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The Canadian document which was previously cited is essentially identical, as is New Zealand 201, British Admiralty Chart 5011, and similar publications from other nations. Although called charts, these are in fact 96 page A4 books. . . . . Jim. . . . Jameslwoodward (talk • contribs) 21:13, 19 December 2009 (UTC)
The British admiralty charts are compiled, drawn and issued by the Hydrographic Office. This department of the Admiralty was established under Earl Spencer by an order in council in 1795, consisting of the Hydrographer, Alexander Dalrymple, one assistant and a draughtsman.
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.
The Admiralty's first Hydrographer was Alexander Dalrymple, [2] appointed in 1795 on the order of King George III and the existing charts were brought together and catalogued. The first chart Dalrymple published as Hydrographer to the Admiralty (of Quiberon Bay in Brittany ) did not appear until 1800. [ 3 ]
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]
The Admiralty appointed Alexander Dalrymple as hydrographer on 12 August 1795, with a remit to gather and distribute charts to HM Ships. Within a year existing charts had been collated, and the first catalogue published. It was five years before the first chart—of Quiberon Bay in Brittany—was produced by the Hydrographer. [1]
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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).