Plain English Meaning

The aircraft figures out where it is using GPS, then continuously transmits that position and other flight information to controllers and nearby aircraft.

Full Definition

A surveillance technology in which an aircraft automatically determines its own position using onboard navigation sources (typically GPS) and broadcasts that position, along with identity, altitude, velocity, and other data, over a digital datalink. The broadcast is received by air traffic control ground stations and by other suitably equipped aircraft, replacing or supplementing traditional radar surveillance.

Context Anchor

Seen in instrument flying, discussions, displays, and requirements where may be required.