What device is used to determine the depth of the seabed by measuring sound echoes?

A fathometer is the device specifically designed for measuring the depth of the seabed by utilizing acoustic echoes. It works by emitting sound waves that travel through the water until they hit the seabed. The time it takes for the sound waves to return is measured, and from this data, the depth can be calculated.

While sonar (which is also a correct term used for sound navigation and ranging) is the overarching technology that includes various applications of sound wave propagation, it is not exclusively used for seabed depth measurement. The fathometer is a specific type of sonar that focuses on determining water depth.

GPS (Global Positioning System) and radar (Radio Detection and Ranging) do not provide information on water depth. GPS is primarily used for determining precise locations on Earth’s surface, while radar is employed for detecting and tracking objects, typically above the water's surface, such as aircraft or ships. They do not involve the measurement of underwater features or depths.