, a device that made it possible to measure the location of a ship with very high accuracy.
The fundamental design of a sextant, i.e. a device using the principle of double reflection of an object in mirrors, was developed by Newton, but was forgotten and only in 1730 was it reinvented by Hadley independently of Newton.
The marine sextant consists of two mirrors: an index mirror and a fixed translucent horizon mirror. Light from a luminary (star or planet) falls on a movable mirror and is reflected on the horizon mirror, on which both the luminary and the horizon are simultaneously visible. The angle of inclination of the index mirror is the height of the luminary.
Since this site is about history, and not about navigation, I will not go into the details and features of various navigational instruments, but I want to say a few words about two more instruments. These are lot (lotlin) and lag (laglin).
In conclusion, I would like to briefly dwell on some historical dates in the history of development navigation in Russia.
The year one thousand seven hundred and one is perhaps the most significant date in domestic navigation, since this year Emperor Peter I issued a decree on the establishment of “Mathematical and Navigational, that is, nautical and cunning sciences of teaching.” The year of birth of the first domestic navigation school.
Two years later, in 1703, Magnitsky, a teacher at this school, compiled the textbook “Arithmetic”. The third part of the book is entitled “Generally about earthly dimensions, and what also belongs to navigation.”
In 1715, the senior school was transformed into the Naval Academy.
1725 is the year of birth of the St. Petersburg Academy of Sciences, where such luminaries of science as Leonhard Euler, Daniil Bernoulli, Mikhail Lomonosov (1711-1765) taught. For example, it was Euler’s astronomical observations and mathematical description of the motion of the planets that formed the basis for highly accurate lunar tables for determining longitude. Bernoulli's hydrodynamic studies made it possible to create perfect logs for accurately measuring the speed of a ship. Lomonosov's work concerned the creation of a number of new navigation instruments, prototypes of which are still in use today: course plotters, recorders, logs, inclinometers, barometers, binoculars...
Navigation translated from Latin means “navigation, navigation.” This is an integral part of the complex of marine sciences, which emerged from them in the process of development of navigation. This includes navigation - focusing on navigational aids, marine astronomy - which studies methods for determining the coordinates of a ship using celestial bodies; and navigation aids, with the help of which dead reckoning is carried out and the location of the vessel is determined.
The very history of people is inextricably linked with the sea and navigation. Human remains dating back more than 30,000 years have been found in the Americas, and many of these ancient people swam across the ocean. How did they do it? Thor Heyerdahl, during his ocean expeditions on prototypes of ancient ships, proved that this was possible. The first ships are known to us from ancient Egyptian records - these are quite sophisticated ships on which the Egyptians carried out brisk trade along the Nile and by sea. These records are more than 4 thousand years old. Since this ancient time, the need for navigation has already arisen.
What questions did the ancient sailors face? Yes, the same as in our time. This is determining your location and direction of travel. At first, busy sea trade routes ran along the coasts, and navigation was carried out along coastal landmarks. If they had to sail across the ocean, then before the eyes of the ancient travelers there was only one landmark - the stars. The cardinal directions were determined by the movement of the sun. And by observing the stars for a long time at night, you can identify stationary objects among them. These are the North Star in the Northern Hemisphere and the stars in the constellation Southern Cross in the Southern Hemisphere. Most likely, focusing on these stars, ancient people explored new spaces and populated continents and islands. The ancients also noticed that although the stars move, the distances between them do not change. Before people's eyes there was a stunning picture of the moving celestial sphere. Now we know that the Earth moves and we move with it. But these observations marked the beginning of astronomy and celestial navigation.
Ancient Phoenician ship. Image on the sarcophagus
The first navigation maps
In order to successfully navigate in space, people sought to build a model of this space in order to know where they were and where to go. Some peoples used an oral tradition, when information about sea routes was transmitted in the form of stories or chants. Sometimes they also used knotted writing. But even a schematic image, a plan of the area, was more clear. This is how cards began to appear. The Polynesians, who crossed the vast Pacific Ocean, had woven mats with the designation of islands and reefs. The Egyptians painted on reeds. However, these maps, despite great accuracy in describing specific areas and their features, did not provide an answer to main question- in what place in this moment is the navigator located? How long does it take him to get to the chosen port? There was already a fixed point of reference - these were the stars. I had to come up with and decide how to indicate my location on the map. But the original maps were unfortunately inaccurate, because the round surface of the Earth is difficult to plot on a map plane without distortion. Moreover, according to ancient ideas, the earth was flat, which introduced even greater inaccuracy. However, trade developed, especially strongly in the Mediterranean region. Gradually, enormous knowledge was accumulated in navigation, astronomy and other sciences, which was later collected in ancient Greece. These sciences were developed later, during the Roman Empire. The Greeks, using their observations and information collected from their predecessors, plotted the outlines of known lands on maps. To indicate the location of these lands and other objects, a coordinate grid was applied to the map. The invention of this well-known grid on maps of parallels and meridians also belongs to the ancient Greeks. The concept of latitude and longitude for determining one's location arose again in Greece as a result of constant observations of the position and height of the Sun during the day and the height of stars above the horizon at night. The measurement measure chosen was the change in the position of the Sun. Observing the luminaries, the Chaldeans divided the circle into 360 parts, where one part - a degree - was the movement of the Sun in the sky by the size of its disk. The degree was divided into 60 minutes of arc, since these people had a sexagesimal number system. This knowledge was learned and developed by the Greeks. Gradually, such concepts as horizon, ecliptic, and celestial equator entered science. Without these astronomical concepts, it is impossible to determine exact coordinates.
Modern three-dimensional star map
Already in the third century BC. The Greek scientist Eratosthenes determined not only that the Earth is round, but also very accurately calculated the circumference and radius of the earth's sphere. He used an equidistant cylindrical projection in his maps, which gave greater accuracy on maps showing small areas of the earth's surface. Another Greek scientist, Hipparchus, in the third century BC, covered the entire earth with a grid of meridians and parallels. Now it became clear in which area of the map you need to find your coordinates. A little later, the Roman geographer Marinus of Tyre compiled accurate sea maps. For some areas, it very accurately calculates longitude and latitude and plots them on a grid of parallels and meridians. His information was later used by the famous scientist Ptolemy in his works. Marinus, like Eratosthenes, even tried to depict a complete model of the Earth - a globe. His calculations and maps were so accurate that they were adopted as a basis by the Portuguese in the 15th century.
The works of a later scientist, Ptolemy, gave a huge impetus to the science of geography and navigation. Ptolemy drew a map of the world in a conical projection, with parallels and meridians; he designated a grid of coordinates, calculated in degrees, where latitudes were measured from the equator, and longitudes from the westernmost point of the then known world. He interviewed a huge number of merchants and sailors and quite accurately described the coasts and countries, even those that he had not seen. He described a huge number of new places and gave their coordinates. In addition to accurate information, he recorded people’s inventions on maps, so in his maps one can find, for example, lands inhabited by the Dog Head people and other miracles. Subsequently, after Ptolemy, nothing new was invented in cartography, and after the collapse of the Roman Empire, completely dark times began.
Ptolemy's map in modern processing. It quite accurately indicates the lands known to the Greeks at that time
Ancient navigational instruments
The very first navigational instrument was the eyes of the ancient navigator. But with the development of navigation, this was no longer enough. To accurately determine the angle of the luminaries above the horizon, special tools were required. This is how the gnomon first appeared, which was a tall pillar; the time and height of the Sun above the horizon were determined by the ratio of the lengths of the pillar and the shadow from it. The gnomon, in the form of a board with a pole on it, was first used by the Greek merchant and navigator Pytheas to determine latitude back in the 4th century BC. The merchant violated the then-existing ban and went beyond the Pillars of Hercules into the open Atlantic Ocean, where he made his observations. Despite the primitive instrument and excitement, the traveler took readings with an accuracy of several arc minutes. Later, a quadrant was used for celestial navigation observations. The quadrant was an ordinary board hewn from stone or wood. On its surface were drawn vertical and horizontal lines and a 90° arc connecting them, divided into degrees and their parts. A ruler was placed in the center of the arc and could be moved.
Quadrant
The astrolabe, which was used starting from the second century BC, became a more advanced instrument. until the 18th. The astrolabe was essentially a model of the celestial sphere with its important points, circles, poles and axis mundi, meridian, horizon, celestial equator and ecliptic. It was not easy to make observations with such a device. Observing the Sun, Moon or known stars, the ancient astronavigator brought the circles of a complex instrument into the correct position, after which, using scales graduated on the circles, he calculated the longitude and latitude of the observed body. The most famous mechanism that has come down to us is the ancient Greek device of 32 gears “Antikythera”, raised from the bottom of the sea. Based on the surviving inscriptions on it, we can conclude that this is a celestial navigation device. The mechanism could calculate the configurations of the movement of the Sun, Moon, Mars, Jupiter, Saturn, lunar and solar eclipses. The estimated time of manufacture is the period between 100 - 150 BC.
Ancient celestial navigation device
Another device that modern navigators cannot do without - a compass - was also invented in ancient times. The inventors of the compass, the Chinese, according to the entries in their books, began to use the magnetic compass not only for religious needs, but also for navigation about 300 years BC. However, copies of a compass from a later period have reached us. It looked like a magnetized spoon, with its handle pointing south. The Chinese associated each side of the world with its own color. For example, the south was associated with the color red - modern compasses follow this tradition.
Chinese compass
Pilot
Since the voyages of the Egyptians and Phoenicians, huge amounts of information have been accumulated about the coastline, ports of refuge, and anchorages. This knowledge formed the basis of maps and was later used even by Europeans in the Middle Ages. Also, ancient sailors, going out into the ocean, were faced with the phenomenon of ebb and flow. Subsequently, the knowledge was systematized, and already in the ancient Greek navigation, for example, they wrote: “The entire Indian country has a lot of rivers and a very high tide, which intensifies during the new moon and full moon for three days, and is weaker in the intermediate phases.” .
A certain difficulty in historical times was precise measurement time and distance. A water or hourglass was used to measure time, and distances were measured by eye. In Ancient Greece, a system of lighthouses was also adopted to assist captains. The Alexandria Lighthouse, 120 meters high, is very famous. Many sculptures placed on the shore also served as coastal landmarks for ships. The famous statue of the Colossus of Rhodes, 36 meters high, was visible for miles. And the entrance to large ports at night was illuminated with light - large fires.
The first seafaring schools
With the development of merchant shipping and the increase in the number of sea voyages, the need arose for the transfer of knowledge. There are no mentions of maritime schools of ancient times; most likely, knowledge was passed on orally and in a close circle. One of the ancient famous schools was the school of navigation in Polynesia. On the island of Raiatea, a place was discovered where the expansion of the Polynesians to the rest of the islands of the Pacific Ocean came from, and a place where knowledge about maritime affairs and navigation was transferred - these were the first nautical schools. Representatives of the AMC Yacht Training Center visited this sacred place on the islands. In 2012 we plan to make a second expedition there.
Tapu Tapu Marae on Raiatea Island. Dating back to the 1st millennium BC. These are the surviving remains of one of the first schools of ocean navigation. Photo by Vladimir Vatrunin.
The first textbooks for sailors were written, probably, along with the invention of writing. One of the astronomical navigation textbooks known to us was compiled by Thales of Miletus back 600 years BC. In Greece, the teaching of astronomy, including astronomy for navigation, was carried out in higher educational institutions of that time. The classical schools of navigation known to us were created much later, in the Middle Ages.
Since ships - the creations of human hands - began to plow the seas and oceans, navigators have been faced with the task of determining their own location. Huge waves, squalls and the need to maneuver on tacks, keeping a course against the wind, complicated multi-day voyages, and the ancient sailors did not have enough of a compass. Today, when the location of a ship is determined automatically thanks to GLONASS, it is difficult to imagine the position of a captain who has at his disposal only simple devices for orientation by the stars. Nevertheless, today graduates of specialized secondary and higher specialized educational institutions own all these devices.
Basic methods of maritime location
Two-coordinate determination of a vessel at (location) is carried out in seven types of ways, including:
- The oldest is visual.
- Later, but not much, is astronomical.
- Topographical-computational, that is, a method of plotting the full path of a ship on a map, indicating points of course change and calculating the distance traveled by multiplying speed by time. It was invented around the same time as the astronomical method, and is often used together with the two previous ones. Today, routine work is performed by automatic calculators;
- Radar, which allows you to combine the picture on the radar screen with a sea chart.
- Radio direction finding. Available in cases where there are signal sources on shore.
- Radio navigation, using communication means through which the navigator receives the information he needs.
- Satellite navigation method.
All methods, except the first three, were a consequence of the technological revolution that occurred in the 20th century. They would have been impossible without the discoveries and inventions made by mankind in the field of radio engineering, electronics, cybernetics and breakthroughs in the space sector. Nowadays, it is not difficult to calculate the point in the ocean where a ship is located; determining its coordinates takes a matter of seconds, and, as a rule, they are tracked continuously. Approximately the same technologies are used in aviation navigation and even in such a “mundane” area as driving a car.
Latitude
As you know, the earth is not flat, it has the shape of a somewhat flattened ball. Points on a three-dimensional figure, it would seem, should be described by three Euclidean coordinates, but two are quite enough for geographers and navigators. In order to make a topographical identification of a vessel, you need to name only two numbers, accompanied by the words “northern” (or “southern”) latitude (abbreviated as N or S) and western or “eastern” longitude (otherwise - W. d. or v.d.). These values are measured in degrees. Everything is very simple. Latitudes are calculated from the equator (0°) to the poles (90°), indicating which direction: if closer to Antarctica, then the southern latitude is indicated, and if towards the Arctic, then the northern latitude. Points of the same latitude form circles called parallels. Each of them has a different diameter - from the largest at the equator (about 40 thousand kilometers) to zero at the pole.
Longitude and length measures
Determining the location of the ship is impossible using one coordinate, so there is a second one. Longitude is a conventional number of the meridian, again indicating the direction in which the count is taken. The circle is divided into 360°, its two halves, respectively, equal to 180. The Greenwich meridian, passing through the famous British observatory, is considered to be the zero. On the other side of the planet is its antipode - the 180th. Both of these coordinates (0° and 180°) are indicated without the name of the direction of longitude.
In addition to degrees, there are also minutes - they indicate the position of objects with 60 times greater accuracy. Since all meridians have equal length, they became the measure of length for sailors. One corresponds to one minute of any meridian and is equal to 1.852 km. The metric system was introduced much later, so ship navigators use the good old English mile. Units such as cables are also applicable - it is equal to 1/10 of a mile. Which is surprising, because before the British often counted in dozens rather than tens.
Visual method
As the name implies, the method is based on what the navigator and captain, as well as other crew members on the deck or rigging, see. Previously, in the days of sailing fleets, there was a position of a forward lookout; the post of this sailor was located at the very top, in a specially fenced off place of the mainmast - the klotik. The view was better from there. Determining the ship's position based on shore objects is similar to simple method a pedestrian who knows that he needs, for example, a house on Staroportofrankovskaya street at number 12, and for accuracy there is one more search criterion - a pharmacy located opposite. For sailors, however, other objects serve as landmarks: lighthouses, mountains, islands or any other noticeable details of the landscape, but the principle is the same. You need to measure two or more azimuths (this is the angle between the compass needle and the direction to the landmark), plot them on the map and get your coordinates at the point of their intersection. Of course, such a vessel, or rather its location, is applicable only in the coastal visibility zone, and then in clear weather. In the fog, you can navigate by the sound of the lighthouse siren, and in the absence of surface signs, you can turn to the shoals in shallow water, measuring the depth with a lot.
Astronomy in naval service
The most romantic location method. Around the 18th century, sailors together with astronomers invented a sextant (sometimes it is called a sextant, that’s also correct) - a device with which you can make a fairly accurate two-coordinate determination of a ship based on the position of luminaries in the sky. Its design is complicated at first glance, but in reality you can learn how to use it quite quickly. Its design has optical system, which should be aimed at the Sun or any star, having previously installed the device strictly horizontally. For precise guidance, two mirrors are provided (large and small), and the angular elevation of the luminary is determined using the scales. The direction of the device is set by a compass.
The creators of the device took into account the centuries-old experience of ancient navigators, who relied only on the light of the stars, moon and sun, but created a system that simplifies both learning navigation and the location process itself.
Calculation
Knowing the coordinates of the starting point (exit port), travel time and speed, you can plot the entire trajectory on the map, noting when and by how many degrees the course was changed. This method could be ideal when direction and speed are independent of current and wind. The unevenness of the course and errors in the lag indicator also affect the accuracy of the obtained coordinates. The navigator has at his disposal a special ruler for drawing parallel lines on the map. Determination of maneuverable elements of a sea vessel is carried out using a compass. Usually, at the point of change of direction, the true position is determined using other available methods, and since it, as a rule, does not coincide with the calculated one, a kind of squiggle is drawn between the two points, vaguely reminiscent of a snail and called a “discrepancy”.
Currently, automatic computers are installed on board most ships, which, taking into account the input speed and direction, perform integration over the time variable.
Using radar
Now there are no blank spots left on sea maps, and an experienced navigator, seeing the outlines of the coast, can immediately tell where the watercraft entrusted to his care is located. For example, noticing the light of a lighthouse on the horizon even in fog and hearing the muffled sound of its siren, he will immediately say something like: “We are on the traverse of the Vorontsovsky fire, a distance of two miles.” This means that the ship is at a specified distance on a line connecting at right angles the course and the perpendicular direction to the lighthouse, the coordinates of which are known.
But it often happens that the shore is far away, and there are no visible landmarks. Previously, in the days of the sailing fleet, the ship was “put into a drift”, collecting sails; sometimes, if the capricious nature of the dominant winds and the unpredictability of the bottom (reefs, shoals, etc.) were known, then they anchored and “waited at sea for weather ”, that is, clarification. Now there is no need for such a loss of time, and the navigator can see the coastline by looking at the locator screen. Identifying a vessel using radar is not a difficult task if you have the qualifications. It is enough to combine the image on the navigation device and the map of the corresponding area, and everything will immediately become clear.
Direction finding and radio navigation method
There is such an amateur radio game - “Fox Hunt”. By using homemade devices its participants are looking for a “fox” hidden in the bushes or behind the trees - a player who has a working low-power radio station. In the same way, that is, by taking bearings, counterintelligence services identify residents of foreign intelligence services (at least, this was the case before) at the time they sent spy reports. A location requires at least two directions intersecting at the location point, but most often there are more. Since there is always some scatter in the readings, and it is impossible to achieve absolute accuracy, the bearings do not converge at one point, but form a kind of multilateral figure, in the geometric center of which one should, with a high degree of probability, assume one’s location. Landmarks can be pilot signals specially created on the shore (for example, in lighthouses) or emissions from radio stations whose coordinates are known (they are plotted on a map).
Coastal course correction using radio communications is also widely applicable.
By satellites
Today it is almost impossible to get lost in the ocean or sea. The movement of moving objects at sea, in the air and on land is monitored by the Russian Cospas and the international Sarsat. They work on the Doppler principle. It is necessary to install a special beacon on the ship, but the safety and confidence in the successful outcome of the voyage is worth the money spent on it. Direction finders are located on geostationary (“hanging” above a fixed point on the earth’s surface) satellites that make up the system. This service is provided free of charge and, in addition to the rescue function, performs a navigational search for the vessel’s location. The satellite navigation method gives the most accurate coordinates, its use does not cause difficulties, and navigators in our technological age use it most often.
Additional parameter - download
The navigability of a vessel and its possible course are significantly affected by its draft. As a rule, the more part of the hull is immersed in water, the higher the level of its hydrodynamic resistance. There are, however, exceptions, for example, in nuclear submarines the underwater speed exceeds the surface speed, and a special bow “bulb”, if completely recessed, creates the effect of better streamlining. One way or another, the speed of movement (stroke) is affected by the mass of cargo (cargo) in holds or tanks. To assess this value, sailors use special marks with marks on the bow, stern and side parts of the hull (at least six scales). These marks are applied individually, each vessel has its own, there is no uniform standard. The technique for determining the weight of cargo on board a ship, called “draft survey,” is based on the use of “draft marks” and is used for many purposes, in particular navigation. The depth of the bottom does not always allow a ship to navigate a specific fairway, and the navigator must take this factor into account.
All that remains is to wish at least those who are going on a voyage.
Just two centuries ago, working with complex navigation instruments was the job of highly trained professionals. Nowadays, any owner of an advanced mobile phone can determine its place on the surface of the earth in a matter of seconds.
At the first stage of navigation, boats and ships did not move far from the shore. Crossing a river or lake, taking a shortcut, or going around a region occupied by a hostile tribe by sea along the shore is a practical and understandable matter, but setting sail on an unknown sea-ocean is a different caliber, you must admit.
The first navigational landmarks were signs visible from the water: Pomors, for example, erected stone crosses, the crossbars of which were oriented in the north-south direction. And at night, you can use the simplest beacons - signal fires, lit to facilitate orientation or warn of danger (shoal, reef, strong current, etc.).
Lighthouses are mentioned already in Homer’s Iliad, and the most famous lighthouse - the Alexandria lighthouse - appeared in the 3rd century BC. e. on the island of Pharos, at the mouth of the Nile on the approach to Alexandria. Its height was 120 m. On the upper platform a huge fire burned around the clock, the light of which was reflected by a complex system of mirrors and was visible, according to historians, at a distance of 30 miles (about 55 km). Another example of a navigation sign from antiquity is the statue of Athena, erected in the 5th century BC. e. on the Acropolis: it was made of bronze, and in the rays of the sun it was far visible from the sea.
With the growing scale of navigation, the need arose to systematize and transfer navigational knowledge. And now the ancient Greeks created periplus - descriptions of coastal voyages in different areas, where everything was included, from the weather to a description of the coastline and the customs of native tribes. The oldest periplus that has come down to us is that of the Carthaginian Hanno; it dates back to the turn of the 6th–5th centuries BC. e. In fact, periplus is an ancient version of modern sailing directions. Illiterate peoples also had their own directions: they passed on such knowledge in the form of oral tales and even songs. Only in the 13th century did more accurate portolan maps appear with marked compass lines diverging from individual points, the so-called wind roses, which were used to plot courses.
How many feet under the keel?
To determine, or rather, identify the location of the ship, you can also use the depth obtained using an echo sounder. This method is used when, during a voyage, it is not possible to carry out observation for a long time - say, poor visibility or the satellite navigation system receiver is faulty - and there are doubts about the correctness of the dead reckoning.
In this case, as soon as at least one known and mapped landmark is discovered on the shore, a bearing is immediately taken to it and at the same time the depth is measured with an echo sounder. After correcting the compass bearing by correcting the compass, the reverse true bearing is plotted on the map and then they are looked at where, within the drawn line, the depth obtained from the echo sounder will be. You can also measure the depth with a hand survey - in this case, a soil sample will also be obtained, which will make it easier to identify the place. Where the depth and type of soil coincide with the bearing is the current location of the ship.
The first documentary evidence of the use of depth measurements to determine the location dates back to the time of Herodotus - ancient Greek sailors knew that if, when sailing to Egypt in the Mediterranean Sea, the depth under the keel decreases to certain value, then there is a day's journey left to Alexandria.
Angles and distances
Ship coordinates can be of two types: relative (relative to some well-known landmark) and absolute (geographic latitude and longitude). The latter began to be used not so long ago, and relative coordinates have been used since time immemorial, because they are simply necessary even during a short voyage along the coast - they allow you to come to the right place and do it safely, without running aground or reefs and without missing “ the right cape." The methods of determining a place used by ancient sailors, in some cases, have survived to this day without any changes.
The simplest and most ancient method is visual determinations: by bearings (this is the compass direction, or point of reference, in which a certain object is visible from us), distances and horizontal angles between directions to coastal landmarks. There are several options for this method of determining your location.
On two bearings. A simple way to determine your location using landmarks that are reliably identifiable and marked on the map used when sailing (they are selected using a map, directions and the “Lights and Signs” manual). In this case, it is necessary to select landmarks with a bearing difference of at least 30° and no more than 150°, so as not to obtain bearing intersections at sharp angles (this increases the error). Direction finding is carried out quickly, starting from landmarks located directly ahead or close to it (the bearing on them changes more slowly), and at night - from lights (beacons) that have a longer period. The measured bearings are corrected to the true ones by correction of the compass used for measurements (the correction is the algebraic sum of declination and magnetic deviation) and plotted in the opposite direction on the map (the so-called reverse true bearing, differing from the true one by 180°). The navigator is located at the place where they intersect.
On three bearings. The method is similar to the previous one, but provides greater reliability and accuracy - by about 10–15%. Usually the return bearings laid down in this case do not intersect at one point, but form a triangle. If it is small, with sides less than half a mile (about 0.9 km), then the ship is considered to be at its center or closer to the smallest side, and if large, the measurements must be repeated.
Based on two bearings measured at different times to one landmark (cruise bearing). The calculations involved in this case are beyond the scope of this article, but a detailed explanation can be found in any available navigation textbook.
By distance. In this case, circles with a radius equal to the distance to the landmark are drawn on the map from landmarks. The observer is located at the intersection of the circles. If a landmark with a known height is visible from the base or edge of the water, then the distance to it is determined by a special formula based on the vertical angle measured by a sextant, and the height of the observer’s eye above the water level is neglected. Naturally, the accuracy of measurements increases if there are three reference points.
Today, radar stations are also used as reference points for determining location - here, a place is most often determined by distances measured by a radar; this is more accurate than measuring radar bearings. In general, there are no fundamental differences between conventional visual and radar observation methods. You just need to be good at “reading” the image on the radar screen in order to identify the landmarks used for observation as accurately as possible. After all, an ordinary map is “drawn” as if from above, and a map on a radar screen is drawn with the help of a radar beam, “drawing” the map at sea level. One mistake in identifying a coastal landmark can (and has) led to serious accidents.
Looking for Greenwich
Until the end of the 19th century, different places served as the starting point for longitude, for example, the island of Rhodes, the Canary Islands, and the Cape Verde Islands. After Pope Alexander VI approved in 1493 the line dividing the spheres of influence of Spain and Portugal, which ran 100 leagues west of the Azores, many cartographers measured longitude from it. And the Spanish King Philip II in 1573 ordered that longitude be measured from the meridian of the city of Toledo on all Spanish maps. An attempt to establish a single reference point for longitude for Europe was made in 1634, but failed. In 1676, the Greenwich Observatory began work, and in 1767, the “Nautical Almanac” was published in Britain (with meridians counted from Greenwich), which was used by sailors from different countries. By the beginning of the 1880s, 12 European countries were already using the Greenwich system on their nautical charts. Finally, as a result of the International Meridian Conference of 1884, it was decided to base everything on Greenwich. By the way, at the conference other options for the starting point were proposed - the islands of Ferro and Tenerife, the Pyramid of Cheops or one of the temples of Jerusalem.
Guiding Stars
Landmarks are useless on the open sea. But already in ancient times, sailors traveled across the Indian Ocean, and then crossed the Atlantic and Pacific from one continent to another. Such voyages became possible thanks to a new science - nautical astronomy. Realizing that the Sun is constantly moving across the sky, and the stars are not scattered across the sky in disorder, sailors soon learned to navigate by them.
Their special attention was attracted by a remarkable star in the constellation Ursa Minor. Its position in the sky was practically unchanged; it was a kind of heavenly beacon by which one could navigate at night. In ancient times, the star was called Phoenician (it is believed that it was the Phoenicians who were the first to learn to navigate by the stars), Guiding, and then it became Polar. Moreover, in ancient times they learned not only to determine the direction by the North Star, but also, based on its height above the horizon, to calculate the time remaining until the end of the voyage.
Around the 6th–5th centuries BC. e. on ships they began to use a gnomon - a vertical pole, by the ratio of the length and the cast shadow of which they determined the time and calculated the angular height of the Sun above the horizon, which made it possible to calculate the latitude (but first, of course, it is necessary to calculate “noon” - the shortest length of the shadow on a sunny day, then Yes, when using a gnomon, it cannot be moved for at least a day). It is believed that it was first used for navigation purposes by the Greek merchant Pytheas from Massilia (present-day Marseille), who in the 4th century BC. e. violated the ban and went beyond the Pillars of Hercules, going north. Since the gnomon is useless while moving, he landed on the shore and there determined the latitude with an accuracy of several minutes. In a similar way, the Vikings controlled their location at the desired parallel in the sea.
Around the 3rd–2nd centuries BC. e. the astrolabe appears (from the Greek words άστρου - “star” and λαβή - “taking, grasping”), for now in a land-based, very cumbersome and complex version. The real marine, or, as it is also called, “new,” astrolabe was invented only at the turn of 1000 AD. e. It was a ring with a device for hanging, where a plumb line from the hanging point fixed vertical line- the horizontal line and center were determined from it. A rotating alidade sight with diopters (small holes) at the ends rotated around the central axis, and degree divisions were applied to the ring on the alidade side. The observations were carried out by three people: one held the instrument by the ring, the second measured the height of the luminary, standing at the same time with his back to the Sun and turning the alidade so that the upper sighting thread cast a shadow on the lower one (this meant that the sighting device was exactly aimed at the Sun), and the third sailor was filming Countdown. At night, the altitude of the North Star was determined using the astrolabe.
In the 15th–16th centuries, new navigational instruments appeared - the astronomical ring and the city pole. The first (one of the varieties of astrolabe) instead of an alidade had a conical hole; the sun's rays entering it were reflected in the form of a bunny on a degree scale placed on the inside of the ring - the place of the bunny corresponded to the height of the Sun. Gradstock (Jacob's staff, astronomical ray, golden rod, geometric cross, etc.) - the most convenient tool for pumping - two mutually perpendicular rods: a long (80 cm, rod) and a short (bar), the latter fit tightly to the long one at a right angle and could slide freely along it. Markings were applied to the rod, diopters were applied to the ends of the bar, and a front sight for the eye was applied to the end of the rod. It was possible to determine the height of the star by looking into the eye spot, moving the block and achieving such a position that the star was visible in the upper diopter, and the horizon in the lower one. To observe the Sun, the navigator stood with his back to it and moved the bar until the shadow of its upper end fell on a small screen installed instead of a front sight on the end of a long rod (the middle of the screen was directed to the line of the visible horizon). With one short bar it was impossible to measure all the heights of the luminaries, so several bars, usually three, were attached to the city rod to measure heights: 10–30°, 30–60° and more than 60°. The hail rod was used only at sea, the accuracy was not
above 1–2°.
Finally, in the 18th century, one of the most famous navigational instruments appeared - the sextant, the successor of the gradstock. After a series of successive “mutations” - the Davis quadrant (1594), the John Hadley octant (1731), which gave an error of only 2-3 minutes - John Campbell’s device was born (1757), who increased the sector in the Hadley octant from 45 to 60 °: so the octant became the sextant, or sextant (from the Latin sexstans, the sixth part of a circle). In a sextant, the central diopter is replaced by a mirror, which allows you to sight two objects located along the different directions, say, the horizon and the Sun (star). Due to its greater measurement accuracy, the sextant replaced other goniometer instruments on ships more than 200 years ago and continues to serve as the main hand-held instrument.
"Killer" longitude
If navigators figured out latitude back in ancient times, the problem of determining the longitude of a place at sea turned out to be more serious, and no satisfactory solution could be found until the end of the 18th century. Let's say Columbus returned home after discovering America and discovered that the error in the longitude measurements on his ship was as much as 400 miles. The French hydrographer Yves-Joseph de Kerguelen did not escape the mistake either. He set off in January 1772 from Port Louis in Mauritius without a chronometer, and therefore the archipelago discovered and named after him was plotted on the map with an error of 240 miles (about 450 km)! It was not possible to determine longitude by celestial bodies (as is the case with latitude): when moving west or east, the picture of the starry sky practically does not change.
Of course, the principle of determining longitude was known to Hipparchus - the difference in longitude of two points on the earth’s surface corresponds to the difference in local time when the moment of any one event is simultaneously observed at two given points. Hipparchus proposed to consider such an event an eclipse of the Moon, which occurred at the same moment in time for all its observers on Earth. But eclipses happen rarely; fixing an eclipse is also not easy, since the boundaries of the shadow are very unclear.
It was also impossible to implement on ships on the high seas the principle of determining longitude using the “lunar distance” method, proposed in the middle of the 15th century by Professor of the University of Vienna Johann Muller, better known under the pseudonym Regiomontanus. He published the famous “Ephemerides”, containing complete and accurate astronomical information, including data for determining latitude and longitude at sea using the “lunar distance” method. Using the tables he compiled for any angle measured in degrees and minutes, it was possible to directly obtain the sine value. This meant that by measuring the angle of the luminary with an accuracy of 1", it was possible to determine the latitude with an accuracy of two kilometers. However, the goniometric instruments known at that time did not provide such accuracy, and even those that existed could not be used during sea motion. Finally, in 1530, the astronomer and mathematician Gemma Frisius proposed a method for determining longitude based on the use of watches: you had to take a watch with local time from the point of departure and “store” this time during the voyage, and, if necessary, calculate longitude - using an astronomical method to determine local time and, comparing it with the “stored” one, get the desired longitude. The advice is good for everyone, but there were simply no accurate mechanical watches at that time, and a clock error at the latitude of the equator of just a minute gave an error in longitude of 15 miles.
For example, in 1707, also as a result of a navigator’s error on the rocks near the Isles of Scilly, 21 ships of Admiral Claudisley Shovel’s squadron were killed - about 2,000 people drowned along with the admiral! One of the reasons for this was the inability to determine longitude. On July 8, 1714, the British Parliament adopted a resolution, which, among other things, guaranteed a reward for the one who solved the problem of determining longitude at sea: with an accuracy of at least 0.5° or 30 miles - 20,000 pounds (today this is more than half a million pounds). Two years later, a special prize for the “determiner of longitude” was established in France.
The British Council on Longitude received a lot of applications - many dreamed of getting rich, but not a single one was approved. There were also funny things. Mathematicians Humphrey Ditton and William Whiston proposed this method back in 1713: on the busiest sea routes, anchor ships at certain intervals, measuring their geographic coordinates. Exactly at midnight local time on the island of Tenerife, ships had to fire a volley of mortars upward in such a way that the shells exploded exactly at an altitude of 2000 m. Passing ships had to measure the bearing of such a signal and range, thereby determining their place. There were plenty of hunters to “master the budget” in those years too.
And the majority of the amount due for solving the longitude problem was received in 1735–1765 by a 72-year-old mechanic, the son of a village carpenter, John Harrison, nicknamed John Longitude, who created a high-precision chronometer clock that made it possible to reliably “keep time” (they no longer there was a pendulum, and there were balancers, and they could work on board the ship) and, accordingly, measure longitude quite accurately. In France, the royal prize "for the chronometer" was awarded to Pierre Leroy, the royal watchmaker. Chronometers even received a second name - “longitude clocks”. Their mass production began only at the turn of the 18th–19th centuries, which can be considered the time for solving the “longitudinal” problem.
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