North Sea helicopters first to be tracked by offshore multilateration

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Surveillance of oil support helicopter operations using wide-area multilateration instead of radar has been launched over the North Sea.

Multilateration is not new, but this is the first use of such a surveillance system in a sea area.

Deployed by UK air navigation service provider NATS and Oil & Gas UK, the system is operated from Aberdeen's air traffic control tower. Signal transmitter and receiver stations, fitted to offshore oil and gas platforms in the central North Sea, identify and track helicopters in real time.

Land-based radar cannot detect helicopters further than about 110km because the aircraft operate at low level, below the radar horizon.

But because the multilateration system's transmitter and receiver stations are on the oil rigs, they can always obtain line-of-sight responses from the helicopters' transponders at enough individual stations to fix the aircraft by triangulation.

An added advantage is that the multilateration system - the hardware for which is provided by US specialist Sensis Corporation - is less costly and more accurate than radar.

Controllers in Aberdeen's tower will be able to monitor the helicopters all the way to the helidecks. This, says NATS general manager at Aberdeen John Mayhew, will improve separation assurance and enable a quicker and more accurate response in an emergency.

NATS started work on the project in 2004. Eventually transmitter and receiver stations will be operational on a total of 16 offshore platforms in four geographic clusters.

At present only three clusters of four stations each have been set up, but the fourth will have been completed by January, and the system will begin operation for flight trials "later this month", says NATS. It will become fully operational over more than 50,000km² of the North Sea by June 2010.