single largefish school, Middle Rocks
multiple small schools, Middle Rocks
demersal fish schools, Hurd Deep
EM710 Watercolumn Imaging Capability
John E. Hughes Clarke
jhc@omg.unb.ca
Ocean Mapping Group
University of New Brunswick
The adjacent animations are examples of Kongsberg EM710 water column
imagery obtained from HMS Endurance as a byproduct of the ship
acceptance tests in July 2005. The system uses three sectors with
centre frequencies ranging from 71-97 kHz. The imagery is similar to
that generated by the EM3002, but by using the three separate sectors,
the specular signature (generated primarily using the 97 kHz central
sector) in much less visible in the sidelobe response of the
outer (71 and 83 kHz) sectors.John E. Hughes Clarke
jhc@omg.unb.ca
Ocean Mapping Group
University of New Brunswick
These examples demonstrate the utility of the new capability to delineate schools of fish, distributed, either throughout the water column, as isolated pockets near the surface or elongate sheet-like bodies close to the seabed. Note that in the bottom example the schools are still visible even when they lie beyond the minimum slant range.
It should be noted that, even if the data is not logged, the sonar operators on the bridge can see a reduced version of these displays (only 1Hz imagery) in real time whilst the sonar is active (one of the panes in the SIS real-time software). These data are particularily good for assessing the role of engine noise and near-surface scatterers (such as bubbles) on the quality of data.