Side scan sonar units are towed in the water, usually behind the vessel, to gather data for nautical charts.
Hydrography is the science that measures and describes the physical features of bodies of water and the land areas adjacent to those bodies of water.
NOAA conducts hydrographic surveys to measure the depth and bottom configuration of water bodies. The data is used to update nautical charts and develop hydrographic models; increasingly, it is used for multiple purposes, through the Integrated Ocean and Coast Mapping program.
The one data type common to all hydrographic surveys is water depth. Of additional concern to many surveys is the nature of the seafloor material (i.e., sand, mud, rock) due to implications for anchoring, dredging, structure construction, pipeline and cable routing, and fisheries habitat.
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