The problem of orientation in space has always faced man very acutely. Naturally, we are not talking about small distances, when you can take as a landmark a lonely tree or a large stone. It is about significant spaces when the compass becomes the main assistant to the traveler. In this case, one cannot do without characterizing such concepts as azimuth and magnetic declination.
Since school, we know that the azimuth is the angle that forms between the direction of a person’s chosen subject and the direction of north, where the compass needle points. However, the whole point is that the compass needle does not point to the North Pole, as is commonly believed, but to the North Magnetic Pole, the position of which not only differs from the geographical, but also changes over time (however, these changes occur so slowly that they can be neglected).
Thus, it turns out that with the help of a compass a person finds the azimuth is magnetic, and not true. If we are talking about a simple camping trip, then this error can be neglected, but here the ships in the sea, airplanes in the sky and a host of other equipment should focus on the true azimuth, otherwise a catastrophe can occur.
True azimuth, as follows from the above text, is the angle between the direction to the object or some other landmark and the direction to the geographic North Pole of the Earth. In this case, the difference between magnetic azimuth and true is called magnetic declination. It is generally accepted that if the magnetic declination has a direction to the east, then it is called "eastern". It is indicated in special tables by the “+” sign. And if on the contrary, the magnetic declination is "western" and is indicated by the sign "-".
The concept of magnetic declination was introduced into science a long time ago: the famous navigator H. Columbus not only used it in his famous voyages to the shores of America, but was also the first to draw attention to the fact that its value varies depending on a particular territory.
Now there is no doubt that the numerical value of magnetic declination is not the same at different points on the globe. So, for example, in the city of Moscow it is +80, and for other regions it reaches more significant indicators. It is especially important to consider magnetic declination when working with geographic maps, when it is necessary to constantly translate the magnetic azimuth into true, and vice versa.
Gunners use a special device, the compass, to adjust their shooting. Using it, the exact direction is determined for any landmark, which is then used as a starting point when shooting. At its core, the magnetic azimuth is converted to true with the help of a bussol.
Thus, magnetic declination is the amount by which the magnetic azimuth differs from the true one. This knowledge is necessary not only during long expeditions, but also during artillery firing, as well as for the normal sailing of ships and aircraft.