Determination of the position of the vessel. Vessel definition: methods

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Since the ships - the creations of human hands - began to plow the seas and oceans, navigators faced the task of determining their own location. Huge waves, squalls and the need to maneuver the tacks, keeping a heading against the wind, complicated multi-day voyages, and the compass alone was not enough for the ancient sailors. Today, when the determination of the position of the vessel is carried out automatically thanks to the GLONASS satellite systems, it is difficult to imagine the position of the 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 methods of sea location

Two-coordinate determination of a vessel in three-dimensional space (location) is carried out in seven ways, including:

• The oldest is visual.
• Later, but not much more astronomical.
• speed for time. Invented at about the same time as the astronomical method, and often used in conjunction with the previous two. Today, routine work is done by automatic calculators;
• Radar, allowing you to combine the picture on the radar screen with the sea chart.
• Radio direction finding. Available when there are signal sources on the shore.
• Radionavigation, 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 occurred 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 "southern") latitude (abbreviated as N or S) and western or "eastern" longitude (otherwise - w. d. or w.d.). These valuesmeasured in degrees. Everything is very simple. Latitudes are calculated from the equator (0°) to the poles (90°), indicating which direction: if closer to Antarctica, then the southern latitude is indicated, and if towards the Arctic, then the northern latitude. Points of the same latitude form circles called parallels. Each of them has a different diameter - from the largest at the equator (about 40 thousand kilometers) to zero at the pole.

Longitude and measures of length

Determining 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 °, two of its 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.

Besides 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 mile (nautical) 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 forward looking position, 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 geographical definition of the 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 the Marine 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. Its deviceAt first glance, it is complicated, but in fact, you can learn how to use it quite quickly. In its design there is an optical system that should be pointed 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 learning to navigate and the location process itself.

Calculation

Knowing the coordinates of the starting point (port of exit), the time of movement 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 the direction and speed are independent of current and wind. The irregularity of the course and the errors of the lag indicator (speed meter) 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, vaguely resembling a snail and called "non-viscous".

Currently on boardmost 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, the coordinates of which 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 immediately everything will become clear.

Direction finding and radio navigation method

There is such an amateur radio game - "Fox Hunting". With the help of homemade devices, its participants are looking fora “fox” hiding in the bushes or behind the trees - a player who has a working low-power radio station. In the same way, that is, 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 shore (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 used.

By satellites

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 navigation and rescue systems, 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 ("hanging" over a fixed point on the earth's surface) satellites,constituting 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 - download

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 bow "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 seven feet under the keel to those who set sail.