How did ground-controlled approach systems help aircraft land in poor visibility?

Ground-controlled approach (GCA) systems facilitate safe aircraft landings during poor visibility by utilizing radar to monitor the aircraft's position from the ground.12

In this process, a ground observer tracks the plane's course and descent angle. The observer then provides the pilot with specific radioed instructions to guide the aircraft along a suitable glide path toward the runway. This method allows pilots to land successfully even under extremely adverse weather conditions.21

While GCA relies on ground-based monitoring and verbal communication, it is distinct from the instrument landing system (ILS), which instead uses onboard instruments to interpret radio beams transmitted from the ground to provide the pilot with visual alignment data. GCA was used extensively by the U.S. military, notably during the 1948 Berlin blockade, before being approved for civil airline use in 1949.234