DME
Distance Measuring Equipment
Last updated: April 20, 2026 · Maintained by Aviatr Editorial Team
What is DME?
DME (Distance Measuring Equipment) is a radio navigation system that measures slant-range distance between an aircraft and a ground station, operating in the 960-1215 MHz frequency band. DME is frequently co-located with VORs and ILS facilities to provide continuous distance information alongside bearing or course guidance.
How is DME used?
DME is the standard distance reference during en-route cruise and instrument approaches. Flying an ILS at '10 DME' means the aircraft is 10 nautical miles slant-range from the station — slightly more than ground distance due to the altitude component, a correction pilots learn in early instrument training. En-route, DME feeds ground-speed and time-to-station calculations; DME/DME/IRU positioning lets aircraft navigate without GPS by triangulating from multiple ground stations. Some approach plates specify step-down altitudes at DME fixes: 'at 8.5 DME descend to 2,300 feet'. Airline arrival planning uses DME distance against planned times to cross-check accuracy. EASA Radio Navigation theoretical knowledge specifically addresses DME principles, paired transponder coding, and slant-range geometry for exam candidates.