The correction system
The UK Hydrographic Office issues weekly editions of Admiralty Notices to Mariners (NMs) that correct paper charts and publications. Permanent notices make a lasting change; Temporary (T) notices cover a change that will be removed later, such as a buoy lifted for maintenance; and Preliminary (P) notices give advance warning of work not yet complete. The Annual Summary of Notices and the cumulative list let a navigator confirm exactly which corrections a given chart should already carry. Between weekly editions, urgent changes reach the ship as navigational warnings by NAVTEX, radio and the ALRS.
Correcting a chart in practice
Applying a Notice to Mariners to a paper chart
- Confirm the chart is affected and that every earlier correction is already recorded (check the bottom-left correction log).
- Work in violet waterproof ink and make the change exactly as the NM block and its associated diagram (tracing) describe.
- Record the NM number and year in the correction record in the bottom-left margin.
- Correct all associated publications — sailing directions, light lists, the ALRS — from the same NM.
- For T and P notices, pencil them in, list them, and rub them out only when the notice is cancelled.
NOTE — Electronic charts still need updating ENCs are corrected automatically by weekly update files from the chart service rather than by hand, but the discipline is identical: confirm the updates have been applied and the charts are current before relying on them, and know the 'last update' status of your ECDIS.
The examiner will expect the OOW to explain not just how to correct a chart but why the system matters: an uncorrected chart may not show a new wreck, a moved buoy, a changed light character or a reduced depth, any of which can put the ship in danger. Keeping the outfit current is a continuous, logged routine, not an occasional chore, and responsibility for it is usually delegated to a specific officer under the Master.
WARNING — T and P notices are easy to forget Because temporary and preliminary changes are pencilled in, they are the ones most often missed. Keep a live list and check it against the chart before using any area they affect.