Navigation devices and instruments. What instruments helped ships sail in the past? A device that allows a sailor to determine coordinates

The art of driving a ship along the shortest route from port to port is called navigation. In other words, navigation is a way of plotting a ship’s course from the point of departure to the destination, monitoring the course, and, if necessary, adjusting it.

On the navigation bridge there are instruments and devices necessary for steering the ship. Navigation instruments - compasses, gyroazimuths, automatic plotters, logs, lots, echo sounders, sextants and other devices, are designed to determine the location of the vessel and measure individual elements of its movement of the vessel.

Compasses

A compass is the main navigation device used to determine the course of a ship and to determine directions (bearings) to various objects. Magnetic and gyroscopic compasses are used on ships.

Magnetic compasses are used as backup and control devices. According to their purpose, magnetic compasses are divided into main and traveling compasses.

The main compass is installed on the upper bridge in the center plane of the ship, so as to provide a good overview over the entire horizon (Fig. 3.1). Using an optical system, the image of the card scale is projected onto a mirror reflector installed in front of the helmsman (Fig. 3.2).

Rice. 3.1. Main magnetic compass

A traveling magnetic compass is installed in the wheelhouse. If the main compass has a telescopic reference transmission to the helmsman's post, then a traveling compass is not installed.

Rice. 3.2. Magnetic compass reflector

The magnetic needle on a ship is affected by the ship's magnetic field. It is a combination of two magnetic fields: the Earth's field and the ship's iron field. This explains that the axis of the magnetic needle is located not along the magnetic meridian, but in the plane of the compass meridian. The angle between the planes of the magnetic and compass meridians is called deviation.

The compass kit includes: a bowl with a card, a binnacle, a deviation device, an optical system and a direction finder.

Lifeboats use a lightweight, small-sized compass that is not permanently fixed (Fig. 3.3).

Rice. 3.3. Boat magnetic compass

Gyrocompass is a mechanical indicator of the direction of the true (geographical) meridian, designed to determine the course of an object, as well as the azimuth (bearing) of the oriented direction (Fig. 3.4 - 3.5). The principle of operation of the gyrocompass is based on the use of the properties of the gyroscope and the daily rotation of the Earth.

Rice. 3.4. Modern gyrocompass

Gyrocompasses have two advantages over magnetic compasses:

• they show the direction to the true pole, i.e. to the point through which the Earth’s axis of rotation passes, while a magnetic compass points in the direction of the magnetic pole;
• they are much less sensitive to external magnetic fields, for example, those fields created by ferromagnetic parts of the ship's hull.

The simplest gyrocompass consists of a gyroscope suspended inside a hollow ball that floats in a liquid; the weight of the ball with the gyroscope is such that its center of gravity is located on the axis of the ball in its lower part when the axis of rotation of the gyroscope is horizontal.

Rice. 3.5. Gyrocompass repeater with direction finder mounted on pelorus

The gyrocompass may produce measurement errors. For example, a sudden change in course or speed causes a deviation, and it will exist until the gyroscope processes such a change. Most modern ships have satellite navigation systems (such as GPS) and/or other navigation aids that transmit corrections to the built-in gyrocompass computer. Modern designs of laser gyroscopes do not produce such errors, since instead of mechanical elements they use the principle of optical path difference.

The electronic compass is built on the principle of determining coordinates through satellite navigation systems (Fig. 3.6). How the compass works:

1. Based on signals from satellites, the coordinates of the satellite navigation system receiver are determined;
2. the moment in time at which the coordinates were determined is recorded;
3. a certain period of time is waited;
4. the location of the object is re-determined;
5. Based on the coordinates of two points and the size of the time interval, the movement speed vector is calculated:
   • direction of movement;
   • movement speed.

Rice. 3.6. Electronic compasses

Echo sounder

The navigation echo sounder is designed to reliably measure, visually represent, register and transmit to other systems data on the depth under the keel of the vessel (Fig. 3.7). The echo sounder must function at all ship speeds from 0 to 30 knots, in conditions of strong aeration of water, ice and snow slush, crushed and broken ice, in areas with sharply changing bottom topography, rocky, sandy or muddy soil.

Rice. 3.7. Sonar indicator

Hydroacoustic echo sounders are installed on ships. The principle of their operation is as follows: mechanical vibrations excited in the vibrator-emitter propagate in the form of a short ultrasonic pulse, reach the bottom and, reflected from it, are received by the vibrator-receiver.

Echo sounders automatically indicate the depth of the sea, which is determined by the speed of sound propagation in water and the time interval from the moment the pulse is sent to the moment it is received (Fig. 3.8).

Rice. 3.8. How the echo sounder works

The echo sounder must provide measurement of depths under the keel in the range from 1 to 200 meters. The depth indicator must be installed in the wheelhouse, and the recorder must be installed in the wheelhouse or chartroom.

To measure depths, a manual lot is also used in cases of a ship running aground, sounding depths at the side while moored at the berth, etc.

The hand lot (Fig. 3.9) consists of a lead or cast iron weight and a lotline. The weight is made in the shape of a cone with a height of 25 - 30 cm and a weight of 3 to 5 kg. A recess is made in the lower wide base of the weight, which is lubricated with grease before measuring the depth. When the lot touches the seabed, soil particles stick to the solid oil, and after the lot is lifted, one can judge from them the nature of the soil.

Rice. 3.9. Hand lot

The breakdown of the lotline is made in metric units and is designated according to the following system: flag dukes of various colors are woven over tens of meters; Each number of meters ending with the number 5 is indicated by a leather stamp with hatchets.

In each five, the first meter is indicated by a leather mark with one prong, the second by a mark with two prongs, the third by three prongs and the fourth by four.

Lag

Around the end of the 15th century. A simple speed meter - a manual lag - became famous. It consisted of a wooden plank with a lead weight in the shape of 1/1 circle, to which a light cable was attached, with knots at regular intervals (most often 7 m). To measure the speed of sailing ships sailing in those days, the log, as an approximately constant mark on the surface of the water, was thrown overboard and an hourglass was turned, measuring a certain length of time (14 s). While the sand was falling, the sailor counted the number of knots that passed through his hands. The number of knots obtained during this time gave the ship's speed in nautical miles per hour. This method of measuring speed explains the origin of the expression "knot".

A log is a navigation device for measuring the speed of a ship and the distance it has traveled. On sea vessels, mechanical, geomagnetic, hydroacoustic, induction and radio Doppler logs are used. There are:

• relative lags, which measure speed relative to water; And
• absolute lags, measuring speed relative to the bottom.

Hydrodynamic lag is a relative lag, the action of which is based on measuring the pressure difference, which depends on the speed of the vessel. The basis of the hydrodynamic log consists of two tubes located under the bottom of the vessel: the outlet of one tube is directed towards the bow of the vessel; and the outlet of the other tube is flush with the casing. Dynamic pressure is determined by the difference in water heights in the tubes and is converted by lag mechanisms into indications of the ship's speed in knots. In addition to speed, hydrodynamic logs show the distance traveled by the ship in miles.

Induction lag is a relative lag, the operating principle of which is based on the relationship between the relative speed of a conductor in a magnetic field and the electromotive force (EMF) induced in this conductor. The magnetic field is created by the electromagnet of the log, and the conductor is sea water. When the ship moves, the magnetic field crosses stationary areas of the aquatic environment, and an emf is induced in the water, proportional to the speed of the ship's movement. From the electrodes, the EMF enters a special device that calculates the speed of the vessel and the distance traveled.

Hydroacoustic log is an absolute log that works on the principle of an echo sounder. There are Doppler and correlation hydroacoustic logs.

Geomagnetic lag is an absolute lag based on the use of the properties of the Earth's magnetic field.

Radiolag is a log whose operating principle is based on the use of the laws of radio wave propagation.

In practice, lag readings are noted at the beginning of each hour and, from the difference in readings, the voyage S in miles and the ship's speed V in knots are obtained. The lags have an error, which is taken into account by the lag correction.

Radio navigation devices

A ship's radar station (radar) is designed to detect surface objects and the shore, determine the location of the vessel, ensure navigation in narrow spaces, and prevent ship collisions (Fig. 3.10).

Rice. 3.10. Radar screen

Radar uses the phenomenon of reflection of radio waves from various objects located along the path of their propagation, thus, the phenomenon of echo is used in radar. The radar contains a transmitter, a receiver, an antenna-waveguide device, and an indicator with a screen for visual observation of echo signals.

The operating principle of the radar is as follows. The station's transmitter produces powerful high-frequency pulses of electromagnetic energy, which are sent into space in a narrow beam using an antenna. Radio pulses reflected from any object (ship, high bank, etc.) return in the form of echo signals to the antenna and enter the receiver. Based on the direction of the narrow radar beam that is currently reflected from the object, the bearing or heading angle of the object can be determined. By measuring the time interval between sending a pulse and receiving the reflected signal, you can obtain the distance to the object. Since the antenna rotates during radar operation, the emitted pulse oscillations cover the entire horizon. Therefore, an image of the ship’s surroundings is created on the ship’s radar display screen. A central luminous dot on the radar indicator screen marks the vessel's position, and a luminous line extending from this point shows the vessel's heading.

The image of various objects on the radar screen can be oriented relative to the center plane of the vessel (heading stabilization) or relative to the true meridian (north stabilization). The “visibility” range of a radar reaches several tens of miles and depends on the reflectivity of objects and hydrometeorological factors.

Ship radars make it possible to determine the course and speed of an oncoming vessel in a short period of time and thus avoid a collision.

Rice. 3.11. ARPA screen

All ships must provide radar plotting on the radar screen; for this purpose, they are equipped with an automatic radar plotting system (ARPA). ARPA processes radar information and allows you to produce (Fig. 3.11):

• manual and automatic target acquisition and tracking;
• displaying on the screen an indicator of vectors of relative or true movement of targets;
• identifying dangerously approaching targets;
• indication on the display of movement parameters and elements of target convergence;
• replaying the maneuver with course and speed for safe divergence;
• automated solution of navigation problems;
• displaying content elements of navigation maps;
• determination of the coordinates of the vessel's location based on radar measurements.

An automatic information system (AIS) is a marine navigation system that uses mutual exchange between ships, as well as between the ship and the coast service, to transmit information about the call sign and name of the ship for its identification, coordinates, information about the ship (size, cargo, draft, etc. ) and its voyage, movement parameters (course, speed, etc.) in order to solve problems of preventing ship collisions, monitoring compliance with the navigation regime and monitoring ships at sea.

Electronic chart navigation information systems (ECDIS) are an effective means of navigation, significantly reducing the load on the watch officer and allowing him to devote maximum time to monitoring the environment and making informed decisions on ship control (Fig. 3.12).

Rice. 3.12. ECDIS

Main capabilities and properties of ECDIS:

• carrying out preliminary installation;
• checking the route for safety;
• conducting executive laying;
• automatic ship control;
• display of “dangerous isobath” and “dangerous depth”;
• recording information in an electronic journal with the possibility of further playback;
• manual and automatic (via Internet) proofreading;
• giving an alarm when approaching a given isobath or depth;
• day, night, morning and twilight palettes;
• electronic ruler and fixed marks;
• basic, standard and full display load;
• an extensive and complementary database of offshore facilities;
• tide base at more than 3000 points in the World Ocean.

A satellite navigation system is a system consisting of ground and space equipment designed to determine location (geographic coordinates), as well as movement parameters (speed and direction of movement, etc.) for ground, water and air objects (Fig. 3.13) .

Rice. 3.13. GPS indicator

GPS is a global navigation satellite positioning system called Global Position System. The system includes a constellation of low-orbit navigation satellites, ground-based tracking and control equipment, and a wide variety of devices used to determine coordinates. The principle of determining one’s place on the earth’s surface in the global positioning system is to simultaneously measure the distance to several navigation satellites (at least three) - with known parameters of their orbits at each moment in time, and calculate one’s coordinates using the changed distances.

Navigation tools

A navigation sextant is a goniometric instrument (Fig. 3.14) that serves:

• in nautical astronomy - to measure the heights of luminaries above the visible horizon;
• in navigation - to measure angles between earthly objects.

Rice. 3.14. Sextant

The word "sextan" comes from the Latin word "Sextans" - the sixth part of the circle.

A marine chronometer is a high-precision portable watch that allows you to obtain fairly accurate Greenwich time at any time (Fig. 3.15).

Rice. 3.15. Chronometer

The ship's time is determined by the meridian of the ship's location and is most often adjusted at night by the watch officer. So, for example, when changing longitude by 15° to the east, the clock is moved 1 hour forward, and when changing longitude by 15° to the west, the clock is moved back 1 hour.

In order to have an accurate and uniform time indication in the engine room, crew mess, cabins, lounges, bars, galley, an electric clock is installed, adjusted from the main clock located on the bridge.

Rice. 3.16. Spacer tool

The spacer tools include (Fig. 3.16):

• measuring compass - for measuring and plotting distances on the map;
• parallel ruler - for drawing straight lines on the map, as well as lines parallel to a given direction;
• navigation protractor - for constructing and measuring angles, courses and bearings on a map.

In addition, on the bridge there are magazines, folders with documentation, navigation maps, mandatory reference books and manuals, etc. (Fig. 3.17).

Rice. 3.17. Documentation

GPS

lines

Navigators' assistants

The most important thing for any ship is to know its exact location at sea. At any time. The safety of the vessel itself, the cargo and the entire crew depends on this. I would not be discovering America if I said that the ship is currently controlled by a computer. Man only controls this process. In this article I will talk about marine assistants - satellite navigation systems that help ships obtain the exact coordinates of their location. I will also tell you what instruments ancient sailors used. Currently, all ships are equipped with GPS receivers - global positioning system. While flying around our planet, navigation satellites continuously send streams of radio signals to it. These satellites belong to the US Naval Navigation Satellite System (NMNSS) and, more recently, the US Global Positioning System (GPS or GPS). Both systems enable ships at sea, day and night, to determine their coordinates with great accuracy. Almost up to a meter.

The operating principle of both VMNSS and GSM is based on the fact that on board a ship a special GPS receiver catches radio waves sent by navigation satellites at certain frequencies. Signals from the receiver are continuously sent to the computer. The computer processes them, supplementing them with information about the transmission time of each signal and the position of the navigation satellite in orbit. (Such information reaches VMNSS satellites from ground-based tracking stations, and GSM satellites have time and orbital instruments on board). The navigation computer on the ship then determines the distance between them and the satellite flying in the sky. The computer repeats these calculations at certain intervals and ultimately receives data on latitude and longitude, that is, its coordinates.

By the beginning of the 15th century, “blind reckoning” began to be used. To do this, they threw logs tied to these ropes overboard - lines. Knots were tied on the ropes at a certain distance. The time of unwinding of the line was noted using a sundial or hourglass. We divided the length by the time and obtained, of course very inaccurately, the speed of the ship.

P.S. Photos belong to their rightful owners. Thank you, good people.

On the other hand, 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 sail close to the coast and determined the location of the ship by coastal landmarks. Brave Phoenicians and Vikings, sailing far from the coast, navigated by the sun and stars. In the 11th century a compass appeared, but the magnetic needle in high latitudes pointed not to the geographic north, but to a magnetic pole that 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 16th century. The outstanding Flemish cartographer G. Mercator calculated the coordinates of the magnetic pole and proposed a new principle for drawing maps in a conformal cylindrical projection. Since then, all nautical charts have been compiled in this projection.

Currently, the direction of movement of the vessel is determined by a magnetic compass (taking into account the magnetic declination) or by a gyrocompass. The gyrocompass is designed on the principle of a top and is rotated by a motor at a frequency of 300,000 revolutions per minute. Like any top, it has the property of maintaining a given axis position 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 a chart. This accounting of the exchange rate is called notation, and the exchange rate is called countable. The result of the navigator's work is called plotting (the ship's course on the map).

Only near the shore, using a lighthouse or a direction finder (a device for determining angular directions to external landmarks: coastal or floating objects, celestial bodies, etc.), can the navigator accurately name the coordinates of the ship. 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 shore, the navigator uses navigational instruments. The ship's speed and distance traveled are measured using a log. Logs can be hydrodynamic or hydrostatic. A hydrodynamic log is a spinner (screw) that is pulled on a cable behind the stern of the vessel. Usually the log is connected to a revolution counter installed on the bottom of the vessel. The faster the ship goes, the faster the log rotates, and the counter shows a higher number of revolutions, and the value of the ship's speed is indicated on its dial.

The hydrostatic log absorbs the force of water pressure. A tube bent at the end is lowered into the water. The tube opening faces forward. The flow of water flowing onto the ship creates Pressure. The higher the speed, the higher the pressure. The pressure value determines the speed of the vessel.

Measuring the speed of a ship in knots involves using 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 nodes that “ran out” from the ship in half a minute corresponded to the number of nautical miles (1111.852 km) traveled by the ship per hour.

However, the log does not give a very accurate idea of ​​the speed of the vessel, because it cannot take into account the speed and direction of currents, wind, and factors influencing the drift of the vessel. Sailors do not need the reckonable course, but the true course of the ship, so the reckonable course is corrected by astronomical observations using a sextant (or sextant) - a goniometric mirror-reflective instrument for measuring the heights of celestial bodies above the horizon or the angles between objects visible on the shore. The structure of the sextant is as follows: a telescope and two mirrors (to reflect rays of light from the celestial body) are attached to a bronze sector, which makes up approximately 1/6 of the circle (the name of the device comes from the Latin word sextantis - “sixth”). The sector has divisions - degrees and minutes - for angular measurements.

When determining the location of a ship or aircraft by the sun or stars, the heights of several celestial bodies above the visible horizon are usually measured using a sextant. Then a number of corrections are made to the obtained result, taking into account, for example, the lowering of the visible horizon, etc. And finally, the corrections to the numerable 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, whose location is precisely known, continuously send radio signals. They are received by a ship's radio 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 vessel's location, the bearings of two radio stations (radio beacons) are taken into account.

In the interests of navigation, a radar is also used (see Radar), which allows you to “see” in the dark and fog, determine the distance and bearing to the shore or to a ship with which you need to disperse at sea.

The location of the vessel can also be determined 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 it takes for an ultrasonic pulse to travel 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 echo sounder readings.

Navigation technology plays an important role in aviation, helping to guide aircraft. In front of the pilot on the instrument panel, among many different instruments, there are navigation instruments. This is an altimeter, the design of which is based on the same principles as a barometer that responds to changes in pressure. The pressure decreases with altitude, and the navigator compares the pressure on the ground with the altimeter readings. This way 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 based on the time from the moment of sending until the return of the impulse. The speed meter at altitude is a pressure gauge that measures the pressure of the oncoming air flow. With altitude it decreases, and the device shows a lower speed. But the airspeed indicator automatically takes this change into account, and as a result, its needle points to the true airspeed. The direction of flight can be judged by the readings of the gyrocompass.

The navigator must be able to determine the place of the ship at sea by coastal landmarks that occupy a constant position on the earth and are accurately plotted on maps, as well as by celestial bodies.
The observations of landmarks made for this purpose and the determination of the ship's position from them are called observations .
The points indicating the ship's location on the map, obtained as a result of observations, are called observational . Observed coordinates are marked in the text with the index “o”, for example, Ш о or Д о.
Mismatch countable place (that is, the place where the navigator believes the ship is located, according to his calculations, at the moment of observation) with an observation (determined in one way or another) is called residual . The discrepancy is denoted by the letter C and is expressed in the text through the distance and direction from the counting place to the observed one, for example, C = 9.5-130°. This means that the observed place is located 9.5 miles from the reckonable one in the direction of 130°.
The landmarks for visually determining the location of the ship are objects marked on maps: first of all, specially installed beacons and signs, the position of which is precisely determined; then other, clearly visible artificial structures - towers, bell towers, factory chimneys - and, finally, natural landmarks clearly visible in the area - capes, mountain peaks, individual rocks. Most often, lines of bearings taken from landmarks are used as position lines.

Determining the location of a ship by bearings of two objects

The simplest and most commonly used method of determining the position of a ship at sea is to determine the position by two simultaneously taken bearings of two different objects. Let object A (the lighthouse) be observed from the ship according to the true bearing IP1, and object B at the same moment according to the bearing IP2. By taking the compass bearings of these objects and correcting them with a general compass correction, we obtain the values ​​of the true bearings of the observed objects. Having drawn the lines of these bearings on the map, at the point of intersection of the lines (point M) we obtain the observed location of the ship.
The resulting location (the point of intersection of the lines of true bearings) is circled. An inscription in the form of a fraction is made near the resulting point, indicating the moment of time in the place of the numerator, and the lag count in the place of the denominator. If a discrepancy is found, it is also indicated. (All work on maps is done with a simple pencil).

Determining the location of a ship by bearings of three objects


Let's say that the compass bearings of three objects A, B and C are taken at the same time and the lines of the corresponding true bearings IPa, IPv and IPs are laid out on the map. It is clear that if the observations are correct and the accepted compass correction is correct, then the lines of all three bearings must intersect at the same point, since the true position of the ship cannot be at different points at the same time.
If an error is made in the observations or accepted values, then the bearing lines will intersect at three points, forming a so-called triangle of errors among themselves. Moreover, if the error triangle is relatively small, then the ship’s position is taken to be in its center.

Determining the location of the ship by two and
three distances


In a similar way, the location of the ship is determined by two and three distances (if it is possible to somehow measure the distance to two or three landmarks, for example, by radar).

Determining the ship's position by
two horizontal corners

In the same way, the position of the ship is determined by two horizontal angles (measuring the horizontal angles with a sextant and plotting them on maps using a protractor).
From the figure below, I think, the principle of determining a place using 2 bearings will be clear to you.

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 at about the same time as the astronomical method, and is often used together with the two previous ones. Today, automatic calculators do the routine work;
• Radar, which allows you to combine the picture on the radar screen with a sea map.
• 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. It's 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 are 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 location by coastal objects is similar to the simplest method of a pedestrian who knows that he needs, for example, a house on Staroportofrankovskaya Street at number 12, and for accuracy there is another 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 includes an optical system that should be aimed at the Sun or any star, after first installing 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 Vorontsov 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”. Using homemade devices, its participants look 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 markings 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.