Preface The expedition ARK XIX/3 with the German icebreaking RV ...

The geophysical mapping of mound area using the ROV based multibeam systems was
also supplemented by a more analytical investigation of multibeam technology performed
in the adjacent Gollum Channel systems.
In this context, this ARK XIX/3a report is separated into 3 study areas (Fig. A4.1-1):
Gollum Channel (Porcupine Seabight) (section 4.2), "Belgica mounds" (Porcupine
Seabight) (section 4.3) and the Porcupine Bank (section 4.4). Investigations from each of
these areas are presented separately below followed by discussions of wider issues
(sections 4.5-4.10).
A. 4.2 Microbathymetry surveys along deep-water canyons (Gollum Channel) in the
Porcupine Seabight
Beyer, A., Krocker, R., Pokorna, M., Rathlau, R., Dabrowski, P.
Technical Aspects of the "Victor 6000" bathymetric system
Two modules are available on the ROV "Victor 6000" intended for sampling and micro
bathymetry. On this cruise the micro bathymetric systems EM2000 (Simrad) and Seabat
8125 (Reson) were available for deployment.
The Reson Seabat 8125 multibeam system operates at 455 kHz. It has a swath width of
120 degrees. The beam spacing is 0.5 and 1 degree for the across and along track
directions respectively. The maximum selectable range scale is 120m. Physical
specifications of the sonar head allow this system to be deployed at depths down to
1700m water depth. Position is computed from inertial navigation systems of "Victor".
Absolute positions (with respect to the vessel) and re-initialisation is determined using
POSIDONIA at appropriate intervals. However, the bathymetric data is effected by
navigation offsets which induce artefacts on the terrain model. These are mainly due to
the pitch of "Victor" and navigation offsets.
Post processing of the recorded data can be caried out using the QINSY software. The
data can also be exported in the XTF (Extended Triton Elics Format) for further
processing utilizing different commercial hydrographic software.
Validation of angular backscatter measurements utilizing "Victor 6000" and video
controlled sediment sampling
Multibeam systems are widely used to cover large seabed areas by bathymetric
measurements in a comparatively short time. For this purpose, the multibeam system
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