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A new ambient noise imaging system for ANI, passive and bistatic active acoustic imaging in shallow water
(NATO. SACLANTCEN, 1997)Shallow water active and passive sonars can be usefully complimented by broadband Ambient Noise Imaging (ANI) systems. The first AN1 system was largely analogue, produced good images at 38 m range, but was bulky and permitted ... 
A noise directionality model including variable bathymetry
(NATO. SACLANTCEN, 1997)In this paper we investigate the noise directionality due to distributed surface sources m several envtronments with a uniformly sloping sea bed. Of particular interest are frequency dependence and the question of the ... 
A note on attenuation and dispersion in marine sediments
(NATO. SACLANTCEN, 1989/04)From the more recent investigations reported ill the literature, 
A note on convergent zones
(NATO. SACLANTCEN, 1962/02)An exact solution for ray paths near a sound channel with parabolic velocity profile is given for rays crossing the sound channel axis at small angles. The convergent zone for such rays for a source on axis is compared ... 
A novel approach for a bistatic scattering calculation suitable for sonar performance model
(CMRE, 2014/01)One of the classical approaches to the calculation of the sound pressure scattered from a rough surface is to sum the contributions to the field from a set of small tiles that approximate the surface. If the tiles are ... 
A novel method to enlarge the scanning region of a focused beamformer
(NATO. SACLANTCEN, 1997)Often focused beamforming systems use the Fresnel approximation to compute the required delays. Unfortunately, such an approximation has a validity region that is very narrow around the broadside direction. To investrgate ... 
A parametric examination of some properties of the lowfrequency ambient noise field
(NATO. SACLANTCEN, 1982/06)Models for shipgenerated ambient noise vary considerably in the detail required of their input data on sources and the environment. This paper describes a model that predicts ambientnoise levels and cumulative distribution ... 
A parametric synthetic aperure sonar for detection of proud and buried mines
(NATO. SACLANTCEN, 1997/12)This paper describes an experimental comparison between a parametric sonar and a conventional sonar for the detection of small objects on and in, the sea bed. Two experiments were performed in France (GESMA site) in October ... 
A PC/Linux software toolkit for coastal swath mapping
(NATO. SACLANTCEN, 1997)Assembly of a PC/Linux based data acquisirion and processing software toolkit for coastal (shallow water) multibeam and sidescan swath mapping sonar systems has been undertaken by the URI Ocean Mapping Development center ... 
A planewave decomposition method for modeling scattering from objects and bathymetry in a waveguide
(NATO. SACLANTCEN, 1996/11)In this paper a straightforward planewave decomposition method which can be used for solving object andlor interface scattering problems in a waveguide is described. The method utilizes the freespace scattering matrix ... 
A real time system for towed array calibration and performance analysis, or how to get 50 dB sidelobes from a towed array
(NATO. SACLANTCEN, 1982/06)Sidelobe suppression levels of 30 dB for a towed array are generally considered excellent; values above that are considered exceptional or unachievable. However, 40 t o 50 dB suppression levels have been achieved and ... 
A relation between multipath group velocity, mode number, and ray cycle distance
(CMRE, 2014/01)Weston's ray invariant or "characteristic time" in a rangedependent environment is exactly equivalent to the WentzelKramersBrillouin phase integral for ducted normal modes. By considering a ray element it is shown that ... 
A review of oceanic fronts
(NATO. SACLANTCEN, 1975/10)This paper will start with a brief account of oceanic frontal research. The definition of oceanic and acoustic fronts and the distinction between them will be discussed. Examples of frontal structure dynamics, correlation ... 
A review of some developments in ray tracing at the Naval Air Development Center
(NATO. SACLANTCEN, 1971/12)The Naval Air Development Center has a comprehensive raytracing program which has been extensively used for a number of years not only by our own laboratory, but also by other naval activities and private contractors . ... 
A review of the application of UUV technology to mine countermeasures
(NATO. SACLANTCEN, 1999/03)The emphasis on littoral warfare, the proliferation of low cost mines available to potentially hostile countries, high exercise costs and risks related to the operation of present NATO MCM units, require the development ... 
A satellite based ocean forecasting system to support naval operations in crisis situations
(NATO. SACLANTCEN, 2000/05)We employ a nonlinear ocean forecasting technique based on a combination of genetic algorithms and empirical orthogonal function (EOF) analysis. The method is used to forecast the spacetime variability of the sea surface ... 
A shallow water system for maximizing echo to reverberation ratio
(NATO. SACLANTCEN, 1993/08)A method for increasing incident energy on middepth targets while at the same range reducing boundary reverberation for shallow water ducts has been devised. The basis of the approach is couched in range dependant normal ... 
A simple deconvolution method for NAPOLI'85
(NATO. SACLANTCEN, 1991/10)An inverse filter (deconvolution in the frequency domain) is applied 
A solution of of the wave sound equation in shallow water for real speed profiles and solid bottom under sediment
(NATO. SACLANTCEN, 1975/10)The wave equation has been solved by using normal mode theory. The medium is assumed to be horizontally stratified. A closed form solution has been found in the case of GANS  PEDERSEN types of density and soundspeed ... 
A spectral ocean wave model
(NATO. SACLANTCEN, 1975/10)An operational wave spectral model has been developed through the cooperative efforts of FLENUMWEACEN, NAVOCEANO and W.J. Pierson. The model contains two subdivisions: 1) wave energy growth based on a modified version of ...