Ocean Pathfinder: Introduction
Back then people didn't have any technology to record their data. So back then hydrographers used lead lines to measure the depth in the ocean. A lead line is a rope or line that has 10 pound lead weight attached to the end. So what the hydrographers do is they lower the line into the water until the weight touches on the bottom. The line has markings to show how much line has been let out. Doing this takes a lot of time to do & to give information about points of the sea floors. So the depth soundings made with lead line are accurate. Now since people don't do that type of technique, they use multi beam to get depth measurements easier & faster.