What a Notice to Mariners Is — and Is Not
A Notice to Mariners (NtM) is the official mechanism by which hydrographic offices instruct mariners to amend paper charts and nautical publications to reflect the latest navigational information. In the UK, the UKHO publishes weekly NtMs. They are the authoritative source for keeping paper charts on board corrected and up to date.
Distinguish clearly:
| Term | What it does |
|---|---|
| Notice to Mariners | Corrects paper charts and publications; issued weekly by UKHO |
| Chart updating (AVCS/ENCs) | Electronic charts updated via cell updates — NtMs do not apply to ENCs directly |
| Navigational Warning (NAVTEX / NAVAREA) | Broadcasts urgent temporary hazards; does not permanently correct a chart |
| T&P Notice | Temporary and Preliminary NtM — marks a temporary change or advance notice; applied in pencil only |
Examiners frequently probe whether candidates confuse NtMs with navigational warnings or assume electronic chart updates replace the NtM obligation for paper charts carried on board.
Applying a Correction
The standard process:
- Source the NtM — UKHO website (free); weekly print editions. Check the Chart affected and Edition date columns — only apply if your chart edition is listed or later.
- Record before correcting — enter the NtM number and year (e.g. NM 1234/25) in the Chart Correction Log and on the chart's title block or border.
- Apply in violet ink (magenta/purple) using a fine-tipped pen — this is the internationally recognised convention for hand-corrections so they are immediately visible.
- T&P corrections — apply in pencil so they can be removed when cancelled.
- Source tracings — complex corrections (e.g. new buoyage layouts) are supplied as printed tracings or blocks to cut out and paste on.
The Correction Log
Every corrected chart must show which NtMs have been applied. The vessel must maintain a Chart Correction Log (or equivalent record) so that anyone joining the vessel can verify the state of correction of each chart. During an MCA inspection or oral, expect to be asked to demonstrate this log and explain the process.
When Corrections Are Not Required
A chart is not corrected for NtMs issued before its print date — those corrections are already incorporated. Always check the edition date / new edition notice before applying.
Never use a superseded chart solely because it appears corrected; if a new edition has been issued, the old chart should be replaced.