topic2 underwater investigations equipments

8/4/2019 Topic2 Underwater Investigations Equipments

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SR SAIFUL AMAN HJ SULAIMAN

DEPARTMENT SURVEYING SCIENCE AND GEOMATICFACULTY OF ARCHITECTURE, PLANNING ANDSURVEYING

UNIVERSITI TEKNOLOGI MARA, MALAYSIA

ACKNOWLEDGEMENTS:SR DR. OTHMAN MOHD YUSOF


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DEPTH MEASUREMENTLEAD LINE MEASUREMENT Lead lines are to be used in situations where use of

electronic sounding would be impractical, impossible, or givefaulty results.

Lead line sounding is especially suited for underwaterinvestigation of rock or concrete placement; on the slopes

of jetties, groins, and revetments; and near bulkheadconstruction.

In such areas, echo sounding may be inaccurate or

contaminated with noise from side echoes


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DEPTH MEASUREMENTLEAD LINE MEASUREMENT


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DEPTH MEASUREMENTSOUNDING POLE Basically a level rod which uses the water surface instead

of a differential levelling instrument for reference. Depths are observed relative to the water surface

Sounding poles, like lead lines, are useful in certainsituations in which an electronic echo sounding system isnot practical or accurate.


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DEPTH MEASUREMENTSOUNDING POLE


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DEPTH MEASUREMENTSINGLE BEAM ECHO SOUNDER Single beam echo sounder is the most widely used for

depth measurement. Single beam echo sounder measure the depth by sending

out an acoustic signal and measuring the time it taken forthat signal to travel to the bottom and return back to echo

sounder. If multiplied by sound velocity, this travel time will given

an indication of the depth below the echo transducer.


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DEPTH MEASUREMENTSINGLE BEAM ECHO SOUNDER


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DEPTH MEASUREMENTSINGLE BEAM ECHO SOUNDER


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INSTALLATION

TRANSDUCER Critical for the correct reliable operation of the echo

sounder

If high and low frequency transducer have to be installed,

both transducer should be mounted as close as possible. Usually standard dual frequency transducer at market is

provided with transducer in same housing.

Transducer is ideally located at third or half of the length ofthe vessel measured from bow

It should also be installed as close as possible to thecenterline. (Minimized effect of roll and pitch)

The position of the transducer should be determinedaccurately as possible. (in relation to other survey system)

The transducer should be located as far as possible fromsource of noise such as propeller and engine.


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INSTALLATION

TRANSDUCER OVER THE BOW


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INSTALLATION

TRANSDUCER OVER THE SIDE


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ECHO SOUNDER CALIBRAIONS (BAR CHECK)

Echo sounder Calibration Routine task which of adjustingthe equipment to ensure correct depth can be measured.

The Bar Check is performed to calibrate the depth readingof the echo sounder.

The Bar Check is recognized throughout the Navy,International Hydrographic Organization (IHO) anddredging industry as the standard reference system for

acoustic depth measurements. The Bar Check calibration should be done before and after

the surveying done every day at the surveyed area.

Two main parameters are directly involve in bar checkcalibration; the draught and the speed of sound.


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BAR CHECK PROCEDURE

Lay down the bar plate 3 meter below the transduser,check the measured depth at the echo sounder. If thevalue of depth is different, adjust the input value of Soundof Velocity or Speed of Sound.

Lay down the bar plate 4 meter until the deepest bar plateas possible below the transducer, adjust the SOS or SOVuntil the depth shown same between the bar plate and echosounder display.

Repeat the procedure in the opposite direction.


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BAR CHECK CALIBRATION


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ECHO SOUNDER SETTING POWER

The operating range of the echo sounder depends on pulse lengthand frequency. To optimize the use of the echo sounder, thetransmitted power should be kept at the lowest valuesconsummate with adequate detection. Increases in power will

result in high levels of echoes and creating poor record. PULSE LENGTH

The pulse length is usually selected automatically as a function ofthe operating range. The short pulses are necessary for a betterresolution. It may be necessary to increase the pulse length inareas with poor reflectivity.


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ECHO SOUNDER SETTING GAIN

The amplification of the signal also amplifies the noise andconsequently the data record may be confused. It isrecommended that the gain is adjusted according to the seabedtype and to the transmission power.

RANGE

Corresponds to the depth scale of the echo sounder recordingwindow. The width of the recording paper is fixed.

DRAUGHTThis parameter corresponds to the immersion of the transducer;in order to record the depth with reference to the instantaneouswater level, the draught should be set and verified before survey

operations commence and regularly thereafter


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ECHO SOUNDER SETTING PAPERS SPEED

This speed is particularly important and should be selected to

ensure good horizontal resolution from depth measurements. SPEED OF SOUND


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INTERPRETATION OF RECORDS Interpretation of the echo trace is a hydrographers

responsibility. The interpretation requires experience

to identify particular shapes, multiple echoes andfalse echoes.


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INTERPRETATION OF RECORDS FALSE ECHO

Caused by foreign matter such as kelp or fish in the water

column.


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INTERPRETATION OF RECORDS MULTIPLE ECHOES

Echoes received subsequent to the very first one due to amultiplicity of reflections back and forth between the seafloor

and the surface. These reflections are often recorded asmultiples of the first depth.


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OPERATION MEASURINGDEPTH USING ECHO SOUNDER


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ANTENNA

INSTALLATION ANTENNA

WITH PARALLEL TO

TRANSUCER


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ASSIGNMENT 2Discuss in detail what is Multibeam Echo Sounder. Your

discussion and explanations must cover on Principle ofoperation, Installation and Calibration and Sample of

applicationDiscuss in detail what is Side Scan Sonar. Your

discussion and explanations must cover on Principle of

operation, Installation and Calibration and Sample ofapplication.

Discuss in detail what is Sub Bottom Profiler. Your

discussion and explanations must cover on Principle ofoperation, Installation and Calibration and Sample ofapplication .


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Instruction Assignment 1

4 - 5 persons in each group

Prepare slide presentation and report on selected topic

Selected group will be present on the selected topic.

Hardcopy and softcopy report and slide presentation must

submit on 23th Feb 2010 before 16:59:59 Malaysia Std

Time.

Your Presentation on 24th Feb 2010


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Multi Transducer


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the geometry of a typical sidescan sonar.

www.oceanicimaging.org


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sidescan image with the center track and data from the port and starboardchannels.


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the geometry of a typical multibeam sonar for mapping

ocean bottom contours.

topic2 underwater investigations equipments

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