This article was originally written and submitted as part of a Canada 150 Project, the Innovation Storybook, to crowdsource stories of Canadian innovation with partners across Canada. The content has since been migrated to Ingenium’s Channel, a digital hub featuring curated content related to science, technology and innovation.

Fathometer side view. Source: Tom Alföldi; Ingenium 1980.0466

Had the fathometer, or echo sounder, been available, it might have changed maritime warfare during the First World War. The Fathometer, first offered for sale in 1923, uses sound waves to quickly and accurately determine water depth and detect underwater objects, like submarines. Before echo sounders, sailors dropped and retrieved weighted hand-held lines (lead lines) to estimate water depth. After the sinking of Titanic in 1912, Canadian engineer Reginald A. Fessenden wanted to improve underwater object detection and communications. An expert in wireless radio technology, Fessenden built an electromagnetic device, called the oscillator, which produced underwater sound waves. These waves bounced off objects and, by measuring the echoes produced by the returning waves, users could estimate the position of the object. Tests in 1914 proved the oscillator could not only detect icebergs, but also determine water depth. Fessenden urged war planners to use the oscillator as a submarine detector, but with his prickly personality, he was rebuffed. After the war, the Submarine Signal Company of Boston incorporated Fessenden’s oscillator technology in the fathometer, opening a new era of navigation, subsurface detection, and marine mapping.

Fessenden was born in Bolton, Quebec, in 1866. In 1929, he won the Scientific American Gold Medal in honour of his work on the oscillator.

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