How Are Ocean Depths Measured?

Depths of oceans are measured using a technique known as Ultrasound measurements. A transmitter is mounted at the bottom of a ocean going vessel which is capable of transmitting ultrasonic waves. These ultrasonic waves are reflected from the floor of the ocean and a sensor receives and records them. since the speed of these ultrasonic waves in water is known, the time taken by these waves to travel to the bottom of the ocean and back gives the depth of the ocean at the point where the measurements was taken. By taking different measurements at various points of the ocean floor, the surface of the ocean bottom can be accurately measured and mapped.