Systems of co-ordinates, applied in navigation complexes

In aircraft navigation systems are used mainly spherical (geographic and orthodromic) and rectangular coordinates.

In the geographic coordinate system (Figure 1) is determined by the position of the aircraft altitude and angular coordinates: longitude and latitude. For the main plane of the system adopted in the geographic equator plane and the plane of the prime meridian. The poles of the system coincide with the geographic poles of the earth elepsoida. The geographic coordinate system as the meridians and parallels is applied to all charts and is the basis for determining the coordinates of points on the map.

Movement of the aircraft relative to the earth's land surface is characterized by a rate of which , , related to geographic coordinates by the following relations.

; ; . (1)

Under certain current speed , , and initial values ​ ​ of the coordinates , , current geographical coordinates are determined by integration of (1).

Orthodromic coordinate system (Figure 2) is also a spherical system, but with arbitrary poles. This system for the main axes adopted two great circle (hence the name). Orthodrome, combined with a line of a given path (LGP), or with the axis of the route, called the principal and is taken as the axis of . Axis is a kind of conditional equator. Another orthodrome perpendicular to the main, carried out through the point of origin of coordinates is taken as the axis . This axis is a conventional meridian. The position of any point on the Earth's surface is indicated by two coordinates and , usually expressed in kilometers.

By selecting the position of the main Great Circle can ensure that the flight took place with the smallest possible deviation from it, ie, for small values ​ ​ of the coordinates . This allows you to within acceptable distance from the main Great Circle (350... 400 km) do not take into account the sphericity of the earth and ease of navigation. Therefore, the system is basic in navigation devices. In addition, orthodromic coordinate system is most useful for keeping a given direction of flight using gyroscopic devices coursework.

Current angular coordinates orthodromic and , the relevant provisions of the aircraft along the equator and orthodromic deviation from it along the meridian orthodromic respectively, are defined by geographical coordinates and by formulas

;

,

where and =-geographical coordinates of the origin of coordinates orthodromic.

In flight from the known and calculated and . Then traveled from origin point distance along the equator orthodromic and linear deviation from it defined as follows

; . (2)
Dependence (2) is used to control the movement of the aircraft.

In the event that the flight path is a polyline with straight lines between successive points of the route can be used by private orthodromic coordinate system for each segment. The equator passes through such a system, the start and end points of the leg.

In any position relative to the Earth's surface the aircraft to withstand a given route and travel programs need to combine signals and know and great circle course . Great circle course determined by the directional gyro, put up in a given direction of flight. However, the high level of measurement error, especially for long flights, making it necessary to use other methods of determining the great circle course. For this purpose, the known values ​ ​ of the coordinates of the start orthodromic , and current values ​ ​ of variables and calculated azimuth correction

,

also known as the angle of convergence of the meridians and orthodromic geographic coordinate systems. Knowledge of the amendment and the azimuthal magnetic course , allows you to calculate the required great circle course . As sensors magnetic course in exchange systems are the inductive sensors used in conjunction with corrective mechanisms.

Cartesian coordinate system (Figure 1) is flat system. Start the system is placed, usually at the current position of the aircraft, the axis head north in the direction of the current meridian axis - along the radius of the sphere up. Axis complements. Small spherical parts of the Earth is almost equal to the plane tangential to the point of this site. Therefore, the rectangular coordinates can quite accurately determine the position of points on the Earth's surface within certain limits.

Cartesian coordinate system is used to solve a number of combat missions, as well as for the automated approach.
Studies show that over 1, 000 km along the main strip in the Great Circle 600 km away orthodromic coordinate system is virtually identical to a rectangular (error in determining the location of the aircraft is less than 1%).

To program a flight path defined by control points, landmarks, correction and navigation stations. These coordinates are in the coordinate system in which the software device receives information specific navigation system. In the navigation system with digital computer introduced geographical coordinates, which are chosen from special catalogs or determined from maps.