A survey vessel is any type of ship or boat that is used for underwater surveys, usually to collect data for mapping or planning underwater construction or mineral extraction. It is a type of research vessel, and may be designed for the purpose, modified for the purpose or temporarily put into the service as a vessel of opportunity, and may be crewed, remotely operated, or autonomous. The size and equipment vary to suit the task and availability. Role The task of survey vessels is to map the bottom, and measure the characteristics of the benthic zone, full water column, and surface for the purpose of: hydrography, the measurement and description of the physical features of oceans and other natural bodies of water, and the prediction of their change over time, for the primary purpose of safety of navigation and in support of other activities associated with those bodies of water, general oceanography, the scientific study of the oceans, mapping of marine habitats as part of the process of assessing the state of the ecology, measurement of environmental impact of natural and anthropogenic changes, planning of marine salvage, the process of recovering a ship and its cargo after a shipwreck or other maritime casualty, dredging, the excavation of material from underwater, to recover materials or to alter the bottom profile, usually for navigational of construction purposes, underwater construction, which is industrial construction in an underwater environment, coastal engineering, the branch of civil engineering concerned with construction at or near the coast, and the development of the coast itself, maritime archaeology, the study of human interaction with the sea, lakes and rivers through the study of associated physical remains, underwater mining and extraction of petroleum. Survey equipment Typically, modern survey vessels are equipped with one or more of the following equipment: Satellite navigation to provide autonomous geo-spatial positioning, Single beam sonar for the measurement of underwater physical and biological components, Multibeam sonar to accurately and efficiently map the seabed Side-scan sonar to efficiently create relief images of large areas of the sea floor. Towed magnetometer for measuring the Earth's magnetic field, in geophysical surveys, to detect magnetic anomalies, Reflection seismology equipment for subsurface profiling. Seismic sources include air guns, sparkers and boomers. Bottom sampling equipment such as Van Veen grab sampler, Box corer, Epibenthic sled or other core sampling equipment. CTD sondes to measure the electrical conductivity, temperature, and pressure of seawater