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INS control display

Inertial Navigation Display Unit.

Inertial Navigation System

The inertial navigation system (INS) is a self-contained unit that is located within an aircraft or rocket. It is programmed with its starting point and destination. An INS measures only movement; it does not measure airspeed or wind velocity. The movement is translated into speed, direction, and distance. Movement is detected with a sensitive device called an accelerometer that functions somewhat like a pendulum. The amount that the pendulum moves depends on the change in speed of the body to which it is attached.

INS accuracy decreases over time. The farther the vehicle with the INS travels, the less accurate it becomes.