Sailors' aid may shut down

SAILORS AND light aircraft pilots are being warned that their navigation equipment could fail on Saturday night because of a millennium bug-type computer glitch.

The problem, known as "end-of-week rollover", could mean Global Positioning System (GPS) equipment will stop working.

GPS is a worldwide satellite-based system, used extensively by British sailors and pilots, which allows navigators with electronic receiving equipment to pinpoint their position anywhere on the globe.

The system, which was originally developed for military use, is run by the United States Defense Department, and the US government has issued warnings to pilots, sailors, hikers, climbers and others who rely on GPS.

The GPS end-of-week rollover happens about once every 20 years. The problem is that the GPS system keeps track of time by counting the number of weeks since its launch on 6 January, 1980 - up to a maximum of 1,024 weeks.

The GPS "counter" has now reached 1,023 weeks, and at midnight on Saturday Universal Time Coordinated (UTC) - the same as GMT (so 1am BST Sunday) - it will roll over to zero, presenting a problem for any user whose receiving equipment has not been programmed to cope. Hand-held receivers more than five years old are considered particularly likely to be affected.