1 © kongsberg november 30, 2015 the evolution of the kongsberg simrad multibeam echo sounders by...

1© KONGSBERG April 22, 2023

The Evolution of the Kongsberg Simrad Multibeam Echo Sounders

Dr. Freddy Pøhner

KONGSBERG main business areas

Defence & AerospaceMaritime

Kongsberg Maritime

Divisions

Human Resources/Administration: Finn H KristensenQuality Management: Finn H KristensenIS/IT systems: Steinar AabelvikCommunication: Gunvor H Midtbø

Business Support

Torfinn KildalPresident

Steinar AabelvikCFO

Torfinn KildalPresident

Steinar AabelvikCFO

Sales & MarketingTor Erik Sørensen

Dynamic Positioning& Navigation

Ole Gunnar Hvamb

Dynamic Positioning& Navigation

Ole Gunnar Hvamb

Process AutomationNils E Standal

Marine AutomationLars Gørvell-Dahll

Satellite Positioning & AIS

Bjørn Fossum

Satellite Positioning & AIS

Bjørn Fossum

HydroacousticsRolf Arne Klepaker

Marine ITBjørn T Frøshaug

Marine ElectronicsJan E Berner

We participate where the action is

Global presence• HEAD OFFICE

• OFFICES

Kongsberg Maritime premises in Horten, Norway

M/K Echo, a 30 m vessel for test and demonstrations

“Pingeline”, a 32 feet hydrographic launch, for testing

Kongsberg transducer test tank with EM 1002 transducer being tested

Testing of a Multibeam Echo Sounder System

In-door test tank: 10 x 6 x 6 meters

Hydrographic Applications

Multibeam Echo Sounders

Single Beam Echo Sounders

Sub Bottom Profiler

Marine Data Management

Operation Support:Cable Laying

Nautical charting

Route Surveying Operation Support:Dredging

Port and HarbourSurveying

Mapping of Riversand Canals

Marine Geology Scientific research Habitat mapping

Exclusive EconomicZones mapping (EEZ)

Detailed Mapping(ROV, AUV applications

Mapping of Riversand Canals

Processing software

Launching sequence of multibeam models

1990 1995 2000 2005

How well does the terrain model represent the seabed terrain?

The Quality of a sounding process(1):

Seabed mapping process

Sounding process (on ship) Data processing

Echosounder

PositioningMotion compensation

Sound velmodeling

Seabed Terrain Terrain model

Plotter WorkstationColour PostscriptPrinter

The terrain model is a mathematical surfaceThe terrain model is a mathematical surfacebased upon a set of depth soundingsbased upon a set of depth soundings

The best terrain model is obtained by:

A. Precise depth soundingsB. Smallest possible acoustic footprint for each soundingC. Precise positioning of each soundingD. High density of soundingsE. Even spacing between soundings

The Quality of a sounding process(2):

These principles have been and still are the guidelines for most of our developments

Acoustic principles developments

1986/EM 100: Basic properties of the Simrad multibeams:

Phase + amplitude bottom detector

Automatic gain steering and bottom tracking

Split beam phase

Fullbeam

amplitude

Phase Detect

Snell’s law of refraction: sin(Ai)/Ci=constant

Refraction of Acoustic Beams

All models have had built-in real time compensation.Early models used lookuptable + interpolation,accurate realtime calculation since 1997.

Multibeams interface MVP’s, no interruption of sounding whena new profile is entered (due to realtime calculation of refraction)

Moving vessel profilers: Frequent sampling of sound velocity profiles

The Mills Cross array was introduced with EM 12 in 1990

Transducer arrayconfiguration

Receive

Forwarddirectionon shipTransmit beam

Receive beamEffective beam footprint

Transmit in sectors, and use different frequencies

Requires a larger transducer+ direct steering of all transducer elements in 2 dimensions

Transmission process: FRDT principle

This was introduced with EM 12 in 1990.

Advantages:

Higher source level (=increased range)+reduced problems with sidelobes from the specular return.

Beam spacing

Equiangle

Equidistant

In-between

EM 1002 beamangles

-80.00

-60.00

-40.00

-20.00

Beam number

equiangle

equidist

inbetween

Equi- distant beam spacing was introduced as an improvement to the EM 12 + EM 1000 in the early 1990’s

Equi-distant beamspacing

Equidistant beamspacing

Improved sounding density in the outer part of the swath

Example at 10m depth

crosstrack beam spacing

beam angle

beam spacing EM3002

beam spacing Reson8125

Manual ModeSector fixed to operator set angles

Sector Coverage

Auto ModeSector limited by:•Max angle set by operator•Max coverage (deg) set by operator•Signal to Noise Ratio

Adapting the system to varying depths and bottom conditions

Introduced early 1990’s

2 different Data Sets are derived:

A. Beam Intensity=Mean Backscatter Strength over the Footprint

B. Sonar Image Data= All the individual Backscatter values

Acoustic Footprint of Beam

Beamformed seabed imagery (Snippets)

This was introduced in 1990 for EM 12 and EM 1000

EM 12D - Surveyed by IFREMER

Bathymetry and Sonar Image combined in 3D

Ifremer pioneered the development of software to processSeabed imagery

Data courtesy of C & C Technologies Inc.

EM 300 (30 kHz) Multibeam Bathymetry & Backscatter

Bathymetry & Imagery

DualSingle

1995/96: EM 3000 was introduced

This step was made possible by availability of more compactelectronics. A sonar head has a mills cross transducer array + 2electronic boards: 1 for transmission and 1 for reception.

CHS was the first client.

Co-ordinate transformations and modelling of

transmission through water Ar=Beam angle rel. transducer

T=2way travel timeH

rface s

Sounding depth (z)

Rel. pos. of sounding (x,y)

Calculation of Depth Data

Exact algorithm was introduced for EM 3000 in 1995, allowed for free mounting angles of sonar heads

Test arrangement for they German Waterways Authority

Accuracy as function of swath width

Construction Drawing

Survey Result

Test Result from a Lock

Stabilization for pitching is obtained by steering the transmit beamelectronically forward or aft at the time of transmission, based upon input from the motion sensor.

Pitch Stabilisation

Introduced from 1990

A multielement transmit array is required, + several steerable transmitters

The effect of pitch stabilisationThe effect of pitch stabilisation

Sounding patterns on the bottom

Competitor result,Without pitch stabilisation

EM 3002 result

Each Receive Beam is stabilized for roll by the Beamformer, using input in real time from the Motion Sensor. All beam pointing angles are thus constant, related to the vertical axis.

The roll angles will be different for the different beams

Roll Stabilization

Since 1986

The effect of roll stabilised beams

Stabilized:The swath is notinfluenced by rollmovements

Unstabilized:The swath is rolling sideways, and the effectiveswath is then reduced.

EffectiveSwath

Unstabilized swath

Compensating for vessel yaw movements

Fulll compensation for pitch and yaw

-1000m

No compensation

-1000m

(As EM 120)

Calculation of sounding pattern on bottom

Ship speed: 10 knotsDepth: 3000mPitch: +/-5 degrees, 15sec periodYaw: +/-6 degrees, 200sec period

Pitch compensation only2000m

-1000m

EM 120 and EM 300 Multibeam echo sounders

With Yaw stabilisation

Without Yaw stabilisation

Calculated by UNB, Canada

From 1997

MBE sounding errors

0 10 20 30 40 50 60 70

Swath angle

EM 120 1x2

Seabeam 2112

EM 12D

System accuracy improves over time

Kongsberg develops its own ASIC’s and HYBRID circuitsfor the sonar front-end boards

TRB 32 Transmit/Receive Board for 32 channels

Plugs for connection totransducerelements Backplane

Backplane P2

Transmitterhybridcircuits

Each transmitter is a special purpose HYBRID circuit

64 channel transmitter board

EM 1002 Optional Retractable Hull Unit

The hull unit provides:- Transducer protection during transit- Good acoustic conditions when extended- Active pitch compensation of beams

It is mounted on a cylindrical trunk which is welded to the ship’s hull

Max survey speed with Hull Unit is 10 knots

“Kilo Moana” - EM 1002 transducer being fitted

Transducer Gondola

Ice breaker solutions

Titanium plates for light protection against ice was introduced in 1990.Ice breaker solutions have been developed since, for 12 and 30kHz

EM 3000D Bow Installation

Near Field

L Beam-width

The acoustic near-field – Beam focussing

Without focussing:Inside the near field the beam is as wide as the physical size of thetransducer

Beam focusing

Near Field

LBeam-width

Dynamic focusing: The focus point is shifted as function of time/range

l poin

Introduced from 2004

Beam focusing of transmit beams

Focus rangeright sector

Focusing in the nearfield on transmit is feasible by using three separate transmit sectors per ping

Footprintalongtrack

Focus rangeleft sector

Focus rangecentral sector

From 2005

Monitoring

Control

Depth Profile

Geographic window

Beam Intensity/Quality

Waterfall

By choosing AUTO for parameters, the system will adapt to changing depth

The Human Interface (MERLIN - Unix)

1995-2004

Operators Display (SIS- Windows or Linux)

Signal strength

Depth profile

3D (waterfall)

Watercolumn(beamformed)

Seabed Imagery

Gridded terrain model: 2D or 3D

Raw hydrophonedata

2004--

Raw data recorder

The raw data recorder is mounted on the side of thetransceiver cabinet.

Introduced approx. 1999Only stave data is recorded

Processed result from raw data recorder

Water column display processed from 1 ping with EM 300Courtesy of Xavier Lurton, Ifremer

Beamformed raw data can now be recorded and post processed

EM 3002 Real time Water Column display - 2004

Some recent improvements

Broad band transducers – composite ceramics

Use of FM sweep/chirp as transmit waveforms

High resolution beam processing

Multiple sounding profiles per ping

Composite ceramics for wide bandwidth

EM 710Transmit

Transducer

30-50% bandwidthcan be obtained

FM sweep/chirp transmit pulses

The use of FM sweep or chirp signals is being implemented on EM 710 as the first system

It requires new beamforming algorithms, pulse compression, and increased capacity for transmitting long pulses.

This is used to increase the energy content of the TX pulse.

A longer range can be obtained without sacrifice of resolution

High resolution beam processing

In EM 3002 the number of soundings (254 per sonar head)

is higher than

the number of acoustic beams (160 per sonar head)

This is a technique to increase and improve the system resolution.

”Soft” beams in between the acoustic beams are generated to produce the extra soundings.

A special signal processing technique, high resolution beam processing,is used in order to reduce the acoustic footprint of each sounding, and produce soundings that are independent. The best horisontal system resolution is then approximately 20cm.

The full number of beams is maintained also when the swath is reduced.

Full swathwidth Reduced swathwidth

254 soundings 254 soundings

This is a unique feature.If the swath width is reduced – on purpose or due to maxrange –the full number of soundings is still produced inside the active swath.

Result: A more dense pattern of soundings+ reduced footprint size of each sounding.

Result example, 18m depth 120 degree swath

Data processing by QPS

Result example, 18m depth 90 degree swath

The details are sharper!

Data processing by QPS

Evolution of resolution

EM 12 1990: 1.8 x 3.5 deg

EM 121 1993: 1 x 1 deg

EM 3000 1995: 1.5 x 1.5 deg

EM 300/120 1997: 1 x 1 deg

EM 710 2005: 0.5 x 1 deg

The no. of soundings/ping and the ping rate is increasing due tomore computer power being available.

EM 3002D and EM 710 will both be able to produce close to 20.000 soundings per second.

Transmit beamReceive beamEffective beam footprint

Transmitbeamwidth

SBP 120 Multibeam Sub Bottom Profiler

Receivebeam width

EM 12012 kHz

SBP 1202.5-7kHz

Common receivearay

SBP 120 block diagram

Frequency 2.5 – 7 kHzPulse forms: Chirp

CWRicker

Floating point receiver A/D

Arrays lengths:

8m - 3 degree beams 4m - 6 degree beams 2m – 12 degree beamsSub Bottom Profiler

Transmit transducer array

Operator Station

O ptional

Interfaces:Ethernet and

- Depth and bottom slopes- Navigation & Position ing -system s

Seria l lines:- Sound Velocity near Transducers/ Sound Speed Sensor

- C lock

Interfaces:- A ttitude (ro ll, p itch and heave)

InternalE thernet

-- 2x4

SBP 120RX/TX Junction Box

Beamformer Unit

SBP 120Transceiver Unit

Hydrophone Signals

EM 120Transceiver Unit

EM 120 TX Trigger

EM 120

In ternalE thernet

S ystem Trigger out

O ther external Trigger

(seria l line)

Contro l

EM 120Receive transducer array

EM 120 PreamplifierUnit

EM 120

Remote On / Off

SBP120 - 3°

Specular return / backscatter

Echogram Multiple beams

Smooth surface layer

Rough buried structure

Image ~4.5km alongtrack,

~450 ms ~ 335 m from top to bottom

-> average slope along ~ - 4°

SBP 120-3°: Sloping terrain

Data © SHOM

1 © kongsberg november 30, 2015 the evolution of the kongsberg simrad multibeam echo sounders by...

norwaynmk echo

seabed terrain

early models

equi distant beam

sounding process2

sounding process1

finn h kristensenisit

accurate realtime calculation

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