The International Maritime Organisation (IMO) has urged maritime users of the Global Positioning System Standard Positioning Service (GPS-SPS) to check their systems ahead of the counter roll over.
Some outdated GPS receiver systems may cease to function properly with serious impacts on navigation.
The roll over occurs because the GPS system transmits time to GPS receivers, using the format of time and weeks as 10-bit value, which started on January 6, 1980 and can only count 1,023 weeks.
The previous roll over occurred on August 21, 1999, when systems reset and began counting towards week 1,023 again. When the GPS system reaches week 1,024, the system will revert to week zero.
Some GPS receivers are known to be unable to make the transition from week 1,023 to 1,024. If the GPS receiver is outdated or has not been properly updated, the receiver will revert to reading the week zero as August 1999.
The internal clocks of these GPS receivers will experience lack of absolute reference and may give the wrong time and position or may lock up permanently. Some of these GPS receivers are repairable with upgrades and others will become unusable.