Scientists primarily use echo sounders to map the ocean floor. LIDAR, or light detection and ranging, can also be used for sections of the ocean with clear water.
Echo sounding uses ships to transmit sound waves to the bottom of the ocean, where they are bounced back to the ship and recorded. Scientists use the time that it takes for the sound wave to bounce back to the ship to measure the depth of each part of the ocean. LIDAR measures the length of time it takes for the light to reflect back to the airplane. Although this method has a limited use, it allows scientists to map large sections of the ocean floor.