1,513 research outputs found
Acoustic calibration and bathymetric processing with a Klein 5410 sidescan sonar
In 2001, NOAA acquired an L-3 Communications Klein 5410 bathymetric sidescan sonar system that simultaneously provided high resolution multibeam acoustic imagery and wide swath bathymetry. The sonar\u27s inability to produce matching bathymetry in overlapping swaths motivated the detailed acoustic and signal processing analyses described in this thesis.
Results of this research include specific corrections for phase distortions introduced by the sonar\u27s transmit pulses, receiver electronics, and transducer elements, which are implemented in a newly-developed full vector bathymetric processing algorithm to estimate accurate acoustic arrival angles for each sample of the seafloor echo acquired by the Klein 5410 sonar. Performance of this algorithm was verified during a survey conducted in New York Harbor during October of 2006. The resulting bathymetry matches bathymetry obtained independently over the same survey area with a Reson SeaBat 8125 focused multibeam echo-sounder operating at the same acoustic frequency
Algorithms for propagation-aware underwater ranging and localization
Mención Internacional en el tÃtulo de doctorWhile oceans occupy most of our planet, their exploration and conservation are one of
the crucial research problems of modern time. Underwater localization stands among the
key issues on the way to the proper inspection and monitoring of this significant part of our
world. In this thesis, we investigate and tackle different challenges related to underwater
ranging and localization. In particular, we focus on algorithms that consider underwater
acoustic channel properties. This group of algorithms utilizes additional information
about the environment and its impact on acoustic signal propagation, in order to improve
the accuracy of location estimates, or to achieve a reduced complexity, or a reduced
amount of resources (e.g., anchor nodes) compared to traditional algorithms.
First, we tackle the problem of passive range estimation using the differences in the
times of arrival of multipath replicas of a transmitted acoustic signal. This is a costand
energy- effective algorithm that can be used for the localization of autonomous
underwater vehicles (AUVs), and utilizes information about signal propagation. We study
the accuracy of this method in the simplified case of constant sound speed profile (SSP)
and compare it to a more realistic case with various non-constant SSP. We also propose
an auxiliary quantity called effective sound speed. This quantity, when modeling acoustic
propagation via ray models, takes into account the difference between rectilinear and
non-rectilinear sound ray paths. According to our evaluation, this offers improved range
estimation results with respect to standard algorithms that consider the actual value of
the speed of sound.
We then propose an algorithm suitable for the non-invasive tracking of AUVs or
vocalizing marine animals, using only a single receiver. This algorithm evaluates the
underwater acoustic channel impulse response differences induced by a diverse sea
bottom profile, and proposes a computationally- and energy-efficient solution for passive
localization.
Finally, we propose another algorithm to solve the issue of 3D acoustic localization
and tracking of marine fauna. To reach the expected degree of accuracy, more sensors
are often required than are available in typical commercial off-the-shelf (COTS) phased
arrays found, e.g., in ultra short baseline (USBL) systems. Direct combination of multiple
COTS arrays may be constrained by array body elements, and lead to breaking the optimal array element spacing, or the desired array layout. Thus, the application of
state-of-the-art direction of arrival (DoA) estimation algorithms may not be possible. We
propose a solution for passive 3D localization and tracking using a wideband acoustic
array of arbitrary shape, and validate the algorithm in multiple experiments, involving
both active and passive targets.Part of the research in this thesis has been supported by the EU H2020 program under
project SYMBIOSIS (G.A. no. 773753).This work has been supported by IMDEA Networks InstitutePrograma de Doctorado en IngenierÃa Telemática por la Universidad Carlos III de MadridPresidente: Paul Daniel Mitchell.- Secretario: Antonio Fernández Anta.- Vocal: Santiago Zazo Bell
An experimental synthetic aperture SONAR
Aperture synthesis is a mature technique that has been used with success in a number
of remote sensing fields. Sonars can also potentially benefit from the technique,
though to date the limitations of slow acoustic propagation and difficulty in
maintaining a stable platform has hindered investigation.
This thesis investigates aperture synthesis for high resolution underwater imaging. A
prototype sonar is designed and fabricated for the study. The performance of the sonar
is assessed in both tank and sea trials and the results presented in this thesis
High-resolution sonar DF system
One of the fundamental problems of sonar systems is the determination of the
bearings of underwater sources/targets. The classical solution to this problem,
the 'Conventional Beamformer', uses the outputs from the individual sensors of
an acoustic array to form a beam which is swept across the search sector. The
resolution of this method is limited by the beam width and narrowing this beam
to enhance the resolution may have some practical problems, especially in low
frequency sonar, because of the physical size of the array needed.
During the past two decades an enormous amount of work has been done to
develop new algorithms for resolution enhancements beyond that of the
Conventional Beamformer. However, most of these methods have been based
on computer simulations and very little has been published on the practical
implementation of these algorithms. One of the main reasons for this has been
the lack of hardware that can handle the relatively heavy computational load of
these algorithms. However, there have been great advances in semiconductor
and computer technologies in the last few years which have led to the availability
of more powerful computational and storage devices. These devices have
opened the door to the possibility of implementing these high-resolution Direction
Finding (DF) algorithms in real sonar systems.
The work presented in this thesis describes a practical implementation of some
of the high-resolution DF algorithms in a simple sonar system that has been
designed and built for this purpose. [Continues.
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