Definition

A-SMGCS (Advanced Surface Movement Guidance & Control System) is a system providing routing, guidance and surveillance for the control of aircraft and vehicles in order to maintain the declared surface movement rate under all weather conditions within the aerodrome visibility operational level (AVOL) while maintaining the required level of safety. AVOL refers to the minimum visibility at or above which the declared movement rate can be sustained.

(Source: ICAO Doc 9830: Advanced Surface Movement Guidance and Control Systems (A-SMGCS) Manual)

SMGCS operations are normally in effect below a certain visibility reading. For example, in the U.S., SMGCS is typically used when Runway Visual Range (RVR) falls below 1,200 feet.