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A ship's draft/draught is the "depth of the vessel below the waterline measured vertically to the lowest part of the hull, propellers, or other reference point". [1] That is, the draft or draught is the maximum depth of any part of the vessel, including appendages such as rudders, propellers and drop keels if deployed.
Used mainly to determine the minimum water depth for safe passage of a vessel and to calculate the vessels displacement (obtained from ships stability tables) so as to determine the mass of cargo on board. Draft, Air – Air Draft/Draught is the distance from the water line to the highest point on a ship (including antennas) while it is loaded ...
Depth contour lines show the shape of underwater relief. Coloured areas of the sea emphasise shallow water and dangerous underwater obstructions. Depths are measured from the chart datum, which is related to the local sea level. The chart datum varies according to the standard used by each national Hydrographic Office.
A sailor and a man on shore, both sounding the depth with a line. Depth sounding, often simply called sounding, is measuring the depth of a body of water. Data taken from soundings are used in bathymetry to make maps of the floor of a body of water, such as the seabed topography. Soundings were traditionally shown on nautical charts in fathoms and
At a basic level, it is typically calculated in metres using the formula: Charted Depth − Draft-/+ Height of Tide = UKC. [3] Ship masters and deck officers can obtain the depth of water from Electronic navigational charts. [2] More dynamic or advanced calculations include safety margins for manoeuvring effects and squat. [7]
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).
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 ...
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.