What does the term "ADF" stand for?

The term "ADF" stands for Automatic Direction Finding. This is a radio navigation tool that helps pilots determine their bearing relative to a radio station. It uses signals transmitted from ground-based stations and is crucial for navigation, especially in adverse weather conditions or when visual aids are not available.

The ADF system consists of an antenna, a receiver, and a display. The antenna picks up signals, and the receiver processes these signals to determine the direction to the station, which is then shown to the pilot on the cockpit display. This capability allows for more accurate positioning and guidance, particularly in less navigationally friendly environments.

The other options, while they include terms related to direction finding, do not accurately represent the definition of ADF in the context of aviation navigation, which is why they do not correctly define the acronym.