side scan sonars t alavosus klein associates

7/28/2019 Side Scan Sonars T Alavosus Klein Associates

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Marine & PowerSystems Group

Recent Developments in Side ScanSonar with Combined

Interferometric Bathymetry

Oceanology International 2010London, England

Timothy J. Alavosus, Ph.D.Director of Sales and Marketing

Sonar Products

L-3 Klein Associates


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Marine & PowerSystems GroupIts All About the (Underwater) Image


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Combining Side Scan Sonar

with Bathymetry

The Benefits of Side Scan Sonar:

Excellent imagery (resolution, shadow detail) often not

possible with optics due to sea conditions

Long-range scanning possible (>1 km swath) Shallow, deep configurations available

AUV, ROV compatible

Can be easily deployed

CAD/CAC possible

The wreck of the Bungsberg; note how SSS shadow imagery

helps reveal important additional information


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with Bathymetry

S5000 V2 Range = 150m


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with Bathymetry

S5000 V2 Range = 150m


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with Bathymetry

The Downside of Side ScanSonar:

SSS is two-dimensional.The images are great, and

give us a wealth of

information; but even with

good shadow imagery,

essentially the side scan

world is flat.


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with Bathymetry

The Downside of SideScan Sonar:

Without bathymetricdata, and thus it can

be almost impossible

to determine the

relative spatial

orientation of the

bottom. This can be

important for many

applications.

Bottom appears completely flat


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with Bathymetry

The Benefits of Adding Bathymetry: Bathymetry gives you the third dimension. Instead of

guessing about topography, it gives us contour lines and

excellent imagery, different than, yet complimentary to, SSS.


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with Bathymetry

The Benefits of AddingBathymetry:

The benefits extend

further than

topographical issues.Bathymetry also

provides the z-axis

measurement of objects

on the ocean floor.

With side scan alone,

this had to be done by

making an estimation

from shadow heights.

The shadow method

often requires multiple

passes on an object. Shadow z measurement Bathy z measurement


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with Bathymetry

The Benefits ofBathymetry :

Back to our firstimage; still looks

pretty flat, yes?


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with Bathymetry

The Benefits of Bathymetry:

Looks can be deceiving,

especially in a 2-

dimensional world. In fact,

theres quite a differencebetween the port and

starboard sides of our

image.

Even with good chart

data, we could not have

interpreted this from SSS

data alone.

>10m difference in slope not discernable from SSS alone


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Marine & PowerSystems GroupInterferometric Bathymetry

Why Interferometry?

Classic Multi-beam

echosounder bathymetry is

an excellent tool for deep

water measurements.

However, in shallow water

environments, it is limited by

the width at which it can take

readings. Its a simple

geometry problem, limiting

swath width to 3-5 times

water depth.1Image courtesy NOAA Coast Survey

Multi-beam echosounder Towed Side Scan Sonar

1. Gostnell, C. et al., NOAA Test and Evaluation of Interferometric Sonar Technology, Proceedings of the 2006

Canadian Hydrographic Conference, 15 May 2006


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Marine & PowerSystems GroupMulti-beam Bathymetry Geometry

Great in Very Deep Environments: Misses a lot in Shallow Environments:

Angle =

Angle =


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Marine & PowerSystems GroupInterferometry Bathymetry Geometry

Limited in Deep Environments: Excellent in Shallow Environments:

(Just not feasible for great depths)

Provides excellent Coverage Rate


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Marine & PowerSystems GroupInterferometry Geometry: Stand-Off

Interferometry has much wider area forrecognition:

Multi-beam has trouble ensonifyingstand-off targets:

Object must be within beam spread;

usually close to z-axis; results in

poorer imagery. This can also be a

dangerous hazard to navigation.

Interferometry naturally allows better

stand-off ensonification, especially

farther away from z-axis; results in

better imagery and safer surveys.


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Marine & PowerSystems GroupInterferometric Bathymetry

Why Interferometry?

In contrast,

interferometric

bathymetry (also

known as PhaseDifferencing

Bathymetric Sonar,

PDBS) provide

high-resolution

wide-swath

bathymetry inshallow water with

swaths of 10-15

times system

altitude.2Shallow-water interferometric bathymetry (max. depth 18m)

2. Ibid


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The Klein System 5000 V2

With Bathymetry

A combined system:

Chirp, true Multibeam, Side Scan Sonar



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System 5000 v2 with


AUV, Pole, Vessel, or Towed Mount Configurations: Vessel or Pole mount best for hydrographic survey

Topography augments side scan in towed operation

AUV 5000 v2 BATHY 5000 v2 BATHY Pole-Mount AUV 5000 v2 Towfish


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Specifications: Side-Scan Sonar:Multi-beam

5 Beams/side

FM Chirp

InterferometricBathymetry:

Frequency 455 kHz 455 kHz

Along Track Res 10 cm to 38m

20 cm at 75m

37 cm at 150m

50 cm at 250m

0.4

Across Track Res 3.75 cm 5.5 cm

Tow Speed 2 to 10 knots 5-6 knots (typical)

Depth Rating 500m 200m

Max Range 250m/side 125m/side


With Bathymetry


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With Bathymetry

Towfish System


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Marine & PowerSystems GroupKlein 5000 v2 Interferometric Bathymetry


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The Wreck of the Empire Knight

Th Kl i S t 5000 V2


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With Bathymetry

Bow/Hull-Mount System:

IHO-Quality Bathymetry


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Marine & PowerSystems GroupKlein S5000 V2 Bathymetry Bow Mount

UNH R/V Coastal Surveyor

Bow mounted underwater

component

Applied Microsystems Micro SVarray sound speed probe

Applanix POS/MV combined GPS

navigation, motion and heading

ODOM Digibar Pro sound speed

profiler


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Marine & PowerSystems GroupKlein S5000 V2 Time Synchronization

Time synchronization of sonar, motion andnavigation data is critical to producing

accurate hydrographic data

Hardware in TPU used to precisely

synchronize time tagging ofsonar/sensor/navigation data to 1PPS

pulse from navigation system (or external

time reference)

Some motion sensors provide time taggeddata referenced to GPS time

Resultant total timing errors < 50 seconds


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Marine & PowerSystems GroupKlein S5000 V2 Bathymetry Test Area

Portsmouth Harbor Survey

1500 x 600 meter area

Speed 5 6 knots

Calm sea, low tide

7 north south lines

Focused on sandy area northeast

Depth 10 25 meters


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Both SDF range / angle and raw(complex stave) data were collected

(Data can be logged in SDF, GSF or

XYZ format)*

Range / angle (roll stabilized), motionand sound speed profile data were

processed using Hypack 9.0 software

Line spacing was set to range scale

(75m) to facilitate viewing nadir area andprovide complete overlap of adjacent

swath data

*In addition to processed data, raw stave data can be logged

together with all motion, navigation, and heading and sound

speed data. This permits reprocessing of both side scan and

bathymetry data in a post processing environment

Data Collection and Processing


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Data in image was cut and joined to

show excellent agreement in data,

both in depth and position

Sand waves 40 to 120 cm high

Spot check of grid cells to either

side of cut were within 20 cm of

each other

Sand waves between lines

2 and 3

0.5 x 0.5 m grid

Data Collection and Processing


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Marine & PowerSystems GroupKlein S5000 V2 Bathymetry XYZ Data

Data from lines 2 4

Inner regions cut and joined

Outer regions single swaths

Sand waves at left can be seen to

edge, although noise is increasing

Feature at lower left is about 1 meter

high by 10 meters across

Upper right region used for depthvariation analysis

There is intentionally a Nadir Gap in this

image, for our testing purposes.

Si l S h D h V i i


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Marine & PowerSystems GroupSingle Swath Depth Variation

Hypack cell editor used for

standard deviation

measurement

Variation is for all pointswithin a grid cell

Data was gridded at 0.5 x 0.5 m and 1 x 1 m for

comparison (negligible difference)

Since no surface reference, variation attributed to sonar

0 10 20 30 40 50 60 70 800

10

20

30

40

50

S5000 V2 two-sigma depth variation

Meters from nadir

Depthvariation(cm.)

Kl i S 000 V2 P f


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Marine & PowerSystems GroupKlein S5000 V2 Performance

At 15 meters altitude, with vessel

mount and proper calibration, the

S5000 V2 provides IHO Special

Order data to about 40m from the

nadir on each side.3

3. M. C. Moser, M.C., Bathymetric Uncertainty Model for

the L-3 Klein 5410 Sidescan Sonar MS Thesis, UNH

Ocean Engineering, 2009. Note: Nadir is assumed to be

20 from center on either side.


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Marine & PowerSystems GroupKlein 5000 v2 Bathymetry Summary

The Klein S5000 V2 System is a

hydrographic survey system whichhas the ability to simultaneously

collect IHO quality swath bathymetry

and high resolution multi-beam side

scan sonar data in a fully corrected

and geo-referenced data set System demonstrated to meet IHO

Special Order requirements up to 12X

water depth

The dual functionality of the Klein

S5000 V2 effectively allows two

surveys to be accomplished in one

pass saving significant ship time and

expense

AUV 5000 pipe inspection surveyImage courtesy of SHOM, GESMA & ECA


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Marine & PowerSystems GroupKlein 5000 v2 Bathymetry Live


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For More Information,Please Contact

Tim Alavosus

Director of Sales and MarketingL-3 Klein Sonar Products

[email protected]

(+1) 603.339.1928

Thank You!

side scan sonars t alavosus klein associates

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