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Wyświetlanie 1-10 z 35
Tytuł:
Sensitivity of echo envelope fractal dimension to bottom type and bottom depth - numerical results
Autorzy:
Łubniewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/332051.pdf
Data publikacji:
2003
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
acoustic
seafloor
hydroacoustics
Opis:
The presented results are a part of those obtained within the author's latest work on application of normal incidence methods in acoustic seafloor characterisation. The work included both theoretical and experimental studies on selection of appropriate methods of seafloor echo processing and feature extraction for characterisation of the bottom type, especially, the study of the usefulness of several echo parameters like fractal dimension or statistical moments of the echo envelope. In this paper, the simulation results of the echo envelope fractal dimension dependence on bottom type and bottom depth are presented. They show that to same extent, fractal dimension of an echo may be useful for bottom identification even in a case of varying depth, however, more detailed, theoretical as well as experimental studies are needed.
Źródło:
Hydroacoustics; 2003, 6; 195-198
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulations of acoustic backscattering on fractally corrugated Seabed surface
Autorzy:
Łubniewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/332288.pdf
Data publikacji:
2000
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The numerical simulations of echosaunder signals scattering by fractally corrugated sea bed surface are presented. In particular, the relations between fractal dimension, describing the large scale roughness of sea bottom, and received echo envelope shape, were investigated. The fractal large scale relief of seabed suiface was generated assuming the power law form of the spatial frequency power spectrum, with exponent related to fractal dimension, and subsequently applying the two dimensional inverse FFT algorithm. In the secand stage, the bottom echo waveform was numerically modelled as an incoherent sum of coruributing echoes from all surface elements. For each element, the echo amplitude was calculated assuming the form of angular dependence of bottom backscattering coefficient for smal! scale roughness. The obtained results of simulations have revealed same conditions for the transferring of the seabed surface fractal structure onto the shape of echo wavefonn.
Źródło:
Hydroacoustics; 2000, 3; 25-28
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Using multibeam echoes in seafloor characterisation and classification
Autorzy:
Łubniewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/331600.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
multibeam echoes
seafloor characterisation
sonars
Opis:
The method of seabed identification and classification from multibeam sonar echoes is presented. The proposed approach is based on calculation of a set of parameters of an echo envelope, similarly as in seafloor classification using single beam echosounder. These parameters are extracted for each consecutive beam allowing the estimation of their dependence on the seafloor incident angle. The relation between seabed type and calculated echo parameters and its angular dependence, is investigated. The results obtained using sonar data records from several bottom types in Gdańsk Bay water region are presented and discussed. It has been primarily justified that the proposed approach may be useful in seafloor characterisation.
Źródło:
Hydroacoustics; 2008, 11; 265-270
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Seafloor characterisation using multibeam data: sonar image properties, seabed surface properties and echo properties
Autorzy:
Łubniewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/331826.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
In the paper, the approach to seafloor characterisation is presented. The multibeam sonars, besides their well verified and widely used applications like high resolution bathymetry and underwater object detection and imaging, are also the promising tool in seafloor characterization and classification, having several advantages over conventional single beam echosounders. The proposed approach relies on the combined, concurrent use of several techniques of multibeam sonar data processing. The first one is based on constructing the grey-level sonar images of seabed using the backscattering strength calculated for the echoes received in the consecutive beams. Then, the set of parameters describing the local region of sonar image is calculated. These include both the first and the second order statistics of the grey level, and the texture analysis. The second technique utilises the 3D model of the seabed surface, which is constructed as a set of (x, y, z) points using the detected bottom range for each beam in the multibeam system seafloor imaging procedure. For the local region of seabed surface, the descriptors like rms height and autocorrelation radius are calculated. The third technique assumes the use of a set of parameters of the multibeam echo envelope, similarly as in single beam classification. The parameters include echo energy and its statistics, as well as the set of echo shape descriptors, and are calculated for each beam allowing the estimation of their dependence on seafloor incident angle. Then, for selected parameters, the characteristic features quantitatively describing their angular dependence, like slope, or range, are calculated. Finally, the features obtained by these 3 techniques have been combined together and used in seabed supervised classification procedure based on standard classifiers. The proposed method has been tested using multibeam data records acquired from several bottom types in the Gulf of Gdańsk region. The obtained results show that application of the proposed combined approach improves the classification comparison with those of using only the one scheme of seafloor multibeam data processing.
Źródło:
Hydroacoustics; 2011, 14; 135-142
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fractal characterisation of 30 kHz echoes from southern Baltic bottom
Autorzy:
Tęgowski, J.
Łubniewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/331844.pdf
Data publikacji:
2000
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The fractal dimension of 30 kHz echo envelope is used for characterise the bottom sediment type in Southern Baltic Sea. Two methods of the echo waveform fractal dimension calculation were applied: the autocorrelation function log-log slope method and the power spectrum log-log slope method. The results are presented and compared. They show that fractal dimension of echo envelope describes well the bottom sediments morphology and may be used as a significant descriptor in the remote sea bed classification procedures.
Źródło:
Hydroacoustics; 2000, 3; 15-18
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of some echo parameters to the seabed classification - methodological analysis
Autorzy:
Tęgowski, J.
Łubniewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/332378.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The paper presents the methodological analysis of acoustical seabed classification procedure, which aim is to define the most appropriate bottom echo parameters as an input set. Several acoustical and statistical features of echo envelope were compared with morphological features of bottom sediments and a set of parameters was proposed: integral backscattering strength, time of reverberation, radius of autocorrelation, fractal dimension, moment of inertia, and skewness. It was shown using real echoes from seafloor, that this set may be a good descriptor of sea bottom sediments and may be used in classification procedures. In addition, the spatial distribution of echo skewness within Polish Economical Zone of Baltic Sea was presented as an example and compared with sediments allocation map.
Źródło:
Hydroacoustics; 2001, 4; 237-240
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multibeam data processing for 3D object shape reconstruction
Autorzy:
Kulawiak, M.
Łubniewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/332626.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
multibeam sonar
3D reconstruction
point cloud
wrecks
rasterization
Opis:
The technology of hydroacoustic scanning offers an efficient and widely-used source of geospatial information regarding underwater environments, providing measurement data which usually have the structure of irregular groups of points known as point clouds. Since this data model has known disadvantages, a different form of representation based on representing surfaces with simple geometric structures, such as edges and facets, is preferred for data featuring seabed surface relief and various underwater objects. In this paper, the authors propose a multiple-step approach to three-dimensional surface reconstruction from multibeam sonar measurements, relying on the proper application of various algorithms for noise reduction, data rasterization and classification. The results obtained by combining several different surface reconstruction algorithms with the proposed data processing technique were tested, and the strengths and weaknesses of each method were highlighted.
Źródło:
Hydroacoustics; 2017, 20; 105-112
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelling the seafloor 3D relief and its reconstruction from multibeam sonar data
Autorzy:
Łubniewski, Z.
Moszyński, M.
Powiązania:
https://bibliotekanauki.pl/articles/331622.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The simple, real-time procedure for seafloor relief reconstruction and simultaneous seabed type identification using echo data from hypothetical multibeam sonar system was proposed. The algorithm was tested using artificially generated relief and seabed type data. In the first stage, 3D surface of seafloor was generated, using the inverse Fourier transformation of the 2D spatial frequency spectrum of power law form. In the second stage, the generation. of the set of multibeam sonar data, which simulated echoes collected from seabed, was performed with account for the distances from transducer to particular surface elements, scattering coefficient and the angles of insonification. Finally, the spatial form of seabed was reconstructed using the simulated data, while bottom type was identified simultaneously using estimated angular dependence of backscattering coefficient. The obtained results showed the good performance of the proposed reconstruction procedure for artificial data and suggested verification of the algorithm using real data.
Źródło:
Hydroacoustics; 2001, 4; 153-156
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On algorithm details in multibeam seafloor classification
Autorzy:
Łubniewski, Z.
Sęk, D.
Powiązania:
https://bibliotekanauki.pl/articles/331668.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
seafloor classification
multibeam sonar
sonar data processing
Opis:
Remote sensing of the seafloor constitutes an important topic in exploration, management, protection and other investigations of the marine environment. In the paper, a combined approach to seafloor characterisation is presented. It relies on calculation of several descriptors related to seabed type using three different types of multibeam sonar data obtained during seafloor sensing, viz.: 1) the grey-level sonar images (echograms) of the seabed, 2) the 3D model of the seabed surface which consists of bathymetric data, 3) the set of time domain bottom echo envelopes received in the consecutive sonar beams. The proposed methodology has been tested using field data records acquired from several bottom types in the Southern Baltic Sea. Using the examples of particular parameters, the influence on the specific manner and details regarding their calculation, i.e. the size of the applied current local window to a sonar image, on the obtained classification performance, is discussed.
Źródło:
Hydroacoustics; 2017, 20; 113-120
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of direct and inverse methods of satellite observations downscaling for the coastal zone area
Autorzy:
Chybicki, A.
Łubniewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/331736.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
Earth observation
land surface temperature
sea surface temperature
PBIM downscaling method
surface effective emissivity
Opis:
The Earth observation satellite imaging systems have known limitations, especially regarding their spatial and temporal resolution. Therefore, approaches which aim to combine data retrieved from sensors of higher temporal and lower spatial resolution with the data characterized by lower temporal but higher spatial resolution are of high interest. This allows for joint utilization of the advantages of both these types of sensors. As there are several ways to achieve this goal, in this paper two approaches, direct and inverse, of downscaling the land surface temperature (LST) derived from low resolution imagery acquired by the Advanced Very High Resolution Radiometer (AVHRR) were evaluated. The applied downscaling methods utilize biophysical properties of the surface sensed using short wave infrared and thermal band. The presented algorithm evaluation was performed on the basis of a specific test case: the coastal zone area of the Gulf of Gdańsk, Poland. In this context, the objective presented in the study was to compare two methods of downscaling for a specific test case in order to evaluate how the proposed approaches cope with the specific conditions of the coastal zone area.
Źródło:
Hydroacoustics; 2016, 19; 55-64
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-10 z 35

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