Glossary of Aviation Terminology |

**GA:** Go around

**Gaussian radius of curvature: **Radius of the earth for the best fitting sphere at a given position; Synonyms: earth radius best sphere; Symbols: rho sub G; Typical Units: ft; Dimensions: Length;

**GCLP: **Guidance control law parameter

**Geocentric latitude: **Latitude measured with respect to horizontal through mass center of the earth; Compare: astronomical latitude, geodetic latitude; Symbols: Phi sub C; Typical Units: rad, deg; Reference: Kayton69. page 16

**Geodetic latitude:** Latitude measured with respect to normal to reference ellipsoid; Compare: astronomical latitude, geocentric latitude; Symbols: Phi sub T; Typical Units: rad, deg; Reference: Kayton69. page 16

**Gimbaled inertial sensor:** Accelerometers mounted to a platform which is free to rotate, with gyroscopes to measure rotation and servomotors to maintain a fixed attitude with respect to the earth Compare: strapdown inertial sensor;

**Glideslope:** Angle approach a runway; Symbols: Gamma; Typical Units: rad, deg;

**Global Positioning System (GPS): **A navigation sensor based on satellites; A Global Positioning System (GPS) provides highly accurate navigation data: position, velocity, and time reference. GPS is often aided by the INU, AHRS, and Doppler data. GPS is accurate with four or more properly oriented satellites. Accuracy is degraded with improperly placed satellites or fewer than four satellites visible. GPS-INS is the most accurate of modes listed, with day/night and all weather capability.

**Go around (GA):** A basic guidance mode, providing lateral guidance, longitudinal guidance and vertical guidance to climb then to accelerate, while maintaining a wings-level roll; in some implementations (such as SOA), individual axes can be overridden by other modes (for example, longitudinal with G/S SEL and vertical with RALT SEL or BALT SEL)

**GPS: **Global Positioning System

**Gravitational acceleration: **Acceleration caused by the force of gravity; Symbols: g; Typical Units: ft/s-squared,g; Dimensions: Length / Time-squared;

**Gravity:** Force exerted by gravity; gravity sometimes includes effects of the earth's rotation; gravity is often treated as a constant, but for greater accuracy gravity is a function of latitude, altitude, and the phase of the moon (yes, it's true); Symbols: g; Typical Units: lbf,kip; Dimensions: Mass * Length / Time-squared;

**Grid north: **Standard aviation term.

**Grivation:** Symbols: nu sub g ; Typical Units: rad, deg;

**Ground track angle (GTA):** Direction of ground speed vector with respect to true north; Synonyms: true track; Symbols: eta; Typical Units: rad, deg;

**Groundspeed:** The speed over the ground; earthspeed projected to a horizontal plane; Symbols: V sub g; Typical Units: kt,ft/s; Dimensions: Length / Time;

**Groundspeed select (G/S SEL): **A basic guidance mode, providing longitudinal guidance to an operator selected groundspeed;

**G/S SEL:** Groundspeed select

**GTA:** Ground track angle

**Guidance:** System, usually software, that determines state errors of desired state minus current state, typically three states: heading, altitude, and speed;

**Guidance control law parameter (GCLP):** One of several parameters for the guidance control laws, generated by individual guidance modes; See Also: altitude error scale factor, altitude integral gain, altitude integral input, altitude integral limit, controlled altitude, controlled speed, course cut limit, crosstrack deviation, crosstrack deviation gain, crosstrack deviation rate, crosstrack deviation rate gain, desired altitude, desired speed, path integral gain, path integral limit, path integral value, reference acceleration, reference acceleration gain, track angle error, track angle error gain, velocity error scale factor; Reference: kilmer89.

**Gyroscope (gyro):** An inertial device for measuring change of attitude (pitch rate, roll rate, and yaw rate); gyroscopes usually consist of a gimbled, rotating mass; gyroscopes are usually included in inertial sensors, such as AHRS and INS; See Also: ring-laser gyro;