Empress of Ireland: Subject of evolving hydrographic technologies
Major nautical advances have been made since the 1914 sinking of the Empress of Ireland ocean liner. At the time of the shipwreck, there was no sonar, no GPS, and navigating with digital charts was still beyond the reach of even the most scientific of imaginations. It was not until 1983 that the Canadian Hydrographic Service was able to indicate the wreck's location on Chart 1236.
Echo-sounder in its infancy
Let us go back in time. The echo-sounder was patented in 1913, just one year before the vessel's tragic sinking. This first-generation technology used a hammer that would strike the ship's hull. It was not until 1929 that the technology was refined and the young Canadian Hydrographic Service began using it. Finally, during the Second World War (1939–1945), sonar (acronym for Sound Navigation and Ranging) was perfected to become the echo-sounder.
Locating the wreck
Shortly after sinking, the Empress of Ireland could be located thanks to air bubbles escaping from its hull. It was found lying just 40 metres below the surface. The location was temporarily marked with buoys, then simply mentioned on a British Admiralty nautical chart, with no specifics about its position or depth.
In 1964, after an article was published on the tragic incident, a group of divers found the wreck by dragging grabs (hooks) along the river bottom. Locator buoys were once again installed. In 1976, a Canadian Hydrographic Service survey pinpointed the wreck's location using a single-beam echo-sounder and a land-based radio positioning system. The first edition of Chart 1236 showing the wreck was published in 1983.
Echo-sounder: from single-beam to multibeam
In the late 1980s, the Canadian Hydrographic Service purchased its first multibeam echo-sounder, a technology that would prove to be revolutionary. For the first time, the entire sea floor could be covered, thanks to the width of the equipment's acoustic swath, which could reach up to 2.4 times the depth.
The first multibeam survey was conducted in July 1989 aboard the CCGS Louis M. Lauzier. The results were so impressive to the trained eye that data outlining the wreck was reproduced on the 1991 Canadian Hydrographic Conference poster, along with an image of the vessel for the benefit of the general public.
Emergence of 3D
Spectacular advances continue to be made in hydrographic technologies. For example, narrower beam angles produce more clearly defined images. Software programs analyze and reject false echoes and produce images in near real time. It is possible to view the seabed in 3D, manipulate the images, scan over them and create animated videos.
To mark its 100th anniversary in 2004, the Canadian Hydrographic Service, in collaboration with the Interdisciplinary Centre for the Development of Ocean Mapping (CIDCO), produced an animation of the Empress of Ireland wreck as it lies on the riverbed. In partnership with Parks Canada and Canadian Heritage, the Canadian Hydrographic Service recently unveiled stunning images of the wreck. The image on the cover of the Canadian Tide and Current Tables for the St. Lawrence River commemorates the centennial of the sinking of the Empress of Ireland. This shipwreck continues to be an excellent subject for demonstrating the evolution of hydrographic technologies.
More can be learned from the Library and Archives Canada’s online exhibit Shipwreck Investigations. The exhibit relates the highlights of the Canadian historic heritage which comprises the Empress of Ireland.
Robert Dorais
Science
Chart 1236, produced in 1983 by the Canadian Hydrographic Service, is the first recent chart to show the Empress of Ireland's location (highlighted in yellow).
Empress of Ireland image produced from acoustic data obtained using a multibeam echo-sounder. The outline of the bow, hawse-hole and deck can be seen. Holes can also be seen in the hull. Valuables were originally recovered through some of these holes. Source: Fisheries and Oceans Canada – Canadian Hydrographic Service.
