摘要 :
An appropriately designed parallax (two-station) range allows a mariner toaccurately determine a range line--the correct path to steer his vessel--at great distances. Less expensive alternatives to parallax ranges are desirable, a...
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An appropriately designed parallax (two-station) range allows a mariner toaccurately determine a range line--the correct path to steer his vessel--at great distances. Less expensive alternatives to parallax ranges are desirable, and many ideas, principally single-station ranges, have been proposed. However, the mariners' abilities to establish range lines with them have not been measured. The present work has quantified the navigational sensitivity afforded by parallax ranges and three different types of single-station range display systems. The single-station ranges used (a) temporal characteristics, (b) spatial representation, or (c) color changes of signal to represent changes in lateral position. Range systems were simulated either opto-mechanically or on a high resolution computer display system. The mariners' ability to determine both lateral position in a channel and direction of motion across a channel was assessed psychophysically for each range system. Performance with single-station range systems was compared with that obtained with parallax ranges. This allowed us to evaluate the implications of replacing parallax ranges with single-station ranges.
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The motion of a buoy may affect the probability that a navigational light signalis detected. Buoy motion is studied to quantify the effect it has on the detection range of a buoy's light signal. Buoy motion data were taken from vi...
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The motion of a buoy may affect the probability that a navigational light signalis detected. Buoy motion is studied to quantify the effect it has on the detection range of a buoy's light signal. Buoy motion data were taken from video recordings of standard USCG buoys in a variety of sea conditions. It became evident during the study that buoy motion is a combination of both list and roll. Properties of a buoy signal light were mathematically combined with the buoy motion data to calculate detection ranges under various conditions. The detection ranges used in the analyses correspond to the distance at which a mariner has an 80% probability of detecting the buoy signal. Results show that buoy motion is a problem. The present buoy lanterns provide an 80% probability of detection range which is only about half of the commonly accepted and published nominal range. This is true for most combinations of weather, buoy size, and flash characteristic. The effect of list alone contributed substantially to buoy signal degradation. Further calculations showed that increasing the vertical divergence of a lens from the currently used 4.2 deg to between 8.3 and 10.0 deg (full-width, half maximum) will increase the detection range by approximately 40%. Keywords: Buoy motion, Signal effectiveness, Lantern divergence, Probability of detection. (JHD)
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A study was conducted to determine whether or not navigation safety is affected when the masthead light is placed aft of amidships and aft of the sidelights light on power driven vessels less than 50 meters in length that have a s...
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A study was conducted to determine whether or not navigation safety is affected when the masthead light is placed aft of amidships and aft of the sidelights light on power driven vessels less than 50 meters in length that have a single masthead light. Computer simulation was used to display oncoming vessels to observers. Vessels were represented only by their navigation lights, which were not always placed in compliance with current regulations. Observers were not informed of the actual navigation light placements, which is akin to the situation on the open water. Two different situations were simulated. In one situation, observers had to judge aspect after a brief look at an oncoming vessel, simular to the situation when an oncoming vessel is first noticed. In the other situation, observers were given a long period of time to watch an oncoming vessel. These observers were asked to judge the vessel's course. In both situations there was no statistically significant difference between the responses given when vessels complied with current regulations and responses given when the masthead was free to vary forward and aft of the sidelights. Keywords: Navigational, lights, Computerized stimulation, Naval vessels,merchant vessels, surface navigation. (rwj)
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The Coast Guard uses atmospheric visibility data collected in 1958 and 1959 when calculating the effective luminous range of aids to navigation. Presently, Coast Guard aid designers question whether or not increases in population ...
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The Coast Guard uses atmospheric visibility data collected in 1958 and 1959 when calculating the effective luminous range of aids to navigation. Presently, Coast Guard aid designers question whether or not increases in population and industry have changed atmospheric visibility along our coasts. Recent atmospheric visibility data in the form of transmissivity curves are presented to answer this question. National Weather Service (NWS) visibility records from the maritime zone form the basis for our study. Data from these records were sorted into 28 geographical zones. Curves were fit to frequency distributions within each zone, forming new atmospheric transmissivity curves, one for each zone. The new and old transmissivity curves differ considerably in many regions. The old transmissivity curves should not be used to estimate atmospheric conditions. Further study has shown that even the new transmissivity curves can be improved. Accurate, localized curves can be obtained by decreasing the area size to the limit that the NWS data will allow. It is recommend that the Coast Guard accept small, localized regions for calculating transmissivity curves. In addition, software needs to be developed which uses new localized curves and the aid design tables and calculations. This product would remove the need for the look up tables and tedious computations presently used during aid design. Keywords: Transmissivity; Aids to navigation; Allard's law; Luminous range; Visibility. (jhd)
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This is the second in a series of reports dealing with selection of materials for daymarks. The first report examined the effect of environmental exposure of fluorescent materials on detection and color identification distances. T...
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This is the second in a series of reports dealing with selection of materials for daymarks. The first report examined the effect of environmental exposure of fluorescent materials on detection and color identification distances. This report is concerned with a comparison of detection and identification distances of non-fluorescent and fluorescent materials to determine if longer life, non-fluorescent materials can provide visual signals equivalent to those of fluorescent materials. If non-fluorescent materials can be used in place of fluorescent materials substantial savings can be realized in terms of material and maintenance costs. This report will guide the engineer in choosing appropriate daymark materials. New fluorescent materials had greater detection and identification distances than most non-fluorescent materials die to their ability to convert ultraviolet light to visible light. As fluorescent materials age, they become more difficult to detect and identify. With one exception, non-fluorescent materials could be detected and identified at greater distances that the aged fluorescent materials. This report also examined the relationship between luminance contrast and Munsell notation on detection and identification distances. Detection distance was positively correlated with luminance contrast and Munsell Value. Munsell Chroma was not a good predictor of detection or identification distance. Keywords: Color vision; Navigational aids. (AW)
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In March 1986, Coast Guard R & D Center engineers deployed two prototype electroluminescent lighting arrays on the main span of the Poplar Street Bridge in St. Louis Harbor. THe objective was to demonstrate the concept of extended light sources as applied to aids-to-navigation engineering. These extended light sources were designed to assist south-bound tug pilots in identifying and safely transiting the main bridge span on the Missouri side of the Mississippi River. In prior years, pilots had experienced difficulty transiting St. Louis Harbor during the high water season, with the Poplar Street Bridge being involved in at least two serious tug/tow incidents and numerous minor ones. No accidents have been reported since the prototype arrays were deployed in March 1986. User feedback concerning the EL arrays, was consistently positive. The report describes the design, fabrication and deployment of the EL array, as well as reasons for perceived improvement in signal effectiveness. Keywords: Navigational aids; Visual aids; Conspicuity; Visual perception. (edc)...
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In March 1986, Coast Guard R & D Center engineers deployed two prototype electroluminescent lighting arrays on the main span of the Poplar Street Bridge in St. Louis Harbor. THe objective was to demonstrate the concept of extended light sources as applied to aids-to-navigation engineering. These extended light sources were designed to assist south-bound tug pilots in identifying and safely transiting the main bridge span on the Missouri side of the Mississippi River. In prior years, pilots had experienced difficulty transiting St. Louis Harbor during the high water season, with the Poplar Street Bridge being involved in at least two serious tug/tow incidents and numerous minor ones. No accidents have been reported since the prototype arrays were deployed in March 1986. User feedback concerning the EL arrays, was consistently positive. The report describes the design, fabrication and deployment of the EL array, as well as reasons for perceived improvement in signal effectiveness. Keywords: Navigational aids; Visual aids; Conspicuity; Visual perception. (edc)
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It has been thought that laser aids to navigation might appear more conspicuous than aids employing conventional light sources. Two experiments rigorously tested the hypothesis that laser light is more conspicuous than incandescen...
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It has been thought that laser aids to navigation might appear more conspicuous than aids employing conventional light sources. Two experiments rigorously tested the hypothesis that laser light is more conspicuous than incandescent light. Incandescent and Helium Neon laser sources were optically filtered and adjusted to present the same illuminance and color to distant observers. Thirty-seven observers viewed 60 random presentations (2 source types, 2 illuminance levels) from a distance of 1500 yards. Group correct source discrimination percentages were 52.6 and 55.2 for the low and high illuminance levels, respectively. The experiment was repeated indoors at higher illuminances with resultant group correct source discrimination percentages of 57, 67.5, and 66 for the low, medium, and high illuminances, respectively. It was concluded that at 'practical' design illuminance levels, no significant conspicuity advantage would be gained by replacing existing navigational aids with laser aids-to-navigation. Calculations show that a significant conspicuity advantage is likely to be obtained if the mariner uses a narrow bandpass filter (3-10 nm) centered at the laser wavelength. The illuminance from the laser will be relatively unaffected, while the illuminances from all background lights will be dramatically diminished. An additional section compares the electrical efficiency of a standard Coast Guard FA-240 range light with a laser aid configured for the same application. For equal input power, the FA-240 is shown to produce 10 times the luminous intensity of the laser aid.
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This report describes the evaluation of the Inogon Leading Mark that was conducted by the Coast Guard Research and Development Center. The device is a single station range designed for short range applications. The Inogon device u...
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This report describes the evaluation of the Inogon Leading Mark that was conducted by the Coast Guard Research and Development Center. The device is a single station range designed for short range applications. The Inogon device uses optical interference techniques to create, against a yellow background, a series of black chevrons (arrows) that point in the direction of the center of the channel. This device was evaluated in both a laboratory and field setting. In the laboratory evaluation, the detection range of the device was measured and accuracy with which one can use the device to navigate was established. In the field evaluation, the device was installed at Constable Hook Channel in New York Harbor immediately beneath the two station range, and user feedback was solicited in the form of a questionnaire. The device was shown to perform as described by the manufacturer, with detection ranges of approximately 1750 and 2250 yards in daylight and darkness, respectively. Responses from the field evaluation were generally negative, mostly because the device was perceived to have too short a detection range for the Constable Hook Channel. It is recommended that the device be considered as a candidate range light for very short range applications.
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The purpose of this work was to devise a method of determining the effective intensity of light flashes composed of multiple pulses (flicks) of light. Detection thresholds were measured for such flashes when the flick frequency an...
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The purpose of this work was to devise a method of determining the effective intensity of light flashes composed of multiple pulses (flicks) of light. Detection thresholds were measured for such flashes when the flick frequency and flash duration were varied. Thresholds decreased with increasing flick frequency and flash duration. At each flick frequency the relationship between threshold and flash duration was well-characterized by the Blondel-Rey relation (a=0.2) provided a multiplicative frequency-dependent fitting parameter was chosen. The fitting parameter, beta, increases linearly with frequency between 5 and 20 Hz. A method of determining effective intensity was described which uses the flick frequency, number of flicks and the calculated effective intensity of a single flick to arrive at the solution. It was concluded that this method should be used for all multiple flick signals provided the single-flick duration is less than 0.01 sec and the frequency is between 5 and 20 Hz. The method of Allard should not be used, as it consistently overestimates effective intensity. Keywords include: Effective intensity, Method of Allard, Allard's law, Multiple-flick flash, Flick frequency, Flash length, and Flashtube.
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