Ground-controlled approach

In aviation, a ground-controlled approach (GCA) is a type of service provided by air-traffic controllers whereby they guide aircraft to a safe landing, including in adverse weather conditions, based on primary radar images. Most commonly, a GCA uses information from either a precision approach radar (PAR, for precision approaches with vertical glidepath guidance) or an airport surveillance radar (ASR, providing a non-precision surveillance radar approach with no glidepath guidance).

Source: Wikipedia — Ground-controlled approach (CC BY-SA 4.0)