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Wide Area Multilateration (WAM)

What it is

WAM is a ground-based surveillance system that can be installed in areas where radar is limited or not possible.


  • Provides surveillance outside of radar coverage
  • Improves safety, efficiency, and capacity
  • Reduces flight delays, cancellations, and diversions to other airports
  • Reduces fuel burn and lowers emissions
  • Saves time and costs

How it works

WAM is comprised of a network of relatively small sensors that can be deployed in areas that are problematic for radar installations. WAM capabilities can be combined within a set of ADS-B ground stations.

WAM sensors send out signals that are received and sent back by aircraft transponders. No other aircraft equipment is necessary. WAM system computers analyze those signals and determine the precise location of aircraft. The surveillance data is used by air traffic control to provide separation services.


Under a partnership with the Colorado Department of Transportation, the FAA installed WAM at a number of airports in the Colorado mountains. WAM has been providing surveillance at these for a number of years, helping to keep flights operating safely and efficiently especially during the busy winter ski season when weather might otherwise cause diversions and cancellations.

WAM is also operational at Juneau, Alaska. Juneau is another mountainous area without radar, and has a notoriously difficult approach. Flights into Juneau are safer and more efficient now with WAM surveillance.

In Charlotte, N.C., WAM was added to correct anomalies resulting from the airport's limited radar input. With WAM in place, Charlotte will be able to fuse radar and ADS-B data, and transition fully to ADS-B surveillance.

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