More information on sonar images

The side-scan sonar generates an acoustic image of the seafloor looking 100 metres to either side of the track that the Parks Canada survey and diving boat Investigator was following. The path of the towfish is represented by the straight line running vertically down the centre of the image. The black area immediately to the left and right of this line represents the water column beneath the sonar towfish where no echo is returned. The contour line bounding the water column on either side is the seabed surface where the first sonar echo is detected by the port and starboard transducers in the towfish.The sonar returns from that point outward map the seafloor over a total swath roughly 200 m in breadth. The wreck is seen from an overhead perspective on the right-hand side of the image. The bow is at the bottom of the image and the stern at the top. Sonar reflections from solid objects and surfaces appear as bright yellow returns while the dark area immediately to the right of the wreck represents the acoustic shadow that it casts, where the sonar beam is blocked by the intervening height of the wreck. The patterns of strong returns and shadows reveal shapes and patterns, all of which are to scale. Dimensions can be derived directly from the sonar software.


The following sequence of photos provides a snapshot of the Parks Canada Underwater Archaeology Team’s work during and after the shipwreck discovery.

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