rely on Global Positioning Systems not certified to handle today's rollover event.

Marine Police Sgt. Gary Venning warned boaters yesterday to check their GPS system's manufacturer's website or phone help line to establish if their system is compliant.

He warned against relying on a non-compliant system during this weekend.

"If you are going out of sight or away from land, you don't want to rely on a GPS,'' he said. "If in doubt, don't go out to sea with only one means of navigation.'' Current production GPS systems will adjust for the August 21, 1999 rollover and continue to operate normally. Most units produced in the past ten years will also operate correctly but may need a software upgrade.

Systems manufactured before 1989 are likely to be inoperative after midnight tonight (SAT), as no upgrades are available.

The system will reset itself at that time to read January 6, 1980 unless previously repaired.