Ground-Based Navigation - Low Power Distance Measuring Equipment (LPDME)



The Distance Measuring Equipment (DME) is a radio navigation aid used by pilots to determine the aircraft's slant range from the DME ground station location. The DME avionics in aircraft send a pulse signal to the ground based DME, which responds with an answer pulse signal. The receiver in the aircraft measures the time delay between the sent and received pulses and calculates the slant range distance. There is no azimuth information, only distance.

Low Power DMEs (LPDMEs) transmit 100 watts of power and used for approach navigation. The LPDME is a component of Instrument Landing System (ILS) approach service for precision and non-precision approaches. The DME measures the distance from the aircraft to the runway out to 18 Nautical Miles (NM) and beyond. The LPDME can also be collocated with a VHF Omni-directional Range (VOR) to provide VOR/DME service with a Terminal Service Volume with a radius of 25 NM.

High Power DMEs (HPDME) transmit 1,000 watts of power and may be collocated with VORs to provide VOR/DME service with a Low and High Service Volume with a radius up 130 NM to support en route and terminal navigation. DMEs are used to support situational awareness and location of fixes for conventional flight operations and lateral guidance for DME/DME RNAV flight operations. Additionally, the distance information from a Tactical Air Navigation (TACAN) and a VOR/TACAN (VORTAC) unit is DME.

Presently the FAA has a contract with Selex Inc. to procure the Selex DME system. The Selex DME completed In-Service Decision in May 2015.

Project Lead: Gonghe Zhang -

Last updated: Friday, February 10, 2023