Plain English Meaning

Routes flown by following a signal from a radio station on the ground. The pilot stays on the line that runs to or from that station, so the available paths depend on where the stations are.

Full Definition

Flight paths defined by ground-based navigation aids such as VORs, NDBs, and localizers, where the aircraft tracks a radial, bearing, or course signal transmitted from a fixed station on the ground. These courses follow straight lines radiating from or pointing to the navaid, and the route structure is built around the location of those stations.

Context Anchor

Seen in instrument procedure discussions when comparing paths with - or -based paths.