The London P&I Club says a recent casualty involving a containership serves as a timely reminder of the consequences of failing to check navigation charts for information about corrections that need to be applied to satellite-derived positions.
In the latest issue of its StopLoss Bulletin, the club refers to an incident in which a containership grounded as a result of total reliance on GPS, coupled with a failure to recognise that a significant correction had to be applied to GPS positions before they were plotted on the chart.
During a coastal passage, the ship ran aground after a navigating officer commenced a significant alteration of course about half a mile before he reached the intended alter-course position.
Investigations suggested that the officer was using no means other than GPS to navigate and, even though the ship was on a regular schedule, he was wholly unaware that a significant correction had to be applied before GPS positions could be plotted onto many of the charts used in the service.
The club says a more detailed passage plan would have alerted the inexperienced officer to the danger and required him to cross-check his position by more than one method.
The club also emphasised that seafarers must be aware that, on many charts still in use, a correction has to be applied to satellite-derived positions before the position is plotted on the chart.