Underwater Visibility Research Articles

Middle ear barotrauma in scuba divers

Middle ear barotrauma is the most common health hazard of scuba diving. To investigate the overall incidence of middle ear barotrauma, a prospective incidence study of 51 novice divers and 46 experienced divers was conducted. Otoscopy was performed on the divers before and immediately following a single dive. The overall incidence of mild barotrauma was 40%, and the incidence of severe barotrauma was 27%. No tympanic membrane perforations were found. The most common presenting symptoms were difficulty clearing ears during descent, ear pressure, and ear pain. Barotrauma was not associated with diver age, sex, experience, otolaryngologic history, or medications. Barotrauma was associated with poor underwater visibility, difficulty clearing ears during ascent, and hearing loss after surfacing.

Viewing method for improving underwater visibility by reduction of backscatter

For improved underwater visibility a method that uses a special intervallic series of light pulses and two acts of emitting and receiving is performed by two specially designed optical shutters and by control signals that are synchronously delayed. Calculations show that the apparent contrast of the target can be improved, and thus the distance over which it is visible can be increased. This method has several advantages that can make it practical for actual use, and its feasibility is demonstrated in experiments.

Underwater visibility and the recall of subsea marker panels

The identification and recall of subsea markers is a common task amongst offshore commercial divers. Two experiments explored the accuracy of reproduction of subsea marker panels by commercial divers and correlations with tests of embedded figures, memory-for-designs, spatial relations, dotted outlines, and block design. Trials were conducted in diving tanks and in open water. In the diving tanks 30% recall errors occurred and performance correlated r= 0·75 with the embedded figures test. In the open sea again 30% recall errors were found and performance was well predicted by the embedded figures test (r= 0·69). All other tests failed to predict performance when the effects of the embedded figures were removed.

Competitive food exploitation of smelt Osmerus eperlanus by great crested grebes Podiceps cristatus and perch Perca fluviatilis at Lake IJsselmeer, The Netherlands.

The impact of predation by an avian predator (great crested grebe Podiceps cristatus) and a predatory fish (perch Perca fluviatilis) on a common resource, the small planktivorous fish smelt (Osmerus eperlanus) was studied in Lake IJsselmeer, The Netherlands, in July-October 1985-1988. At this time of the year the grebes are in simultaneous wing-moult and therefore temporarily flightless. Four factors limit the predation pressure by grebes: (1) an underwater visibility threshold of c. 40 cm Secchi depth is the lower limit at which large numbers attend the moulting site, (2) a lower density threshold of exploitable smelt biomass of c. 30 kg/ha determines the actual fishing areas, (3) a fish size threshold of 6.5 cm total length further limits prey availability, and (4) the vertical movements of the prey impose a strong (diel) time constraint on the birds, allowing only crepuscular foraging. Perch, the other main predator in this system, is less restricted in its foraging. Perch were found to be in direct competition with the grebes, preying heavily on the juvenile smelt. Over the 4 years of study 90% of all predation from 15 July to 15 October (72-233 kg/ha) was due to perch. The high level of predation by birds and fish was only possible due to a continuous immigration of smelt into the area (1.45 kg/ha per day). In three of the four years, however, the combined predation by fish and birds surpassed the immigration rate of the prey, which led to a strong reduction in smelt stocks in the study area. A conceptual model is developed to describe the different sets of constraints on the grebes' foraging. First, the state of eutrophication in relation to the weather condition determines the degree of algal blooms, and thus underwater visibility, in late summer. This is the major factor governing the numbers of grebes on the moulting area. Second, the size of the population of predatory fish determines the overall food availability (biomass and size distribution of smelt). These factors are partly interconnected and related to human action (pollution, fisheries). It is suggested that, despite deteriorating visibility conditions, the largest moulting site for grebes in Europe at Lake IJsselmeer exists because the stocks of predatory fish are kept low by overfishing.

水中灯の明るさの増加による水中視程の増加

水中灯の明るさの増加による水中視程の増加

Fuel Removal Equipment for Three Mile Island Unit 2

The basic defueling system used at Three Mile Island Unit 2 consisted of (a) a shielded work platform mounted on the reactor vessel, (b) cylindrical canisters suspended from the work platform with intravessel debris loading, (c) dry cask handling of the canisters inside containment from the vessel to the fuel transfer system, (d) wet transfer of canisters from inside containment to the spent-fuel pit, and (e) wet storage in the spent-fuel pit until processed for shipping. Requirements for removing core debris changed substantially as knowledge of actual core conditions was attained, thwarting efforts to anticipate tooling demands. Logistics, operator proficiency, and tooling reliability determined overall productivity. Poor underwater visibility dramatically reduced productivity. Operator training and tool testing on full-scale mock-ups were essential to effective operations. The experience gained in designing and using the various tools is summarized as lessons learned.

Rates of erosion of till in the nearshore zone

AbstractMeasurements of vertical erosion of till in water depths ranging from 1.1 m to 5 m have been obtained using a modified micro‐erosion meter. Measurements in this environment are hindered by poor underwater visibility and losses due to high erosion rates and ice action. There is considerable spatial and temporal variability in the erosion rates measured but average values show a general increase from 11 mm y−1 in 6 m of water to about 35 mm y−1 in 2.3 m of water and even higher rates closer to shore. The measured values in shallow water are in good agreement with long‐term rates extrapolated from shoreline recession. It is suggested that erosion occurs through abrasion and fluid stressing, and that these mechanisms are aided by softening of the upper surface of the till, possibly through cyclic ‘fatigue failure’.

Use of Underwater Observations to Estimate Cutthroat Trout Abundance in the Yellowstone River

The abundance of cutthroat trout (Salmo clarki) in four study areas of the Yellowstone River in Yellowstone National Park was estimated three times in 1981 by a team of observers equipped with snorkeling gear. Divers spaced themselves along lengths of PVC pipe to maintain individual counting lanes. Three replicate counts were normally made in the main channel and one count was conducted along the banks. Cutthroat trout generally were not disturbed by the presence of the divers and replicate counts were consistent. Population estimates were made for each study area and date, and confidence limits varied from the point estimate by an average of 24.5%. The technique appears to be applicable to a number of larger rivers with underwater visibilities in excess of 3 m. Factors that could affect both the precision and accuracy of the technique include water depth, fish behavior, underwater visibility, and the degree to which fish densities in areas counted are representative of densities in stratified habitat zones.

Luminance Measurements in Oceanic Illumination and Thir Assessments

In the past papers, the author described that the underwater visibility is shorter than that in the air and luminosity of red, orange and yellow in vision is lower underwater than that in the air. Visibility of color chips against various back grounds is assessed according to contrast of luminance underwater. The author measured contrast of luminance for basic lighting expeeriments in the test water tank and discussed these visibilityes.These results of underwater lighting studies wiel be useful for planning and execution of underwaterlighting design.

水中視程に影響をおよぼす付着物質の反射率について

Colour and size of an object change as a result of adhesive organisms after it is set under-water for a long time and results in a great difference in underwater visibility. Samples of articles hung in the sea and removed at different time intervals for examination in the laboratory of its luminous reflectance. Underwater visibility of net twines (blue, grey and natural twine) increases with the adhesion of organisms on the twines and it was found that in about 40 days after being set it increases about two fold. In the present estimation, the apparent contrasts increase rectilinearlly with the decrease of visual angles and the luminous reflectances of objects decrease with the increasing of the underwater visibility. Apparently, it shows that the optical properties of the adhesive organisms greatly influence on the underwater visibility.

人間の目による網糸の水中規程の研究-II

The visual ranges of dyed and transparent twines and also of knots of the net were measured succesively in tank water, illuminated by diffused light from flourescent lamps for varying the physical conditions, namely, colour and reflectance of an object, turbidity of water and brightness which might have direct effects upon underwater visibility. The measurements of the visual range were made through three light filters; blue, green and orange. The visual rangs of the yellow twine was the largest under less turbid conditions but decreased remarkably with the increase of turbidity. Transparent twines were less visible than dyed opaque twines. The visual range was longer than that of twine for knots in brighter surface irradiance but both values become almost the same with the increase of burbidity. The slopes of the curves of the visual range of niyed twines plotted against the wave-length of maximum transmittance of three light filters provided a means to classify them into two types. Twines belonging to the first type are more visible under long wave-legths, such as, yellow, green, and blue twines and those of the other type are most visible in the wave-length, 530 mμ, such as, red, violet, brown, kacchi and grey twines.

人間の目による網糸の水中視程の研究-III

人間の目による網糸の水中視程の研究-III

An Oceanographic Radiance Distribution Camera System

An oceanographic optical instrument has been designed and constructed to record the radiance distribution of natural radiant energy underwater. The instrument contains two cameras placed back-to-back, each equipped with a fisheye (180 degrees field of view) lens and is fabricated so that film can be exposed by remote control. The instrument is designed to operate at depths up to 100 m. Values of underwater radiance can be obtained from the exposed films by means of photographic photometry. Radiance distributions obtained in natural waters will provide basic information needed for the study and solution of several problems in optical oceanography. First, the radiance distribution is an important input for the study of the interaction of electromagnetic radiation with the sea. From the distribution of radiance in the natural light fields in the ocean, many of the important optical properties which relate to radiative transfer processes in the ocean can be calculated. Second, from these optical properties one can compute the magnitude of the deterioration of image contrast of submerged objects and thus furnish information for the study and solution of underwater visibility problems, which include problems in underwater television and photography. Finally, since radiant energy is critical to the beginning of the marine food chain through photosynthetic plankton, radiance distribution measurements will provide information of fundamental importance to the problem of primary productivity in natural waters.

A comparative evaluation of three methods used to tag South African linefish

Tagging effects and loss rates of 60 Roman Chrysoblephus laticeps tagged with dart tags with barbs (D-tags), T-bar filaments (T-tags) and visible implant fluorescent elastomer (VIFE) tags were investigated. The fish were tagged and monitored in a controlled tank experiment over a period of 198 days. Application technique and underwater visibility of VIFE tags were assessed in a preliminary experiment on Roman and on fransmadam Boobsoidia inornata. The use of 25-gauge needles improved VIFE tag application. Whereas VIFE tagging caused fin rot in fransmadam, it had no negative effect on Roman. VIFE tag codes could be identified underwater from a distance of 3m under ambient light. There was no significant difference in growth rates among groups of Roman with different tags and controls, but rates of tag loss were high for D-tags (53%) and T-tags (73%). Although some of the VIFE marks were incomplete, all VIFE-tagged fish were individually recognised at the end of the study. The results highlight the need to take cognisance of the high tag loss rate of conventional tags during the design of mark and recapture studies.

Visual contrast thresholds of the goldfish ( Carassius auratus)

Contrast thresholds of the goldfish eye were determined by the method of constant stimuli using a yes-no conditioned cardiac-response. Computerized probit analysis was used to treat the data. Thresholds were determined for varying temperatures, target sizes, fish sizes, target positions and adaptive radiance levels. Positive contrast, circular targets were used throughout. Both target and adaptive radiance were monochromatic light. Threshold was found to decrease as fish size increased. This change was attributed to the density of cones which decline more slowly as the eye grows than is required to compensate for the calculated expansion of image area in the larger eye. Threshold was found to be temperature dependent, being lowest at 20°C. Threshold was found to vary with the position of the target image on the retina in general agreement with cone topography. Binocular thresholds were lower than monocular thresholds. The relation between target size and contrast threshold was studied at four adaptive levels from a photopic level of 85 μW/cm 2/ω to a near scotopic level of 0.07 μW/cm 2/ω. The data were examined to determine critical visual angle and the region of complete summation. Single-point visual acuity for the goldfish was interpolated from the data. The use of contrast threshold data in underwater visibility problems is discussed. No evidence was found to indicate a special contrast-enhancement mechanism in fishes.

2.7 - Underwater optical range gating

The applicability of underwater optical range gating, designed to extend the range of underwater visibility, was demonstrated in a series of experiments. With black tape patterns on a Scotchlite background as the target, comparison photographs of gated and nongated exposures illustrated the feasibility of extending the range of underwater photography by reducing the intermediate veiling luminance caused by backscattered light. Theoretical and experimental results of these tests are presented.

Visibility of colors underwater.

The underwater visibility of various colors, both fluorescent and nonfluorescent, was measured in four different bodies of water. The waters were selected to sample the continuum from very murky to clear. SCUBA divers observed with a horizontal path and other subjects on the surface looked down vertically. Fluorescent colors were always more visible than nonfluorescent, but the specific colors that were easiest and most difficult to see depended upon the body of water.

Improvement of Underwater Visibility by Reduction of Backscatter with a Circular Polarization Technique

This report presents a brief resume of the underwater visibility problem and explains the circular polarization approach for improving contrast. Experimental apparatus was set up at the Morris Dam facility of the U.S. Naval Ordnance Test Station, Pasadena Annex, and tests were conducted both with and without polarization. Results show that use of the polarization technique increased the visibility range in turbid water by at least a factor of two.

Underwater Photographic Instrumentation Design

Limited space and all weather working conditions are requiring the Pascagoula Fisheries Station of the U. S. Fish and Wildlife Service to design a special line of underwater photographic instrumentation systems. Light metals and plastics are being explored in a continuing effort to develop lightweight yet strong and corrosion proof underwater housings. Designs are selected which offer maximum protection from accidental con tact with the sea bottom and the ship's hull. Color is used to enhance or subdue the underwater visibility of both photographic and test gear.

THE FINITE DIFFERENCE FLOW ANALOGUE

Naval Engineers JournalVolume 74, Issue 3 p. 533-544 THE FINITE DIFFERENCE FLOW ANALOGUE HILBERT SCHENCK JR., HILBERT SCHENCK JR. THE AUTHOR was born in Boston, Feb. 12, 1926. Attended primary schools in the New England area and served two years in the Navy during World War II as an electronic technician. Attended Williams College receiving a B.A. degree, then Stanford University for an M.S. in Mechanical Engineering. Employed for four years as a test engineer in heat transfer research at Pratt and Whitney Aircraft. Joined the staff of Clarkson College, Potsdam, New York as an Assistant Professor and was recently promoted to Associate Professor of Mechanical Engineering. Author of several papers and books on underwater visibility, photography and diving plus the book Heat Transfer Engineering recently published by Prentice-Hall, IncSearch for more papers by this author HILBERT SCHENCK JR., HILBERT SCHENCK JR. THE AUTHOR was born in Boston, Feb. 12, 1926. Attended primary schools in the New England area and served two years in the Navy during World War II as an electronic technician. Attended Williams College receiving a B.A. degree, then Stanford University for an M.S. in Mechanical Engineering. Employed for four years as a test engineer in heat transfer research at Pratt and Whitney Aircraft. Joined the staff of Clarkson College, Potsdam, New York as an Assistant Professor and was recently promoted to Associate Professor of Mechanical Engineering. Author of several papers and books on underwater visibility, photography and diving plus the book Heat Transfer Engineering recently published by Prentice-Hall, IncSearch for more papers by this author First published: August 1962 https://doi.org/10.1111/j.1559-3584.1962.tb04849.xCitations: 2 AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume74, Issue3August 1962Pages 533-544 RelatedInformation