Echosondy

Echosondy, known in English as echosounders, are sonar devices used to measure water depth and map underwater features. They operate by emitting a short acoustic pulse into the water and recording the time it takes for the echo to return from the seabed or other objects. Depth is calculated from the travel time and the speed of sound in water, which depends on temperature, salinity, and pressure. Because water conditions influence sound speed, many systems apply corrections or use local sound velocity profiles for accurate measurements.

A typical echosounder system comprises a transducer, a transmitter, a receiver and signal processor, and a display or data-logging unit. Modern systems are often integrated with navigation equipment and can stream data to hydrographic survey software. Data are stored as depth values, echograms, or bathymetric grids for mapping.

Configurational variations include single-beam echosounders, which emit from a single point, and multi-beam echosounders, which use an array to sweep wide swaths and provide higher-resolution depth information. Sidescan sonar systems are used to image the seabed's texture, while sub-bottom profilers investigate materials beneath the seabed. Applications include hydrographic surveying for nautical charts, coastal engineering, dredging planning, offshore construction, fisheries science, and underwater archaeology.

In practice, echosounder data may be combined with motion and GPS data to produce georeferenced bathymetric maps, and processing steps may include tide and water-corrected adjustments, noise removal, and seabed classification.