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Depths which have been measured are indicated by the numbers shown on the chart. Depths on charts published in most parts of the world use metres. Older charts, as well as those published by the United States government, may use feet or fathoms. Depth contour lines show the shape of underwater relief. Coloured areas of the sea emphasise shallow ...
Longshore drift plays a large role in the evolution of a shoreline, as if there is a slight change of sediment supply, wind direction, or any other coastal influence longshore drift can change dramatically, affecting the formation and evolution of a beach system or profile. These changes do not occur due to one factor within the coastal system ...
A tuck seine or tuck net about 70 fathoms (420 ft; 130 m) long, and very deep in the middle, was used to take fish from a larger seine. A line attached to a whaling harpoon was about 150 fathoms (900 ft; 270 m). A forerunner — a piece of cloth tied on a ship's log line some fathoms from the outboard end — marked the limit of drift line. [25]
The use of bathymetry and the development of bathymetric charts dates back around the 19th century BC to ancient Egypt.Depictions on tomb walls such as the bas-relief carvings of Deir al-Bahri commissioned by Queen Hatshepsut in the 16th century BC show ancient mariners using long slender poles as sounding poles to determine the depth of the Nile River and into the Nile River Delta.
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.
Ignoring set and drift can cause a mariner to get off their desired course, sometimes by hundreds of miles. A mariner needs to be able to steer the ship and compensate for the effects of set and drift upon their vessel while underway. The actual course a vessel travels is referred to as the course over the ground.
The North Atlantic Current (NAC), also known as North Atlantic Drift and North Atlantic Sea Movement, is a powerful warm western boundary current within the Atlantic Ocean that extends the Gulf Stream northeastward.
Natural lines of drift are those paths across terrain that are the most likely to be used when going from one place to another. These paths are paths of least resistance: those that offer the greatest ease while taking into account obstacles (e.g. rivers, cliffs, dense unbroken woodland, etc.) and modes of transit (e.g. pedestrian, automobile, horses.).