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

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DSTO-GD-0215rθdInsonified Section of the SeafloorFigure 19: Insonified circle on the SeafloorThe level of insonification in the circle (shown in Figure 19) will be equal to thepower in the angular beam of width 2θ which produced the circle.Therefore the level of insonification in the circle will be:1B =2( 1 − Cos θ )Peq(20) (from eq(18))where P = Power level of the ping coming from the source.B = Level of insonification in the circle. (see Figure 19)Since a spherical coordinate system was used to calculate eq(20), sphericalspreading has already been considered 4 .The size of the insonified circle increases with time (ie. θ will increase with time),but only exists between the two constraining times (eq (19)). The level of insonificationwill vary over the circle, with the strongest insonification in the centre of the circle.Since eq(20) is the level of insonification in the circle, and the circle is increasing indBdiameter with time, will equal the level of insonification at the outside edge of thedθinsonified circle (this is only true for a constant power ping, since it requires that anypoint in the insonified circle have a constant insonification level with time).4 For a constant angle beam, the amount of energy in the beam will be constant if there is noabsorption in the water. This is because the diameter of the beam increases with range at thesame rate as the signal at any one point decreases.36
DSTO-GD-0215dB P= Sinθeq(21)dθ2Therefore the power level emitted by an insonified ring towards the source will be:PβSinφ.dφeq(22) (see Figure 20)2where β = The backscatter ratio.dφφ θ r φdInsonified ringInsonified circleFigure 20: Insonified ring on the seafloor.Summing the effect of all the rings and correcting for spherical spreading gives thepower level backscattered by the insonified circle (see Figure 20) to the hydrophone atany one time:37
Page 1 and 2: The ABCS Program for the Analysis o
Page 3: The ABCS Program for the Analysis o
Page 7 and 8: DSTO-GD-02151. IntroductionThe type
Page 9 and 10: DSTO-GD-02153.1 Depth Normalisation
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: DSTO-GD-0215Substituting y=µSinω
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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