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The GEBCO chart series was initiated in 1903 by an international group of geographers and oceanographers, under the leadership of Prince Albert I of Monaco.At that time there was an explosion of interest in the study of the natural world and this group recognized the importance of a set of maps describing the shape of the ocean floor.
The depth predicted by the square root of seafloor age found by the 1974 cooling mantle derivation [4] is too deep for seafloor older than 80 million years. [5] Depth is better explained by a cooling lithosphere plate model rather than the cooling mantle half-space. [5] The plate has a constant temperature at its base and spreading edge.
The beams update many times per second (typically 0.1–50 Hz depending on water depth), allowing faster boat speed while maintaining 100% coverage of the seafloor. Attitude sensors allow for the correction of the boat's roll and pitch on the ocean surface, and a gyrocompass provides accurate heading information to correct for vessel yaw .
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.
The project aims to identify and pool all Bathymetry data in the Southern Ocean and use that data to produce gridded bathymetric maps of the seafloor. The extent of the project is bound by 50°S, stretching from the southern tip of South America to the coastal waters of Antarctica .
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.
The outcome of the study was a class of vertical-beam depth sounders, which is still widely used. It simultaneously pinged at two acoustic frequencies, separated by more than 2 octaves, making depth and echo-amplitude measurements that were concurrent, both spatially and temporally, albeit at a single vertical grazing angle. [clarification needed]
A sub-bottom profiler is another sonar system used in geophysical surveys of the sea floor to not only map depth, but also to map beneath the sea floor. [14] Mounted to the hull of a ship, the system releases low-frequency pulses which penetrate the surface of the sea floor and are reflected by sediments in the sub-surface.