Multibeam Water Column Data
Processing Techniques to Facilitate
Scientific Bio-Acoustic Interpretation
Ian Church1, Lauren Quas2, Maxwell Williamson2
1. Assistant Professor, Ocean Mapping Group
Department of Geodesy and Geomatics
Engineering
University of New
Brunswick
2. Division of Marine Science
School of Ocean Science and Technology
University of Southern Mississippi
Stennis Space Center, MS
Multibeam Water Column Data
Plankton?
Bubbles?
Suspended sediment?
Mixing / Turbulence?
Internal waves?
CONsortium for oil spill exposure pathways in
COastal River-Dominated Ecosystems
Student Training - 9 Graduate Student & 10 Post-Docs
Lauren Quas: Application of High-Resolution Multibeam Sonar Backscatter to Guide
Oceanographic Investigations in the Mississippi Bight. Thursday 9:00am
Maxwell Williamson: Using multibeam sonar water column backscatter to examine
physical oceanography variability in the coastal environment of the Northern Gulf of
Mexico - Lightening Round Talk, Thursday, 9:20 AM
CONCORDE explores
water movements and
organism distributions
in the northern Gulf of
Mexico to see how oil
and dispersants from
future oil spills might
impact the biota.
Three Year Project
2015-2018
Objectives:
1) Characterization of
plankton distributions
2) Observations of
pathways for oil
exposure to the coastal
region
3) Modelling biogeochemical processes
from nearshore to
continental shelf
2,200
Gulfport, MS
East
Middle
West
New Orleans, LA
Mobile, AL
CONCORDE Domain
Fresh Water
Deep Water
Horizon
Fresh Water
Salt Water
http://www.wwu.edu/salishsea/estuary.shtml
Data Collection
• Seabat 7125 SV2
– 200 / 400 kHz
1. Water Column
2. Seafloor
Backscatter
3. Bathymetry
In Situ Ichthyoplankton
Imaging System (ISIIS)
• Towed undulating shadowgraph
imaging of plankton and zooplankton
• Conductivity, temperature, pressure,
dissolved oxygen, PAR, and
chlorophyll-a fluorescence
400µm – 13cm
Project Goals and Challenges
• Correlation of ISIIS Observables with Water Column
Acoustic Data
• Transform the Multibeam Water Column data so that it
is directly comparable to the profiling observations
• Data Volumes
– Each Corridor: 6 hours = 1.5 TB
– Total of 12 passes = ~ 40 TB of raw data
2 GB / min
2 GB / min
Interpreting Water Column Data
Features of interest
are the scattering
response patterns
Receiver
sidelobe
interference
The sonar provides
the intensity of
samples along the
beam and the
direction.
Seabed
Isolating the “Signal” from the “Noise”
Methods:
Ray Tracing
– Geographically
reference all samples
within a defined range
– Sound Speed
CONCORDE
Study
Area
Measured:
• Direction
• Travel Time
θ
Need
• Depth
• Across
Methods:
Time / Depth
Average
1. Average data
into depth / across bins
2. Time average binned data
Methods: Averaging Result
Water Column Data File Averaging: Single 30-second Data File
• WC Signal Results
2D Time
Average
Depth
Average
Peaks indicate
persistent
anomalous layers
of interest
Water Column Section  2D Time Averaged Wedge
2D Time Averaged Wedge  1D Acoustic Profile
Time and Depth Average Water Column
Backscatter Along CONCORDE Corridors
Two Dimensions  Three Dimensions
•
•
•
Segmented Multibeam
Water Column Backscatter Data
Isolate areas for
comparison
View segmented
backscatter in threedimensions
Allow for comparison
and extrapolation of
observed data
variables (Plankton,
Salinity, etc.)
Initial Results
ISIIS Data
Acoustic Data
Discussion and Conclusions
• MBES = Imperfect Tool for Water Column Acoustics
– Make use of existing data
– Remove artifacts ( “noise” )
• Complex Correlations
– Scattering is likely not due to a single mechanism
– Analysis continues…
• Water Column Filtering
– Allows for comparison over wide areas to better
characterize local environment
– Other filtering methods to be tested
Future Work
Examine salinity stratification from the Mobile Bay
Plume (Williamson, et al. Presentation)
Compare to Model Output (Quas, et al. Presentation)
This research was made possible by a grant from The Gulf of
Mexico Research Initiative. Data are publicly available through
the Gulf of Mexico Research Initiative Information & Data
Cooperative (GRIIDC) at https://data.gulfresearchinitiative.org
Questions?