The ABCS Program for the Analysis of Echo Sounder Returns for ...

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DSTO-GD-0215DSTO Sydney work boat to record the echo waveforms. A program (called ABCS.exe)was then written to analyse the returned waveforms. This report describes the runningof the ABCS program, what shape statistics it produces, and what needs to beconsidered when running the program. The current version of the ABCS program isnot trying to obtain the sediment type. It was written to see how selected shape andenergy statistics from the returned echo sounder signal change with sediment type,thus determining which shape statistics are important for sediment classification.2. The DataThe data used to test the ABCS program was produced using an Echo ListenerDevice. This data was supplied in CSV (comma separated variable) format, and wasobtained at a sampling frequency of 13.6 kHz. The echo sounder depth setting was setto 110 m giving 2000 samples per ping. If the data format is changed from CSV a slightmodification will have to be made to the ABCS program.The Echo Listener device is an A/D converter that has been connected in parallel tothe Furuno echo sounder on the DSTO Sydney work boat. The Echo Listener devicecan continuously log the returned echo sounder signal onto a PC or laptop withoutaffecting the operation of the echo sounder. The Echo Listener was manufactured andsupplied by Sonar Data Tasmania Pty Ltd 2 .3. The ‘ABCS’ ProgramThe ABCS program was written in Visual Basic and consists of five display forms.These are the main display form (which is used to enter the data), three plot displays,and a statistics display form. Only the main display form needs to be open, the otherscan be opened and closed as required.This program was not designed to process the pings in real time, but reads theoutput files from the Echo Listener device and calculates the statistics from them inpost processing. The current version will be used to examine how selected shape andenergy statistics change with sediment type; it is not trying to classify the sedimenttypes.2 For more information on Sonar Data and the Echo Listener see their web site athttp://www.verdant.com.au/SonarData/2
DSTO-GD-02153.1 Depth NormalisationThe shape and power of the returned signal from the seafloor can changesignificantly with seafloor depth as a result of spreading losses and absorption (seeappendix 1), even if the seafloor sediment remains the same. Seafloor depth changesalso cause dilation or compression (see appendix 1) of the returned ping. Thesechanges due to seafloor depth variation will effect the shape statistics being calculatedby the ABCS program, thus obscuring the changes due to variations in sediment type.To overcome this, the returned signal is transformed to a reference seafloor depth andthe statistics calculated at the reference seafloor depth.To transform a returned signal to the reference seafloor depth, time and poweradjustments need to be made. The time adjustment is first made to adjust the durationof the returned ping, which changes due to the different path lengths involved inbackscattering the ping from different seafloor depths. The power adjustment thenremoves the effect of spherical spreading.3.1.1 Time AdjustmentThe time adjustment enables returns from the actual seafloor (depth d) and thereference seafloor (depth d 0) to maintain the same time/angle relationships (Caugheyet al 1994). Sampling at the same angles for different seafloor depths removes the needto allow for beam patterns, and for the bottom backscatter function changing withincidence angle.3
Page 1 and 2: The ABCS Program for the Analysis o
Page 3: The ABCS Program for the Analysis o
Page 7: DSTO-GD-02151. IntroductionThe type
Page 11 and 12: DSTO-GD-0215By combining these two
Page 13 and 14: DSTO-GD-02153.1.3 Effect of Transfo
Page 15 and 16: DSTO-GD-0215If a longer ping durati
Page 17 and 18: DSTO-GD-0215SamplingRate =2 × Soun
Page 19 and 20: DSTO-GD-0215If a return is not foun
Page 21 and 22: DSTO-GD-0215The FFT plot was calcul
Page 23 and 24: DSTO-GD-0215Figure 10 : Statistics
Page 25 and 26: DSTO-GD-02153.4 Problems found from
Page 27 and 28: DSTO-GD-0215R.E. Francois and G.R.
Page 29 and 30: DSTO-GD-0215Appendix 1: Returned Pi
Page 31 and 32: DSTO-GD-0215Therefore the time take
Page 33 and 34: DSTO-GD-0215Appendix 2: Geometric E
Page 35 and 36: DSTO-GD-0215Appendix 3: The ‘Leve
Page 37 and 38: DSTO-GD-02151st input2nd inputRetur
Page 39 and 40: DSTO-GD-0215Appendix 4: Calculation
Page 41 and 42: DSTO-GD-0215Substituting y=µSinω
Page 43 and 44: DSTO-GD-0215dB P= Sinθeq(21)dθ2Th
Page 45 and 46: DSTO-GD-0215Calculating the Insonif
Page 47 and 48: DSTO-GD-0215Appendix 5: Search Area
Page 49 and 50: DISTRIBUTION LISTThe ABCS Program f
Page 51: Page classification: UNCLASSIFIEDDE

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