echosonding

Echosounding, also known as echo sounding, is a hydroacoustic method used to determine water depth and map underwater features by transmitting a sound pulse from a transducer and measuring the time until the echo returns. Depth is calculated from the round-trip travel time and the speed of sound in water, which depends on temperature, salinity, and pressure. Modern systems use frequencies from a few kilohertz to hundreds of kilohertz, with higher frequencies providing finer vertical resolution but shorter range.

Two main configurations are used: single-beam echosounders emit a downward beam, while multibeam echosounders use a fan-shaped array to cover wide swaths. Side-scan sonar and bathymetric LiDAR are complementary technologies. Data are processed to produce depth profiles and bathymetric maps, with corrections for transducer tilt, vessel motion, and water-column sound speed.

Applications include nautical charting, coastal engineering, dredging, fisheries research, and underwater archaeology. Return strength depends on bottom type, texture, and target size, so interpretation must consider sediment and object properties; echoes may also reveal subsurface features such as thermoclines or gas pockets.

Limitations include variability of sound speed, water-column stratification, reverberation, and seabed roughness. Accuracy declines with depth, adverse sea conditions, and vessel motion. The field continues to advance with higher-resolution multibeam surveys, improved data integration, and the use of autonomous survey platforms.