Correcting and upgrading a navigation chart is a constant process. Once a chart is published, constantly changing navigational features and aids or other relevant information have to be promulgated in order to update the ships navigating in those areas.
Admiralty Notices to Mariners or Weekly Notices serve the purpose of correcting and updating charts, which are being supplied to the vessels electronically or in paper format.
Various Means to update and keep corrected the chart outfit system onboard are –
Weekly Notices to Mariners
Issued on a weekly basis by the Admiralty, these notices contain corrections to charts and various other publications such as Admiralty sailing directions and Admiralty list of lights and radio signals. They also include temporary and preliminary notices to correct charts. The year begins with notice no .1 being issued in first week of January and the numbering increases chronologically till last week of the year. They also notify about any new charts or new editions being published and their previous editions being cancelled.
The corrections are mentioned either in the form of co ordinates with instructions or in the form of overlay chart tracings and blocks to be cut and pasted. New editions of Admiralty list of lights and fog signals, Admiralty Sailing directions and Admiralty List of Radio Stations are provided when available.
Cumulative List of Notices to mariners
These are published twice a year in January and July. The main purpose of them is to provide a list of current editions of all Admiralty Charts and the serial numbers of notices affecting them which have been issued in previous two years. The charts present onboard can be verified for any missing corrections by checking them against the Cumulative Lists.
Annual Summary of Notices to Mariners
All the temporary and preliminary notices for a previous year are being published collectively in Annual Summary of Notices to Mariners. They are quick and handy references available to determine which all temporary and permanent corrections are applicable to a chart. They also contain summary of corrections to sailing directions.
Chart correction software and computer ( Chart Co)
The paper copy of weekly notices to mariners is digitized using software popularly named as Chart Co. Being online with a chart correction service provider, this organizes chart folios onboard in the form of a database and the corrections received being individually listed under respective charts. A navigating officer can then access the system using chart number to print and apply any specific or all applicable corrections for any chart present onboard. There is an offline database and software in use onboard ships where corrections are supplied in the form of weekly mail attachments. These are used to keep the chart correction database up to date exactly like the paper copy of Weekly Notices to Mariners.
Navarea Warnings: Navarea warnings are promulgated to ships operating in various areas. The world is divided into 16 NAV AREAS and these warnings are broadcasted by World Wide Navigational Warning Service. Through a network of Area Coordinators and National coordinators important international, coastal and local warnings and notices related to navigation are transmitted to ships which they receive using MF/HF radio frequencies and satellite networks.
Navtex Warnings: These are broadcasted by Telex Broadcasting stations established in various coastal areas. Mostly they broadcast navigational, meteorological and distress warnings. They play a vital source of providing early warning in coastal navigation. A receiver onboard named as a Navtex Receiver is used to receive Navigational warnings. E.g. In Dec. 2004 the Navtex stations were the first to broadcast urgency and distress warnings related to Tsunami to fishing and other merchant vessels operating in Indian ocean and adjacent coastal areas.