A new surveillance system introduced by the Federal Aviation Administration (FAA) in Colorado allows air traffic controllers to track aircraft not covered by radar in remote, mountainous regions.  The new system, called Wide-Area Multilateration (WAM), lets air traffic controllers see aircraft they could not see before due to the rugged terrain. It improves the safety and efficiency of those flights and saves time and money for passengers and operators,” the FAA says. WAM began initial operations on Sept. 12 at Yampa Valley-Hayden, Craig-Moffat, Steamboat Springs and Garfield County Regional-Rifle Airports. The mountains in those areas are popular ski destinations but make radar coverage impossible because radar signals cannot pass through solid objects.
The resulting flight limitations are compounded by seasonal bad weather, which causes flight delays and cancellations. The new system is comprised of a network of relatively small sensors deployed in remote areas. The sensors send out signals that are received and sent back by aircraft transponders. No other aircraft equipment is required. System computers are able to determine the precise location of aircraft by triangulating the time and distance measurements of those signals. Controllers are able to see those aircraft on their screens as if they were radar targets. WAM is being used in the near term while the FAA rolls out Automatic Dependent Surveillance–Broadcast (ADS-B), the satellite-based surveillance system that will be fully deployed nationwide by 2013. WAM will then serve as a backup to ADS-B in the event of a GPS outage and provide an additional source of traffic broadcast to properly equipped aircraft.