Editing Nautical chart (section)

== Chart correction ==

The nature of a waterway depicted by a chart may change, and artificial aids to navigation may be altered at short notice. Therefore, old or uncorrected charts should never be used for navigation. Every producer of nautical charts also provides a system to inform mariners of changes that affect the chart. In the United States, chart corrections and notifications of new editions are provided by various governmental agencies by way of [[notice to mariners|Notice to Mariners]], [[Local Notice to Mariners]], [[Summary of Corrections]], and [[Broadcast Notice to Mariners]]. In the U.S., NOAA also has a printing partner who prints the "POD" (print on demand) NOAA charts, and they contain the very latest corrections and notifications at the time of printing. To give notice to mariners, radio broadcasts provide advance notice of urgent corrections.

A good way to keep track of corrections is with a ''Chart and Publication Correction Record Card'' system. Using this system, the navigator does not immediately update every chart in the portfolio when a new ''Notice to Mariners'' arrives, instead creating a card for every chart and noting the correction on this card. When the time comes to use the chart, he pulls the chart and chart's card, and makes the indicated corrections on the chart. This system ensures that every chart is properly corrected prior to use. A prudent mariner should obtain a new chart if he has not kept track of corrections and his chart is more than several months old.

Various Digital Notices to Mariners systems are available on the market such as Digitrace, Voyager, or ChartCo, to correct British [[Admiralty chart]]s as well as NOAA charts. These systems provide only vessel relevant corrections via e-mail or web downloads, reducing the time needed to sort out corrections for each chart. Tracings to assist corrections are provided at the same time.

The [[Canadian Coast Guard]] produces the Notice to Mariners publication which 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.

Various and diverse methods exist for the correction of electronic navigational charts.

=== Limitations ===

In 1973 the cargo ship ''MV Muirfield'' (a merchant vessel named after [[Muirfield]], [[Scotland]]) struck an unknown object in the [[Indian Ocean]] in waters charted at a depth of greater than 5,000 metres (16,404&nbsp;ft), resulting in extensive damage to her [[keel]].<ref>Calder, Nigel. ''How to Read a Navigational Chart: A Complete Guide to the Symbols, Abbreviations, and Data Displayed on Nautical Charts.'' International Marine/Ragged Mountain Press, 2002.</ref> In 1983, [[HMAS Moresby (1963)|HMAS ''Moresby'']], a [[Royal Australian Navy]] [[survey ship]], surveyed the area where ''Muirfield'' was damaged, and charted in detail a previously unsuspected hazard to navigation, the [[Muirfield Seamount]]. The dramatic accidental discovery of the Muirfield Seamount is often cited as an example of limitations in the vertical [[geodetic datum]] accuracy of some offshore areas as represented on nautical charts, especially on small-[[Level of measurement|scale]] charts.

A similar incident involving a passenger ship occurred in 1992 when the [[Cunard Line|Cunard]] liner ''[[Queen Elizabeth 2]]'' struck a submerged rock off [[Block Island]] in the [[Atlantic Ocean]].<ref>British Admiralty. ''The Mariner's Handbook''. 1999 edition, page 23.</ref> In November 1999, the [[semi-submersible]], [[heavy-lift ship]] ''[[Mighty Servant 2]]'' capsized and sank after hitting an uncharted single underwater isolated pinnacle of granite off Indonesia. Five crew members died and ''Mighty Servant 2'' was declared a total loss.<ref>{{cite web | title=Maritime Casualties 1999 And Before | url=http://www.cargolaw.com/presentations_casualties_a.html | work=The Cargo Letter | year=2007 | access-date=August 25, 2018 | archive-date=December 16, 2017 | archive-url=https://web.archive.org/web/20171216192817/http://www.cargolaw.com/presentations_casualties_a.html | url-status=dead }}</ref> More recently, in 2005 the submarine [[USS San Francisco (SSN-711)|USS ''San Francisco'']] ran into an uncharted [[seamount]] (sea mountain) about 560 kilometres (350 statute miles) south of Guam at a speed of {{convert|35|kn|mph km/h|1|lk=in}}, sustaining serious damage and killing one seaman. In September 2006 the [[jack-up barge]] ''Octopus'' ran aground on an uncharted sea mount within the [[Orkney Islands]] (United Kingdom) while being towed by the tug ''Harold''. £1M worth of damage was caused to the barge and delayed work on the installation of a tidal energy generator prototype. As stated in the Mariners Handbook and subsequent accident report: "No chart is infallible. Every chart is liable to be incomplete".<ref>Marine Investigation Accident Branch (2007) Report Number 18/2007.</ref>