Bathymetry

Summary

Bathymetry (bə'θɪmətri; ) 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. The first recorded evidence of water depth measurements are from Ancient Egypt over 3000 years ago. Bathymetric charts (not to be confused with hydrographic charts), are typically produced to support safety of surface or sub-surface navigation, and usually show seafloor relief or terrain as contour lines (called depth contours or isobaths) and selected depths (soundings), and typically also provide surface navigational information. Bathymetric maps (a more general term where navigational safety is not a concern) may also use a Digital Terrain Model and artificial illumination techniques to illustrate the depths being portrayed. The global bathymetry is sometimes combined with topography data to yield a global relief model. Paleobathymetry is the study of past underwater depths. Synonyms include seafloor mapping, seabed mapping, seafloor imaging and seabed imaging. Bathymetric measurements are conducted with various methods, from depth sounding, sonar and Lidar techniques, to buoys and satellite altimetry. Various methods have advantages and disadvantages and the specific method used depends upon the scale of the area under study, financial means, desired measurement accuracy, and additional variables. Despite modern computer-based research, the ocean seabed in many locations is less measured than the topography of Mars. Hydrographic survey#Methods Originally, bathymetry involved the measurement of ocean depth through depth sounding. Early techniques used pre-measured heavy rope or cable lowered over a ship's side. This technique measures the depth only a singular point at a time, and is therefore inefficient. It is also subject to movements of the ship and currents moving the line out of true and therefore is not accurate.

Official source

https://en.wikipedia.org/wiki/Bathymetry

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Related publications (3)

Bathymetry and latitude modify lake warming under ice

Damien Bouffard, Hugo Nicolás Ulloa Sánchez, Tomy Doda, Cintia Luz Ramon Casanas, Kraig Bates Winters

In late winter, solar radiation is the main driver of water motion in ice-covered lakes. The resulting circulation and mixing determine the spatial distribution of heat within the lake and affect the heat budget of the ice cover. Although under-ice lake warming is often modeled as a onedimensional (1D) vertical process, lake bathymetry induces a relative excess heating of shallow waters, creating horizontal density gradients. This study shows that the dynamic response to these gradients depends sensitively on lake size and latitude – Earth’s rotation – and is controlled by the Rossby number. In the ageostrophic limit, horizontal density gradients drive cross-shore circulation that transports excess heat to the lake interior, accelerating the under-ice warming there. In the geostrophic regime, the circulation of the near- and off-shore waters decouples, and excess heat is retained in the shallows. The flow regime controls the fate of this excess heat and its contribution to water-induced ice melt.

2021

Bathymetry is a crucial variable for many researches, such as monitoring of the coral ecosystems. Traditional bathymetric measurements are made by echo-sounder, a type of sonar, measuring water depth from sea surface. Nevertheless, this acquisition process remains expensive and cannot be applied everywhere. Despite less accurate results, passive satellite derived bathymetry can provide a large-scale resolution at a lower cost. This study explores the potential of empirical models applied on images provided by Sentinel-2 sensor for bathymetry retrieval. Technical issues and suitable conditions are described here. In addition, a different approach is proposed. It is composed of an initial step designed to classify areas relying on their bottom reflectance and their water optical properties. Tests are achieved in New Caledonia, in the South West part of the lagoon. The method showed its ability to produce bathymetric data at a large scale, including shallow coral areas, which are difficult to measure by boat. The proposed approach allowed to improve the results of traditional empirical models. For this reason, satellite derived bathymetry can provide a valuable alternative for researchers needing to study coral ecosystems.

2018

The objective of this project is to develop a low-cost and flexible solution for mapping the nearshore bathymetry using a small quadcopter that hovers above the surf zone.

2017

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