Hydrographic surveying
Hydrographic surveying is one of the oldest forms of marine research, and comprises a process of collecting depth information that can be used in developing and maintaining nautical charts. In essence, a hydrographic survey collects depth, position and time data, which can be used to create a model of the seabed.
Until the 1920s hydrographic surveys used sounding lines (with a plumb bob at the end) to measure depth. Echo sounding techniques were then introduced as a new way to gather depth information. Echo sounding techniques became the most widely used for conducting hydrographic surveys; they made survey processes more efficient and made it possible to survey at greater depths. Previously unsurveyed areas of ocean floor were surveyed after the introduction of echo sounding and the tecnology quickly grew to be standard ships'equipment. All merchant ships and fishing vessels have echo sounding technology to aid their navigation.