three acoustic measurements combined to provide high...
TRANSCRIPT
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1Company Confidential
Three acoustic measurements
combined to provide high efficiency
and better resolution for coastal, near
shore and offshore habitat mapping
Using C3D Technology
Presented by Francois Leroy
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2Company Confidential
Presentation
• C3D Technology Description
• Value Extracted from Combined Data
• Side Scan – Bathy – Amplitude – Sub-Bottom
• 3D view helps interpretation on unusual topography
• Efficient in shallow and very shallow waters
• Higher Resolution for Deeper Waters
• Versatile in Multiple Applications
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3Company ConfidentialCompany Confidential
Side Scan Sonar or Multibeam
vs.
C3DSide Scan Sonar
Good Imagery
Poor Bathymetry
Wide Swath
Multibeam Sonar
Poor Imagery
Good Bathymetry
Narrow Swath
Side Scan Sonar with Bathymetry
Good Imagery + Good Bathymetry
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Theory - CAATI
Seafloor with a vertical feature
Acoustic
pulse
Sonar
arrayZ
X
Y
Computed Angle-of-Arrival Transient Imaging (CAATI)
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2 Row Interferometry
• Knowing:
– Distance “d”
– Wavelength
– Phase at each transducer
• The wave direction can be calculated
• However there are multiple wave
directions that will satisfy the equation
d
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Interferometry Using Phase Only
Interferometry
All 3 returns are equal phase angle
estimation and create confusion1
2 3
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C3D - Using Phase & Amplitude
C3D
High Amplitude (1)
Good Estimation
Lower Amplitudes (2, 3) for same angle
estimations are eliminated1
2 3
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Signal to Noise Ratio is Important
Low SNR will limit the efficiency of the C3D angle estimation
High SNR will produce C3D angle estimation at wide swath
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SNR Sensitivity
• Analysis varying SNR on test target of an angle reflector
SNR= 60dB
SNR= 30dB SNR= 40dB
•Clearly, we must keep SNR high in
order to obtain satisfactory results
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C3D Swath vs. Multibeam
Swath Coverage is Range dependant Swath Coverage is Depth dependant
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C3D Side Scan and Bathy
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C3D Detailed Imagery
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Same Bottom- Two Stories
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C3D Precise Merging
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C3D Sediment Analysis
Sediment in light area is
Deeper that surroundings
Sediment in light area is
Shallower that surroundings
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C3D – Side Scan Data
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C3D - Amplitude Data
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Side Scan vs. Amplitude
Company Confidential
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Bathymetry
Side Scan Amplitude
Side Scan + Amplitude + Bathymetry
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Detection from Imagery
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Confirmation with Sub Bottom
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Ground Truth
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Dragging Into the Data
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Analysis
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High Reflective Limestone
Formation
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C3D Bathymetry
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C3D – Side Scan with Bathy
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Unusual Topography - Interpretation
Complex return with
difficult interpretation
from side scan record only
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Unusual Topography - Interpretation
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Dynamic Flow
Scour mark around
hard object Flow
Unusual Topography - Interpretation
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Unusual Topography - Interpretation
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C3D - Flexible Configuration
Swath Bathymetry3D Side Scan
Towed AUV/Hull Mounted Fix Mounted
DeepShallow
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C3D-LPM Shallow Water Performance
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C3D-LPM Shallow Water Performance
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Estimated Area Coverage Comparison
• Assumptions
• 10 times depth below transducer for C3D and 3.5 times water depth for multibeam
• 2m water depth
• 1m tidal variation
• 6 tidal cycles
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Comparison between C3D data and
macroalgae distribution, 2006.
Published by F.Hegg, 2007
Recent High-Resolution Aerial
Photograph of Waquoit Bay
C3D Bathymetry C3D Backscatter
Max Depth 2.5m Averaged for
0.25m Contours 2m Resolution
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C3D Comparison with Multibeam DatasetThe pictures were presented at the fourth International Conference ”Oil and Gas of the Arctic Shelf”, Murmansk, Russia, November 12-14,
2008: Modern Technologies of the Geophysical Investigations on the Shelf for the Purposes of Geohazards Detection. A. Fyodorov, S.
Mironyuk, S. Kleshchin (Peter Gaz Ltd., Russia)
Images courtesy of Peter Gaz Ltd, Russia
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C3Dwith Sub-Bottom Profiler
All-in-One Solution!
200kHz C3D with
Focused Chirp Sub-bottom
1 - Hi-res Sidescan Imaging
2 - Wide Swath Bathymetry
3 - Focused Sub-Bottom
and Chirp technology
40+m
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Conclusion
• C3D Advanced Technology
• Combined data with good swath coverage
• Fully Correlated data
• Easy data processing and merging
• Efficient in shallow and very shallow waters
• High resolution for deeper waters
• 3D view helps interpretation on unusual topography
• Versatile and Competitively priced