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The computational time of the proposed measurement system was about 30 ms with TOSHffiA EWS (engineering work station) AS4080 from the acquisition of the sensor outputs to the measurement of the ship's attitude. If advanced computer technology will be used or the sampling time is a little enlarged, a microcomputer will be available for the on-line measurement. Furthermore, by increasing the number of the candidates, the accuracy of the measurement is much more improved, and for that aim a multiprocessor technique which enables the parallel computation in a bank of Kalman filters is efficiently used. 40IEEE JOURNAL OF OCEANIC ENGINEERING, VOL. 20, NO.4, OCTOBER 1995 ISOlation of Resonance in Acoustic Backscatter from Elastic Targets Using Adaptive Estimation Schemes Mahmood R. Azimi-Sadjadi, JoEllen Wilbur, and Gerald 1. DobeckAbstract-The problem of underwater target detection and classification from acoustic backscatter is the central focus of this paper. It has been shown that at certain frequencies the acoustic backscatter from elastic targets exhibits certain resonance behavior which closely relates to the physical properties of the target such as dimeusion, thickness, and composition. Several techniques in both the time domain and frequency domain have been developed to characterize the resonance phenomena in acoustic backscatter from spherical or cylindrical thin shells. The purpose of this paper is to develop an automated approach for identifying the presence of resonance in the acoustic backscatter from an unknown target by isolating the resonance part from the specular contribution. An adaptive transversal filter structure is used to estimate the specular part of the backscatter and consequently the error signal would provide an estimate of the resonance part. An important aspect of this scheme lies in the fact that it does not require an underlying model for the elastic return. The adaptation rule is based upon fast Recursive Least Squares (RLS) learning. The approach taken in this paper is general in the sense that it can be applied to targets of unknown geometry and thickness and, further, does not require any a priori information about the target and/or the environment. Test results on acoustic data are presented which indicate the effectiveness of the proposed approach. V. CONCLUSIONThe paper proposed an on-line automatic measurement system which accurately measured the heaving, rolling, and pitching of ship by adequately processing the outputs of four accelerometers and one inclinometer appropriately located on the ship. By modeling the heaving, rolling, and pitching signals by adequate linear dynamic systems and using a bank of Kalman filters, on-line accurate measurement of ship's attitude was realized. Further improvement of the accuracy of the measurement is achieved by increasing the number of the candidates used in a bank of Kalman filters. REFERENCES[1] S. Tanaka, "On automatic attitude measurement system for ships using servo-type accelerometers

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A method is proposed to estimate the geoacoustic parameters of the uppermost seafloor strata using normal-incidence backscattered acoustic data obtained with a parametric sonar in the 4–12 kHz frequency range. A model-based identification approach has been pursued. The time-domain backscattering model BORIS [Bergem et al., SACLANTCEN Memorandum SM-328 (1997)] has been selected as a forward model. A specific wavelet transform has been defined in order to obtain a significant measure of the discrepancy between data and model predictions in the wavelet-transformed domain. This discrepancy is minimized as a function of the bottom parameters. The technique has been tested on experimental data gathered in different locations in order to assess its perfomance on different bottom types. Identification results have been compared with independent ground truth collected by core analysis and video camera inspection. The comparison shows excellent agreement between acoustically determined parameters and ground truth. [This work has been partially supported by European Union, Contract No. MAS3-CT95-046, project ISACS.]

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