Browsing by Type "Scientific Report (SR)"
Now showing items 61-80 of 110
-
Optimum bearing resolution for a moving towed array and extension of its physical aperture
(NATO. SACLANTCEN, 1989/04)This report examines the limits of the angular resolution capability of a moving towed array (MTA) by -
Passive localization using propagation models
(NATO. SACLANTCEN, 1987/06)Passive ranging using propagation models can be effected in two different ways: forward modeling -
Passive ranging with the SNAP model: a performance study
(NATO. SACLANTCEN, 1987/07)A passive ranging technique which uses SNAP, the SACLANT Centre's normal-mode model, is studied. An examination is made of the sensitivity of the technique to errors in the assumed sound -
PC-based propagation and sonar prediction models
(NATO. SACLANTCEN, 1995/12)Six acoustic models available for use on PC's are tested on a series of typical propagation situations from the North Atlantic and the Mediterranean. The model set includes both early US Navy models (ASTRAL, FACT, RAYMODE) ... -
Penetration of acoustic waves into sandy seafloors at low grazing angles: the Helmholtz-Kirchhoff approach
(NATO. SACLANTCEN, 1998/08)The Helmholtz-Kirchhoff integral is applied to model the penetration of sound waves into sandy seafloors at grazing angles above and below the critical angle. Although the conditions for the validity -
Performance assessment of propagation models in AESS-6.0
(NATO. SACLANTCEN, 1999/08)A set of AESS propagation-loss predictions has been generated for typical operational scenarios in both deep and shallow water, for two sonar frequencies (500 and 3500 Hz) and for several source-receiver combinations. ... -
Perturbation theory applied to sound scattering from a rough sea-floor
(NATO. SACLANTCEN, 1992/09)Perturbation theory is applied to acoustic scattering from a rough sedimental sea-floor. Realistic -
Physics of 3-D scattering from rippled seabeds and buried targets in shallow water
(NATO. SACLANTCEN, 1998/05)The new OASES-3D code developed at MIT is used to investigate the spatial and temporal characteristics of reverberation from rippled seabeds insonified by narrow beam sonars such as the TOPAS parametric source. It is shown ... -
Range and depth estimation by line arrays in shallow water
(NATO. SACLANTCEN, 1982/01)In shallow water sound propagates in terms of normal modes. The interference between the modes can be utilized to estimate range and depth of an acoustic source in shallow water by applying high resolution power estimators ... -
Reduction of low frequency active sonar clutter through image processing
(NATO. SACLANTCEN, 1997/12)Large numbers of false clutter detections arise in the use of low frequency active sonar for the detection of low Doppler submarine targets in shallow water. Traditional detection algorithms operate individually on each ... -
Remote sensing of topographically-induced upwelling in the southern coastal region of Sicily
(NATO. SACLANTCEN, 1998/09)Upwelling signatures caused by variations in bottom topography along the southeastern Sicilian coast are identified, using spaceborne remote sensing Advanced Very High Resolution Radiometer (AVHRR) imagery, ERS-1 and ... -
Resonance analysis of the acoustic response of a water-filled cylindrical shell
(NATO. SACLANTCEN, 1998/09)The resonance analysis approach developed for characterizing free-field air-filled cylindrical shells in terms of geometrical and mechanical pararneters is extended to fluid-filled shells either in the freefield or proud ... -
Resonance scattering analysis by autoregressive models applied to air-filled, cylindrical, thin walled shells in water
(NATO. SACLANTCEN, 1997/10)Autoregressive (AR) parametric spectral estimation of the scatterer transfer function is applied to the analysis of acoustic scattering by elastic objects. In accordance with Resonance Scattering Theory (RST), the specular ... -
Results on the detection of narrow-band low-level signals in a ship-induced noise field using high-resolution beamforming
(NATO. SACLANTCEN, 1988/07)In this report the performance of a high-resolution beamformer is compared to that of the conventional -
Review of numerical models in underwater acoustics including recently developed fast-field program
(NATO. SACLANTCEN, 1984/12)Two papers given by SACLANTCEN personnel at the NATO Advanced Research Workshop on Hybrid Formulation of Wave Propagation and Scattering at Castel Gandolfo, Rome, Italy on 30 August to 3 September 1983 are published as a ... -
Robust broadband matched-field processing: performance in shallow water by simulation
(NATO. SACLANTCEN, 1993/11)An issue of concern for matched-field processing is the strong dependence between performance and -
Robust normalization algorithms for low-frequency active sonar signals
(NATO. SACLANTCEN, 1995/12)Two normalization processors of active sonar signals are presented. Due to their specific design, these algorithms are particulary good candidates to normalize the data stream before applying postprocessing methods based ... -
SAFARI Seismo-Acoustic Fast field Algorithm for Range-Independent environments: user's guide
(NATO. SACLANTCEN, 1988/09)An efficient algorithm has been developed for solving the depth-separated wave equation in general fluid/solid horizontlly stratified media. The algorithm has been built into a general-purpose package of computer codes ... -
Satellite measurements of sea surface temperature: some consequences of variability on validation and applications
(NATO. SACLANTCEN, 1990/07)Sea-surface temperature (SST) measurements from both spaceborne and in situ sensors are analysed to determine likely temperature differences that can arise between two measurements separated in space and time. This has ... -
Sea-surface winds in the Iceland-Faeroe area, as derived from the ERS-1 scatterometer
(NATO. SACLANTCEN, 1994/04)This report presents measurements of surface meteorological data taken during three cruises of R/V Alliance to the Iceland-Faeroe frontal area during August 1991 (NORDIC'91), March 1992 (NORDIC'92a) and October 1992 ...