Hydrography

The applied science of measuring and describing the physical features of oceans, seas, coastal waters, lakes and rivers for navigation and other marine purposes.

Hydrographic work determines depth, seabed character, coastline, hazards, tides, currents and the positions of relevant features. Surveys combine methods such as echo sounding, positioning, water-level observation, sonar and remote sensing, with quality control and uncertainty assessment.

The results support nautical charts, sailing directions, route planning, dredging, engineering, environmental management and maritime boundaries. Survey date, coverage and data quality matter because depths and features can change and older or sparse surveys may not reveal every hazard.