Navigationsinstrument

A navigationsinstrument, or navigation instrument, is any device, instrument, or system used to determine a vehicle's position, course, or estimated time of arrival. They span traditional terrestrial and celestial tools to sophisticated electronic systems and are used in maritime, aviation, and land navigation.

Traditional celestial navigation instruments include the astrolabe (ancient, largely historical), the back-staff and cross-staff, and most commonly the sextant or octant. These instruments measure the altitude of celestial bodies above the horizon. When paired with precise timekeeping, typically a marine chronometer, they enable determination of latitude and longitude at sea. Chronometers are key to longitude computation.

Magnetic and gyro-based instruments provide direct or stabilized headings. The magnetic compass indicates direction relative to magnetic north, while the gyrocompass uses rotational inertia to maintain a reference to true north. In coastal and open-water navigation, radio and radar aid situational awareness; VHF radio navigation aids such as VOR/DME and non-directional beacons (NDB) help determine position relative to fixed stations. LORAN, once common, has largely been superseded by GNSS.

Modern electronic navigation relies on global navigation satellite systems (GNSS) such as GPS, GLONASS, Galileo, and BeiDou. Receivers, often integrated with inertial navigation systems, form part of autopilots, electronic chart displays (ECDIS), and digital navigation databases. These systems provide continuous position, velocity, and time data, with redundancies and safety features to mitigate errors and interference.

Limitations include signal loss, atmospheric effects, magnetic variation, and deliberate jamming. Effective navigation combines multiple instruments, procedures, and charts to ensure accuracy and safety.