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This method revolutionized hydrographic surveying, as it allowed a quicker, less laborious, and far more complete survey of an area than did the use of lead lines and sounding poles. From a navigational safety point of view, a wire-drag survey would not miss a hazard to navigation that projected above the drag wire depth.
The first recorded evidence of water depth measurements are from Ancient Egypt over 3000 years ago. [3] Bathymetry has various uses including the production of Bathymetric charts to guide vessels and identify underwater hazards, the study of marine life near the floor of water bodies , coastline analysis and ocean dynamics , including ...
Bathymeric 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.
These types of survey may be done in or of the underwater environment, in which case they may be referred to as underwater surveys, which may include bathymetric, hydrographic, and geological surveys, archaeological surveys, ecological surveys, and structural or vessel safety surveys.
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 main product of the VORF project was the gridded vertical correction files which deliver the capability to transfer heights and depths from one vertical reference system to another, "allowing the direct use of depth data from surveys which is referred to a WGS84 compatible datum rather than Chart Datum and thus enabling Hydrographic surveyors to survey without the need to measure tides".
The "leadsman" called out the depth as he read it off the line. If the depth was at a mark he would call "by the mark" followed by the number, while if it was between two marks, he would call "by the deep" followed by the estimated number; thus "by the mark five", since there is a five-fathom mark, but "by the deep six", since there is no six ...
Satellite-derived bathymetry (SDB) is the calculation of shallow water depth from active or passive satellite imaging sensors. The technology requires a sensor (hardware) and relevant algorithms (software) to derive bathymetric measurements from the data recorded by the sensor. [1]