three acoustic measurements combined to provide high...

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


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

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

4

Theory - CAATI

Seafloor with a vertical feature

Acoustic

pulse

Sonar

arrayZ

X

Y

Computed Angle-of-Arrival Transient Imaging (CAATI)


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

6

Interferometry Using Phase Only

Interferometry

All 3 returns are equal phase angle

estimation and create confusion1

2 3

7

C3D - Using Phase & Amplitude

C3D

High Amplitude (1)

Good Estimation

Lower Amplitudes (2, 3) for same angle

estimations are eliminated1

2 3

8

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

9

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


C3D Swath vs. Multibeam

Swath Coverage is Range dependant Swath Coverage is Depth dependant


C3D Side Scan and Bathy


C3D Detailed Imagery


Same Bottom- Two Stories


C3D Precise Merging


C3D Sediment Analysis

Sediment in light area is

Deeper that surroundings

Sediment in light area is

Shallower that surroundings


C3D – Side Scan Data


C3D - Amplitude Data

18

Side Scan vs. Amplitude

Company Confidential


Bathymetry

Side Scan Amplitude

Side Scan + Amplitude + Bathymetry

20

Detection from Imagery

23

Confirmation with Sub Bottom

24

Ground Truth

25

Dragging Into the Data

26

Analysis

27

High Reflective Limestone

Formation


C3D Bathymetry


C3D – Side Scan with Bathy


Unusual Topography - Interpretation

Complex return with

difficult interpretation

from side scan record only


Dynamic Flow

Scour mark around

hard object Flow



C3D - Flexible Configuration

Swath Bathymetry3D Side Scan

Towed AUV/Hull Mounted Fix Mounted

DeepShallow


C3D-LPM Shallow Water Performance

38

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

39

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


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


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


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

three acoustic measurements combined to provide high...

Documents