Page 13: of Marine Technology Magazine (November 2014)

features on the ground. A smooth target like the ocean will bounce back an ex- pected pulse shape, but if something like an iceberg, island, or ship is present, the shape of the echo will change.

In 2007, Tournadre was poring over hordes of satellite data for signs of ice- bergs in polar seas, when he noticed an odd shape in the data.

“We had some unconventional data in a region, and careful analysis showed us that it was a lighthouse near shipping lanes,” he said. “As we processed the data over the whole globe, we also detected ships.”

Tournadre found that the altimetry data accurately reproduced known shipping lanes and could be used to estimate the number of vessels on the ocean world- wide. The study used altimetry data from seven different satellites to map ship traf-