RELYING solely on global positioning satellite without the right navigational corrections could put ships in danger, the London P&I Club has warned.
The club highlights its concerns with the grounding of a containership on a regular schedule, which got into trouble because the officer was using only GPS to navigate the vessel.
GPS positions are referenced to the World Geodetic System 1984 Datum (WGS 84), which may not be the same as the horizontal datum of charts in use. This means that a GPS-only plotted position could be wrong.
This can be avoided by first checking to see if any chart corrections are necessary. However, in the grounding case raised by the club, the officer had failed to do this.
“During a coastal passage, a containership ran aground after a navigating officer commenced a significant alteration of course about half a mile before he reached the intended alter course position,” the London P&I Club noted.
The officer was “wholly unaware that a significant correction had to be applied before GPS positions could be plotted on to any of the charts used in the service”.
The club added that 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 London P&I Club said that navigating officers should always check the charts for information about corrections to be applied to satellite-derived positions when preparing a passage plan. Navigating officers should alert navigators to any existing corrections that are required before positions are plotted on the individual charts, it added.
The club declined to name the ship involved in the incident.