Cutting-edge technology is being installed in some of the most challenging South Island high country to help air traffic controllers better track aircraft through increasingly busy airspace.
State-owned enterprise Airways, which provides New Zealand's air navigation services, has been installing multilateration (MLAT) surveillance technology at nine sites in Otago and Canterbury.
The organisation says the specialist technology is used in only a handful of airspaces around the world.
It will give air traffic controllers visibility in valleys and behind mountains - areas that are out of reach of radar surveillance.
Airways engineering and maintenance head Peter O'Regan said installing the technology had its challenges but that was outweighed by the benefits it would bring.
''We've been working in some really remote spots to install the equipment, using helicopters to fly heavy gear to mountain tops, with high exposure to wind, rain and snow throughout the year.
''At Wether Range near Omarama, for instance, we drove a digger to the peak to dig the foundations, and then used a helicopter to fly in the 13 tonnes of concrete needed for the station foundations.
''In terms of access to the various sites, we are very appreciative of the co-operation shown by Twin Peaks Station and Dunstan Peak Station.
''The MLAT equipment will allow air traffic controllers to confirm that aircraft are exactly where they say they are, removing the need to rely on position reports, which is crucial for improving safety in this complex airspace,'' Mr O'Regan said.
The technology would also ''assist greatly'' with search and rescue operations, he said.
''The main benefit lies in our ability to use the recorded track information to assist with search and rescue activity should such be required.''
Airways completed installation of 18 MLAT sites near Queenstown in 2009.
The nine additional sites would expand the network into the upper controlled airspace towards Dunedin and Invercargill and over the Tasman Sea to the west of Queenstown, Mr O'Regan said.
And for those interested in a more technical explanation of how they will do what they do: the network incorporates Automatic Dependent Surveillance-Broadcast (ADS-B), satellite-based surveillance technology using GPS position data.
The sensors are deployed with minimal environmental impact, using existing communication sites, or are solar powered.
Mr O'Regan said MLAT technology provided a three-dimensional picture of air traffic and allowed Airways to reduce the separation between aircraft because the radar surveillance indicated the exact position of each aircraft.
This would result in fuel efficiencies and decreased costs for airlines because they no longer needed to hold aircraft at lower levels, and there would be fewer disruptions for passengers.
