Notice to mariners
A notice to mariners (NTM or NOTMAR,) advises mariners of important matters affecting navigational safety, including new hydrographic information, changes in channels and aids to navigation, and other important data. Over 60 countries which produce nautical charts also produce a notice to mariners. About one third of these are weekly, another third are bi-monthly or monthly, and the rest irregularly issued according to need. For example, the United Kingdom Hydrographic Office issues weekly updates. United States. The U.S. "Notice to Mariners" is made available weekly by the National Geospatial-Intelligence Agency (NGA), prepared jointly with the  National Ocean Service (NOS) and the U.S. Coast Guard. The information in the "Notice to Mariners" is formatted to simplify the correction of paper charts, "List of Lights", "Light Lists", "United States Coast Pilots", and other publications produced by NGA, NOS, and the U.S. Coast Guard. Information for the "Notice to Mariners" is contributed by: the National Geospatial-Intelligence Agency (Department of Defense) for waters outside the territorial limits of the United States; National Ocean Service (National Oceanic and Atmospheric Administration, Department of Commerce), which is charged with surveying and charting the coasts and harbors of the United States and  its territories; the U.S. Coast Guard (Department of Homeland Security) which is responsible for the safety of life at sea and the establishment and operation of aids to navigation; and the Army Corps of Engineers (Department of Defense), which is charged with the improvement of rivers and harbors of the United States. In addition, important contributions are made by foreign hydrographic offices and cooperating observers of all nationalities. The Notice consists of a page of Hydrograms listing important items in the Notice, a chart correction section organized by ascending chart number, a product catalog corrections section, a publications correction section , a summary of broadcast navigation warnings, and a page of additional miscellaneous information. It is the responsibility of users to decide which of their charts and publications require correction. Mariners are requested to cooperate in the correction of charts and publications by reporting all discrepancies between published information and conditions actually observed and by recommending appropriate improvements. A reporting form is provided in the back of each "Notice to Mariners". Issue No. 1 of each year contains important information on a variety of subjects which supplements information not usually found on charts and in navigational publications. This information is published  as Special Notice to Mariners Paragraphs. Additional items considered of interest to the mariner are also included in this Notice. Much of the data in the U.S. "Notice to Mariners" is obtained from foreign notices. Canada. In Canada, the Canadian Coast Guard (CCG) Notice to Mariners publication informs mariners of important navigational safety matters affecting Canadian Waters. This electronic publication is published on a monthly basis and can be downloaded from the Notices to Mariners (NOTMAR) Web site. The information in the Notice to Mariners is formatted to simplify the correction of paper charts and navigational publications. The NOTMAR.gc.ca site  is a free 24/7 service providing mariners with up-to-date safety advisories. It provides mariners with a quick and easy to use interface to access Notices to Mariners information. This system also generates weekly and monthly notification mailers, for its registered users. These on-line mail services provides the monthly Notices to Mariners publications as well as the weekly (section II - chart corrections) notices that advise the mariner of the notices that have been issued against their chart selections. These mail services simplify the process for registered clients to update their publications and charts as required under the Canada  Shipping Act. The NOTMAR web site also includes the historical Chart corrections and historical Sailing Direction corrections; as well, it provides access to downloadable Chart Patches, contains links to CHS’s Chart Number 1, instructions for applying Notices to mariners to manually update their paper charts, and other useful information. Summary of Corrections. A close companion to the "Notice to Mariners" is the Summary of Corrections. The "Summary" is published in five volumes. Each volume covers a major portion of the earth including several chart regions and many subregions. Volume 5 also includes special charts and publications corrected by the  Notice to Mariners. Since the Summaries contain cumulative corrections, any chart, regardless of its print date, can be corrected with the proper volume of the Summary and all subsequent "Notice to Mariners". References. The text of this article originated from sections 418 and 419 of The American Practical Navigator, a document produced by the government of the United States of America.