GPS reliability warning

Cruising sailors have long been warned of overreliance on that oh-so-handy GPS but now University of NSW researchers have added extra weight to the warning.

They say GPS systems are becoming increasingly vulnerable to accidental interference or deliberate jamming.

Professor Andrew Dempster, of the University of New South Wales School of Surveying and Spatial Information Systems, said low-powered GPS signals could be easily drowned out by other sources which are increasing in number.

These include cheap jamming systems used by criminals.

“GPS signals are weak and can easily be outpunched by poorly controlled signals from television towers, devices such as laptops and MP3 players, or even mobile satellite services,” he said.

"This is not only a significant hazard for military, industrial and civilian transport and communication systems, but criminals have worked out that they can jam GPS."

Professor Dempster said his research team had already detected interference from a television tower in Sydney’s northern suburbs, although no instances of deliberate jamming.