Handling of Bathymetric Data at BAS: Past and Present

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Handling of Bathymetric Data at BASPast and
Present
Rob Larter British Antarctic Survey, Cambridge, UK
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Talk Plan

• Where? Scotia Sea region
• How?
• Past single beam echo sounding
• Present multibeam echo sounding
• Why?

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Where? Scotia Sea regionTectonic Map of the
Scotia arc (1985)
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UK Single-Beam Echo Sounding Lines (to 2000)
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How? PastSingle-Beam Echo Sounding
10 kHz echo sounder towfish being
deployed Advantages Roll pitch reduced Ship
noise reduced Disadvantage Towing noise at gt8 kts
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How? PastSingle-Beam Echo Sounding
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How? PastSingle-Beam Data Correction
Uncorrected soundings (1500 m/s assumed)
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How? PastShips Used to Collect Single-Beam
Echo Sounding Data
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JCR
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How? 19922000Single-Beam Echo Sounding on RRS
James Clark Ross
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Single Beam Echo Sounding Data Coverage
ExampleSouth Georgia Area
Figure provided by Peter Morris, BAS
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How? 1995 (one cruise only)HAWAII-MR1 Phase
Swath Bathymetry
Two rows of transducers each side 11 kHz port 12
kHz starboard Advantages Roll pitch
reduced Ship noise reduced Towed below noisy
surface zone Disadvantages Complications of
deployment, towing and recovery Low resolution
(compared to modern hull-mounted systems)
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HAWAII-MR1Data from East Scotia Ridge
Coincident gridded bathymetry and sidescan sonar
data However Phase bathymetry results not
available in real time Low resolution compared to
modern hull-mounted multibeam systems
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How? PresentMultibeam Echo Sounder
Advances in hull-mounted multibeam echo sounders
during 1990s Increasing swath width More
beams Higher resolution 2000 - Kongsberg Simrad
EM120 system installed on RRS James Clark
Ross Swath width up to 150 191 beams 1 x 1
resolution
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How? PresentEM120 Multibeam Echo Sounder
Installation
Operating frequency 11.25 12.75 kHz 1 x 1
resolution requires Tx and Rx transducer arrays 8
m long Real-time electronic beam steering
corrects for roll, pitch and yaw
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How? PresentMultibeam Data Acquisition and
Processing
Sound velocity profile from Sound Velocity Probe,
XBT or CTD cast Corrected depths available in
near real-time Raw data automatically copied to
RAID storage Data processed using Kongsberg
Simrad Neptune package or public domain MB
software Main processing steps Automatic data
cleaning Manual ping editing Sound velocity
profile adjustment Gridding
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RRS James Clark Ross Multibeam Echo Sounding
Lines (2000 2004)
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Why?

• Safe navigation soundings sent to UKHO
• Science projects, e.g.
• Tectonic history and processes
• Palaeoceanography
• Glacial history and processes

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Southern Shackleton Fracture Zone and part of the
West Scotia Ridge dead spreading centre
Livermore et al. 2004, Geology 32, 797 800
200 km
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Former Glacial Channel below Larsen A Ice Shelf
10 km
Evans et al. 2004, Quaternary Science Reviews
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Scotia Sea - Present Multibeam Data Coverage
Figure provided by Peter Morris, BAS
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Summary

• BAS has extensive single beam echo sounding data
  collected in the Scotia Sea region since 1960s
• Since 2000, high resolution, full ocean depth
  multibeam echo sounder data have been collected
  on RRS James Clark Ross
• Multibeam data are essential to a wide range of
  marine science projects. They also provide base
  maps for seafloor sampling, deep-towed instrument
  and ROV investigations