Air traffic surveillance beyond radar will surely rely on the GPS-based position reports of Automatic Dependent Surveillance-Broadcast (ADS-B), but likely also on the transponder replies of multilateration (MLat) and its application as wide area multilateration (WAM). That was one of the takeaways from this year’s ATC Global conference, held March 9-11 in chilly Amsterdam.
While ADS-B is steadily progressing in the United States, Canada and Australia especially, WAM systems are popping up like a spring tulip bloom. Announcements by leading multilateration system providers at ATC Global covered opposite corners of the North Sea. Era a.s, in partnership with Holland Institute of Traffic Technology B.V., has installed a WAM system for Dutch air navigation service provider Luchtverkeersleiding Nederland affording low-level and overflight surveillance of the Dutch portion of the sea. In January, the system passed functional performance testing.
NATS Services of the United Kingdom is using a Sensis Corp. WAM system for helicopter flight-following initially, and separation service eventually, off the coast of Scotland, providing visibility of thousands of ferry flights between Aberdeen and North Sea oil and gas platforms.
Multilateration surveillance is being applied for special use airspace by the U.S. military services and for precision runway monitoring, terminal area or enroute surveillance in locations including Europe, Russia, China, the United States, Canada, Australia, Saudi Arabia and South Africa.
Three years ago this month, we published an article on multilateration with what at the time seemed like a provocative headline: “Multilateration: Radar’s Replacement?” Given the rapid rate of adoption of multilateration systems that was evident in April 2007 and continues apace, that headline is not so edgy anymore. Discussions among air-traffic managers and ground system suppliers at ATC Global suggested that multilateration will be more than a bridge to ADS-B but a complement and backup to that technology as well.
Ludmilla Gonzales, Thales ATM business development manager, gave an excellent primer on MLat, WAM and ADS-B, covering some of the pros and cons of each. Chief among the pros of multilateration, of course, is that all it requires of the airplane is a working Mode A/C, Mode S or military IFF transponder to reply to secondary surveillance radar or ground station interrogations, hence no new onboard equipment required. The system also monitors ADS-B broadcasts over 1090 MHz Extended Squitter or Universal Access Transceiver.
Thales ATM has a product strategy that covers each of the surveillance options, Gonzales said. “We have developed an ADS-B, multilat and WAM product family that is able to answer any operational needs enough for ADS-B only, for multilat only, for WAM only,” she said. “But as the trend is to mix those technologies, we have three technologies that can be combined on one platform.” Air traffic managers “need to perform a kind of balance and to maybe address the mix of technology in order to optimize the surveillance solution in your dedicated area.”
Later that same day, I worked my way into a crowded workshop sponsored by Sensis with the apt title, “Multimode Surveillance the Cornerstone of NextGen Surveillance.”
Multimode surveillance combining multilateration and ADS-B “provides cooperative surveillance in a mixed equipage environment that is, ADS-B equipage universally is something that is going to take place over multiple years,” said Mike Gerry, Sensis vice president of air traffic systems, products and programs.
“A multi-mode surveillance system provides surveillance throughout that transition period,” he added. “And if you believe that the transition is the end state, it’s a system that can be deployed now while providing services now and for the future.”
Andrew Desmond-Kennedy, Eurocontrol senior expert for surveillance, offered validation of the idea of multi-mode surveillance as an end state. According to his presentation, Eurocontrol “fully supports WAM as an acceptable means of surveillance.” Through its CASCADE data link services program, the agency will support “an integrated approach to WAM and ADS-B.”
WAM, he concluded, is “one of the cornerstones of European surveillance.”