In the wheelhouse of each merchant ship, a variety of navigational equipment, instruments, devices and tools are installed, with the help of which the captain and navigator ensure the safe management of the vessel.
Navigation equipment- these are ship technical means with which the ship is equipped to solve navigation problems.
Navigation- the process of decision-making and management of the course and speed of the vessel when moving from one point to another, taking into account the surrounding conditions and the intensity of navigation.
navigation device- this is a ship's technical tool designed to solve one or more navigation tasks.
navigation tool is a ship navigation device designed to perform manual work in solving navigation problems.
navigation device is a device designed to perform certain functions of measuring navigational parameters, processing, storing, transmitting, displaying and recording data when solving problems of navigation on a ship.
For a better view, all photos are clickable.
Ship clock.The ship's clock records the time of all events. The ship's clock must be checked daily against the exact time signals and must have an accuracy of not more than one minute. All ship clocks must be set to the same time zone. One ship's clock must be set to Greenwich Mean Time or Coordinated Universal Time (UTC).
magnetic compass (magnetic compass). The most reliable and irreplaceable device. Unless, of course, it is serviceable and regularly checked in the coastal workshop. At least once every two years, the magnetic compass must be destroyed, the residual deviation determined and a deviation table (Deviation card) compiled. On some ships, a main magnetic compass and a directional compass are installed. If only one compass is fitted on board, one spare compass should normally be available. The magnetic compass is a backup source of guidance for the autopilot and ECDIS. A separate article on the magnetic compass is located. Lifeboats and rescue boats must have magnetic compasses for heading guidance.
gyrocompass (Gyro compass). Gyro-compass. The main source of guidance. Heading guidance from the gyrocompass is fed to radars, ARPA, ECDIS, autopilot, digital heading indicator, gyrocompass repeaters in the wheelhouse, navigational cabin, bridge wings, tiller compartment.
Repeater gyrocompass With (Gyro repeater with bearing device). They are mounted on the wings of the bridge and serve to take visual bearings. The bearing of lighthouses and signs are taken to determine the position of the ship in the sea near the coast. The bearing of the celestial bodies is taken to determine the compass correction. The bearing of approaching ships is taken to determine if there is a risk of collision with them. The photo shows a simple direction finder. There are also optical direction finders, in which lenses are installed to approach the direction-finding objects.
Digital indicator course(transmitting heading device). Device for digital display of the ship's heading. Mandatory device.
Binoculars (Binocular). It serves to recognize objects located at some distance from the vessel and poorly visible to the naked eye. Also used for surveillance under regulation 5 of COLREG 72.
Radar (radar). The radar is used to prevent collisions with other vessels and for navigational purposes - determining the position of the vessel by bearings and distances of coastal landmarks measured using the radar. Serves to monitor the environment in accordance with regulation 5 COLREG-72.
ARPA (ARPA). A device for avoiding collision with other ships and floating objects. Serves to monitor the environment in accordance with regulation 5 COLREG-72. In most modern radars, the ARPA function is implemented and, therefore, ARPA is practically never found as a separate device.
Electronic cartographic navigation and information system - ECDIS (Electronic chart display and Information System ECDIS). Electronic cartography devices are used to display a navigation chart, navigation information and the position of the vessel according to the coordinates of the GPS receiver on the displays. Many ships have two sets of ECDIS equipment and paper navigational charts are not available.
Receiver satellite navigation(Global Positioning System - GPS). Serve to determine the coordinates of the vessel using the global satellite system. Displays the boat's speed over the ground. Traveled distance. Serves for entering the coordinates of the waypoints of the transition route, compiling the transition route, transmitting the transition route to the radar. Shows the direction and distance to waypoints, deviation from the route, time of arrival at waypoints.
echo sounder (echo sounder). A device for measuring depth under the keel of a vessel.
lag(Speed and distance Log). The device is used to measure the speed of the vessel and the distance traveled by the vessel. Measures the speed of the vessel both through the water and over the ground. The speed through the water is necessary for transmission to the radar and ARPA to solve problems of divergence from other vessels.
Automatic identification system (Automatic Identification System – AIS ). Serves for receiving and transmitting ship data using a VHF transceiver. Displays data received from other ships on the display of the device and transmits them to the radar and ECDIS. Serves to monitor the environment in accordance with regulation 5 COLREG-72.
Navigation lights panel (Navigation Lights ). Each vessel must display lights in accordance with COLREGs 72. The navigation lights panel provides visual and audible warning in case any light goes out.
ship's whistleship’ s whistle). The ship's whistle is used to give warning and fog signals in accordance with COLREGs-72.
Vessel's Fog Signal Device (Automatic fog signal device). To give fog signals in automatic mode.
Watch officer's capacity control system (Bridge navigational watch Alarm System – BNWAS. Serves to give an audible signal in case of incapacity of the officer in charge of the watch. Should be switched on at all times after the ship has left the berth and before mooring at the berth.
Autopilot (Autopilot). Serves to keep the vessel on course in automatic mode. If the device has a ship-on-track mode, then the autopilot will change the ship's heading itself to bring it to the next waypoint. When approaching a waypoint at a predetermined distance, the device will beep, if the officer on duty presses the confirmation button, the device will shift the rudder and bring the vessel to the next predetermined course.
Flight data recorder –VDR – Voyage Data recorder . The ship's black box. Data logging device for navigation instruments and devices.
NAVTEX receiver -NAVTEX receiver. Serves for receiving various warnings in automatic mode: navigational, meteorological, distress and others.
Terminal Inmarsat - C (Inmarsat – C). Serves for receiving and sending messages via satellite communication system.
The system of long-range identification and control of the location of ships - OSDR (Long Range Identification and tracking System – LRIT ). Serves for the transmission of vessel data (coordinates, heading, speed, vessel identifier) in automatic mode via a satellite communication system.
Rudder axiometer (Rudder Angle indicator). A device that indicates the direction and angle of the rudder.
Rate of turn indicator (rate of turn indicator). Shows the rate of turn of the vessel.
Sound receiving and playback device (sound reception System). The device serves to reproduce external sounds in closed bridges.
sextant (Sextant). Sextant (Sextant) navigational is used to measure the heights of celestial bodies, which are used to calculate the lines of position and determine the position of the vessel by astronomical methods. They also measure the heights of coastal and floating navigation marks, and other objects. In addition, true navigators-navigators measure the horizontal angles between three navigation marks with a navigational sextant and determine the position of the ship in the sea by two horizontal angles. But only very zealous navigators determine the place of the vessel in this way, unfortunately most modern navigators can be attributed to “GPS navigators”, that is, to those who, except for GPS, are no longer able to determine the position of the vessel in the sea. Professional degradation however. About the navigational sextant separate article
Chronometer (Chronometer). Shows the time on the Greenwich meridian. Before the invention of radio, the chronometer was the only source of accurate time on board. The accuracy of determining the location of a sailing ship in the sea depended on the accuracy of the chronometer and knowledge of its daily course. Chronometers were verified by astronomers in observatories, their daily course was determined with the greatest possible accuracy, and before the ship sailed to the sea, they were brought on board with the greatest care. After a long ocean voyage, at the first opportunity, the chronometers were brought ashore to check them and determine the daily course. Each ship had several chronometers. With the advent of radio receivers, it became possible to receive radio signals of exact time to determine the daily rate of chronometers, and the requirements for their accuracy decreased somewhat. With the advent of satellite navigation and a significant weakening of the role of astronomical observations in navigation, chronometers on almost all merchant ships were replaced by accurate clocks. However, until now, individual accurate watches used to keep time are called chronometers. The navigator responsible for navigational instruments is obliged to keep a chronometer log in which to record the daily course of the chronometer.
Mechanical stopwatch (Stopwatch). Serves for fixing the time at the time of astronomical and navigational observations, for determining the correction of the chronometer, for comparing and setting ship's clocks. To determine the characteristics of lighthouse lights and other navigational signs and buoys. Used to determine the ship's roll and pitch period and wave period.
star globe (star Globe). Used to solve problems of nautical astronomy. You can read more about the device of the star globe
Hand Anemometer (Wind anemometer). Used to measure wind speed.
Automatic device for measuring wind speed and direction (Wind speed and direction indicator ). Serves for measurement of the direction and speed of a wind in the automatic mode.
ship gongship’ s gong). Serves for giving fog signals in accordance with the rules of COLREG-72. Mandatory for all vessels of 100 meters or more in length. The gong is a brass disc with a rim. It is hit by hand with a beater, which is a handle with a spherical impact part at the end.
Signal flags - MCC (ICS). The flags are used to give signals in accordance with the International Code of Signals - MCC (International Code of Signal - ICS).
Signal figures - balls, cylinder, rhombus (Signaling Shapes). Serve for exhibiting signals in accordance with the rules of COLREG-72.
Chart table. Installed in the holy of holies for each navigator - in the navigator's cabin. On it, a navigation chart with a preliminary plotting is laid out at sea, and an executive plotting with observations of the vessel's position is also being carried out on it. Nautical charts are stored in the drawers of the table. Navigational tools can be stored in the side lockers.
Weights for cards. Serve to hold the navigation chart on the chart table while the ship is rolling. They are usually made from rubber. As a weighting agent, there is lead inside the weight. More information about the use of weights can be found in the article.« ».
Navigator's magnifying glass (magnifier). Enlarges hard-to-see images on the navigation chart.
Navigator's parallel ruler (navigational ruler).
Navigation Protractor (Protractor ). Serves for laying, determining the position of the vessel and other navigational tasks on the navigation chart.
Navigation meter (navigational divider). Serves for laying, determining the position of the vessel and other navigational tasks on the navigation chart. Meters are made of brass or chrome-plated steel. They come in various types and sizes.
Pilot compass. As a rule, ordinary drawing compasses of various sizes and types are used for navigational purposes, the main thing is that they are convenient to use on the navigation chart and do not cause significant damage to the chart.
Navigation protractor.A navigational tool that is used to determine the position of the vessel at two horizontal angles.
The procedure for determining the position of the vessel on two horizontal angles.
Inclinometer. Used to determine the ship's heel angle.
barometer (Barometer). Used to determine atmospheric pressure.
barograph (barograph ). Serves to determine the atmospheric pressure and monitor its change. The barometer reading is recorded on paper tape.
Thermometer (thermometer). Used to measure the ambient temperature.
Hygrometer(Hygrometer ). Serves for measurement of humidity of air.
Computer with satellite internet connection. Used to receive weather maps and plan a safe route based on weather forecasts. It also serves to transmit and receive operational information to ensure the safe operation of the vessel.
Depending on the special purpose, special instruments and devices are installed on the bridge, and the watch officer uses them to solve special problems.
Vessel positioning
Let's talk about a few simple, but very necessary, ways to determine the location of a yacht in the sea. The task is simple, but extremely important for your safety. It can be roughly divided into two cases:
1. You are sailing within sight of the shores and navigation marks that are marked on your chart.
2. You are sailing a yacht on the high seas in the absence of any landmarks.
By the way, if the course passes near the coast, but in conditions of limited visibility (for example, at night or in dense fog), then the method of determining the location will most likely refer to the second case.
So, we are making a coastal voyage and the yacht does not lose sight of the land (or signs of navigational conditions). It is important for us that at the moment of determining our location, we see the required number of landmarks that we can identify on the map.
There is another issue that needs to be discussed. We live in the 21st century, and the development of electronic navigation aids has reached fantastic heights. And if you rely only on electronics, then navigation turns out to be no more difficult than a computer game - you just need to study the instructions attached to the device.
But pay attention to one circumstance: according to the laws of any country, all ships going to sea - merchant, military and sports, sailing and motor - are required to have on board a complete set of traditional navigation aids: a set of paper charts, a laying tool, a sextant, sailing directions and etc. Navigators, skippers and captains are required to plot on traditional charts during any sea passage. I must say that I fully agree with this order. It must be understood that the sea is an element hostile to man, and he is alone with it.
Is it really possible to unconditionally entrust the lives of people on board, the life and fate of the yacht to a small plastic box with electronic filling?! Sea air is a very aggressive environment, which sooner or later will disable fine microelectronics; sooner or later you will forget to take on board a spare set of batteries for her; on the GPS can get sea spray, rain; lightning can strike a mast and disable all electronics - after all, according to the theory of reliability, any device can fail on its own - and what to do?
Life has shown that knowledge of navigation and stable skills in navigation by traditional methods are simply necessary for any person who goes to sea as a navigator, skipper or captain.
Therefore, let's move on, in fact, to the methods of determining the location of the vessel using traditional methods.
1. Reckoning, or Dead Reconing
Imagine that the yacht is sailing on the open sea and there are no visible landmarks. To understand the principle of the method, suppose that at 10.00 our yacht was at point A, which we have plotted on the map. The speed of the yacht is 7 knots (we read it from the ship's log), the true course is 045ºT (they counted from the directional compass and took into account the magnetic declination). We want to determine where the yacht will be at 11.30. Naturally, according to the conditions of our problem, from 10.00 to 11.30 the yacht sails without changing course (045ºT) ( see fig. one), at a constant speed (7 knt). The distance traveled is calculated by the elementary formula:
D = S X t, where
D– distance traveled in miles;
S is the speed of the boat in knots;
t- time in hours.
D = 7knt x 1.5 = 10.5 n.m.
Rice. 2
This is, in the simplest case, the calculated location of our yacht (indicated by the + sign and the letters DR with time).
Rice. 3
But this method can be used in the case when the previous coordinates of the yacht are known exactly ( fix), its speed and heading, and there is no drift associated with wind and currents.
2.Estimate Position (EP)
If the direction and speed of the current are known, we can plot the location of the yacht on the map using a simple graphical method. Suppose, when calculating DR in step 1 ( see fig. four) we learned from the atlas of tidal currents that from 10.00 to 11.30 in the navigation area there was a current with a speed of 3 knots and a direction of 110ºT. Please remember that the current always flows "in" the indicated direction, unlike the wind, which always blows "out" of the indicated direction.
Rice. four
So, using the principle of independence of motions, known from the school physics course (he says that any movement of the body can be represented as a vector sum of simple rectilinear displacements), from the point DR 11.30 we will postpone with the help of the plotter the direction 110ºТ ( see fig. 5). Please note that the current vector is denoted exactly as in the figure.
Rice. 5
Then we calculate the length of the vector, the time of the yacht’s movement: 1.5 hours = 90 min, the current speed is 3 knots ( knts). This means that during the movement from 10.00 to 11.30 the yacht moved in the direction of 110ºT under the influence of the current by: 3 knots x 1.5 hours = 4.5 nautical miles. Set aside on a segment measuring 4.5 n.m. and get a point EP 11.30 (standard symbol) ( see fig. 6). This is the calculated position of our yacht at 11.30, which from 10.00 from point A was moving on a course of 045ºT at a speed of 7 knt under the influence of the current direction 110ºT and speed 3 knt. Further laying the course, we must do already from the point EP 11.30. We also completed the task - we know where the yacht is.
Rice. 6
3.FIX
The specific position of a vessel at a given time is denoted by the English term FIX. There are many ways to define it. We will consider the most widely used and general way: finding FIX-A on two or more compass bearings (preferably three).
Let's say our yacht is heading 0ºE (360º) at a speed of 7 knots. You pass a section of the coast where you can clearly and distinctly see the lighthouse BUT, lighthouse AT and a small island FROM. The time is 10.15 and the last EP was determined at 9.30 ( see fig. 7).
Rice. 7
Turning to the map of the area, you must absolutely accurately identify the selected landmarks A, B and FROM with their image on the map. (All land features depicted on a navigation chart are clearly visible from the sea (day and night) and can be used for navigation.) Charts always show lighthouses, water towers, tall, free-standing buildings, radio masts, etc. visible from the sea.
Using a manual direction finder compass, we will take magnetic bearings to selected landmarks A, B and FROM (see fig. eight). We understand that in order to map a magnetic bearing, we must convert it to true bearing using a declination correction.
Rice. eight
Recall the rule: when moving from a magnetic bearing to a true bearing, the western declination is subtracted, and the eastern declination is added.
Let's assume that after we took the bearings one by one to the lighthouse BUT, lighthouse AT and the island and converted them into true bearings, we got the following values:
True bearing to the lighthouse BUT– 045ºT
True bearing to the lighthouse AT– 90ºT
True bearing to the island FROM– 135ºT
With the help of the plotter, we set aside these true bearings from our objects A, B, C, as shown in rice. 9.
Rice. 9
As we can see, the bearings did not intersect at one point, but formed a kind of triangle ( hat). This was due to small errors in taking bearings. But we can say that the yacht is at 10.15 somewhere inside this triangle. For our purposes, this accuracy is quite enough - we found FIX. Remember, please, a few rules that must be observed in order to FIX your yacht was as accurate as possible:
1. choose the nearest, more clearly visible objects for taking bearings;
2. try to keep the angles between objects not too sharp or too obtuse (optimal angles are in the range of 30-110º);
3. take bearings as accurately as possible;
4. If the speed of the yacht is high (for example, a motor yacht), then try to take bearings for as little time as possible in order to reduce the error caused by the movement of the yacht during this time.
Of course, there are many more ways to define FIX, for example, with the help of a radar, using leading objects, the height of objects measured by a sextant, astronomical methods, etc. These methods are beyond the scope of our course for dummies.
Perhaps it is necessary to mention the simplest way of taking FIX by using GPS- your GPS it will simply show you the coordinates of the vessel - plot them correctly on the map and set the time.
Navigation for dummies. (Lesson 4)
Rescue cruise bearing
A very experienced yachtsman once told me that many years ago, on a small yacht, he got into a five-day storm in the Mediterranean Sea. The yacht's electrical equipment failed on the second day of the storm due to a lightning strike, a pocket battery GPS exhausted their resource a little later, the sky was covered with clouds, so there was no opportunity to get a fix using celestial navigation, and how to use a sextant on a small yacht (32 feet) with a wave height of 5-6 meters ?! For five days and nights, a wind of force 8-9 raged and changed its direction several times, and the only thing that could be said with certainty about the location of the yacht was that it was somewhere in the Mediterranean Sea.
And then on the fifth evening, through the rain and splashing waves, the skipper noticed a gleaming red light. Noticing the period of fire, the skipper determined the lighthouse using the light guide, and then, despite the strong sea, using the cruise-bearing method, determined his position with an accuracy of one nautical mile!
So, we have only one visible object that we can reliably identify on the map. Within our visibility, for example, one lighthouse or a sign of navigational conditions, or a small island, a cape, a rock, a radio mast.
In this case, to determine the position of the yacht, we can use a method called running fix, or cruise bearing. The method is based on the fact that we take two bearings for one object at different times. A necessary condition for the application of this method is that the boat's speed and heading must be maintained for at least the time interval between taking the first and second bearing to this object.
Let's see how this looks in practice. Suppose our yacht is on a true course of 080°T at a speed of 8 knots. We clearly and clearly see the rock ( rock) indicated on our map. Using a direction finder compass ( hand bearing compass) at 0900 we take the bearing to this rock and, taking into account the magnetic declination, we recalculate it to the true one and put it on the map. Please note that we plot the course (080°T) on the map at an arbitrary location, since we do not yet know where the yacht is.
Suppose the first bearing taken by us at 0900 is 45°M. Let's set the magnetic declination equal to 07 ° 30 "W. We recalculate the magnetic bearing into true: 045 ° M - 07 ° 30" W \u003d 37 ° 30 "T. Put it on the map. We continue to walk, say, 30 minutes, trying to keep as accurate as possible heading 080 ° T and maintaining a speed of 8 knots. At 0930 we take the second bearing to this rock. Suppose it is 015 ° M. Convert it to true: 015 ° - 07 ° 30 "= 07 ° 30" T and put on the map - see pic 1.
Rice. one
In 30 minutes (the time between taking the first and second bearings), our yacht covered 4 nautical miles on a course of 80°T. On the course line from the point of its intersection with the first bearing, we set aside the distance traveled (4 nautical miles). We transfer the first bearing parallel to itself to this point. The point of intersection of the bearing taken at 0930 and the transferred bearing is our boat's position at 0930, or RF 0930 ( running fix), --see fig. 2 and rice. 3.
Rice. 2
Rice. 3
The accuracy of this method depends on how accurately you can keep your course, speed and, of course, how accurately you can take two bearings. On relatively calm water and with a well-calibrated log, this method can be used to obtain a fix with almost accuracy. GPS.
Since the ships - the creations of human hands - began to surf the seas and oceans, navigators faced the task of determining their own location. Huge waves, squalls and the need to maneuver the tacks, keeping the course against the wind, complicated multi-day voyages, and the old-time sailors lacked only a compass. Today, when positioning of a ship is done automatically thanks to GLONASS, it is difficult to imagine the position of a captain who has at his disposal only simple devices for orienting by the stars. Nevertheless, even today, graduates of specialized secondary and higher specialized educational institutions own all these devices.
Basic Marine Location Methods
The two-coordinate determination of the vessel in (location) is carried out by seven types of methods, including:
- The oldest is visual.
- Later, but not much - astronomical.
- Topographic-computational, that is, a method of plotting the full path of the vessel on a map, indicating the points of course change and calculating the distance traveled by multiplying speed by time. Invented at about the same time as the astronomical method, and often used in conjunction with the previous two. Today, automatic calculators do the routine work;
- Radar, which allows you to combine the picture on the radar screen with the sea chart.
- Radio bearing. Available in cases where there are signal sources on the shore.
- Radio navigation, using means of communication, through which the navigator receives the information he needs.
- Satellite navigation method.
All methods, except for the first three, were the result of the technological revolution that took place in the 20th century. They would not have been possible without the discoveries and inventions made by mankind in the field of radio engineering, electronics, cybernetics and a breakthrough in the space sector. Now it is not difficult to calculate the point in the ocean where the 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. It would seem that points on a three-dimensional figure should be described by three Euclidean coordinates, but two are enough for geographers and navigators. In order to make a topographic determination of the vessel, you need to name only two numbers, accompanied by the words "northern" (or "south") latitude (abbreviated as N or S) and western or "eastern" longitude (otherwise - z. d. or w.d.). These values are measured in degrees. Everything is very simple. Latitudes are calculated from the equator (0°) to the poles (90°), indicating in 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 measures of length
Determination of the ship's position is impossible by one coordinate, so there is a second one. Longitude is a conditional number of the meridian indicating, again, the side in which the countdown is being conducted. The circle is divided into 360 °, its two halves, respectively, are equal to 180. The Greenwich meridian passing through the famous British observatory is considered 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 are of equal length, it was they who 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. What is surprising, because before the British more often counted in dozens than in tens.
visual way
As the name implies, the method is based on what the navigator and captain, as well as other team members on deck or gear, see. Previously, in the days of sailing fleets, there was a position of looking ahead, the post of this sailor was located at the very top, in a specially fenced off place of the main mast - a closet. From there it was better to see. Determining the position of a vessel by coastal objects is similar to the simplest method of a pedestrian who knows what he needs, for example, a house on Staroportofrankivska 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), put 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 zone of coastal visibility, 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, turn to the shoals in shallow water, measuring the depth with a lot.
Astronomy in maritime service
The most romantic location method. Around the 18th century, sailors, together with astronomers, invented a sextant (sometimes called a sextant, that's also correct) - a device with which you can make a fairly accurate two-coordinate determination of the vessel by the position of the stars in the sky. At first glance, its device is complicated, but in fact, you can learn how to use it quite quickly. It has an optical system in its design, which should be aimed at the Sun or any star, having previously installed the device strictly horizontally. For precise pointing, two mirrors (large and small) are provided, and the angular elevation of the luminary is determined by the scales. The direction of the device is set by the compass.
The creators of the device took into account the centuries-old experience of ancient navigators who focused only on the light of the stars, moon and sun, but created a system that simplifies both navigation training and the location process itself.
calculation
Knowing the coordinates of the starting point (port of exit), the time of movement and speed, it is possible to plot the entire trajectory on the map, noting when and by how many degrees the course was changed. This method could be ideal when the direction and speed are independent of current and wind. The unevenness of the course and the errors of the lag indicator also affect the accuracy of the obtained coordinates. The navigator has at his disposal a special ruler for laying parallel lines on the map. The determination of the maneuvering 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, remotely resembling a snail and called "discrepancy".
Currently, most ships are equipped with automatic calculators, which, taking into account the input speed and direction, perform integration over the time variable.
Using radar
Now there are no white spots left on the sea charts, and an experienced navigator, seeing the outlines of the coast, can immediately tell where the watercraft entrusted to his care is located. For example, having noticed the light of a lighthouse on the horizon even in the fog and hearing the muffled sound of its siren, he will immediately say something like: “We are on the traverse of the Vorontsovsky fire, the distance is two miles.” This means that the vessel is at the indicated distance on a line connecting at right angles the course and the perpendicular direction to the lighthouse whose coordinates are known.
But it often happens that the coast is far away, and there are no visible landmarks. Earlier, in the days of the sailing fleet, the ship was “laid adrift”, 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 in the sea for weather ", that is, clarification. Now there is no need for such a waste of time, and the navigator can see the coastline by looking at the locator screen. Determining a ship using radar is a simple task if you have 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 Hunting". With the help of home-made devices, its participants are looking for a "fox" hiding in the bushes or behind the trees - a player who has a working low-power radio station. In the same way, i.e. by bearing, the counterintelligence services identify the residents of foreign intelligence services (at least, this was the case before) at the moment they sent spy reports. Locating requires at least two directions intersecting at the location point, but more often than not. Since there are 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 assume one's location with a high degree of probability. Reference points can be pilot signals specially created on the coast (for example, on lighthouses) or radiation from radio stations, the coordinates of which are known (they are plotted on a map).
Coastal course correction using radio communications is also widely applicable.
By satellite
Today it is almost impossible to get lost in the ocean or the 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 radio beacon on the ship, but the safety and confidence in the successful outcome of the voyage are worth the money spent on it. Direction finders are located on geostationary satellites (“hanging” over a fixed point on the earth's surface) 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 location of the vessel. The satellite navigation method gives the most accurate coordinates, its application does not cause difficulties, and navigators in our technological age use it most often.
Additional parameter - loading
The navigability of a vessel and its possible course are significantly affected by its draft. As a rule, the greater part of the body is immersed in water, the higher the level of its hydrodynamic resistance. There are, however, exceptions, for example, in nuclear submarines, the underwater course exceeds the surface, and a special nasal "bulb" in the event of its complete drowning creates the effect of better streamlining. One way or another, but the speed of movement (stroke) is affected by the mass of cargo (cargo) in holds or tanks. To assess this value, sailors use special marks with risks on the bow, stern and side parts of the hull (at least six scales). These signs are applied individually, each ship has its own, there is no single 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 the ship to pass through a particular fairway, and the navigator must take this factor into account.
It remains only to wish at least those who go on a voyage.
Navigation in Latin means "navigation, navigation." This is an integral part of the complex of marine sciences, which stood out from them in the process of the development of navigation. This includes sailing - focusing on navigational aids, nautical astronomy - which studies methods for determining the coordinates of a ship from celestial bodies; and means of navigation, with the help of which dead reckoning is carried out and the position of the vessel is determined.
The very history of people is inextricably linked with the sea and navigation. The remains of people who are more than 30 thousand years old have been found in North and South America, many of these ancient people swam across the ocean. How did they do it? Thor Heyerdahl, during his oceanic expeditions on the prototypes of ancient ships, proved that this is possible. The first ships are known to us from ancient Egyptian records - these are quite advanced ships on which the Egyptians carried out a brisk trade along the Nile and by sea. These records are over 4,000 years old. From this ancient time, the need for navigation has already arisen.
What questions did ancient sailors face? Yes, just like today. This is the definition of your location and the direction of the path. At first, busy sea trade routes ran along the coast, and navigation was carried out along coastal landmarks. If it was necessary to sail across the ocean, then before the eyes of the ancient travelers there was only one landmark - the stars. The directions of the cardinal points were determined by the movement of the sun. And for a long time watching the stars at night, you can distinguish among them motionless objects. This is the North Star in the Northern Hemisphere and the stars in the constellation of the Southern Cross in the Southern. Most likely, guided by these stars, ancient people mastered new spaces, populated the continents and islands. The ancients also noticed that although the stars move, the distances between them do not change. Before the eyes of the people was a stunning picture of a moving celestial sphere. Now we know that the Earth is moving and we are with it. But these observations laid the foundation for astronomy and celestial navigation.
Ancient Phoenician ship. Image on the sarcophagus
First navigation charts
In order to successfully navigate in space, people sought to build a model of this space in order to know where they were and where to go after all. Some nationalities used the oral tradition, when information about sea routes was transmitted in the form of stories or chants. Sometimes they also used knot writing. But even a schematic representation, a plan of the area, was more illustrative. And so the cards began to appear. The Polynesians who crossed the vast Pacific Ocean had woven mats with the designation of islands and reefs. The Egyptians painted on reeds. However, these maps, despite the great accuracy in the descriptions of specific areas and their features, did not answer the main question - where exactly is the navigator at the moment? How long does it take him to go to the selected port? There was already a fixed point of reference - these are the stars. It was necessary to come up with and decide how to mark your location on the map. But the original maps were unfortunately inaccurate, because it is difficult to plot the round surface of the Earth on the plane of the map without distortion. Moreover, according to ancient ideas, the earth was flat, which introduced even greater inaccuracy. However, trade developed, especially in the Mediterranean region. Gradually, vast knowledge was accumulated in navigation, astronomy and other sciences, later they were collected in ancient Greece. These sciences were developed later, during the Roman Empire. The Greeks, using their observations and collected information from their predecessors, mapped the outlines of known lands. To indicate the location of these lands and other objects, a grid of coordinates was put on the map. The invention of this widely known grid on maps of parallels and meridians also belongs to the ancient Greeks. The concept of latitude and longitude for determining one's location arose again in Greece as a result of constant observations of the position and height of the Sun during the day and the height of the stars above the horizon at night. The change in the position of the Sun was chosen as a measure of measurement. Observing the luminaries, even the Chaldeans divided the circle into 360 parts, where one part - a degree - was the movement of the Sun in the sky by the size of its disk. The degree was divided into 60 minutes of arc, since this people had a sexagesimal number system. This knowledge was assimilated and developed by the Greeks. Gradually, such concepts as the horizon, the ecliptic, and the celestial equator entered science. Without these astronomical concepts, it is impossible to determine the exact coordinates.
Modern 3D sky map
Already in the third century BC. The Greek scientist Eratosthenes determined not only that the Earth is round, but also very accurately calculated the circumference and radius of the earth's sphere. He used an equidistant cylindrical projection in his maps, which gave greater accuracy on maps showing small areas of the earth's surface. Another Greek scientist - Hipparchus - in the third century BC covered the whole earth with a grid of meridians and parallels. Now it became clear in which area of the map you need to find your coordinates. A little later, the Roman geographer Marinus of Tire compiled accurate nautical charts. For some areas, it calculates longitude and latitude very accurately and plots them on a grid of parallels and meridians. His information was subsequently used by the famous scientist Ptolemy in his writings. Marinus, like Eratosthenes, even tried to depict a complete model of the Earth - a globe. His calculations and maps were so accurate that they were adopted by the Portuguese in the 15th century.
The works of a later scientist - Ptolemy - gave a huge impetus to the science of geography and navigation. Ptolemy drew a map of the world in a conic projection, with parallels and meridians, he designated a grid of coordinates calculated in degrees, where latitudes were measured from the equator, and longitudes from the westernmost point of the then known world. He interviewed a huge number of merchants and sailors and quite accurately described the coasts and countries, even those that he had not seen. He described a huge number of new places and gave their coordinates. In addition to accurate information, he recorded on maps and inventions of people, so in his maps you can find, for example, lands inhabited by the people of dogheads and other miracles. In the future, after Ptolemy, nothing new was invented in cartography, and after the collapse of the Roman Empire, dark times came at all.
Ptolemy's map in modern processing. It accurately indicates the lands known to the Greeks at that time.
ancient navigational tools
The very first navigational tool was the eyes of an ancient navigator. But with the development of navigation, this was not enough. To accurately determine the angle of the luminaries above the horizon, special tools were required. This is how the gnomon first appeared, which was a tall pillar; by the ratio of the lengths of the pillar and the shadow from it, the time and height of the Sun above the horizon were determined. The gnomon in the form of a board with a pole on it was first used by the Greek merchant and navigator Pytheas to determine the latitude as early as the 4th century BC. The merchant violated the then existing prohibition and went beyond the Pillars of Hercules into the open Atlantic Ocean, where he made his observations. Despite the primitive device and excitement, the traveler took readings with an accuracy of a few arc minutes. Later, a quadrant was used for astronavigational observations. The quadrant was an ordinary board carved from stone or wood. On its surface were drawn vertical and horizontal lines and a 90° arc uniting them, divided into degrees and their parts. A ruler was placed in the center of the arc, which could move.
Quadrant
A more perfect instrument was the astrolabe, which was used from the second century BC. up to the 18th. The astrolabe was essentially a model of the celestial sphere with its important points, circles, poles and axis of the world, meridian, horizon, celestial equator and ecliptic. It was not easy to make observations with such an instrument. Observing the Sun, the Moon or known stars, the ancient astronavigator brought the circles of a complex instrument into the correct position, after which, using the scales graduated on the circles, he calculated the longitude and latitude of the observed star. The most famous mechanism that has come down to us is the ancient Greek device of 32 Antikythera gears, raised from the bottom of the sea. According to the surviving inscriptions on it, we can conclude that this is an astro-navigation device. The mechanism could calculate the motion configurations of the Sun, Moon, Mars, Jupiter, Saturn, lunar and solar eclipses. Estimated time of manufacture - the period between 100 - 150 years BC.
ancient celestial instrument
Another device that modern navigators cannot do without - the compass - was also invented in ancient times. The inventors of the compass - the Chinese, according to the records in their books, began to use the magnetic compass not only for religious purposes, but also for navigation about 300 years before our era. However, copies of the compass of a later period have come down to us. It was like a magnetized spoon, with a handle pointing south. The Chinese assigned their own color to each side of the world. For example, the south was associated with the color red - modern compasses follow this tradition.
Chinese compass
Location
Starting with the voyages of the Egyptians and Phoenicians, huge amounts of information about the coastline, ports of refuge, anchorages have been accumulated. This knowledge formed the basis of maps and was further used even by Europeans in the Middle Ages. Also, the ancient sailors, going out into the ocean, faced with such a phenomenon as the ebbs and flows. In the future, knowledge was systematized, and already in the ancient Greek sailing directions, for example, they wrote: “The entire Indian country has a lot of rivers and a very high tide and ebb, which intensify during the new moon and full moon for three days, and in the intermediate phases they are weaker” .
A certain difficulty in historical times was the accurate measurement of time and distance. To measure time, a water or hourglass was used, and distances were measured by eye. In ancient Greece, a system of lighthouses was also adopted to help captains. The lighthouse of Alexandria, 120 meters high, is very famous. Many sculptures placed on the shore also served as coastal landmarks for ships. The famous statue of the Colossus of Rhodes, 36 meters high, was visible for miles. And the entrance to large ports at night was illuminated by light - large bonfires.
The first seafaring schools
With the development of merchant shipping, with an increase in the number of sea voyages, the need arose for the transfer of knowledge. There are no references specifically to maritime schools of ancient times; most likely, knowledge was transmitted orally and in a close circle. One of the oldest known schools was the school of navigation in Polynesia. On the island of Raiatea, a place was discovered from which the expansion of the Polynesians to the rest of the Pacific Islands came from, and a place for transferring knowledge about maritime affairs and navigation - these were the first nautical schools. Representatives of the AMS Yacht Training Center visited this sacred place on the islands. In 2012 we plan to make a second expedition there.
"Tapu tapu marae" on Raiateya island. Dated to the 1st millennium BC. This is the surviving remains of one of the first schools of ocean navigation. Photo by Vladimir Vatrunin.
The first textbooks for sailors were probably written on a par with the invention of writing. One of the astronomical navigation textbooks known to us was compiled by Thales of Miletus as early as 600 BC. In Greece, the teaching of astronomy, including astronomy for navigation, was carried out in higher educational institutions of that time. The classical schools of navigation known to us were created much later, in the Middle Ages.
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, it is not possible to perform an observation for a long time - say, poor visibility or a satellite receiver is faulty. navigation system- 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 exactly pointed 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 luminary with an accuracy of 1 ", it was possible to determine the latitude with an accuracy of two kilometers. However, the goniometric instruments known at that time did not 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 early 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” (they no longer 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.