Notice to Mariners (NM)

Notices to Mariners are the periodical updates that keep charts and nautical publications current: new dangers, depth changes, light alterations, buoy moves, and new editions. The UKHO issues a Weekly Edition of Admiralty Notices to Mariners; the US NGA and NOAA publish their own. T (temporary) and P (preliminary) notices cover short-lived or pending changes. A chart is only as safe as its last correction, so the navigator logs the last NM applied and corrects every chart before use.