Autonomous underwater vehicles (AUVs) often operate close to the seabed (5m-15m) enabling higher resolution surveys using high frequency sonars. Compact Autonomous surface vessels (ASVs) are often deployed in shallow water environments where deeper-draft manned survey vessels are unable to operate. On such vehicles there is limited space to deploy separate imaging, mapping and sub-bottom sonars. This presentation describes the technology deployed in the EdgeTech 2205 sonar system, which enables combined data acquisition in one system on AUVs and ASVs. Examples of the data acquired are given, which can include dual- or triple- frequency side scan, Multiphase Echosounder (MPES) swath bathymetry, and sub-bottom profiler data.

1. Advantages of a combined sonar data
acquisition system for AUVs and ASVs
Tom Hiller
tom.hiller@edgetech.com

2. Abstract:
• Autonomous underwater vehicles (AUVs) often operate close to the
seabed (5m-15m) enabling higher resolution surveys using high
frequency sonars. Compact Autonomous surface vessels (ASVs) are
often deployed in shallow water environments where deeper-draft
manned survey vessels are unable to operate. On such vehicles
there is limited space to deploy separate imaging, mapping and
sub-bottom sonars. This presentation describes the technology
deployed in the EdgeTech 2205 sonar system, which enables
combined data acquisition in one system on AUVs and ASVs.
Examples of the data acquired are given, which can include dual- or
triple- frequency side scan, Multiphase Echosounder (MPES) swath
bathymetry, and sub-bottom profiler data.

3. There are 4 factors that make a successful Unmanned Vehicle:
The Vehicle
Positioning
Data Acquisition
Control

4. What does an autonomous vehicle do?
The AUV/ASV must:
• Be able to carry out a mission plan
• Be able to position itself accurately and reliably
• Collect useful data
A lot of development effort has gone into the vehicle and control
Positioning is a whole other presentation
The point of having the system in the field is to collect data

5. • Industry leader in Underwater Acoustics
• EdgeTech (formerly EG&G Marine Instruments)
– Started in 1966 by Doc Edgerton
• ORE Offshore
– Formed in 1963
• Manufacturing and Support - Massachusetts USA
• R&D – Florida USA
• + Worldwide rep network and regional Authorised Service Centres
EdgeTech Background
Common Technologies
Underwater Acoustics
Digital Signal Processing

6. • Sonar Systems
– Side Scan Sonar
– Sub-bottom Profilers
– Bathymetry
– Combined Systems
– AUV/ROV Systems
• Actuated Products
– Acoustic Releases
– Pop-up Systems
– Acoustic Actuators
• Navigation & Positioning
– USBL Acoustic Tracking Systems
– Motion Reference Unit (MRU)
EdgeTech Products & Solutions

7. • A Modular and Configurable Sonar System for Hosted Platforms
• For installation on Unmanned Underwater Vehicles (UUVs /
AUV), Remotely Operated Vehicles (ROVs), Unmanned Surface
Vehicles (USVs), and other hosted platforms.
• Modular units able to be configured, based on the application,
to collect side scan sonar imagery, sub-bottom profiler data and
wide swath bathymetry data, singly or in concert with one
another.
Designing Data collection for AUVs and ASVs

8. • Stage 1 Introduced 1st Qtr 2013
– Dual frequency side scan
• Option for Dynamic focused capability : 230 / 850 DF one of the first frequency sets
– Sub-bottom capability with linear amplifier card
• Various transmit / receive array options
• Stage 2 Completed 2014
– Bathymetry capability
• Needs an additional board (24 ch A/D)
• Needs bathymetry capable arrays
– Tri-Frequency side scan
• Can run dual simultaneous side scan, where the operator can choose any two frequencies from
the three available
As of end 2015 over 50 types of unmanned vehicles have integrated
EdgeTech sonars
2205 Development:

9. • Side Scan
– Single or dual frequency Arrays
– Dynamic Aperture / Dynamic Focussing options
• Sub-bottom Profiler
– Range of frequencies / Transducer Options
• Swath Bathymetry
– Multiphase Echosounder wide swath bathymetry
Combinations of frequency options to suit the application
2205 Options

10. Configuration 1 – SSS / Bathymetry only
SSS / Bathy
Port Array
Starboard Array
AUV control/
ROV Mux

11. Sub-Bottom
Configuration 2 – SSS / Bathymetry / SBP
SSS / Bathy
Port Array
Starboard Array
AUV control/
ROV Mux
Hydrophones
Hydrophones
Tx Tx

12. 2205 Board Set Building Blocks
PSU
CPU
SAIBU
Cap Banks
SIM
(blue board)
HCCA
(bathymetry only)
Board Stack Weight in Air with Cabling = ~3.2lbs

13. Size – Housing for SSS / SBP / Bathymetry

14. • Ethernet
– Data out
– Navigation data in
– Command and Control
• Backward compatible with existing EdgeTech Interface
• RS232
– 2 low latency ports as standard
– Navigation and motion data in
• Triggers
– 3 configurable as in / out
– Typically configured as trigger in, PPS in, and Trigger out
• Expansion capability
– 2 x USB 2.0 ports
– SATA interface for onboard storage
Standard Interfaces

15. JSF File Format
• May contain the following (depending on what sensors are
configured/installed):
– Dual Frequency SS
– Bathymetry
– Sub Bottom
– Navigation (lat/lon)
– Attitude (roll/pitch/heave)
– Heading
– Pressure (or Depth)
– All with a common time stamp
A Common, Standardised File Format

16. Deployment Examples

17. ASV Deployment Examples :
ECA Inspector
• Side Scan / Bathymetry
system
• Automated Bow mount

18. ASV deployment example: swath bathymetry +
dual frequency side scan

19. C&C / ASV 6300
• Side scan sonar
• Sub-bottom Profiler
• Hull mounted systems
Deployment examples :

20. ASV example :
Sea Robotics
• Side Scan Sonar
• Sub-Bottom Profiler

21. AUV / ROV Systems

22. 2205 Example Configurations
Application Sensor Frequencies Survey Goals & Considerations
Military MCM
Side Scan only
540/1600 kHz High resolution small size target location and identification.
230/850DF kHz Highest resolution-to-range on a standard military COTS side scan sonar
Side Scan + Bathymetry
540/1600 kHz
with Bathymetry at 540kHz
High resolution small size target location and identification that has
bathymetry for added 3D verification.
Commercial Survey
(small vehicle 4-9”)
Side Scan only
410/850 kHz Maximum range-to-resolution package for a small auv
540/1600 kHz
Higher resolution survey solution for small auv with added Bathymetry
capability
Side Scan + Bathymetry 540/1600 kHz (bathy on 540 kHz) Higher resolution survey solution for small auv
Commercial Survey
(large vehicle 10”+)
Side Scan only
120/410 kHz Maximum range surveying on a large vehicle.
230/540 kHz Best mid-range compromise between range/resolution for surveying
230/850DF High res on a large auv. DF for extra focus on small targets
230/540/1600 kHz Tri-Frequency
Any two frequencies at the same time, with the selection optimized for
the mission
Side Scan + Bathymetry
230/540 kHz (bathy on 540 kHz) Best mid-range compromise with added Bathymetry
230/540/1600 kHz (bathy on 540 kHz)
Tri-Frequency (any two side scan frequencies at the same time) , with
bathymetry also available if 540 kHz is selected as one of the frequencies
Sub-bottom Profiler
(Optional)
4-24 kHz Smallest size, highest resolution, but least penetration
2-16 kHz Good balance between size and performance (penetration & resolution)
1-8 kHz Best penetration, largest size and power consumption

23. Technology Details
• Side scan
• Sub bottom
• Bathymetry

24. • Sideways looking ; 2 sides
• Wide vertical beam
• Narrow horizontal beam
2205 : Side Scan Sonar
• The sonar sends out sound pulses or
pings from each side of the tow fish
and then receives or listens for the
pulse to return.
• Each ping returns a line of imagery.
These pings are combined together
to create an image.

25. 2205 : Side Scan Frequencies
Chirp Centre
Frequency
Nominal
Frequency*
Range
120 kHz 100 kHz 250 to 500m
230 kHz 300 kHz 150 to 300m
410 kHz 400 kHz 130 to >200m
540 kHz 600 kHz 100 to 150m
850 kHz 900 kHz 50 to 75m
1600 kHz 1600 kHz 20 to 35m
You will sometimes see the ‘nominal’ frequency quoted
in specifications and marketing material.
The selection of the best side scan
sonar frequency for any
application is a compromise
between range and
resolution. Lower frequency
systems provide longer range
(allowing a larger area to be
covered in each pass), whilst
higher frequency systems provide
a higher definition image

26. • Standard or Customised Arrays
– Standard arrays from towed systems
– Customised arrays for a particular
vehicle
• Rear radius to fit vehicle
• Different connection options
• Dual Frequency Combinations
– Lower frequency provides a search
capability
– Higher frequency provides
classification / identification
– Typical Combinations:
• 120 / 410 kHz
• 230 / 540 kHz
• 230 / 850 kHz
• 400 / 900 kHz
• 600 / 1600 kHz
• Tri-Frequency
– Operator selects two from three
– Selection depends on mission
– Typical Combinations:
• 230 / 540 / 850 kHz
• 230 / 540 / 1600 khz
Dual Frequency or Tri-Frequency Side Scan

27. Dynamic Focussing : Results
300 kHz 8 Element Dynamic Focusing300 kHz No Dynamic Focusing
• Various configurations have been built
– Different Frequencies
– Different number of segments
– Variable length segments
– Not necessarily symmetrical

28. • Range of SBP Transducer Options
2205: Sub-bottom Profiler
DW-424 DW-216 DW-106
Frequency Range 4 – 24 kHz 2 – 16 kHz 1 – 8 kHz
Pulse Type
Full Spectrum chirp frequency modulated pulse
with amplitude and phase weighting
Vertical Resolution
(depends on Pulse selected)
4 – 8 cm 6 – 10 cm 15 – 25 cm
Penetration (typical)
In coarse calcareous sand
In clay
2 m
40 m
6 m
80 m
15 m
150 m
Beam Width
(depends on centre frequency)
15° - 25° 15° - 25° 28° - 36°

29. • EdgeTech “Full Spectrum” pulse characteristics
– Bandwidth
• The wider the bandwidth, the better the resolution
– Length
• Longer pulses provide more acoustic energy
– Waveform
• For “FM” shaped pulses the Full Spectrum wavelet is weighted in the frequency domain to have a Gaussian like
shape (Blackman-Harris window) which provides a great rejection of the side lobes.
• Wideband (WB) pulses have a flat response over the entire pulse bandwidth, so more low frequency content.
• Sweep has a linear variation of frequency with time.
• Quadratic Pulses
– Waveform
• Sweep rate varies with time, with greater proportion of pulse length spent at lower part of the frequency range.
• Designed to help improve penetration.
• Dual Frequency Mode
– Two data streams
• Two data streams, each utilising a different pulse.
Sub-bottom Profiler Pulse Options

30. • Transmit and Receive on the Transducer
– Reduced Hardware
• Adds a T/R (Transmit/Receive) switch, but removes the need for separate receive hydrophones.
– Limits Pulse Length
• Limits the pulse length that can be used when close to the seabed – need to stop transmit pulse, and eliminate
ringing, before 1st receive.
• Not recommended for AUV’s.
• Separate PZT receive Hydrophone arrays
– Pulse length independent of altitude
• Can receive on hydrophones whilst still transmitting.
– Linear arrays in parallel used to define receive beam pattern
• Separate PVDF receive Hydrophone panels
– Pulse length independent of altitude
• Can receive on hydrophones whilst still transmitting.
– Standard panel sizes or Custom built
• Custom sizes can be designed to fit vehicle
• Multiple receive options for different applications.
Sub-bottom Profiler Receive Options

31. Sub-bottom Profiler on an AUV
AUV Sub-Bottom data
DW-106 Transmit
Quadratic pulse
PVDF receive arrays

32. Applications : Pipeline and cable detection

33. 2205 Bathymetry Technology
• Multi-Phase Echo Sounder (MPES)
technology (same as EdgeTech 6205)
• Swath up to 10 x water depth, and IHO SO
to up to 9 x water depth.
• Two Bathymetric frequency Options
– 230 kHz, longer range
– 540 kHz, higher resolution
• Integrated Dual Frequency Side Scan
• Better Spatial Resolution, but without the
Nadir gap traditionally associated with
Interferometers
Typical Multibeam Footprint
Typical 6205 Footprint

34. 2205 Bathymetry: Frequency Options
• The 6205 is available in several standard frequency
configurations:
– 230 kHz Bathymetry : to 215m depth below transducers
With 230 & 550 kHz Dual Frequency Side Scan
– 550 kHz Bathymetry :to 75m depth below transducers
With 230 & 550 kHz Dual Frequency Side Scan
– 550 kHz Bathymetry
With 550 & 1600 kHz Dual Frequency Side Scan
The modular design of the 6205 also allows for multi-frequency
bathymetry options with field exchangeable array design for
survey operations in both shallow and deep water operations.

35. Data Examples

36. 6205 Performance across swath-Data Example
Data Resolution
retained across swath
Cross Section
Shown

37. 1600kHz SS Data Sample, 5m Altitude

38. 1600kHz Data Sample, MLO

39. 1600kHz Data Sample, MLO

40. • Bathymetry & Simultaneous
Dual Frequency Side Scan
Sonar
• Precisely Co-Registered
Bathymetry & Side Scan
Imagery
Co-Registered Bathymetry & Side Scan

41. 550kHz SS Data Sample, 12m Altitude

42. Matching 550kHz Bathymetry

43. High-Density Cloud
View of Processed
Bathymetry
Sand Waves
Swath Bathymetry with Side Scan

44. Co-Registered Bathymetry & Side Scan

45. Co-Registered Bathymetry & Side Scan
Nadir Coverage

46. Data: Examples

47. Data: Examples

48. Swath Bathymetry : Pipeline Data Example

50. Eel Grass in Side Scan & Co-Registered Bathymetry
Water Depth less than 1 meter at Chart Datum

51. Side Scan and Bathymetry : AUV Data
At this resolution, the
Bathymetry data quality is
limited by the quality of
the motion data.

52. AUV Swath Bathymetry with Co-registered Side Scan
The Great Lakes Research Center (GLRC) at Michigan
Technological University, deployed an OceanServer
Iver AUV with an EdgeTech 2205 combined Side Scan
Sonar and Bathymetry system with the goal of imaging
an underwater pipeline.
Side scan sonar and bathymetry images were used to
check the location and integrity of the pipeline over a
long and varied terrain. Using side scan sonar co-
registered with bathymetry the team was able to view
intricate details about the pipeline and the bottom
topography, helping accomplish their mission.

53. Conclusion
• Flexible and configurable sonar data collection via the
EdgeTech 2205 sonar system now enables AUV and ASV
technology to carry out a variety of offshore survey, search
and inspection tasks.

54. Advantages of a combined sonar data
acquisition system for AUVs and ASVs
Tom Hiller
tom.hiller@edgetech.com