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Part of an early "new style" Admiralty chart, of Risavika in Norway, published in 1970. Depth in metres (and tenths of metres for depths less than 20m). Metrication of Admiralty charts began in 1967, and it was decided to synchronise this with the introduction of a new style of chart, with increased use of colour, which continues in use today.
On nautical charts, the top of the chart is always true north, rather than magnetic north, towards which a compass points. Most charts include a compass rose depicting the variation between magnetic and true north. However, the use of the Mercator projection has drawbacks. This projection shows the lines of longitude as parallel.
In the UK, the Admiralty issues 76 volumes covering the world and these are used frequently by most merchant ships. [8] In the US, the United States Coast Pilots is a nine-volume American navigation publication distributed yearly by the National Ocean Service. Its purpose is to supplement nautical charts of US waters.
The oldest sailing directions, dating back to the middle ages, descended directly from the Greek and Roman periplii: in classical times, in the absence of real nautical charts, navigation was carried out using books that described the coast, not necessarily intended for navigation, but more often consisting of reports of previous voyages, or celebrations of the deeds of leaders or rulers.
An Electronic Navigational Chart (ENC) is a digital representation of a real-world geographical area for the purpose of Marine navigation.Real-world objects and areas of navigational significance, or to a lesser degree - informational significance, are portrayed through Raster facsimiles of traditional paper charts; or more commonly through vector images, which are able to scale their relative ...
A TSS is typically created in locations with large numbers of ship movements and vessels travelling in different directions and where there might otherwise be a high risk of collisions. Details of traffic separation schemes and similar routing-systems can be found on Admiralty charts. [1]
A chart datum is the water level surface serving as origin of depths displayed on a nautical chart and for reporting and predicting tide heights. A chart datum is generally derived from some tidal phase, in which case it is also known as a tidal datum. [1] Common chart datums are lowest astronomical tide (LAT) [1] and mean lower low water (MLLW).
The charts are stored in BSB format. "[The BSB file format] is a proprietary format of BSB Electronic Charts, LLP (bought by MapTech, Inc.)." [1] Image manipulation tools such as GDAL can read the image information, but there also is georeferenced data in the navigational charts.