Discoverer of the Titanic Is Mapping Underwater America

Maps generated by sonar have been important for Ballard and his team.

Courtesy Ocean Exploration Trust

When I was in the Navy, I was in naval intelligence and I learned about it. I worked hard to get them to let us use some of these maps, which they did. We used them in the artwork for my very first article for National Geographic magazine, "Dive into the Great Rift," in May 1975. That was the first time the Navy released these maps to the general public. Then we got them to let a company build an unclassified version. It wasn't as good as the military version. Now they finally have declassified the best version.

I've been after this sonar forever.

How does the sonar make maps?

Think of it as a lawnmower. It's a big, monstrous, nine-ton sonar that's attached to bottom of the ship. It sends out a signal like a fan, and then the signal hits the [ocean] bottom and it comes back up. It can digitize and produce a topographic map in real time at full speed, which for us is 12 knots, and the area that the lawn mower is cutting is seven kilometers wide.

You see everything in great detail. It's like someone turns on the light and you can see the mountain ranges, you can see the volcanoes and the calderas, you can see river patterns.