Technical aids to navigation (introduction)

To ensure safety of navigation and use of weapons, submarines and surface vessels are equipped with technical navigational aids (TNA). TNA equipment includes: course indicators and course-indicating systems, dead reckoning systems, speed and distance meters, echo sounders, analogue-digital computers, position coordinates and course deflection correction update aids.

The course-indicating system generates and transmits the course expressed as an angular distance from a reference direction (True North) and the direction of the ship's diametrical centre plane which divides it into two symmetrical parts. The course indicates the direction of the ship's movement at sea, provided the ship is not drifting with or without the current. Otherwise the ship drifts at a certain angle to the reference direction; the angular difference between the direction of the ship's centre plane and the ship's selected course is the drift angle.

The magnetic and gyrocompasses, directional gyros, and integrated course-indicating systems work out and maintain a fairly exact course.

Reliable control of a ship at any given moment of time implies that not only the direction of the ship's movement is known but also its position. To determine the position we must know the distance the ship has covered from the point of departure or the ship's speed and travel period. The speed can be determined with the help of different logs, but they are rarely used. The most widely used speed meters are dynamic-pressure (relative) logs and electromagnetic (induction) logs.

Dead reckoning systems or dead reckoning tracers are built around analogue-digital computers capable of showing the present dead reckoning position of the ship either on a map or a plotting board. The systems use the course reference data supplied by the course indicator, and speed data transmitted by the log.

To ensure safety during coastal navigation or when operating in the navigation-hazardous areas ships are equipped with echo sounders. Echo sounders are devices for measuring the depth of water beneath the ship by observing the time between the emission of the UHF (ultrahigh frequency) sound waves downwards and the return of their echoes from the sea bottom.

To verify the position coordinates and correct course deflection the ship's navigational equipment is provided with various navigational correction aids, namely, star-tracking, radio, radar and sonar aids, etc.

The star-tracking position correction aids include sextants used for measuring the altitudes and azimuths of celestial references.

The position of the ship can be obtained with the help of radio navigational systems (RNS), namely, direction finding RNS, phase-modulated RNS, PCM RNS (pulse-code modulation) and PPM RNS (pulse-position modulation).

Word List

technical navigational aids — технические средства кораблевождения /ТСК/

safety of navigation — безопасность плавания

to indicate — указывать

course indicator — курсоуказатель

dead reckoning — счисление

dead reckoning systems — системы навигационного счисления

a meter (metre) — измерительный прибор

speed and distance metres — измерители скорости и дистанций

sound — звук

echo sounder — эхолот

analogue computer — аналоговый компьютер

digital computer — цифровой компьютер, цифровая ЭВМ

deflection - отклонение

to transmit — передавать

reference direction — начальное /исходное/ направление

the ship's head — диаметральная плоскость корабля

provided that — при условии, что ...

angle — угол

current — течение

directional gyro — гироскоп направления, гидроазимут

to maintain a course — сохранять курс

exact accurate — точный