Ground-Based Navigation and Performance Based Navigation

  • Ground-Based Navigation: VOR, DME, ILS.
  • Performance Based Navigation (PBN) is comprised of Area Navigation (RNAV) and Required Navigation Performance (RNP).

RNAV enables aircraft to fly on any desired flight path within the coverage of ground or space based navigation aids

RNP is RNAV with the addition of onboard performance monitoring and alerting capability.

Many airports are replacing VOR and NDB approaches with RNAV (GPS) approach procedures.

Ground-Based Navigation


VOR: VHF Omnidirectional Range

VOR uses band from 108.00 to 117.95 MHz. Short-range radio navigation system, on the ground. Stations are being decommissioned with widespread adoption of GPS.

Minimum Operational Network (VOR MON): The FAA is transitioning the National Airspace System (NAS) to Performance Based Navigation (PBN). As a result, the VOR infrastructure in the Contiguous United States (CONUS) is being repurposed to provide a conventional backup navigation service during potential Global Positioning System (GPS) outages. This backup infrastructure is known as the VOR MON.

DME: Distance Measuring Equipment

Different from VOR, DME operation will continue and possibly expand as an alternate navigation source to space-based navigational systems such as GPS and Galileo.

The fifth-generation equipment proposed in 2020 provides greater accuracy (down to 5 meters using DME/DME triangulation), with a further reduction to 3 meters using a further refinement.

NDB: Non-directional beacon

Being deprecated.

TACAN: Tactical air navigation system

Used by military. Use "Channel" number instead of a frequency input to get DME.

VORTAC: combining VOR and TACAN.



Wide Area Augmentation System (WAAS): to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability.

WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including precision approaches to any airport within its coverage area.

WAAS uses a network of ground-based reference stations to measure small variations in the GPS satellites' signals in the western hemisphere.

A primary goal of the WAAS system was to allow aircraft to make a Category I approach without any equipment being installed at the airport. A Category I approach requires an accuracy of 16 metres (52 ft) laterally and 4.0 metres (13.1 ft) vertically. Measurements from the reference stations are routed to master stations, which queue the received Deviation Correction (DC) and send the correction messages to geostationary WAAS satellites

GPS => WAAS ground-based reference stations (measure small variations in GPS signals) => master stations = (Deviation Correction, DC)=> WAAS satellites => (correction messages) => Earth users.