How Are Nautical Charts Corrected On Board Ships?

Whenever a new area is to be added to a chart or it has to represent an area different from the previous chart, or the depth units shown on previous charts have to be changed or if the scale on which a previous chart was made has to be renewed, then Admiralty publishes a New Chart.

However if there are major changes in a chart or large amount of data is to be inserted  for e.g. Insertion of a New Traffic Separation Scheme not present on the previously used chart, the Admiralty then publishes a New Edition of that chart replacing the existing one.

The Catalogue of Admiralty Charts and Publications is published every year with current and updated editions of charts, however, if during the year the Weekly Notices to Mariner indicate any new editions or new charts, they are to be inserted in the chart catalogue by the navigating officer.

An updated and corrected chart folio system comprises of  Chart correction Log and Folio Index, Admiralty Chart catalogue, Admiralty Sailing Directions , Weekly Notices to Mariners , Annual Summary of Notices to Mariners,   Admiralty List of Lights , Admiralty List of Radio Signals , Admiralty Tide tables , Chart – 5011 Symbols and abbreviations to be used  on charts.  The following points to be considered in order to maintain updated chart folio onboard:

• The chart correction log should have details of all charts present onboard with index of corrections (temporary and preliminary also) mentioned against each chart number. All the charts and publications are to be corrected on weekly basis following instructions provided in weekly notices to mariners and the correction numbers to be entered in the same index mentioned above against chart numbers respectively, so that it can be used as a quick reference to check status of corrections for any chart
• There should be a designated chart supplier or service provided on a timely basis without delays to supply new charts and new editions applicable to the folios onboard. Other than that weekly Notice to mariners, Annual summary of Notices to Mariners, their supplements should be provided
• There should be equipment onboard and services to receive Navigational warnings, and Navtex warning

• Whenever a new chart or new edition is published, Weekly Notices to Mariner carry a notification of the same. On receiving a new edition or a new chart the chart correction log is to be updated with the relevant folio number against the chart number in the index and ‘NC’ or ‘NE’ to be inserted adjacent to the chart number in the correction index. The chart to be verified for any pending temporary and preliminary corrections and navigational warnings
• On receiving a chart or a notification through weekly notices to mariners which replaces a previous chart , insert in the chart correction log ‘replaced by’ or ‘cancelled by’ against the mentioned chart. The folio number to be inserted on the replacement chart received.

The Admiralty Chart Catalogue ( NP 131),Weekly Notices to Mariners , Cumulative Notices to Mariners and Annual summary of Admiralty Notices to mariners are important sources of keeping a Chart folio system updated and corrected. For guidance on correcting charts Admiralty has published – How to Correct Charts the Admiralty Way which describes various forms of corrections applied to charts and upkeep of folios. The importance of keeping charts updated can be understood from the below incident.

Real life incident: Due to negligence of a navigating officer a vessel was not allowed to enter a port for 2 days. After 2 days special permission was granted by USCG to the vessel upon request by the agents. The vessel did not have the latest edition of approach charts for the Port of Baltimore. The new edition had been published 4 weeks ago and vessel had received notification of the same. The USCG during their annual inspection pointed the error and the vessel was fined and allowed to berth after two days only when agents procured the new edition.                            

It is therefore important that during correcting charts the navigating officer has to exercise due diligence and care.                                                                              

Real Life Incident: Near Batu Berhanti Light in Singapore Straits a wreck is marked by 4 cardinal buoys surrounding it. During chart corrections the notice read as ‘Insert Isolated Danger Mark’ adjacent to the light. The duty officer misread it as ‘Delete’ and instead of inserting deleted the mark. The courses were laid from that area and while transit it was observed that the vessel passed very closed to the Isolated Danger Marks which were wrongly indicated on the chart.