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Bathymetric charts showcase depth using a series of lines and points at equal intervals, called depth contours or isobaths (a type of contour line). A closed shape with increasingly smaller shapes inside of it can indicate an ocean trench or a seamount, or underwater mountain, depending on whether the depths increase or decrease going inward.
Bathymetry (/ b ə ˈ θ ɪ m ə t r i /; from Ancient Greek βαθύς (bathús) 'deep' and μέτρον (métron) 'measure') [1] [2] is the study of underwater depth of ocean floors (seabed topography), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography.
GEBCO is the only intergovernmental body with a mandate to map the whole ocean floor. At the beginning of the project, only 6 per cent of the world's ocean bottom had been surveyed to today's standards; as of June 2022, the project had recorded 23.4 per cent mapped. About 14,500,000 square kilometres (5,600,000 sq mi) of new bathymetric data ...
A "sea-gage" for measuring ocean depth was described in Philosophia Britannica in 1747. [3] But it wasn't until 1775 and the development of a depth gauge by the inventor, scientific instrument, and clock maker Isaac Doolittle of New Haven, Connecticut , for David Bushnell 's submarine the Turtle , that one was deployed in an underwater craft.
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.
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.
Floats measure the physical and chemical aspects of the ocean in detail, such as measuring the direction and speed of water or the temperature and salinity. [2] A float will descend to a predetermined depth where it will be neutrally buoyant .
The depth at which the disk is no longer visible is taken as a measure of the transparency of the water. This measure is known as the Secchi depth and is related to water turbidity . Since its invention, the disk has also been used in a modified, smaller 20 cm (8 in) diameter, black-and-white design to measure freshwater transparency.