Changes

Deviation from true north can also occur due to the presence of nearby large metal objects, such as ships at sea. At sea, this additional magnetic deviation is tracked, logged, and factored in to reading a magnetic compass in order to determine true north. In an aircraft the aircraft's movement can affect a compass, causing it to give inaccurate readings during turns and other maneuvers.

Deviation from true north can also occur due to the presence of nearby large metal objects, such as ships at sea. At sea, this additional magnetic deviation is tracked, logged, and factored in to reading a magnetic compass in order to determine true north. In an aircraft the aircraft's movement can affect a compass, causing it to give inaccurate readings during turns and other maneuvers.

A gyrocompass, also known as a ''direction indicator'', is another instrument designed to indicate north. They are mainly used in aircraft, where the change in atttude of an aircraft can affect the direction of a normal magnetic compass. The principle of a gyrocompass relies upon a rapidly spinning wheel (usually run electrically) which maintains its original orientation. Due to the [[law of conservation of angular momentum]], a gyrocompass can be set to point to true north when it is initialized, and it will continue point true north. Gyrocompasses will drift over time, and therefore need to be resynchronized with a magnetic compass at regular intervals.

A gyrocompass, also known as a ''direction indicator'', is another instrument designed to indicate north. They are mainly used in aircraft, where the change in atttude of an aircraft can affect the direction of a normal magnetic compass. The principle of a gyrocompass relies upon a rapidly spinning wheel (usually run electrically) which maintains its original orientation. Due to the [[law of conservation of angular momentum]], a gyrocompass can be set to point to true north when it is initialized, and it will continue to point to true north. Gyrocompasses will drift over time, and therefore need to be resynchronized with a magnetic compass at regular intervals.

Magnetic compasses were in early use by [[Portugal|Portuguese]] explorers in the [[Age of Exploration]].

Magnetic compasses were in early use by [[Portugal|Portuguese]] explorers in the [[Age of Exploration]].