'Daleks' to help planes land in Perth airport fog A Singapore Airlines jet takes off in the fog after delays at Perth Airport. NEW devices are to be installed at Perth Airport to help planes land in foggy conditions. The six transmissometers, used to measure the distance from which a pilot can see runway markings, will be in place later this year. The devices, sometimes known as hazemeters or affectionately as Daleks, use beams to determine visibility. A spokeswoman for Perth Airport said the transmissometers would enable arriving aircraft to make an approach with a visibility of 550 metres, compared to the current 800 metre visibility. The privately-owned company is also consulting with airlines and Commonwealth-owned air traffic control provider Airservices Australia to assess the need for a higher category Instrument Landing System that would bring ground-based auto-land capability to Perth Airport. Currently, Melbourne is the only city in Australia that has ground-based auto-land technology. Auto-landings still occur in other Australian cities, as pilots can rely on their aircraft's on-board equipment. But full auto-land is considered more precise as the plane "talks" to the airport. The spokeswoman said a final proposal would be put to airlines within three months. If airlines representing the majority of passenger movements were supportive of the investment, Perth Airport would proceed, she said. Thick fog blanketed Perth overnight, causing domestic and international flights to be diverted, and delaying subsequent flights. Last year, there were less than 10 days where flights to and from Perth were hampered by fog.