Hydrography

Hydrography is the measurement and description of navigable waters and coastal regions, including their depths, seabed features, tides, and hazards.

Bathymetric survey: A survey that measures water depth and maps the shape of a submerged surface. Soundings provide the depth measurements that form a hydrographic survey’s core.
Bathymetry: The measurement and mapping of water depth and underwater topography. It is the depth-mapping component of hydrography.
Nautical chart: A map for marine navigation that depicts water depths, hazards, coastlines, and aids to navigation. Hydrographic data supplies the depths and hazards mariners need to avoid groundings.
Portolan chart: A medieval nautical chart showing coastlines, ports, and compass-direction lines. Portolan charts represent an early tradition of practical coastal mapping for mariners.
Seabed 2030: A global initiative to compile a complete map of the ocean floor by 2030. Large areas remain poorly mapped despite hydrography’s long charting history.
Multibeam echosounder: An acoustic instrument that measures water depth across a swath beneath a vessel. Its wide swaths efficiently map seabed depth and shape.
Sounding: A measurement of water depth at a particular position. Individual soundings are the basic observations used to map navigable waters.
Electronic navigational chart: A standardized digital chart used by an electronic chart display and information system. It presents hydrographic information in an interactive format for ship navigation.
James Cook: A British naval officer and explorer whose Pacific voyages included extensive surveying and chartmaking. His voyages advanced systematic charting of coastlines and navigable waters.
Satellite-derived bathymetry: The estimation of shallow-water depths from satellite measurements of reflected light. It may extend coverage where vessel-based surveys are costly or difficult.

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