The process whereby mapping technologies are used to produce highly detailed images of the sea floor. High-resolution images of the sea floor are used to locate and manage marine resources such as fisheries and oil and gas reserves, identify offshore faults and the potential for coastal damage due to earthquakes, and map out and monitor marine pollution, in addition to providing information on what processes are affecting the sea floor, where these processes occur, and how they interact. Marine geology

Side-scan sonar provides a high-resolution view of the sea floor. In general, a side-scan sonar consists of two sonar units attached to the sides of a sled tethered to the back of a ship. Each sonar emits a burst of sound that insonifies a long, narrow corridor of the sea floor extending away from the sled. Sound reflections from the corridor that echo back to the sled are then recorded by the sonar in their arrival sequence, with echoes from points farther away arriving successively later. The sonars repeat this sequence of “talking” and listening every few seconds as the sled is pulled through the water so that consecutive recordings build up a continuous swath of sea-floor reflections, which provide information about the ture of the sea floor.

The best technology for mapping sea-floor depths or bathymetry is multibeam sonar. These systems employ a series of sound sources and listening devices that are mounted on the hull of a survey ship. As with side-scan sonar, every few seconds the sound sources emit a burst that insonifies a long, slim strip of the sea floor aligned perpendicular to the ship's direction. The listening devices then begin recording sounds from within a fan of narrow sea-floor corridors that are aligned parallel to the ship and that cross the insonified strip. By running the survey the same way that one mows a lawn, adjacent swaths are collected parallel to one another to produce a complete sea-floor map of an area.

The most accurate and detailed view of the sea floor is provided by direct visual imaging through bottom cameras, submersibles, remotely operated vehicles, or if the waters are not too deep, scuba diving. Because light is scattered and absorbed in waters greater than about 33 ft (10 m) deep, the sea-floor area that bottom cameras can image is no more than a few meters. This limitation has been partly overcome by deep-sea submersibles and remotely operated vehicles, which provide researchers with the opportunity to explore the sea floor close-up for hours to weeks at a time. But even the sea-floor coverage that can be achieved with these devices is greatly restricted relative to side-scan sonar, multibeam sonar, and satellite altimetry.

The technology that provides the broadest perspective but the lowest resolution is satellite altimetry. A laser altimeter is mounted on a satellite and, in combination with land-based radars that track the satellite's altitude, is used to measure variations in sea-surface elevation to within 2 in. (5 cm). Removing elevation changes due to waves and currents, sea-surface height can vary up to 660 ft (200 m). These variations are caused by minute differences in the Earth's gravity field, which in turn result from heterogeneities in the Earth's mass. These heterogeneities are often associated with sea-floor topography. By using a mathematical function that equates sea-surface height to bottom elevations, global areas of the sea floor can be mapped within a matter of weeks. However, this approach has limitations. Sea-floor features less than 6–9 mi (10–15 km) in length are generally not massive enough to deflect the ocean surface, and thus go undetected. Furthermore, sea-floor density also affects the gravity field; and where different-density rocks are found, such as along the margins of continents, the correlation between Earth's gravity field and sea-floor topography breaks down.