There are a myriad of techniques and instruments available to assist the pilot in navigating the aircraft. The type of instrument that can be found on a given aircraft depends on its level of sophistication: a light VFR aircraft is equipped with simple instruments while a airliner requires much more complex instruments.
Since the magnetic compass works on the principle of magnetism, it is well for the pilot to have at least a basic understanding of magnetism. A simple bar magnet has two centers of magnetism which are called poles. Lines of magnetic force flow out from each pole in all direc- tions, eventually bending around and returning to the other pole. The area through which these lines of force flow is called the field of the magnet..
An inertial navigation system (INS) is a navigation aid that uses a computer, motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position, orientation, and velocity (direction and speed of movement) of a moving object without the need for external references.
The platform is kept horizontal with respect to land landmarks, regardless of aircraft movement. This is achieved by using gimbals that allow the platform to move freely in all three axes (pitch, roll and yaw).
The ring laser gyro (RLG) is widely used in commercial aviation. The basis for RLG operation is that it takes time for light to travel around a stationary, nonrotating circular path. Light takes longer to complete the journey if the path is rotating in the same direction as the light is traveling. And, it takes less time for the light to complete the loop if the path is rotating in the direction opposite to that of the light, the path is made longer or shorter by the rotation of the path. This is known as the Sagnac effect.