Mountain Guidance.

Small airports in mountainous terrain with no radar coverage may follow the lead of Innsbruck, Austria, which plans to use "multilateration" this fall to allow air traffic controllers to track aircraft in the vicinity of the airport. Multilateration is a technique employing ground-based sensors to triangulate aircraft position by comparing the time of arrival of pulses from the aircraft's transponder. In the U.S., it's also known as multistatic dependent surveillance. Pilots require special training before flying into Innsbruck because the approach uses an offset from the instrument landing system, which is not directly on the runway, according to Heinz Bartacek, director of air traffic management engineering at Austro Control, the Austrian air navigation service provider. .