Estimation of space-time characteristics of surface roughness based on video images

Borodina, E. L.; Salin, M. B.

doi:10.1134/s000143381002012x

Cited by 6 publications

(5 citation statements)

References 8 publications

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“…The method for measuring the surface oscillations using optical marks is described in [28] in sufficient detail and is not considered in this work. The marks are equipped by an anchor, an element with positive buoyancy, and the length standards in the vertical and, optionally, horizontal directions (in the latter case, we have a disc of known diameter).…”

Section: Measurement Layoutmentioning

confidence: 99%

“…2a) is recorded, which allows one to obtain a three-dimensional (two coordinates and time) data array on the surface-image brightness. Second, to measure the local surface oscillations (analog of string wave-recorder measurement), a video record with large magnification of one or several so-called "optical" markers [28], which are located in the same water area (see Fig. 2c), is performed.…”

Section: Measurement Layoutmentioning

confidence: 99%

“…The first results of the works on the considered measurement method are presented in [28]. The materials of this paper, which are partially presented in [7,29], contain a description of the upgraded scheme for video-image processing and new data for measuring three-dimensional wave characteristics.…”

Section: Introductionmentioning

confidence: 99%

“…Optical measurement methods can be divided into those which work in the transmission mode [16] (refracted-light recording), stereoscopic [17,18], and the brightness technologies based on the fundamental dependence of the local brightness of the surface parts on their slope angle with respect to the horizon [19][20][21][22][23][24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

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Combined Method for Measuring 3D Wave Spectra. I. Algorithms to Transform the Optical-Brightness Field into the Wave-Height Distribution

Salin

2015

Radiophys Quantum El

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Although optical tools for measuring the surface-wave characteristics provide the best spatial and temporal resolutions compared with other methods, they face some difficulties while converting the results of indirect measurements into the absolute levels of waves. In this paper, we propose a combined optical method for measuring the 3D spectral density of the heights and the time realizations of the surface-wave profiles. The method involves, first, synchronous recording of the optical-brightness field on a rough-surface area and the surface-oscillation measurement at one or several points and, second, filtering of the spatial image spectrum, so that the filter parameters are also chosen from the condition of maximum correlation of the reconstructed and measured surface oscillations at one or two points. The second part of this work deals with the results of measuring the multi-dimensional wave spectra on the basis of the proposed method.

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Section: Measurement Layoutmentioning

confidence: 99%

Section: Measurement Layoutmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Combined Method for Measuring 3D Wave Spectra. I. Algorithms to Transform the Optical-Brightness Field into the Wave-Height Distribution

Salin

2015

Radiophys Quantum El

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“…2b shows the one dimensional power spectral density of surface waves, , obtained from both the direct measurements in the water area (solid line) and the reconstruction by integration of on the K x , K y plane (dashed line). The aforementioned data were obtained in the course of the comprehensive measurements in the Baltic Sea (Primorsk region) in August 2006 with the use of the "optical" scheme for measuring the three dimensional spectra of surface waves [12].…”

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confidence: 99%

Calculation of the reverberation spectrum for Doppler-based sonar

Salin

Spindel

2012

Acoust. Phys.

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220When the monostatic sonar is used with long tone pulses the duration of which is 5-10 s, the main mech anism responsible for the broadening of the received signal spectrum is reflection from a rough sea surface. The computational schemes used for calculating the parameters of reverberation are usually based on the Bragg scattering of an acoustic field by the spatial structure of wind waves [1][2][3][4][5]. In [6,7], for a homoge neous waveguide with a constant depth, we derived and analyzed an expression that, in application to insonification of a shallow water area with tone sig nals, allows calculation of the normalized reverbera tion spectrum in the form (1)Here is the ratio of the power spectral den sity of reverberation at the point r 0 to the direct signal level p(r 0 ) measured at the same point,(2) k is the wave number of the insonifying tone signal with a frequency f; H is the characteristic depth of the waveguide;is the ray capture angle in the waveguide; χ m and χ n are the grazing angles corresponding to the modes of the homogeneous waveguide with the numbers m and n and the longitudinal wave numbers k m and k n , respectively; and is the power spectral density of surface waves, which is mea sured at a frequency Ω with the wave vector K deter mined by the formula ,where r and r 0 are the vectors determining the coordi nates of the scattering point and the reception point with respect to the source position (see Fig. 1). Here and below, the wave vector of surface waves is denoted by K and the wave vector of acoustic waves by k. From the product of quantity (1) and the square of quantity (2), we easily obtain the expression for the nonnormalized reverberation spectrum,which is convenient for use, e.g., in the case of monostatic sonar (r 0 = 0) or in calculating the rever beration for pulsed radiation modes.The reverberation spectrum for frequencies Hz is mainly formed by scattering by a rough sea surface; therefore, it is convenient (see para graph 8.12 in [8]), for the given frequency band, to ( ) 2 , G Ω K sgn , ( ) m n = − Ω K K r 0 0 , ( ) , m n m n k k r − = + − r r r K r r r ( ) ( ) ( ) ( ) ( ) ( ) 0 0 sgn 2 2 2 2 2 2 0 4 , 2 , sin sin 4 , cos cos ( ), , m n rev m n m n m n S k p p H G ds r0.01 Ω π ≥ Abstract-For monostatic sonar using long pulsed tone signals, the problem of evaluating the spectrum of reverberation due to sound wave scattering by a rough sea surface is solved. Relatively simple computational schemes are proposed, which make it possible (i) to transform the three dimensional spectra of surface waves to the frequency-angular characteristics of reverberation and (ii) to choose the optimal operating frequency band for a Doppler sonar from the point of view of reverberation. For typical wind wave characteristics mea sured in shallow water areas, the spectral levels of reverberation are estimated in the frequency band of acous tic signals within 0.4-2 kHz.Keywords: scattering by the rough sea surface, scattered signal spectrum, acoustic reverberation, Bragg scat tering, shallow wate...

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Usage of Single-Camera Video Recording to Measure Sea Surface Roughness with Machine Learning Methods

Salin

2023

Lecture Notes in Electrical Engineering

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Estimation of space-time characteristics of surface roughness based on video images

Cited by 6 publications

References 8 publications

Combined Method for Measuring 3D Wave Spectra. I. Algorithms to Transform the Optical-Brightness Field into the Wave-Height Distribution

Combined Method for Measuring 3D Wave Spectra. I. Algorithms to Transform the Optical-Brightness Field into the Wave-Height Distribution

Calculation of the reverberation spectrum for Doppler-based sonar

Usage of Single-Camera Video Recording to Measure Sea Surface Roughness with Machine Learning Methods

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