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 in adverse weather conditions based on radar images. Most commonly a GCA uses information from either a Precision Approach Radar (PAR, for precision approaches with vertical, glide path guidance) or an Airport Surveillance Radar (ASR, providing a non-precision Surveillance Radar Approach with no glide path guidance). Technically, the term GCA applies specifically to the precision radar approach with glide path guidance.