Position fixing - a crucial element in Navigation

Warning: Position-fixing is vital to ship navigational safety

Bridge teams not fixing ship positions on charts often enough are putting their vessel and the environment at risk. Ships have been grounded partially because navigation officers use excessive onboard position-fixing intervals, according to insurers. This may not be an issue in open oceans, but it can be a problem if ships are sailing close to coastlines and islands.

According to London P&I Club, infrequency of position-fixing has been a contributory factor in some recent costly claims. Loss prevention manager Carl Durow said officers of the watch may not detect an error in navigation early enough if they extend intervals of position-fixing. He said that this can be due to issues with ship safety management.

“Club inspectors continue to note a lack of guidance in passage plans for the frequency of position-fixing necessary on individual legs of each voyage,” Mr Durow explained. “This is often accompanied by excessive intervals in closer proximity to land on inbound voyage charts.”

He continued “Naturally, every passage is different, but it is recommended that the passage planning stage considers the appropriate fixing intervals and provides guidance to the officer of the watch.”

London P&I Club provided two examples involving ships that grounded when crew were not checking the vessel’s position frequently enough.

The mutual marine liability insurer highlighted that a laden bulk carrier grounded on a shoal because of navigational and environmental condition factors. One of these was that a previous inaccurate dead-reckoning plot was not detected in time.

“If a more appropriate position-fixing interval had been employed, it is likely that the discrepancy between the erroneous dead-reckoning plot and the ship’s subsequently plotted position would have been observed in time to correct the situation and execute the course alteration safely,” London P&I Club said.

In a second case, a ship proceeding in a ballasted condition between two small islands struck one of these because it was unexpectedly affected by a strong current. This affect was not identified early enough by bridge officers before the next fix was to be plotted. “The ship was not employing parallel indexing, thus denying the officer of the watch two methods of detecting its heavy set to port,” said London P&I Club in the latest StopLoss Bulletin.