Method for practical calculation of underwater vehicle's television communications

В статье обосновывается и предлагается для практического применения методика расчёта подводных телевизионных коммуникаций, апробированная при проведении испытаний отечественных подводных аппаратов на морских акваториях Белого и Баренцева морей. Последовательно проводится расчет освещенности толщи воды между осветителем и объектом наблюдения; определяется суммарная освещенность на входе объектива телевизионной камеры, создаваемая отраженным от объекта светом и помехой обратного рассеяния; рассчитывается контраст белых и черных объектов. В заключении показан расчет изменения пороговой чувствительности камеры в зависимости от дальности наблюдения. Представленная методика может использоваться при проектировании систем технического зрения обитаемых и необитаемых подводных аппаратов для получения данных о предполагаемых дальностях наблюдения объектов с различными коэффициентами отражения с заданными параметрами прожекторного осветителя. The article proposes a technique for calculating underwater television communications, which was confirmed during tests of domestic underwater vehicles in the waters of the White and Barents Seas. First, the illumination of the water between the illuminator and the object of observation is calculated; then the total illumination at the entrance of the TV camera lens, created by the light reflected from the object and the backscattering interference, is determined; and finally, the contrast of white and black objects is calculated. In conclusion, the calculation of the change in the threshold sensitivity of the camera depending on the observation range is shown. The presented technique can be used in the design of computer vision systems of crewed and unmanned underwater vehicles to obtain data on the estimated observation ranges of objects with different reflection coefficients and with the specified parameters of the searchlight illuminator.

Burrow emergence rhythms of Nephrops norvegicus by UWTV and surveying biases

Underwater Television (UWTV) surveys provide fishery-independent stock size estimations of the Norway lobster (Nephrops norvegicus), based directly on burrow counting using the survey assumption of “one animal = one burrow”. However, stock size may be uncertain depending on true rates of burrow occupation. For the first time, 3055 video transects carried out in several Functional Units (FUs) around Ireland were used to investigate this uncertainty. This paper deals with the discrimination of burrow emergence and door-keeping diel behaviour in Nephrops norvegicus, which is one of the most commercially important fisheries in Europe. Comparisons of burrow densities with densities of visible animals engaged in door-keeping (i.e. animals waiting at the tunnel entrance) behaviour and animals in full emergence, were analysed at time windows of expected maximum population emergence. Timing of maximum emergence was determined using wave-form analysis and GAM modelling. The results showed an average level of 1 visible Nephrops individual per 10 burrow systems, depending on sampling time and depth. This calls into question the current burrow occupancy assumption which may not hold true in all FUs. This is discussed in relation to limitations of sampling methodologies and new autonomous robotic technological solutions for monitoring.

The method of highlighting underwater objects using initiating radiation

Изложены особенности метода увеличения дальности видимости подводных телевизионных систем за счёт использования лазерных технологий. Предлагаемый метод основан на возможности усиления света в воде при пропускании его через среду с инверсной населённостью энергетических уровней. Подобная среда создаётся за счёт вспомогательного излучения, формируемого, например, лазерным излучением. Рассмотрены необходимые условия усиления света. С учётом шкалы энергий излагаются основные принципы создания инверсной населённости энергетических уровней в воде. Приведена методика расчёта дальности засветки лазерного излучателя в воде с прозрачностью 15 м, что соответствует прозрачности Баренцева моря в зимний период. Методика базируется на расчёте наблюдаемого и минимально разрешаемого (порогового) контрастов объекта поиска. Анализируются пути увеличения эффективности вновь создаваемых подводных телевизионных систем. В статье предложена концепция создания подводных световых приборов, способных существенно увеличить дальность видения систем технического зрения обитаемых и необитаемых подводных робототехнических комплексов. Актуальность работы определяется реализацией лазерных технологий при проектировании и создании подводных телевизионных систем, что представляет собой прорывное направление научно-технического прогресса и неотъемлемый элемент импортозамещения. The features of the method for increasing the visibility range of underwater television systems through the use of laser technologies are described. The proposed method is based on the possibility of amplifying light in water when passing it through a medium with an inverse population of energy levels. Such a medium is created due to auxiliary radiation generated, for example, by laser radiation. The necessary conditions for amplification of light are considered. Taking into account the energy scale, the basic principles of creating an inverse population of energy levels in water are stated. A method for calculating the exposure range of a laser emitted in water with a transparency of 15 m, which corresponds to the transparency of the Barents Seain winter, is presented. The technique is based on the calculation of the observed and minimum resolved (threshold) contrasts of the search object. The ways of the increasing the efficiency of newly created underwater television systems are analyzed. The article proposes the concept of creating underwater lighting devices that can significantly increase the range of vision systems for the technical vision of inhabited and uninhabited underwater robotic systems. The relevance of the work is determined by the implementation of laser technologies in the design and creation of underwater television systems, which represents a breakthrough in scientific and technological progress and an integral element of import substitution.

GEOLOGICAL RISKS OF BAIKAI COASTAL ZONE

The geologic-geophysical researches including focused on geological dangers in 2015 captured a coastal zone of the southern hollow of Baikal. The methodical basis of these works is made by lake profile and areal surveillance with application of side location, continuous seismoacoustic profiling, a protsezionny ekholotirovaniye, underwater television monitoring, interpretative sampling and reconnoitering coastal monitoring from a board and from the water area. These forms most often represent openings in Baikal seabed with various shapes, depth and width of disclosure. In many cases the central openings or "craters" of these forms are sources of eruption of gas bubbles. Intensity of this eruption changes from minimum to massive in the form of vertical gas streams. On sonar records these forms are represented as black points or lines. Echo sounding presents it as powerful vertical images "columns" which are often going from ground objects to the water surface and defined these forms as "gas griffins". Big attention considering possible geological risks (connected with mass methane saturation of water) payed to larger forms of a ground relief which are conditionally assigned to group of "pockmark".

GEOLOGICAL RISKS OF BAIKAI COASTAL ZONE

The geologic-geophysical researches including focused on geological dangers in 2015 captured a coastal zone of the southern hollow of Baikal. The methodical basis of these works is made by lake profile and areal surveillance with application of side location, continuous seismoacoustic profiling, a protsezionny ekholotirovaniye, underwater television monitoring, interpretative sampling and reconnoitering coastal monitoring from a board and from the water area. These forms most often represent openings in Baikal seabed with various shapes, depth and width of disclosure. In many cases the central openings or "craters" of these forms are sources of eruption of gas bubbles. Intensity of this eruption changes from minimum to massive in the form of vertical gas streams. On sonar records these forms are represented as black points or lines. Echo sounding presents it as powerful vertical images "columns" which are often going from ground objects to the water surface and defined these forms as "gas griffins". Big attention considering possible geological risks (connected with mass methane saturation of water) payed to larger forms of a ground relief which are conditionally assigned to group of "pockmark".

Investigating the link between Nephrops norvegicus burrow density and sediment composition in Scottish waters

Campbell, N., Allan, L., Weetman, A., and Dobby, H. 2009. Investigating the link between Nephrops norvegicus burrow density and sediment composition in Scottish waters. – ICES Journal of Marine Science, 66: 2052–2059. Nephrops norvegicus is a burrowing decapod, found in the North Atlantic and Mediterranean Sea at depths of 10–1200 m, and currently the most valuable species taken by the commercial fishing industry in Scotland. It constructs and inhabits extensive burrow complexes in suitable muddy sediments. Owing to its variable emergence patterns, catch rates from traditional trawl surveys are not considered a good indicator of population size. Nephrops populations around Scotland are assessed using an underwater television (UWTV) survey method. Sediment samples are collected at the end of each UWTV deployment. This study focuses on two areas off the coast of Scotland and investigates the accuracy of the sediment maps used for assessment purposes, and the relationship between Nephrops burrow density and sediment composition, over the period 2002–2007. Nephrops have a stock-specific relationship with the sediment they inhabit, which retains the same form through fluctuations in population size.

Investigating and mitigating uncertainties in the assessment of Scottish Nephrops norvegicus populations using simulated underwater television data

Campbell, N., Dobby, H., and Bailey, N. 2009. Investigating and mitigating uncertainties in the assessment of Scottish Nephrops norvegicus populations using simulated underwater television data. – ICES Journal of Marine Science, 66: 646–655. Nephrops norvegicus is a commercially significant decapod crustacean that excavates and inhabits burrows in muddy sediments throughout the Northeast Atlantic and Mediterranean Sea. Because of its variable emergence behaviour, traditional surveys are considered a poor indicator of the status of its populations, and underwater television (TV) survey methods have been developed. The approach involves towing a TV camera over patches of muddy sediment and counting the number of Nephrops burrow complexes within a known area. Assuming a 1:1 rate of occupancy, the average population density can be estimated. This is raised to the known area of suitable sediment to give a measure of population size. Recently, underwater TV surveys have been used to provide absolute measures of abundance for a number of Nephrops stocks in the North Sea and Northeast Atlantic. It is therefore imperative to identify, quantify, and control for uncertainties in this process. Previous workers have suggested that visual recognition of Nephrops burrows and “edge effects”, where single openings of burrow complexes at the sides of the viewed transect are counted, are important sources of uncertainty. This study shows edge effects to be responsible for an overestimation of population size of between 4 and 55%, depending on the width of the field of view and the mean size of the burrow complex. This overestimation is countered to some extent by variability in burrow entrance structure, which leads to Nephrops burrows going unrecognized. The scales of these errors are discussed in relation to observed sediment softness, sediment distribution, and burrow dimensions from sites around Scotland.

Underwater television as a fishery-independent method for stock assessment of Norway lobster (Nephrops norvegicus) in the central Adriatic Sea (Italy)

Morello, E. B., Froglia, C., and Atkinson, R. J. A. 2007. Underwater television as a fishery-independent method for stock assessment of Norway lobster (Nephrops norvegicus) in the central Adriatic Sea (Italy). – ICES Journal of Marine Science, 64: 1116–1123. Norway lobster is of great commercial importance throughout the NE Atlantic and Mediterranean, where it lives in burrows in muddy sediments. The fact that the species is caught in commercial gear only when it emerges from its burrow and the absence of hard structures available for age determination complicate the application of normal fishery-dependent stock-assessment methodologies. This study provides more evidence of the usefulness of underwater television surveys as a fishery-independent technique to assess the Nephrops stocks of the Adriatic Sea. The results are compared with those of previous studies, and the advantages and disadvantages of using such methodology discussed in an Adriatic context.