Canadian Backscatter Images Web Mapping Service

This collection consists of digital multibeam sonar backscatter strength images derived from data collected by the Geological Survey of Canada (Atlantic) of Natural Resources Canada and the Canadian Hydrographic Service of Fisheries and Oceans Canada. The data were collected during multibeam sonar bathymetric surveys using multibeam echosounders to map seafloor topography, structures and sediments.

Multibeam echosounders transmit sound toward the seabed in a horizontal swath of discrete beams formed using an array of piezoelectric transducers. As the vessel moves through the water, the acoustic signals or "pings" emitted from the vessel bounce off the seabed and return to the transducer where they are recorded.

In addition to providing depth information (bathymetry), the intensity of energy returned to the transducers (backscatter strength) yields information on the nature of the seabed. Compilation and processing of these data within a Geographic Information System (GIS) accomplishes a synthesis into a regular spatial grid of backscatter strength. Processed as an image, the backscatter information is used by geoscientists to infer surface roughness and, by proxy, sediment type as well as to distinguish marine benthic habitat characteristics (e.g. hard, soft, rough, smooth, mud, sand, clay, cobble).