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Marine charts are a graphical representation of a maritime area and adjoining coastal areas. Depending upon the scale of the chart, it may display depths of water and heights of land (topographic map ), natural features of the ocean floor, particulars of the coastline, navigational hazards, positions of natural and human-made aids to navigation , data on tides and currents , local particulars of the Earth's magnetic field , and human-made constructions such as harbours , buildings, and bridges.
Marine charts are indispensable tools for marine navigation; a lot of countries call for vessels, particularly commercial ships, to carry them. Nautical charting may take the form of charts printed on paper or computerized electronic navigational charts.
Modern technologies have made available paper charts which are printed "on demand" with cartographic information that's been downloaded to the commercial printing company as recently as the night before publishing. With each daily download, vital data such as Local Notice to Mariners is added to the on-demand chart files therefore these charts will be up to date at the time of printing.
Sources and publishing of nautical charts marine charts are based on hydro graphic surveys. As surveying is laborious and time-consuming, hydrographic data for a lot of areas of ocean may be dated and not all of the time reliable. Depths are calculated in a assortment of ways. Historically sounding line was applied. In modern times, echo sounding is used for measuring the seabed in the open sea.
When measuring the safe depth of water over an intact obstruction, such as a wreck, the minimum depth is checked by sweeping the area with a length of horizontal wire . This ensures that hard to find projections, such as masts, don't present a danger to vessels navigating over the obstacle.
Nautical charts are issued by the national hydro graphic agencies in a lot of countries. These charts are considered "official" in contrast to those made by commercial publishers. A lot of hydrographic offices provide regular, occasionally weekly, manual updates of their charts through their sales agents. Individual hydro graphic offices produce national chart series and international chart series.
Coordinated by the International Hydro graphic Organization, the international chart series is a global system of charts ("INT" chart series), which is being developed with the goal of amalgamating as many chart systems as possible.
There are also commercially published charts, some of which may carry supplementary information of particular interest, e.g. for yacht masters. Marine charts used for a vessels navigation also make excellent nautical gift as décor for any seaman’s collection of memorabilia.
The nature of a waterway portrayed by a chart may alter, and artificial aids to navigation may be altered at short notice. Consequently, older or uncorrected charts should never be applied for navigation. All producers of nautical charts also supplies a system to inform mariners of alterations that affect the marine charts.
In the U.S.A., chart corrections and notifications of new editions are supplied by respective governmental agencies by way of Notice to Mariners, Local Notice to Mariners , Summary of Corrections ,and Broadcast Notice to Mariners . In the U.S., NOAA also has a printing process partner who prints the "POD" (print on demand) NOAA charts, and they incorporate the very latest corrections and notifications at the time of printing.
Notice to mariners, Radio broadcasts generate advance notice of urgent corrections. A good way to maintain track of corrections is with a Chart and Publication Correction Record Card system. Applying this system, the navigator doesn't immediately update every chart in the portfolio when a new Notice to Mariners comes, instead creating a card for every chart and taking down the correction on this card.
When the time comes to use the chart, he pulls the chart and chart's card, and establishes the indicated corrections upon the chart. This system controls that every chart is properly corrected prior to use. A responsible mariner should obtain a new chart if he or she has not kept track of corrections and his chart is more than several months old.
Various Digital Notices to Mariners systems are acquirable on the market such as Digitrace, Voyager, or ChartCo, to correct British Admiralty charts besides NOAA charts. These systems supplies only vessels relevant corrections via e-mail or web downloads bringing down time needed to sort corrections for each chart. Also, tracings to assist corrections are furnished at the same time.
The Canadian Coast Guard in addition to produces the Notice to Mariners publication which informs mariners of crucial navigational safety matters involving Canadian Waters. This electronic publication is published every month and can be downloaded from the Notices to Mariners (NOTMAR) Web site.
The selective information in the Notice to Mariners is formatted to simplify the correction of paper charts and navigational publications. Various and diverse techniques exist for the correction of electronic navigational charts.
In 1973 the cargo ship MV Muirfield (a merchant vessel named after Muirfield , Scotland collided with an unknown object in waters charted at a depth of bigger than 5,000 metres (16,404 ft), resulting in extensive damage to her keel In 1983, HMAS Moresby , a Royal Australian Navy , surveyed the region where Muirfield was damaged, and charted in detail this previously unsuspected hazard to navigation, the Muirfield Seamount.
The dramatic accidental discovery of the Muirfield Seamount is frequently quoted as an good example of limitations in the vertical geodetic datum accuracy of some sea areas as defended on marine charts, particularly on small-scale charts.
A similar incident affecting a passenger ship happened in 1992 when the Cunard liner Queen Elizabeth 2 struck a submerged rock off Block Island in the Atlantic Ocean . More recently, in 2005 the submarine USS San Francisco (SSN-711) bumped into an uncharted sea mount about 560 kilometers (350 statute miles) south of Guam at a velocity of 35 knots (40.3 mph; 64.8 km/h), suffering severe damage and killing one seaman.
On the 8th Sept 2006 the jack-up barge Octopus got stranded on an uncharted sea mount within the Orkney Islands (United Kingdom) when being towed by the Harold tug. £1M worth of damage was caused to the barge and held up work on the installation of a tidal energy generator prototype. As stated in the Mariners Handbook and subsequent accident written report "No marine chart is infallible. All marine charts are apt to be incomplete.
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