How to determine the location in the waters of the ocean. Determining the location of the vessel. Vessel definition: methods. Longitude and measures of length
The history of navigation, and, consequently, piracy, is closely connected with the history of navigation and cartography. The history of navigation, and, therefore, of piracy is closely connected with the history of navigation and cartography. When did nautical charts appear? How did people in ancient times navigate the sea? Answering these questions is not as easy as it might seem at first.
Of course, sailing along the coast does not require maps or any special means of orientation. Enough to explore the coastline. Most of the ancient navigators did just that, which, by the way, greatly simplified the equipment of the vessel: it was not necessary to have a significant supply of provisions and fresh water. And if so, it would seem that navigation devices should have appeared quite recently. But the whole point is that long voyages were made already millennia 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 "trace" in the places of residence of the Mayans, Incas, Aztecs and other tribes. 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 through 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 voyages across the ocean, far from the coast, where the only reference could be the starry sky, the sun and the moon. Today it is believed that the first navigators used entrete orientation (i.e., by eye) according to the heavenly bodies. East and west were determined by sunrise and sunset, and north and south were determined by the position of the North Star or stars from the constellation of the Southern Cross.
Ancient sailors often took bird cages with them.. If the ship was lost at sea, then the sailors periodically released a bird (often a black crow). If the bird returned back, then there is no land nearby, but if it flew away in a certain direction, then the ship followed it, completely trusting the bird: it means that the bird is flying to land. This technique was especially popular among the Scandinavians.
Map of Ptolemy (II century AD) Thanks to a survey of merchants and navigators, as well as reading all the reports of ancient travelers, he managed to draw a map of the world in a conic projection, with parallels and meridians
This probably gave impetus to the appearance of portolans, although I would not dare to name the exact time of the birth of these cards, even approximately. What are portolans?
Mediterranean navigators felt the need to have accurate guides that would help to trade at very great distances from their home ports. Due to the inconsistency of the winds, it was not always possible to move away from the coast in the Mediterranean Sea, since the capricious weather of the Mediterranean made these travels very dangerous. Even in the Middle Ages, most movement in this region was still within sight of the coast.
At the time of the Cretan, Phoenician and Egyptian navigators, many ships plowed the Mediterranean, but due to the need to stay on the coast, 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 whole months.
Thus, in ancient times and in the early Middle Ages, the first maps became more guides for moving from port to port than an accurate description of the coast. The pilots were more interested in the exact knowledge of the coastline, the presence of shoals, the constancy of the winds, the location of port cities, than in the scientific idea of the Earth's surface. Without a compass to steer the ship, without any means of determining latitude (especially when clouds covered the sky), the only way out for the pilot - whether he was Egyptian, Greek, Venetian or Catalan - was to draw a map! He needed a portulan (from the Italian "portolano", that is, "guide to the ports"). In other words, a guidebook was required that combined information about the coasts, ports, winds, depths and currents collected by navigation professionals since antiquity, with the help of which trade was carried out in the Mediterranean ports in the Middle Ages.
The first information about the directly nautical charts of Marina 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.
The maps of that period differed little from very schematic plans, and the larger the territories were depicted, the less accurate the maps were: after all, the Earth is round, and large sections 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 Erastofen who, observing the midday height of the sun in Alexandria and Aswan, 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 counting 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 problem in geometry about the similarity of two triangles, but in those days it was a miracle.
To better read the map you need a location. Lotsiya (from the Dutch loodsen - to guide the ship) - a guide for swimming in a certain water basin with a detailed description of its navigational features. The oldest of the surviving sailing directions is the Greek Skylak (VI century BC), which described in detail the distances between ports, their equipment, anchorages, navigational dangers ...
In general, long before medieval cosmographers, man made attempts to depict the Earth in the form of a globe. Such were the already mentioned Eratosthenes and Marinus of Tyre, such was Ptolemy: they boldly drew maps based on their own calculations. When Palla Strozzi brought to Constantinople a complete copy of Ptolemy's Geography, his translation into Latin became, as they would say today, one of the "bestsellers" of the emerging book printing! Ptolemy was a Greek scholar from Alexandria who lived from about 90 to 160 AD. Thanks to a survey of merchants and navigators, as well as reading all the reports of ancient travelers, he managed to draw a map of the world in a conic projection, with parallels and meridians, that is, a grid of coordinates calculated in degrees, where latitudes were measured from the equator, and longitudes were measured from the westernmost point 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 height of stars and determining latitude.
As it has already become clear, the concepts of geographic latitude and longitude for an unambiguous determination of location on the surface of the Earth 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 given 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 purpose.
In 1342, the mathematician Levi Ben Gershon first described the device, later called the "Levi's Wand". 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 with respect to the horizon. Thanks to the tables of Zacuto and Visigno (1465), used simultaneously, it was possible to determine your location with an accuracy of 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 in order to form an idea of the world, drawing information from the crude empiricism of the Portolans. Thus, little by little, sailors get the opportunity to enjoy all the fruits of the scientific knowledge of the Earth. In place of descriptions, even fairly accurate, but always incomplete, come 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 navigation "devices" can be considered solarstein (translated from Old Norse - "sun stone"). With it, 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, various views and ideas.
Today it is believed that for the first time the properties of magnetic iron ore were described by Thales of Miletus in the 6th century BC. e. These were purely theoretical calculations, not confirmed by experiments. Thales gave an obscure explanation of the properties of the magnet, attributing to it "animation." A century after him, Empedocles explained the attraction of iron by a magnet by some kind of “outflow” from it of some immaterial substance. Later, a similar explanation in a more definite form was presented in Lucretius' book On the Nature of Things. Statements about magnetic phenomena were also in the writings of Plato, where he described them in poetic form. The scientists of a later time, Descartes, Huygens and Euler, had ideas about the essence of magnetic actions, and these ideas in some respects did not differ too much from the ideas of the ancient philosophers.
In maritime navigation, magnetic phenomena have been used since the early Middle Ages. At the end of the 12th century, in the writings of the Englishman Nekame and the Frenchman Gio de Provence, the simplest compass (fr. 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 XIII century.
The first experimenter who took up magnets was Peter Peregrinus of Maricourt (XIII century). He empirically established the existence of magnetic poles, the attraction of opposite poles and the repulsion of like ones. Cutting the magnet, he discovered the impossibility of isolating one pole from the other. He carved a spheroid from magnetic iron ore and tried to experimentally show an analogy in the magnetic relation between this spheroid and the earth. This experience was later (in 1600) even more clearly reproduced 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 plank floating in a shell filled with water. Attached to one of its ends was a piece of calamite, a stone with natural magnetic properties brought from Magnesia in Greece, where it is very common. Such a compass worked well only with slight pitching on the ship.
a). One of the first compasses, which was a plank floating in a shell filled with water. A piece of magnetic stone was attached to one of its ends;
b). An ordinary compass, consisting of a steel magnetic needle rotating on a point located in the center of a small round or square box (in Italian - "bossola"), was most common on board the first caravels.
v). A compass or a dry compass with an arrow, improved at the Sagra school, was made from a cardboard disk on which a wind rose was drawn. A small magnetized steel strip was fixed under the northern point of the wind rose. This is already a more accurate tool to keep the right course.
So was the information contained in the portolans reliable? I think that it depended on the tasks assigned to them. For solving "local" applied problems - getting from point A to point B - they were quite suitable. Navigation in the Mediterranean was fairly well understood, as it was constantly supported by major pilot schools, such as the Genoese, Venetian or Lagos. For the knowledge of the whole world, portolans were completely unsuitable, more confusing researchers than helping them.
Only from the end of the 13th century, the first attempts at ocean navigation, as well as the wider use of the compass, revealed the need for a real display on a flat sheet of paper of the relief of the coast, indicating the winds and the main coordinates.
After the 14th century, portolans are often accompanied by rough contour drawings of the Mediterranean coast and the Atlantic coasts of Western Europe. Gradually, ships leaving for ocean voyages begin to be included in the work of compiling more accurate portolans and drawings.
Somewhere by the beginning of the 15th century, real navigational charts appeared. They already represent a complete set of information for the pilot: coast relief, 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 successor to the mathematical knowledge acquired by the ancients, the ever more accurate knowledge of astronomy, and thousands of years of experience in navigating from port to port, becomes one of the main fruits of the scientific thought of the pioneers: from now on, during long voyages, it is required to draw up reports necessary for a complete display of knowledge about the world. And what's more, the first ship's logs appeared! Of course, sea travel has been described before, but now it is starting to become a regular occurrence. The first to introduce a mandatory log book for the captains of his caravels was Infante Heinrich. The captains had to record daily information about the coast with the indication of coordinates - a matter extremely useful for compiling reliable maps.
Despite the desire to clarify and verify that moved the most famous cartographers (Fra Mauro in 1457 claimed that he could not fit into his map all the information that he managed to collect), fantasies, legends, fiction surrounded any cartographic work with a kind of “folklore” halo : on most maps dated before the 17th century, we see how, in place of little-known or insufficiently explored regions, images of various monsters appear, drawn from ancient and early Christian mythologies.
Quite often, the compiler, describing the inhabitants of remote corners, resorted to speculation. Areas that were explored and fell under the rule of European kings were marked with coats of arms and flags. However, the magnificently painted vast wind roses could not be useful if they were incorrectly oriented or marked in erroneous lines of "diamonds" (a primitive system of orientation that preceded the system of meridians and parallels). Often the work of a cartographer became a real work of art. At the courts of kings, planispheres were looked at like canvases, sailors set off on long journeys were guessed behind them, monsters caused shivers, the distances traveled and intriguing names fascinated. It took a long time before the custom of making a map decorative gave way to really useful cartography, devoid of all fiction.
This explains the distrust with which the great navigators, and primarily Christopher Columbus, treated the painted maps of the 15th century. Most sailors preferred to rely on their knowledge of the 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 mankind was able to practically test the calculations of the ancient Greeks and ideas about the sphericity of the Earth. Many navigators now in practice received specific knowledge testifying to the sphericity of our planet. The curved line of the horizon, the shifting of the relative heights of the stars, the rise in temperature as we approached the equator, the change of constellations in the southern hemisphere - all this made obvious the truth that contradicted Christian dogma: the Earth is a ball! It remained only to measure the distances that had to be covered on the high seas in order to reach India, in a southerly direction, as the Portuguese did in 1498, or in a western direction, as it seemed to Columbus, when in 1492 he met an insurmountable obstacle in his path in face of the 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 on the basis of available atlases, modern and ancient treatises on cosmography. True, he made, following Pierre Ayi and his Imago Mundi (1410), a gross mistake in estimating the distance between Portugal and Asia, underestimating it (there is a hypothesis that he did this intentionally). 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 Beheim (later the author of a fairly accurate globe).
Beginning in 1435, Portuguese and Italian sailors made it a habit to sail at a distance from the African coast to avoid dangerous areas and changeable winds. The coastal zone, 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 in a flat, uniform space without lighthouses, limited only by the horizon line. And the sailors of the 15th century 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 really good at what they did. The maps, although constantly updated, had significant gaps.
To appreciate the extraordinary courage of the navigators who explored the near and then the far Atlantic, one must remember what miserable means they had at their disposal to determine their location on the high seas. 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 going on a long voyage: to keep a course, measure the distance traveled, know with accuracy their present location.
The 15th-century sailor had only a primitive compass (in various variations), a crude hourglass, error-ridden maps, approximate tables of declination of the luminaries and, in most cases, erroneous ideas about the size and shape of the Earth! In those days, any expedition across the ocean became a dangerous adventure, often fatal.
In 1569, Mercator drew up the first map in a conformal cylindrical projection, and the Dutchman Luke Wagener introduced an atlas. This was a major step in the science of navigation and cartography, because even today, in the twenty-first century, modern nautical charts are compiled in atlases and made in the 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, because the clock appeared much earlier?
The fact is that watches in those days could rarely run without stopping during the day, and their accuracy did not exceed 12-15 minutes a day. And the clock mechanisms of that time were not adapted to work in conditions of sea rolling, high humidity and sudden changes in temperature. Of course, in addition to mechanical ones, sand and sundials were used in maritime practice for a long time, but the accuracy of the sundial, the winding time of the hourglass were completely insufficient for the implementation of the chronometric method for determining longitude.
Today it is believed that the first accurate clock was assembled in 1735 by the Englishman John Harrison (1693-1776). Their accuracy was 4-6 seconds per day! At that time it was simply fantastic accuracy! And what's more, the watch was adapted for sea travel!
Ancestors naively believed that the Earth rotated uniformly, lunar tables were inaccurate, quadrants and astrolabes introduced their own error, so the final errors in calculating coordinates were 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 line 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 position of the ship with very high accuracy.
The fundamental device of the sextant, i.e., a device that uses the principle of double reflection of an object in mirrors, was developed by Newton, but was forgotten and only in 1730 was reinvented by Hadley independently of Newton.
The marine sextant consists of two mirrors: an index mirror and a stationary translucent horizon mirror. Light from a luminary (star or planet) falls on a movable mirror, is reflected on the horizon mirror, on which both the luminary and the horizon are visible at the same time. The angle of inclination of the pointing mirror is the height of the luminary.
Since this site is about history and not about navigation, I will not go into 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 price Russia.
The year 1701 is perhaps the most significant date in Russian navigation, since this year Emperor Peter I issued a decree on the establishment of "Mathematical and Navigational, that is, nautical artful sciences of learning." The year of birth of the first domestic navigational school.
Two years later, in 1703, the teacher of this school, Magnitsky, compiled the textbook Arithmetic. The third part of the book is entitled "Generally about the earthly dimension, and even belongs to navigation."
In 1715, the senior classes of the school were transformed into the Naval Academy.
1725 is the year of birth of the St. Petersburg Academy of Sciences, where such luminaries of science as Leonard 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 of high-precision lunar tables for determining longitude. Bernoulli's hydrodynamic studies made it possible to create perfect logs for accurately measuring the speed of a vessel. Lomonosov's works dealt with the creation of a number of new navigational instruments, the prototypes of which are still used today: course plotters, recorders, logs, inclinometers, barometers, binoculars...
Two centuries ago, working with complex navigational instruments was the lot of high professionals. Nowadays, any owner of an advanced mobile phone can determine his 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 coast. Crossing a river or lake, shortening the path, or bypassing the land occupied by a hostile tribe by sea along the coast is a practical and understandable matter, but setting sail on an unknown sea-ocean is another calico, you must agree.
Signs visible from the water became the first navigational landmarks: Pomors, for example, put up stone crosses, the transverse bars 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 warning of danger (stranded, reef, strong current, etc.).
Lighthouses are already mentioned in Homer's Iliad, and the most famous lighthouse, Alexandria, appeared in the 3rd century BC. e. on the island of Pharos, at the mouth of the Nile on the way to Alexandria. Its height was 120 m. A huge bonfire burned around the clock on the upper platform, 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 an ancient navigation sign 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, it became necessary to systematize and transfer navigational knowledge. And now the ancient Greeks create peripluses - descriptions of coastal voyages in different areas, where everything was entered, from the weather to a description of the coastline and the customs of the native tribes. The oldest periplus that has come down to us is the Carthaginian Hanno, it dates from the turn of the 6th-5th centuries BC. e. In fact, the periplus is an ancient version of the modern sailing direction. Illiterate peoples also had their own pilotage: they transmitted such knowledge in the form of oral stories and even songs. Only in the 13th century did more accurate portolan charts appear with plotted 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 place of the ship, you can also use the depth obtained with the help of an echo sounder. This method is used when, during a voyage, for a long time it is not possible to perform an observation - say, poor visibility or a satellite navigation system receiver is faulty - and there are doubts about the correctness of the calculation.
In this case, as soon as at least one known and mapped landmark opens on the coast, a bearing is immediately taken on 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 look at where the depth obtained from the echo sounder will be within the drawn line. You can also measure the depth with a hand lot - in this case, a soil sample will also be obtained, which will facilitate the identification of the place. Where the depth and type of soil coincide with the bearing - the current position of the ship.
The first documentary evidence of the use of depth measurements to determine the location dates back to the time of Herodotus - the ancient Greek sailors knew that if, when sailing to Egypt in the Mediterranean Sea, the depth under the keel decreases to a certain value, then a day's journey remains to Alexandria.
Angles and distances
Ship coordinates can be of two types: relative (relative to some well-known landmark) and absolute (geographical latitude and longitude). The second began to be used not so long ago, and relative coordinates were used already in 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 not missing " desired cape. The methods of determining the place used by ancient sailors, in some cases, have survived to this day without any changes.
The simplest and oldest way is visual definitions: by bearings (this is the compass direction, or rhumb, in which a certain object is visible from us), distances and horizontal angles between directions to coastal landmarks. There are several options for this way to determine your location.
On two bearings. A simple way to determine the location using landmarks that are reliably identifiable and marked on the map used when sailing (they are selected using a map, sailing directions and the Lights and Signs manual). At the same time, it is necessary to choose landmarks with a bearing difference of at least 30° and no more than 150° in order not to get bearing intersections at sharp angles (this increases the error). Direction finding is carried out quickly, starting from landmarks located directly on the course 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 the correction of the compass used for measurements (the correction is the algebraic sum of declination and magnetic deviation) and plotted on the map in the opposite direction (the so-called reverse true bearing, which differs from the true one by 180 °). At the place of their intersection is the navigator.
On three bearings. The method is similar to the previous one, but gives greater reliability and accuracy - by about 10–15%. Usually, the reverse 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 it is considered that the vessel is in its center or closer to the smallest side, and if it is large, the measurements must be repeated.
According to 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 of them can be found in any available navigation textbook.
By distance. In this case, circles are drawn from the landmarks on the map with a radius equal to the distance to the landmark. At the intersection of the circles, the observer is located. If a landmark with a known height is visible from the base or the water's edge, then the distance to it is determined by a special formula according to 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 with the presence of three landmarks.
Today, radar stations are also used as reference points for determining the location - here, most often, the place is determined by the distances measured by the radar, this is more accurate than measuring radar bearings. In general, there are no fundamental differences between conventional visual and radar methods of observation. You just need to be good at “reading” the image on the radar screen in order to identify the landmarks used for the observation as accurately as possible. After all, an ordinary map is “drawn” as if with a view from above, and a map on a radar screen is “drawn” with the help of a radar beam “drawing” a map at sea level. One mistake in recognizing a landmark can (and has) led to serious accidents.
Looking for Greenwich
Until the end of the 19th century, different places served as a reference point for longitude, for example, the island of Rhodes, the Canary Islands, the Cape Verde Islands. After the approval in 1493 by Pope Alexander VI of the line of division of the spheres of influence of Spain and Portugal, which took place 100 leagues west of the Azores, many cartographers counted longitude from it. And the Spanish king Philip II in 1573 ordered on all Spanish maps to count longitude from the meridian of the city of Toledo. An attempt to establish a single longitude reference point for Europe was made in 1634, but failed. In 1676, the Greenwich Observatory began work, and in 1767, the Nautical Almanac (with meridian readings from Greenwich) was published in Britain, which was used by sailors from different countries. By the beginning of the 1880s, 12 European states were already using the Greenwich system on their charts. Finally, based on the results of the International Meridian Conference of 1884, it was decided to count everyone from Greenwich. By the way, other variants of the starting point were also proposed at the conference - the islands of Ferro and Tenerife, the pyramid of Cheops or one of the temples of Jerusalem.
guiding stars
Landmarks are useless on the high seas. But already in ancient times, navigators 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 scattered across the sky by no means in disorder, navigators 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 celestial 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 first learned to navigate by the stars), Guiding, and then it became Polar. Moreover, in ancient times they learned not only to determine the direction of the North Star, but also, based on its height above the horizon, calculate the time remaining until the end of the voyage.
Approximately in the VI-V 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, you need to calculate "noon" - the shortest length of the shadow for a sunny day, then eat when using a gnomon, it cannot be moved for at least a day). It is believed that for navigational purposes it was first used by the Greek merchant Pytheas from Massilia (now Marseille), who in the 4th century BC. e. broke the ban and went beyond the Pillars of Hercules, going north. Since the gnomon is useless on the move, he landed on the shore and there determined the latitude with its help with an accuracy of several minutes. In a similar way, the Vikings controlled their location on the desired parallel in the sea.
Approximately in the III-II centuries BC. e. an astrolabe appears (from the Greek words άστρου - “star” and λαβή - “taking, grasping”), while in a land-based, very cumbersome and complex version. A real sea, or, as it is also called, “new”, astrolabe was invented, but only at the turn of 1000 AD. e. It was a ring with a hanging device, where a plumb line from the suspension point fixed a vertical line - it was used to determine the horizontal line and the center. A rotary alidade with diopters (small holes) at the ends rotated around the central axis, and degree divisions were applied on the ring from 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, while turning 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 took pictures Countdown. At night, the height of the North Star was determined by the astrolabe.
In the 15th-16th centuries, new navigational instruments appeared - the astronomical ring and the gradstock. The first (one of the varieties of the astrolabe), instead of an alidade, had a conical hole, the sun's rays falling into it were reflected in the form of a hare on a degree scale placed on the inner side of the ring - the place of the hare corresponded to the height of the Sun. Gradstock (Jacob's staff, astronomical ray, golden rod, geometric cross, etc.) - the most convenient tool for rolling - two mutually perpendicular rods: a long one (80 cm, rod) and a short one (bar), the latter fit snugly against the long one at a right angle and could move freely along it. Divisions were applied on the stem, diopters were applied at the ends of the bar, and a front sight for the eye was applied at the end of the stem. It was possible to determine the height of the star by looking into the eye fly, moving the bar 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 him and moved the bar until the shadow of its upper end fell on a small screen, which was installed instead of a front sight at the end of a long rod (the middle of the screen was directed to the line of the visible horizon). With the help of one short bar, it was impossible to measure all the heights of the luminaries, so several bars, usually three, were attached to the hailstone to measure heights: 10–30°, 30–60°, and more than 60°. Gradstock 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 heir to the gradstock. After a series of successive "mutations" - Davis's quadrant (1594), John Hadley's octant (1731), which gave an error of only 2-3 minutes, - John Campbell's device was born (1757), which increased the sector in the Hadley octant from 45 to 60 °: so the octant became a sextant, or sextant (from the Latin sexstans, a sixth of a circle). In the sextant, the central diopter is replaced by a mirror, which allows you to view two objects at once located in different directions, say, the horizon and the Sun (star). The sextant, due to the greater measurement accuracy, replaced other goniometric 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 in ancient times, then the problem of determining the longitude of a place in the sea turned out to be more serious, and no satisfactory solution could be found until the end of the 18th century. For example, returning home after the discovery of America, Columbus discovered that the error in the measurements on his ship of longitude was as much as 400 miles. The French hydrographer Yves-Joseph de Kerguelen did not escape the mistake. He set off in January 1772 from Port Louis in Mauritius without a chronometer, and therefore the archipelago discovered and named after him was mapped with an error of 240 miles (about 450 km)! It was not possible to determine longitude from the celestial bodies (as in the case of latitude): when moving west or east, the picture of the starry sky practically does not change.
Of course, the principle of determining longitude was already known to Hipparchus - the difference in longitudes of two points on the earth's surface corresponds to the difference in local time when simultaneously observing the moment of any one event at two given points. Hipparchus suggested that such an event be considered an eclipse of the Moon, which occurred at the same time for all his observers on Earth. But eclipses are rare, and fixing an eclipse is also not an easy task, since the boundaries of the shadow are very fuzzy.
It was impossible to implement on ships on the high seas the principle of determining longitude using the method of “lunar distances”, proposed in the middle of the 15th century by the professor of the University of Vienna, Johann Müller, 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 distances" method. According to the tables compiled by him, for any angle measured in degrees and minutes, it was possible to directly obtain the value of the sine. This meant that, by measuring the angle of the star 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 give such accuracy, and even those that were could not be used for sea rolling. Finally, in 1530, the astronomer and mathematician Gemma Frisius proposed a method for determining longitude based on the use of clocks: it was necessary to take a clock with local time from the point of departure and “keep” this time while sailing, and if necessary, calculate longitude - to determine local time astronomically and, comparing it with the “stored”, get the desired longitude.Advice is good for everyone, but then there was simply no accurate mechanical clock, and the error of the clock at the latitude of the equator in just a minute gave an error in longitude of 15 miles.
For example, in 1707, also as a result of a navigational error on stones near the Isles of Scilly, 21 ships of the squadron of Admiral Claudisley Shovel died - about 2000 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 passed a resolution that, among other things, guaranteed a reward to those who solve the problem of determining longitude at sea: with an accuracy of at least 0.5 ° or 30 miles - 20,000 pounds (today it is more than half a million pounds). Two years later, a special prize for the “determinant of longitude” was also established in France.
The British Longitude Council received a lot of applications - many dreamed of getting rich, but not a single one was approved. There were also curiosities. As far back as 1713, mathematicians Humphrey Ditton and William Whiston proposed this method: on the busiest sea routes, set ships at anchor at certain intervals, measuring their geographical coordinates. Exactly at midnight local time on the island of Tenerife, the ships were supposed to fire a volley of mortars upwards in such a way that the shells exploded exactly at an altitude of 2000 m. The ships passing by had to measure the bearing for such a signal and range, thereby determining their place. Hunters "master the budget" was enough in those years.
A received most of the amount due for solving the problem of longitude, in 1735-1765, the 72-year-old mechanic, the son of a rural carpenter, John Harrison, nicknamed John Longitude, who created a high-precision chronometer clock that made it possible to reliably “keep time” there was a pendulum, but there were balancers, and they could work on board the ship) and, accordingly, accurately measure longitude. In France, the royal prize "for the chronometer" was awarded to Pierre Leroy, the royal watchmaker. Chronometers even got a second name - "longitude hours". Their mass production began only at the turn of the 18th-19th centuries, which can be considered the time for solving the “longitudinal” problem.
Imagine that the ship is on the high seas. It is surrounded on all sides only by sky and water; no shore or island is visible around. Swim wherever you want! when there were no Earth satellites or radio communications? If the captain of a ship does not know how to make astronomical observations, he will not be able to determine the location of his ship. There is only one way out - to surrender "to the will of the waves." But in this case, the ship is doomed to almost certain death.
Parallels and meridians
The entire surface of the globe is covered with a series of imaginary mutually perpendicular lines, which are called parallels and meridians, and their combination makes up the so-called degree grid. The line that is formed by a section of the globe by a plane passing through the center of the Earth perpendicular to the axis of its rotation is called equator. The equator is equally distant from both the South and North Poles. longitude called the distance in degrees from some "zero" meridian to the west (western longitude) and to the east (eastern longitude). Longitude is measured from 0 to 180 degrees along the earth's equator. latitude called the distance in degrees from the equator to some point lying either between the North Pole and the equator (North latitude), or between the South Pole and the Equator (South latitude). Latitude is measured from 0 to 90 degrees. The introduction of the concept of longitude and latitude is of great importance: it made it possible to mark, to fix the location of one or another distant expedition in little-known areas of the earth's surface, or to determine the location of a ship on the high seas. Latitude and longitude at the same time serve as the basis of any geographical map. The longitude and latitude of any place are determined by astronomical observations. Safe navigation in the open seas and oceans was based on these observations.Nautical mile
The coordinates of the location of the ship on the high seas were determined only by astronomical observations. From here the value is taken nautical mile- the basic unit of measurement for the distances traveled by a ship. A nautical mile corresponds to a change in the position of any luminary by exactly one minute of arc. For clarity, let's imagine that the Sun is in the meridian and it is observed from two ships. If, in this case, the difference in the heights of the Sun is one minute of arc, then, consequently, the distance between these ships will be equal to one nautical mile.Nautical Science
The lack of precise knowledge about the movement of celestial bodies and the inability to make astronomical observations have long served as a huge obstacle to the development of navigation. Thus, there was an urgent need to improve navigation science and nautical astronomy. The English Parliament in 1714 awarded a prize of 20,000 pounds to anyone who would offer a method for determining the longitude of a place at sea, even with an accuracy of half a degree. Many people have been working on this issue for decades. It was tempting to become the author of such an important invention, it was no less tempting to be entitled to such a solid prize. More than half a century has passed, and the task set by the Parliament has not yet been solved.Method for determining longitude
Finally, in 1770 the watchmaker Arnold proposed to Parliament longitude method In the open sea. This method was based on the transportation of chronometers. The first chronometers suitable for this purpose were built Harrison back in 1744. This method was as follows. Going to sea from some port, the longitude of which is known, they use a correctly running chronometer, which shows the time of the starting point. While on the high seas, travelers determined the local time by observing the heavenly bodies. From the comparison of local time with the reading of the chronometer, the time difference was found. This time difference is the difference between the longitudes of the starting point and the point of location. Using this method, in 1843, the longitude of the Pulkovo Astronomical Observatory was determined with great accuracy (up to a hundredth of a second).The position of a point on the earth's surface
So, the position of a point on the earth's surface determined by longitude and latitude. The magnitude of the meridian arc from the earth's equator to a given location determines its latitude. The magnitude of the arc of the equator from the zero (main) meridian to the meridian of a given place determines its longitude. The main, or zero, meridian is considered to be the one that passes through the famous Greenwich Astronomical Observatory, located in England, not far from London. To determine the longitude of any point on Earth, it is enough to know the clock readings at that place and at Greenwich at the same moment.. This is based on the fact that the difference in the readings of clocks at the same moment in any two places is equal to the difference in the longitudes of these places. The whole circle, as we know, is 360 degrees, which corresponds to 24 hours; One hour corresponds to 15 degrees, and one minute of time corresponds to 1/4 degree, or 15 minutes of arc. So, for example, the difference between clock readings for the same time in Leningrad and Greenwich is 2 hours and 1 minute. Therefore, Leningrad is 30 degrees and 15 minutes east of Greenwich. Or, as they say, Leningrad has 30 degrees and 15 minutes of east longitude. Latitude is the arc of a meridian from the earth's equator to a specific location. Or, in other words, the latitude of a point on the earth's surface is equal to the angular height of the pole above the horizon. Therefore, to determine the latitude of the location of the ship in the sea, a series of astronomical observations were carried out. These observations were usually made with a goniometric instrument called sextant. During the day, with the help of this instrument, the height is measured, and at night the height of the Moon, Polaris or some other star. In connection with the invention of radio, determining longitude at sea is much easier.International Time Commission
A special International Time Commission, which conditionally divided the entire globe into nine zones. A special scheme has been developed, obligatory for all countries of the world, for the transmission of accurate, so-called rhythmic, time signals based on observations of stars. Rhythmic time signals were transmitted several times a day by radio from nine of the most powerful radio stations at various hours of Greenwich time. The most famous of these radio stations were AyRugby in England and the Comintern Station in Moscow. Therefore, at whatever point on the globe the ship was, with the help of radio, at least from one of the nine stations, it received a signal of the exact time and, consequently, knew the clock reading for the main meridian at the given moment. Then, with the help of astronomical observations, the exact local time was determined and, by the difference of these two times, the longitude of the ship's location.On the movement of continents
famous geologist Wegener once suggested that continents several are moving. This movement, in his opinion, is so significant that it can be detected with the help of astronomical observations in a relatively short time. From this it followed that the longitude of the place also changes, and this change can be noticed over a relatively short period of time. The assumption made by Wegener aroused great interest among specialists. A commission of representatives of the International Astronomical and International Geodetic Unions has developed a project for determining world longitudes by radio every few years. For the first time this determination of longitudes was carried out in 1926. Three groups of observatories were chosen as the peaks of the main polygon. The first group - in Algeria (Africa), Zi-Ka-Wei (China) and San Diego (California); the second group - in Greenwich, Tokyo, Vancouver and Ottawa (Canada); the third group - Manilla (Philippines), Honolulu (Sandwich Islands), San Diego and Washington. These observatories had a connection with a number of observatories working on the service of time. At the same time, longitudinal observations were carried out by many observatories and temporary stations. The work was carried out successfully. Radio signals were received over great distances. So, for example, radio signals from Bordeaux (France) stations were received in America and Australia. Longitudes were determined with exceptionally high accuracy, and the error of closing the main polygon did not exceed 0.007 seconds. In 1933, this enterprise was repeated on an even grander scale, and the technical level of the work carried out was even higher than in 1926. As a result, it turned out that the assumption made by Wegener was not fully confirmed. If there is a secular displacement of America relative to Europe, then its magnitude, in any case, cannot exceed three centimeters per year. It is interesting, however, to note that from a comparison of the reception of time signals systematically carried out by the observatories of Europe and America, a noticeable (about 18 meters) fluctuation in longitude with a period of about 11 years, almost coinciding with the period of sunspots, was found.The main tasks of sailors going on a long voyage are to determine their exact location, measure the distance traveled and maintain the desired course. These simple goals at all times contributed to the successful completion of the journey, and navigational instruments help sailors in this.
Navigational instruments of antiquity
In order to appreciate the courage and bravery of the brave Vikings, Phoenicians and other discoverers, it is worth saying that they had only heavenly bodies and a primitive compass at their disposal.
Navigational instruments of antiquity
The navigators of the Age of Discovery had many more navigational tools for successful sailing. But this list is also small:
- marine chronometer - before the invention of mechanical watches, an hourglass was used to measure time and longitude with a chronometer on ships, measuring 1 hour, 30 minutes and 30 seconds;
- laglin - used to calculate the speed of the vessel, a device with a plank (lag) on a long line with knots located at a distance of 14, 46 meters;
- Lotlin - a device, which is a heavy lead weight, fixed on a line with tied knots, was used to determine the depth of the sea;
- quadrant - a primitive device that determines the position of the ship by the stars, was used before the invention of the astrolabe;
- astrolabe - a tool that allows you to calculate the coordinates of latitude by the height of the celestial bodies;
- sextant - an improved astrolabe, allows you to determine not only latitude, but also longitude with a fairly high accuracy;
- compass - used to set and maintain the course of the vessel.
Modern navigation instruments
At present, even small vessels are equipped with modern equipment, which allows to determine the location of the vessel, the sailing time, the wind course and other indicators with high accuracy. This data ensures fast and safe sailing.
The magnetic compass allows you to determine the course of the vessel and the direction of the wind. On large ships, as a rule, two compasses are installed. The main compass is located on the upper bridge as far as possible from the ship's metal plating.
Modern navigation instruments According to it, the captain sets the course of the vessel and finds the direction of the nearest objects on land. The steering compass is located in the wheelhouse and serves to maintain a given direction.
The mechanical log calculates the ship's speed and distance travelled. Usually the laglin reel is located at the stern. The counter flow of water rotates the blades of the lag, lowered into the water. The speed of the vessel depends on the speed of rotation. Laglin data is transmitted to an electric meter, which calculates the speed of the vessel and the number of miles traveled.
Hand lots are still used on ships to measure shallow depths. They are very easy to use and do not require much maintenance. It is a marked lotlin with a cast-iron or lead weight suspended at the end. At the bottom of the weight there is a recess filled with a mixture of chalk, lard and softened soap. When hitting the ground, particles remain on the base of the weight, which can be used to determine the nature of the surface of the seabed.
- hydroacoustic lots for measuring depths up to 2 thousand meters. They work on the principle of measuring the time of passage of ultrasonic waves emitted by a vibrator to the seabed and back. As a rule, vibrators - receivers and emitters are made of cobalt, nickel or iron.
Radio navigation beacons and direction finders work on the principle of reflecting radio waves from obstacles that appear on the way. They are excellent assistants in establishing the location of the vessel and the coastline in conditions of poor visibility.
Also, all ships going to sea have all the necessary tools for laying a route on navigation charts:
- compasses;
- parallel rulers;
- protractors and protractors.
In the other, it is important to choose the most profitable path and stick to it, constantly monitoring your location. This is where navigation helps people.
Ancient sailors tried to navigate near the coast and the location of the vessel was determined by coastal landmarks. The brave Phoenicians and Vikings, sailing far from the coast, were guided by the sun and stars. In the XI century. a compass appeared, but the magnetic needle at high latitudes did not point to the geographical north, but to the magnetic pole, which did not coincide with the north pole. This means that the higher the latitudes in which the ships sailed, the greater the error in the compass readings. The compass was far from a universal means of orientation. In the middle of the XVI century. the outstanding Flemish cartographer G. Mercator calculated the coordinates of the magnetic pole, proposed a new principle for compiling maps in a conformal cylindrical projection. Since then, all nautical charts have been compiled in this projection.
Currently, the direction of the vessel's movement is determined by a magnetic compass (taking into account magnetic declination) or by a gyrocompass. The gyrocompass is arranged according to the principle of a top and is rotated by an engine with a frequency of 300,000 revolutions per minute. Like any top, it has the property of maintaining a given position of the axis in space, for example, the direction from north to south.
When a ship is on the high seas, its course and distance traveled are constantly plotted on the map. Such accounting of the rate is called reckoning, and the rate is reckonable. The result of the navigator's work is called laying (the ship's course on the map).
Only close to the coast using a lighthouse or a direction finder (a device for determining the angular directions to external landmarks: coastal or floating objects, celestial bodies, etc.) can the navigator accurately name the ship's coordinates. It determines the direction to two landmarks, the position of which is known from the map. Lines are drawn from these landmarks on the map, and the point of their intersection will be the location of the vessel at sea.
Away from the coast, the navigator uses navigational instruments. Vessel speed and distance traveled are measured using a log. Logs are hydrodynamic and hydrostatic. A hydrodynamic lag is a turntable (screw) that is pulled on a cable behind the stern of the ship. Usually the log is connected to a rev counter installed on the bottom of the vessel. The faster the ship goes, the faster the log rotates, and the counter shows a greater number of revolutions, and the value of the ship's speed is indicated on its dial.
The hydrostatic log perceives the force of water pressure. A tube is lowered into the water, bent at the end. The tube opening faces forward. The flow of water running on the ship creates pressure. The greater the speed, the greater the pressure. The pressure value is used to determine the speed of the vessel.
Measuring the ship's speed in knots is associated with the use of the first simple log, similar to a float. He was thrown from the ship on a rope, divided into parts by knots. The number of knots that “ran out” from the ship in half a minute corresponded to the number of nautical miles (1111.852 km) covered by the ship per hour.
However, the log does not give a very accurate idea of the ship's speed, because it cannot take into account the speed and direction of currents, wind, and factors that affect the ship's drift. Sailors need not a reckonable, but a true course of the ship, so the reckonable course is corrected by astronomical observations using a sextant (or sextant) - a goniometric reflective instrument for measuring the heights of celestial bodies above the horizon or the angles between objects visible on the shore. The device of the sextant is as follows: a telescope and two mirrors are attached to the bronze sector, which is approximately 1/6 of the circle (the name of the device comes from the Latin word sextantis - “sixth”), and two mirrors (to reflect the rays of light from the heavenly body). The sector has divisions - degrees and minutes - for angular measurements.
When determining the location of a ship or aircraft by the sun or stars, a sextant usually measures the heights of several celestial bodies above the line of the visible horizon. Then a number of corrections are made to the result obtained, taking into account, for example, a decrease in the visible horizon, etc. Finally, corrections to denumerable coordinates are determined (most often graphically) using the formulas of nautical and aviation astronomy.
With the development of radio technology, radio communications came to the aid of ship navigation. Radio beacons, the location of which is precisely known, continuously send radio signals. They are received by a ship direction finder - a special radio receiver, with the help of which the bearing is determined - the angle between the meridian on which the ship is located and the direction to the source of radio waves. When determining the position of the vessel, the bearings of two radio stations (radio beacons) are taken into account.
In the interests of navigation, radar is also used (see Radar), which allows you to "see" in the dark and fog, determine the distance and bearing to the coast or to the ship with which you need to disperse at sea.
The location of the vessel can also be specified by the bottom topography shown on the map. For this, an ultrasonic device is used - an echo sounder (see Acoustics, acoustic technology). By measuring the time of passage of an ultrasonic pulse to the seabed and back, the device determines the depth, and the auto-recorder draws a depth curve - the bottom topography. The navigator compares the image on the map with the readings of echo sounders.
An important role is played by navigation technology in aviation, helping to drive aircraft. In front of the pilot on the dashboard, among the many different instruments, there are also navigational ones. This is an altimeter, the device of which is based on the same principles as a barometer that responds to pressure changes. The pressure decreases with altitude, and the navigator compares the pressure on the ground with the readings of the altimeter. So you can find out the approximate flight altitude. The true flight altitude is determined by a radio altimeter - a small radar. It sends radio pulses to the ground and receives them back. The speed of the radio wave is known - 300,000 km / s, and the device determines the flight altitude in time from the moment of sending and until the return of the pulse. The altitude meter is a manometer that measures the pressure of the oncoming air flow. With altitude, it decreases, and the device shows a lower speed. But the speed indicator automatically takes this change into account, and as a result, its arrow points to the true airspeed. The direction of flight can be judged by the readings of the gyrocompass.
