Guidance, navigation and control (engineering)

"GN&C" redirects here. For the Great Northern and City Railway, see Northern City Line.

Guidance, navigation and control (abbreviated GNC, GN&C, or G&C) is a branch of engineering dealing with the design of systems to control the movement of vehicles, especially, automobiles, ships, aircraft, and spacecraft. In many cases these functions can be performed by trained humans. However, because of the speed of a rocket's dynamics, human reaction time is too slow to control this movement. Therefore, systems—now almost exclusively based around digital electronics—are used for such control. Even in cases where humans can perform these functions, it is often the case that GNC systems provide benefits such as alleviating operator work load, smoothing turbulence, fuel savings, etc. In addition, sophisticated applications of GNC enable automatic or remote control. In general,

• Navigation refers to the determination, at a given time, of the vehicle's location and velocity (the "state vector") as well as its attitude,
• Guidance refers to the determination of the desired path of travel (the "trajectory") from the vehicle's current location to a designated target, as well as desired changes in velocity, rotation and acceleration for following that path, and
• Control refers to the manipulation of the forces, by way of steering controls, thrusters, etc., needed to track guidance commands while maintaining vehicle stability.

Examples for GNC systems include:

• Autopilots
• Driverless cars, like Mars rovers or those participating in the DARPA Grand Challenge
• Guided missiles
• precision-guided airdrop systems
• Spacecraft launch vehicles

See also

• Guidance system
• Navigation
• Control engineering