Periodical or casual notices issued by the hydrographic offices of maritime nations, or other competent authorities, regarding changes in aids to navigation, such as buoys and lighthouses, dangers to navigation, important new soundings, and, in general, any information affecting charts, sailing directions, light lists, and other nautical publications. Most major hydrographic offices issue such notices on a weekly basis but others issue them at two-weekly or monthly intervals. Traditionally issued as printed paper booklets, the navigator adds the corrections to the publication. Larger corrections, known as ‘patches’, can be cut out and pasted on to the chart.
There is an increasing trend to post the notices on websites from which they can be downloaded by the navigator. For updating electronic charts the information is frequently incorporated on a compact disk which is inserted into the system and automatically updates it. As there is a legal obligation for mariners to carry and use up-to-date charts and publications, the acquisition and application of the notices is essential for safe navigation.
Subjects: Maritime History.