Determination of ship position. Vessel definition: methods

Since the ships - the creations of human hands - began to plow the seas and oceans, the navigators faced the task of determining their own location. Huge waves, squalls and the need to maneuver the tack lines, keeping the course against the wind, complicated the days-long voyages, and only the compass of the ancient seafarers was not enough. Today, when the location of the ship is automatically determined by the GLONASS satellite systems , it is difficult to imagine the position of the captain, who has only simple devices for orienting the stars. Nevertheless, even today graduates of specialized secondary and higher specialized educational institutions own all these devices.

Basic methods of marine location

Two-coordinate definition of a vessel in three-dimensional space (location) is produced by seven types of methods, including:

• The oldest is the visual one.
• Later, but not much - astronomical.
• Topographical-computational, that is, a method for mapping the full path of a ship to the map, indicating the points of course change and calculating the distance traveled through multiplying the speed by time. Invented around the same time as the astronomical method, and is often applied together with the two previous ones. Today, automatic work is performed by automatic calculators;
• Radar, which allows you to combine the picture on the radar screen with a naval map.
• Radio direction finding. Available when there are signal sources on the shore.
• Radio navigation, using the means of communication, according to which the navigator gets the information he needs.
• Satellite-navigation method.

All methods, except the first three, were the result of a technological revolution that occurred in the XX 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 cosmic sphere. Now it is not difficult to calculate the point in the ocean in which the ship is located, the definition of its coordinates takes a few seconds, and, as a rule, they are monitored in continuous mode. 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 the points on the three-dimensional figure should be described by three Euclidean coordinates, but two geographers and navigators are enough. In order to make a topographic definition of a ship, it is necessary to name only two digits, accompanied by the words "northern" (or "southern") latitude (abbreviated to north or south) and western or "eastern" longitude (in other words, z. Etc. or E). These values are measured in degrees. Everything is very simple. Latitudes are considered from the equator (0 °) to the poles (90 °) indicating which direction: if closer to Antarctica, then the southern latitude is indicated, and if to the Arctic, then the north. 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

The location of the vessel can not be determined from one coordinate, so there is a second one. Longitude is the conditional number of the meridian, indicating again the side to which the reference is being counted. The circle is divided into 360 °, its two halves, respectively, are 180. The zero is the Greenwich meridian, passing through the famous British observatory. On the other side of the planet is its antipode - 180th. Both these coordinates (0 ° and 180 °) are indicated without the name of the longitude direction.

In addition to degrees there are also minutes - they indicate the position of objects with a 60 times greater accuracy. Since all meridians are of equal length, they have become a measure of the length of seamen. One mile (sea) corresponds to one minute of any meridian and is equal to 1,852 km. The metric system was introduced much later, so navigators use the old good English mile. Also applicable are units such as cables - it is equal to 1/10 miles. What is surprising, because before the English were often considered dozens, than dozens.

Visual method

As the name implies, the method is based on what the navigator and the captain see, as well as other team members on deck or tackle. Earlier, in the time of sailing fleets, there was a post ahead of the beholder, the post of this sailor was placed at the very top, in a specially fenced-off place of the mainmast-the cloak. It was better from there. Determining the location of the vessel alongshore objects is similar to the most simple method of a pedestrian who knows that he needs, for example, a house along Staroportofrankovskaya street at number 12, and for accuracy there is one more criterion of search - a drugstore located opposite. Sailors, however, serve as reference points for other objects: beacons, mountains, islands or any other noticeable details of the landscape, but the principle is the same. It is necessary to measure two or more azimuth (this is the angle between the compass needle and the direction to the landmark), apply them to a map and get their coordinates at the point of their intersection. Clearly, 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 can be guided by the sound of the siren of the lighthouse, and for lack of surface signs - turn to the shallows in shallow water, measuring the depth of the lot.

Astronomy in the marine service

The most romantic method of location. Approximately in the XVIII century, seafarers together with astronomers invented sextant (sometimes it is called a sextant, so it is also correct) - an instrument through which it is possible to produce a fairly accurate two-coordinate definition of the ship by the position of the sky in the stars. The device at first glance is difficult, but in fact you can learn how to use it quite quickly. In its design there is an optical system, which should be aimed at the Sun or any star, having pre-installed the device strictly horizontally. For accurate guidance, two mirrors (large and small) are provided, and the angular elevation of the light is determined on the scales. The direction of the instrument is specified by the compass.

The creators of the device took into consideration the centuries-old experience of ancient navigators, oriented only to the light of stars, moon and sun, but they created a system that simplifies both the training of navigation and the process of location.

Calculation

Knowing the coordinates of the starting point (exit port), driving 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 in the case where the direction and velocity do not depend on the flow and wind. The unevenness of the course and the error in the lag gauge (speed meter) also affect the accuracy of the coordinates obtained. At the disposal of the navigator there is a special ruler for laying parallel lines on the map. Determination of the maneuvering elements of the sea-going vessel is made with the help of a compass. Usually, at the point of direction change, the true position is determined using other available methods, and since it usually does not coincide with the computed one, a peculiar haw is drawn between two points remotely resembling a cochlea and called a "discrepancy."

Currently, on board most ships installed automatic instrumentation-calculators, which, taking into account the entered speed and direction, integrate over a variable time.

Using radar

Now there are no white spots on the maps of the sea, and an experienced navigator, seeing the outline of the shore, can immediately tell where the ship is entrusted to his care. For example, having noticed on the horizon even in the fog light of the lighthouse and hearing the muffled sound of his siren, he will immediately say something like: "We are on the traverse of the Vorontsovsky fire, a distance of two miles." This means that the vessel is at the specified distance on a line connecting at a right angle the course and perpendicular direction to the lighthouse whose coordinates are known.

But it often happens that the shore is far away, and there are no visible landmarks. Earlier, during the time of the sailing fleet, the ship was "drifted", collecting sails, sometimes, if the capricious character of the dominant winds and the unpredictability of the bottom (reefs, shoals, etc.) were known, they anchored and "waited in the sea of weather ", That is, clarifications. Now there is no need for such a loss of time, and the navigator can see the coastline by looking at the locator screen. The definition of a vessel using a radar is a simple task with the availability of 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 radionavigation method

There is such an amateurish game - "Fox hunting". With the help of homemade devices, participants are looking for a "fox" hidden in bushes or behind trees - a player who has a working radio station of low power. In the same way, that is, bearing data, counterintelligence services calculate the residents of foreign intelligence services (at least earlier it was so) at the time they sent spy reports. Locating requires at least two directions that intersect at the point of location, but more often more. Since there are always some variations in the readings, and absolute accuracy is impossible, bearings do not converge at one point, but form a kind of multilateral figure, in the geometric center of which it is highly probable to assume its location. Landmarks may be specially created on the shore pilotage signals (for example, on lighthouses) or radiation stations, the coordinates of which are known (they are plotted on the map).

Coastal correction of the course using radio communication facilities is also widely applicable.

By satellites

Today, it is almost impossible to get lost in the ocean or the sea. Navigation of the moving objects on the sea, in the air and on land is observed by navigation and rescue systems, the Russian "Cospas" and the international Sarsat. They work according to the Doppler principle. It is necessary to install a special radio beacon on the vessel, but safety and confidence in the successful outcome of the voyage are worth the money spent on it. The direction finders are placed on geostationary satellites ("hovering" above 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 complications, and navigators in our technological age use it most often.

Additional parameter - download

The ship's shipping qualities 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 its hydrodynamic resistance level. There are, however, exceptions, for example, in nuclear submarines, the underwater course exceeds the surface one, and the special nasal "bulb" in case of its full drowning creates an effect of better streamlining. One way or another, but the speed of movement (stroke) affects the weight of cargo (cargo) in holds or tanks. To assess this value, sailors use special labels with risks on the bow, stern and side parts of the hull (scales of at least six). These signs are applied individually, each ship has its own, there is no single standard. The method of determining the weight of cargo on board a vessel, called "draft survey", is based on the use of "grades of draft" and is used for many purposes, in particular navigation. Depth of the bottom does not always allow the ship to pass through a particular channel, and the navigator must take this factor into account.

It remains only to wish at least seven feet under the keel to those who go on a voyage.