Development of Sonar

Development of Sonar
Sonar or Seafloor mapping is largely a matter of measuring depth. Before the First World War, the depth of the oceans was measured by lead lining. Lead lining is where someone lowers a piece of lead like a cannonball on a thin long wire until the cannon ball hits the bottom of the ocean. But World War I changed all of this. The Germans started to use sonar first. Sonar was first put into submarines against the allied forces. Since the ships had no sonar they had no clue the submarines were even coming. Allied forces didn’t like this so they created their own sonar which involved using sound. With sound it was easier to tell how close the submarine or ship was to them. The quicker the sound comes back the closer the ship or submarine is. Later on researchers realized that if the sound device was pointed down at the seafloor, the depth could be accurately determined. Early "echo sounders", as they were called, had very bad directivity, and relied on the assumption that the echoes were coming from directly beneath the ship. This was a poor assumption because if there was any shape to the seafloor below the angle of the seafloor and the ship would change due to hills and rocks. But in the end sonar has changed dramatically over time and has improved greatly. From dropping a cannonball of the side of a ship, to now where we can see how deep the seafloor is and what it is shaped like.