Browsing CMRE Publications by Title
Now showing items 34-53 of 882
-
A method of estimating the influence of ship's noise on ambient noise measurements
(NATO. SACLANTCEN, 1982/06)Ambient noise measurements are often adversely affected by noise from passing ships. Here, a method is presented which allows the estimation of this influence. The method is especially suitable for shallow water applications. ... -
A method to quantify shortfalls and cost benefits for the MO 2015 ASW advanced concepts study
(NATO. SACLANTCEN, 1997/06)An ASW Advanced Concepts Study (ACS) has been initiated as part of Phase 2 of NATO Study, "Implications of New Technology for Maritime Operations in 2015". In this paper, a method to assess ASW search operations is described ... -
A micro-programmable correlator for real-time radar processing
(NATO. SACLANTCEN, 1979/12)This paper presents a novel design of a multibit, digital correlator for incoherent scatter radar observations. By utilizing bit-slice microprocessor elements and internal control by microcode instructions, a high-speed ... -
A microcomputer-controlled digital acquisition and analysis system for the expendable bathythermograph
(NATO. SACLANTCEN, 1985/10)For a number of years the expendable bathythermograph (XBT) has been an important tool for basic and applied oceanographic survey work. This has led to a significant body of work being done on the accuracy of the XBT system ... -
A modular approach to signal processing
(NATO. SACLANTCEN, 1979/12)This paper outlines work in progress on modular systems for beamforming and signal processing. The modules described were developed using commercially available digital L.S.I circuits and the emphasis during development ... -
A modular signal processing software development system
(NATO. SACLANTCEN, 1979/12)A software development system is being built by the U.S. Naval Research Laboratory (NRL) to aid production of modular signal processing software for U. S. Navy airborne ASW platforms using the Navy's Advanced Signal Processor ... -
A neural-network-fusion architecture for automatic extraction of oceanographic features from satellite remote sensing imagery
(NATO. SACLANTCEN, 1999/06)This report describes an approach for automatic feature detection from fusion of remote sensing imagery using a combination of neural network architecture and the Dempster-Shafer (DS) theory of -
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 low-frequency ambient noise field
(NATO. SACLANTCEN, 1982/06)Models for ship-generated ambient noise vary considerably in the detail required of their input data on sources and the environment. This paper describes a model that predicts ambient-noise 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 plane-wave decomposition method for modeling scattering from objects and bathymetry in a waveguide
(NATO. SACLANTCEN, 1996/11)In this paper a straightforward plane-wave decomposition method which can be used for solving object andlor interface scattering problems in a waveguide is described. The method utilizes the free-space 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 range-dependent environment is exactly equivalent to the Wentzel-Kramers-Brillouin 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 ...