The London P&I Club said 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 emphasises 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. It adds that navigating officers should always check the charts for information about corrections that need to be applied to satellite-derived positions when preparing a passage plan and alert the navigators to any existing corrections which are required before positions are plotted on the individual charts.