Wyniki wyszukiwania - BazTech

1

Conditions for multiple acquisition of echoes from stationary targets in successive transmissions of active sonars

Kilian Lech, Schmidt Aleksander, Rudnicki Mariusz

Vibrations in Physical Systems

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2022

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Vol. 33, nr 3

art. no. 2022308

EN

In echolocation, the highest possible number of contacts with a detected target is clearly decisive on the possibilities of echo processing to optimise the estimation of distinctive characteristics of the observed target. In hydrolocation, the slow propagation of acoustic waves in water reduces the number of contacts of echosounders and sonars with detected targets. The article considers model conditions for acquiring multiple contacts with stationary targets detected by various sounding methods - with echosounders, classic active sonars and side looking sonars. Appropriate formulas explicitly linking the possible number of echo signals from the target in a specific geometry of the survey performed at the assumed speed are presented. These formulas are intuitively clear and not very complicated, but their value lies in the ability to instantly combine the vessel speed with the sounding effects, and may be a clear argument for imposing a low sounding speed, which make it difficult to steer the vessel.

2

Analysis of the accuracy of shoreline mapping in inland navigational charts (Inland ENC) using photogrammetric and sonar images

Łubczonek Jacek, Łącka Małgorzata, Zaniewicz Grzegorz

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2019

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nr 58 (130)

45--54

EN

Shoreline mapping is one of the key stages in navigational charting. In terms of navigation, the shoreline marks the boundary of a river, which is often equivalent to the navigable water area. In cartographic terms, it is an important topological element between different objects that are adjacent to it. Currently, topographic objects are often mapped using photogrammetric materials obtained from various altitudes – satellite, airborne or low, which is associated with the use of an airborne UAV. Depending on the type of materials, the shoreline can be obtained in vector form with differing situational accuracy and differing degree of detail. In addition to the standard methods of processing vector data, the research in this paper also included the use of sonar images, enabling the detection of the shoreline with the use of a surveying hydrographic unit. On the basis of the collected photogrammetric and sonar images of different spatial resolution, an analysis of the accuracy of shoreline mapping was performed in terms of the situational accuracy and the level of detail in its representation. The results of the research provided the basis for the determination of dedicated remote sensing materials enabling the development of maps for inland navigation.

3

Inversion of side scan sonar motion and posture in seabed geomorphology

Tao W., Liu Y., Hu H.

Polish Maritime Research

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2017

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S 2

81--88

EN

Side scan sonar measurement platform, affected by underwater environment and its own motion precision, inevitably has posture and motion disturbance, which greatly affects accuracy of geomorphic image formation. It is difficult to sensitively and accurately capture these underwater disturbances by relying on auxiliary navigation devices. In this paper, we propose a method to invert motion and posture information of the measurement platform by using the matching relation between the strip images. The inversion algorithm is the key link in the image mosaic frame of side scan sonar, and the acquired motion posture information can effectively improve seabed topography and plotting accuracy and stability. In this paper, we first analyze influence of platform motion and posture on side scan sonar mapping, and establish the correlation model between motion, posture information and strip image matching information. Then, based on the model, a reverse neural network is established. Based on input, output of neural network, design of and test data set, a motion posture inversion mechanism based on strip image matching information is established. Accuracy and validity of the algorithm are verified by the experimental results.

4

Solid rocks on the nearshore seabed : the distribution and potential impact on coastal processes in the Kołobrzeg region, the Southern Baltic

Rudowski S., Sitkiewicz P., Wróblewski R., Makurat K.

Oceanological and Hydrobiological Studies

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2017

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Vol. 46, No. 1

62--73

EN

The Southern Baltic seabed is mainly composed of marine sediments situated on glacial and fluvioglacial deposits. In the Kołobrzeg region, however, solid rocks are located at the shallow subbottom. In order to determine the exact distribution of the rocks, some analyses of sonar images, underwater photos, sediment samples, seismoacoustic profiles and bathymetric data have been performed. The outcrops of Jurassic sandstones and mudstones have been documented. The geological structure of the area is presented, while the fact that the present seafloor relief is determined by the shallow uneven top surface of the Jurassic rocks is emphasized. The seabed has been classified as rock platform-constrained. The seafloor is a sediment-poor abrasion platform, within which marine sandy sediments are transported, mainly toward offshore, on the firm, stiff or hard surface of glacial deposits and Jurassic solid rocks. This results in a lack of material for the reconstruction of the beach after storms. Many of the commonly used methods for studying the condition and changes of the coast cannot be used in this type of terrain due to the presence of a thin and discontinuous dynamic layer lying on the erosion-resistant rocks of the geomorphologically complex seafloor.

5

Determining hotspots of sonar targets related to chemical munitions dumped in Bornholm Deep and Gotland Deep using GIS

Majcher J., Grabowski M., Bełdowski J.

Hydroacoustics

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2017

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Vol. 20

121--128

EN

According to the Helsinki Commission report from 1994 around 15000 tonnes of chemical warfare agents were dumped to the Baltic Sea after World War II as part of the demilitarization process of the former Nazi Germany. Continuing corrosion of metal encasements makes the dumped munitions a ticking time-bomb, which could potentially harm the whole Baltic Basin. The presented work addresses important aspects for a proper evaluation of the threat; side scan sonar survey data storage and analysis of a spatial distribution of the sonar targets potentially related to chemical weapons. The chosen software environment was GIS oriented. ESRI ArcGIS built-in tools were used to determine the hotspots of the targets on the official post-war munitions dumping sites; Gotland Deep and Bornholm Deep. The automation process of mapping in GIS was also proposed. Therefore, a holistic approach for digital mapping of the sonar targets related to dumped munitions was created.

6

Automatyczna detekcja obiektów sonarnych

Wąż M., Grządziel A., Nowak D.

Acta Scientiarum Polonorum. Geodesia et Descriptio Terrarum

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2013

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Vol. 12, nr 1

29--41

PL

Współczesne systemy sonarowe wykorzystywane są głównie do poszukiwania i wykrywania obiektów podwodnych, które mogą wpłynąć na bezpieczeństwo pływania i postoju jednostek pływających. Zadaniem operatora takich systemów jest optymalne ustawienie zobrazowania oraz odpowiedni dobór parametrów operacyjnych umożliwiających detekcję ech a następnie identyfikację wykrytych celów. Operator dokonuje korekty uzyskanych danych sonarowych, poprawiając tym samym jakość zobrazowania i możliwości interpretacji wyników pomiarów. W artykule rozpatrywanym problemem badawczym jest przekształcanie obrazów, dokonywanie korekcji geometrycznej oraz ekstrakcja obiektów z tła obrazu sonarowego. Zaprezentowana metoda automatycznego wyszukiwania obiektów wykorzystuje cechy morfologiczne sonogramów oraz geometryczne i arytmetyczne metody przetwarzania sygnałów stosowane do obróbki i analizy obrazów cyfrowych. Na etapie wyszukiwania cech obiektów sonarowych wykorzystano metody minimalno-odległościowe stosowane w rozpoznawaniu obrazów. Opracowana aplikacja umożliwiła przeprowadzenie eksperymentu badawczego przedstawiającego kolejne etapy detekcji obiektów sonarowych. Otrzymane wyniki mogą wskazywać na poprawność przyjętych założeń do badań oraz poprawność ich przeprowadzenia.

EN

Contemporary sonar systems are used mainly to search for and detect underwater objects which might affect the safety of navigation or the safety of moored watercraft. The task of the sonar operator is to display the optimal settings of the sonar image and to select the proper operational parameters that enable detection and identification of hidden targets. The operator performs corrections of the recorded sonar data, thereby improving the image quality and the ability to interpret the survey results. The paper deals with the research problem of changing display images, conducting geometric corrections, and extracting objects from the sonar imagery background. The presented method for the automatic searching of objects utilizes the morphologic features of sonograms and geometric and arithmetic methods of digital signal processing. In searching for the features of a sonar target, the minimal-distance methods used in pattern recognition were applied. The developed application makes it possible to perform research experiments that follow the stages of sonar detection of objects. The obtained results can indicate the validity of the research assumptions and the appropriateness of the methods used.

7

Optymalizacja techniki użycia systemu sonarowego do realizacji pomiarów w basenie portowym

Grządziel A., Felski A.

Logistyka

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2012

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nr 3

PL

Artykuł przedstawia techniczne aspekty optymalizacji hydroakustycznego poszukiwania obiektów podwodnych za pomocą sonaru bocznego. Zwrócono w nim uwagę na możliwości mocowania sonaru do jednostki portowej. Przedstawiono przykłady platform pomiarowych przeznaczonych do wykonywania badań na akwenach portowych.

EN

The paper presents technical aspects of the optimization of the side scan sonar survey. Special attention was paid to the possibilities of mounting of the sonar to the survey boat. Examples of the platforms designed for conducting of survey in harbour area were presented in the paper.

8

Extraction of seabed geomorphologic features of Svalbard fjords using high-resolution side scan sonar

Tęgowski J., Giżejewski J., Zieliński A.

Hydroacoustics

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2008

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Vol. 11

401-411

EN

This paper presents results of a study on the relationship between features of side scan sonar acoustic imagery of zones with active bedforms and geomorphologic seafloor characteristics. Acoustic measurements were conducted in Hornsund, a Svalbard fjord representing a periglacial environment with great intensity of morphodynamic processes and rapidly progressing changes of tidewater glaciers. Due to the intensity of these processes, Arctic fjords are the most promising areas to study the effects of climate change on the ecosystem. Acoustic identification of sedimentary structures and morphological forms created by currents and iceberg transport of glacier sediment away from the ice margin was performed. The spectral and fractal features of the recorded signals were analysed. The proposed analysis scheme allows identification of the morphodynamic active zones in the changing Arctic fjord environments. Measurements of acoustical features of seafloor surface were made during the 2006 Arctic cruise of r/v Oceania.