Wyniki wyszukiwania - BazTech

1

Application of Shape From Shading Technique for Side Scan Sonar Images

Bikonis K., Moszynski M., Lubniewski Z.

Polish Maritime Research

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2013

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nr 3

39--44

EN

Digital signal processing technology has revolutionized a way of processing, visualisation and interpretation of data acquired by underwater systems. Through many years side scan sonars were one of the most widely used imaging systems in the underwater environment. Although they are relatively cheap and easy to deploy, more powerful sensors like multibeam echo sounders and sonars are widely used today and deliver 3D bathymetry of sea bottom terrain. Side scan sonar outputs data usually in a form of grey level 2D acoustic images but the analysis of such pictures performed by human eye allows creating semi-spatial impressions of seafloor relief and morphology. Hence the idea of post-processing the side scan sonar data in a manner similar to human eye to obtain 3D visualisation. In recently developing computer vision systems the shape from shading approach is well recognized technique. Applying it to side scan sonar data is challenging idea used by several authors. In the paper, some further extensions are presented. They rely on processing the backscattering information of each footprint (pixel in sonar image) along with its surroundings. Additionally, a current altitude is estimated from the size of shadow areas. Both techniques allow constructing 3D representation of sea bottom relief or other investigated underwater objects.

2

A novel method for archiving multibeam sonar data with emphasis on efficient record size reduction and storage

Moszynski M., Chybicki A., Kulawiak M., Lubniewski Z.

Polish Maritime Research

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2013

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nr 1

77--86

EN

Over the past few years considerable advances in sonar technology, spatial positioning capabilities and computer processing power have lead to significant improvements in mapping, imaging and technologies of seafloor exploration. Recently, modern multibeam echosounder systems (MBES) capable of recording backscatter data for the whole water column, not just for the seabed, have become available thus providing data allowing for visualization and analysis of objects other than the seabed such as single fish, fish schools or pollution. Unlike bathymetric sonars, which only capture the seafloor, multibeam systems produce very large amounts of data during surveys. Because of this, storing the data collected during hydrographic or scientific cruises becomes a crucial problem. In this context, the paper proposes a new approach for efficient reduction and storage of MBES records. The results of a sample implementation of the algorithm being tested on several different sets of MBES data are also discussed.

3

A spice equivalent circuit for modeling the performance of dual frequency echo-sounder

Moszynski M., Lis W.

Hydroacoustics

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2011

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Vol. 14

165-170

EN

The paper presents novel network equivalent circuit of piezoceramic circular disc transducer that takes into account thickness and radial mode of vibrations. The starting point of the analysis is 4-port description of circular disc element representing the solution of wave equation set in radial and thickness directions. The approximate solution for harmonic case is represented in the form of 4x4 matrix, which is synthesized and implemented in circuit analysis software. The network is extended with acoustical port that allows for pressure calculations in the similar manner as when measuring echo-sounder transmitting and receiving parameters. The model is especially useful for simulating complete electronic circuit of dual frequency echo-sounders based on single circular disc transducer.

4

Light yield non-proportionality and intrinsic energy resolution of doped CsI scintillators

Chewpraditkul W., Swiderski L., Moszynski M.

Nukleonika

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2008

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Vol. 53, No. 2

51-56

EN

The light yield non-proportionality and energy resolution of doped CsI scintillators have been studied for gamma-ray energies ranging from 16.6-1274.5 keV. The light yield non-proportionality of about 20% and the energy resolution of 7.6 š 0.4% for 662 keV gamma-rays have been achieved for empty set 25 mm × 25 mm CsI(Na) crystal, coupled to an XP 5200 photomultiplier tube. The intrinsic resolution of the crystals vs. energy of gamma-rays has been determined after correcting the measured resolution for photomultiplier tube statistics. The different shapes of intrinsic resolution curves observed with various samples of doped CsI are discussed.

5

The statistics of fish echo traces - models and validation

Moszynski M., Stepnowski A.

Hydroacoustics

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2000

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Vol. 3

155--160

EN

Beam pattern probability density function (PDF) plays important role in indirect fish target strength estimation methods as it constitutes the kernel of any form of a "single-beam integral equation" that should be solved for unknown target strength PDP. Typically, the beam pattern PDF is calculated under the assumption of uniform spatial distribution of fish targets in beam pattern cross-section. However, in some cases this assumption can not be justified due to fish or vessel movement, and different number of fish echoes in fish traces. In the paper, two different models of fish traces statistics were investigated: one assuming the vessel movement with stationary fish and the other with stationary vessel and moving fish. Both approaches were modelled numerically and later verified experimentally using data obtained from a dual-beam system.

6

Using single-beam observations off fish echoes from sidelobe in fish target strength estimation

Moszynski M., Hedgepeth J. B.

Hydroacoustics

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1999

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Vol. 2

21--26

EN

Fish target estimation when using single-beam echosounder data is based on solving integral equation by inverse technique with probability density functions (PDFs) of echo envetope and heam pattern as known variabies. Typically - by setting threshold on echo level - only main-tobe observation are used due to difficulties in beam pattern PDF evaluation and signal-to-noise ratio constraints. This paper presents a method that uses side-tobe observations in the beam pattern probability density function and all collected echo peak values. These side-tobe echo observations indifferentiable when using single-beam system are combined with those from main-tobe. The smoothed Expectation Maximization metbod (EMS) is used to estimate densities and acoustic sizes of fish main-tobe with side-tobe observations.