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Memorandum Reports

Report that covers interim results during the course of a project. Note: Unless linked to the full text, reports are only available to NATO member nations from designated distribution centres.

Documents

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Manual of BORIS-SSA: Bottom Response from Inhomogeneities and Surface using the Small-Slope Approximation, version 1.0 Manual of BORIS-SSA: Bottom Response from Inhomogeneities and Surface using the Small-Slope Approximation, version 1.0

Date added: 07/01/2005
Date modified: 08/14/2012
Filesize: Unknown

Manual of BORIS-SSA: Bottom Response from Inhomogeneities and Surface using the Small-Slope Approximation, Version 1.01. M-152. July 2005.

The description of a software tool capable of simulating, in the time domain, the acoustic time series resulting from scattering from various seafloor types and acoustic source/receiver geometries is presented in the form of a user manual. This package, named BORIS-SSA, is an upgrade, with various new features, of BORIS-3D. The parameters of the model characterize the sonar directivity and pulse shape, the geometrical configuration of the scattering problem and the geo-physical characteristics of the seafloor (but also sea surface or other surface). This surface can be generated to have various statistical behaviours or can be obtained from deterministic data based on the surface heights (profilometry, stereo-photogrammetry, bathymetry, etc). The package is platform independent and user friendly. This report is intended as a detailed description of the implementation on a source code level. A short introduction to the model underlying the package and a comprehensive demonstration program are also given.

Effects of the internal waves on the acoustic propagation Effects of the internal waves on the acoustic propagation

Date added: 07/01/2005
Date modified: 08/14/2012
Filesize: Unknown

Effects of the internal waves on the acoustic propagation. SM-433. July 2005.

A simple 2D model called SOFIA has been developed in order to predict sound-speed fluctuations in the water column due to linear internal waves. It is based on solving the equation governing the vertical particle velocity associated with the internal waves, using a modal decomposition of the internal wave field. The main feature of the model is the use of experimental data: the Brunt-Väisälä profile is calculated from the density profile registered by the CTD cast, the amplitudes of the normal modes are determined using ADCP data and the spectrum is deduced from the thermistor chain measurements. The effects of the linear internal waves on the acoustic propagation were studied through several numerical simulations using some sound-speed profiles predicted with the SOFIA model. The acoustic simulations were performed with the REVPA model, based on a wide-angle approximation of the parabolic equation (PE) method. Through these simulations, the possible relation between the influence of the internal waves and different values of the environmental parameters was assessed. The environmental parameters considered in this study were the source depth, the acoustic frequency and the sediment properties.

Effects of source and receiver positional offsets in multistatic range determination Effects of source and receiver positional offsets in multistatic range determination

Date added: 07/01/2005
Date modified: 08/14/2012
Filesize: Unknown

Effects of source and receiver positional offsets in multistatic range determination. SM-432. July 2005.

During the Adults’03 sea trial (a joint research project between NATO URC and TNO-FEL, The Netherlands) a number of experiments were conducted to investigate the effects of equipment offsets in multistatic range determination. The analysis presented in this report is based on data collected during experiment P02b where the two participant ships, both towing an LFAS source-receiver pair, were arranged into an in-line configuration and proceeded with same speed and heading. The direct blast arrivals are used to acoustically calculate the distance between sources and receivers. The comparison between the expected arrival times (according to the geometry) and the measured arrival times gives an indication on how equipment offsets, latencies, positional errors and unknown sound speed effect range determination.

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