Wyniki wyszukiwania - BazTech

1

Detection and Mapping of Shipwrecks in Al-Hoceima Coastal Using Remote Sensing

Taher Morad, Mourabit Touafik, Etebaai Issam, Bourjila Abdelhak, Errahmouni Ali, Lamgharbaj Mustapha

Ecological Engineering & Environmental Technology

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2022

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Vol. 23, iss. 5

218--223

EN

On the Mediterranean coast of Morocco, many military ships were sunk in the Al-Hoceima region during Rif war between Spanish army and the local Riffians. The aim of this study is to detect and to map shipwrecks embedded in sea-floor sediments in Al-Hoceima coastal. It has been carried out using free satellite radar image and the open-source software Sentinel Application Platform. The result of this study shows five possible locations of shipwrecks in the study area, two of them were confirmed by data shipwrecks of the Spanish hydrographic institute.

2

An Efficient Edge Preserving Interpolation Method for Underwater Acoustic Image Resolution Enhancement

Priyadharsini R., Sree Sharmila T.

Archives of Acoustics

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2022

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Vol. 47, No. 2

267--274

EN

Underwater acoustic images are acquired using sonar instrument that uses sound propagation to navigate and map the sea floor. The sonar devices are effectively used to create images of large area of the seabed. However, the visual perception of the object in the acoustic image depends on refraction, which is a function of changes in the speed of sound in successive layers of water. And refraction depends mainly on temperature, slightly on salinity and hydrostatic pressure. The quality and resolution of sonar imaging of the bottom depends on many other factors such as pitch, yaw and heave of the side scan sonar, the presence of volume scatterers in the water body, the distance of the sonar from the bottom and orientation of the object. Generally, the objects in an acoustic image would be of small size compared to their normal size as the distance between the sonar and object is larger. To detect and recognize the objects in the images, the resolution should be enhanced. In this paper, we propose an efficient edge preserving interpolation method for underwater acoustic image resolution enhancement which preserves the edge sharpness. The method handles the diagonal pixels in the first pass, in turn fills the horizontal and vertical pixels in the second pass. The results obtained are compared with the state-of-the-art interpolation techniques and the performance measures such as Peak Signal to Noise Ratio (PSNR) and Structural Similarity Index Measurement (SSIM) shows an improved result.

3

Underwater image enhancement via efficient generative adversarial network

Qian Xin, Ge Peng

Optica Applicata

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2021

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Vol. 51, nr 4

483--497

EN

Underwater image enhancement has been receiving much attention due to its significance in facilitating various marine explorations. Inspired by the generative adversarial network (GAN) and residual network (ResNet) in many vision tasks, we propose a simplified designed ResNet model based on GAN called efficient GAN (EGAN) for underwater image enhancement. In particular, for the generator of EGAN we design a new pair of convolutional kernel size for the residual block in the ResNet. Secondly, we abandon batch normalization (BN) after every convolution layer for faster training and less artifacts. Finally, a smooth loss function is introduced for halo-effect alleviation. Extensive qualitative and quantitative experiments show that our methods accomplish considerable improvements compared to the state-of-the-art methods.

4

An analytical model of the power spatial distribution for underwater optical wireless communication

Wei W, Xiao-Hui Z, Yue-Yun C, Xue-Jun Z

Optica Applicata

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2012

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Vol. 42, nr 1

157--166

EN

Employing optical propagation theory in Hankel transform, an analytical model of the optical power spatial distribution is derived for the ideal point optical source and the Gaussian laser, respectively. Experimental measurements of the spatial distribution of a Gaussian laser are presented. The expected results of our analytical model are in good agreement with experimental data.

5

Reflection of low-frequency long-range sound in the ocean

Didenkulov I.

Hydroacoustics

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2003

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Vol. 6

117--124

EN

Experimental results on energetic characteristics of low frequency (about 200 Hz) underwater channel sound reflection by ocean mountains and islands are presented. lt is investigated also sound penetration into shallow water. Transformation of vertical structure of sound field over continental slope is considered. Continental slope and shelf-wedge reflection coefficients of law frequency sound propagating in the underwater waveguide were measured. Results of the work show that low-frequency sound reflections from large-scale bottom irregularities can be important in ocean acoustics.