Browsing CMRE Publications by Title
Now showing items 754-773 of 882
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Summary and recommendations
(NATO. SACLANTCEN, 1971/12)An unfortunate first impression might be that ray tracing is dull, simply because the idea is a very old one. In fact, ray tracing is the single most powerful method available to us for understanding the complexities of ... -
Supporting AUV localisation through next generation underwater acoustic networks: results from the field
(CMRE, 2017/11)This work describes how the localisation of autonomous underwater vehicles can be supported through net-worked acoustic communication. The localisation approach in-cludes timing information within acoustic messages to ... -
SUPREMO: a multistatic sonar performance model
(NATO. SACLANTCEN, 2002/11)Multistatic sonars introduce new problems to the modeller such as mutual interference from multiple sources and variable target aspect in a background of range-dependent bistatic reverberation. A multistatic sonar performance ... -
Surface duct propagation loss measurements and model predictions at low and mid frequencies
(NATO. SACLANTCEN, 1993/08)Side-by-side measurements of low- and mid-frequency propagation loss were obtained during a sea test conducted in the North Atlantic during February of 1992. These measurements are compared to each other and with model ... -
Surface measurements made during the Icelandic Current Experiment (ICE 89) from the R/V Alliance
(NATO. SACLANTCEN, 1991/10)Measurements of surface meteorology and sea temperature taken during the GIN '89A cruise of the research vessel Alliance are presented in the form of time-series plots. The cruise was in the southern Icelandic and Norwegian ... -
Surface measurements made from the R/V ALLIANCE during the Mediterranean aircraft-ship transmission experiment (MASTEX), June 1990
(NATO. SACLANTCEN, 1992/12)Measurements of sea-surface temperature, surface meteorology and atmospheric profiles taken during the June 1990 cruise of the R/V Alliance in the Aegean and Ionian Seas are presented in graphical form. True winds, net ... -
Surface wave spectra
(NATO. SACLANTCEN, 1975/10)A classification is made of the different types of wave elevation spectra namely lD time spectra, lD spatial spectra, 2D spatial spectra and 3D space-time spectra. Relations with simple single parameter measures of surface ... -
Swath bathymetry and SAS autofocus using a Chirp source
(NATO. SACLANTCEN, 1997)Swath bathymetry and SAS autofocus can both be treated as problems in correlating echoes from a scatterer distribution on the seabed. Using a chirp source, the phase derived from quadrature match-filtering can replace the ... -
System functional migration: high-level language to hardware
(NATO. SACLANTCEN, 1979/12)This paper intends to examine system functional allocation among available processing resources in a systematic way. The discussion will focus first on the criteria for assigning functions to processors, that is, horizontal ... -
Tactical data acquisition experiences
(NATO. SACLANTCEN, 1972/05)The requirements of Tactical Data Acquisition systems are discussed and summarized. Experiences with equipment and their utilization are described including : quantities measured, input signal conditioning, analogue ... -
Tank measurements of elastic scattering by a resin-filled fiberglass spherical shell
(NURC, 2007/12)Acoustic elastic scattering measurements were conducted in a tank on a 6cm radius fibreglass spherical shell filled with a low-shear-speed epoxy resin. Preliminary measurements were conducted also on the void shell before ... -
Tank measurements of scattering from a resin-filled fibreglass spherical shell with internal flaws
(NURC, 2008/09)This paper presents results of acoustic inversion and structural health monitoring achieved by means of low to midfrequency elastic scattering analysis of simple, curved objects, insonified in a water tank. Acoustic elastic ... -
Target detection and location with ambient noise
(NURC, 2008/09)By placing a vertical array in an ambient noise field and forming an upward and a downward beam one obtains two time series which can be cross correlated to reveal a subbottom profile of the seabed [Siderius et al., J. ... -
Target detection using a three-layered neural network trained by supervised back-propagation
(NATO. SACLANTCEN, 1990/05)In any sonar system a detection process has to be performed at -
Target localization with multiple sonar receivers
(NATO. SACLANTCEN, 2000/01)Deployable Underwater Surveillance Systems (DUSS) are a network of small multistatic transmitter/receiver sonar nodes. This study analyzes the contact localization capabilities of DUSS in term of range, time and bearing ... -
Target motion effects on passive sonar: an appraisal of basic factors
(NATO. SACLANTCEN, 1986/12)Detection and tracking by passive sonar involve the observation of the target-radiated noise in bearing-cells and time-cells that have their dimensions predetermined by a combination of physical limitations, e.g. the size ... -
Target time smearing with short transmmissions and multipath propagation
(NURC, 2012/04)In active sonar the target echo level is often estimated with a propagation model that adds all multipath arrivals. If the (post-correlator) transmitted pulse is short compared to the multipath time spread then there is ... -
Temporal and spatial variabilities in shallow water acoustics: measurements and predictions
(NATO. SACLANTCEN, 1985/03)An acoustic signal propagating in the sea is generally degraded not only by interactions with the bottom and surface boundaries, but also by volume inhomogeneities caused by non-uniformities in temperature, density, and ... -
Temporal fluctuation of backscattered field due to bioturbatioon in marine sediments
(NATO. SACLANTCEN, 1997)Biological activity in marine sediments creates a time-varying, randomly fluctuating medium. A bio-diffusive model is proposed for predicting the temporal and spatial spectrum of sediment density fluctuations. Perturbation ... -
Temporal modeling of high frequency (30-100 kHz) acoustic seafloor backscatter: shallow water results
(NATO. SACLANTCEN, 1997)A temporal model of high frequency seafloor acoustic backscatter is presented and compared to recorded echoes from terrigenous sediments. Using acoustic properties correlated with mean grain size, the echo shapes and ...