BIMCO advices members to check GPS systems before 6 April


On 6 April 2019, the maritime GPS-SPS system will undergo a week counter roll over which may affect some GPS receivers.

Ships are urged to check with their GPS manufacturer before 6 April, as this counter roll over could potentially cause some GPS receivers to show the wrong time and position of the ship or stop functioning.

The GPS system is designed with a 10 bits format for counting time and weeks. This gives a counting limit of 1023 weeks. The GPS-SPS system was launched 6 January 1980 and the previous week counter roll over was on the 21 August 1999.

When the GPS system reaches week 1024, the system will start counting again from week zero which will be on 6 April 2019. However, experience from 1999 shows that not all GPS receivers are able to make this transition and therefore will read week zero as August 1999 instead of April 2019. Some GPS receivers can be repaired with an update, but others might potentially remain unusable.

The International Maritime Organization (IMO) has issued a circular explaining the situation and advises ships and other GPS-users to check with their GPS manufacturer regarding the status of their receiver.

BIMCO advises members and ships to show extra caution when navigating and to follow the IMO’s advice.


Christian Baekmark Schiolborg
in Copenhagen, DK


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