• Journal of Environmental Impact Assessment
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• v.13 no.4
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• pp.197-211
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• 2004

Visibility impairment was known as an indicator of the increased air pollution. In many previous studies, it is known that both directly emitted fine particles mainly from vehicles and secondary aerosols from photochemical reactions could contribute to this visibility impairment in addition to the meteorological condition. Furthermore, the visibility showed different change patterns according to the geographical condition. In order to research into the influence of these factors on visibility, this study analyzed the visibility at 15:00, observed from 1990 to 2001 in Seoul, Ganghwa, Susan, Gwangju, Jeju. As a result, the visibility was increased in Seoul except the rainfall period, but in Susan, Gwangju, Jeju, it decreased with the relative humidity (RH). Especially, in Seoul, the number of low visibility days was larger than other sites and variations of the visibility were sensitive to the concentration of air pollutants, such as TSP, $NO_2$, $O_3$. The visibility impairment was mainly observed in meteorological condition of RH<50% and relatively stationary front. Therefore it is inferred that photochemical smog could lead to the low visibility in Seoul. On the other hands, in Ganghwa and Susan, when RH was 60~70%, the low visibility observed under the influence of the transports of air pollutants from nearby cities as well as humid air mass from coastal region. And in Jeju, sea fog and humid air mass caused the visibility impairment when the RH was larger than 80%. Finally, during the observational period, some cases of low visibility phenomena were simultaneously observed in the vast region including Seoul, Susan, Ganghwa. It not only includes the visibility aggravation by Asian Dust, but also could be caused by the movement and diffusion of flying dust or secondary aerosols. Moreover, the result shows that these phenomena could be mainly influenced by meteorological factors covering the wide regions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.9-10
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• 2008

• Korean Institute of Interior Design Journal
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• v.18 no.4
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• pp.97-104
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• 2009

This thesis analyzed arrangement and mixture method of function elements, which are getting more important in museum planning. It used quantitative method, Space Syntax and Visibility Graph Analysis tool to analyze five case museums. Through this analysis, advantages and disadvantages of two methods were derived and case museums' arrangement and mixture attributes were grasped. Results of the analysis were derived differently by two kinds of plan form which were room to room type and open type. Open typed museum recorded similar graphs of Integration, Visual Integration and Visual Connectivity. Since whole space structures were relatively simple and structure of exhibition halls were opened, the results of Space Syntax and Visibility Graph Analysis had similar graphs. Room to room typed museum showed differences in Integration, Visual Integration and Visual Connectivity. In the result, the most accessible space was lobby and Mediation Space became the center of visibility. Also, the exhibition hall, where the opening of room to room typed exhibition hall was penetrated visually, became a center of visibility. Lobby space, which was close to entrance, had the highest Visibility Connectivity. As Space Syntax could analyze the museum as whole space structure, Space Syntax showed strength in room to room typed museum analysis compared to open typed museum analysis which has relatively simple structure. Visibility Graph Analysis could expect the flow of exhibit distance including visibility analysis unlike the flow of exhibit distance with space arrangement. The exhibition hall, which secures the sight to penetration of an opening, couldn't be analyzed in existing Space Syntax. However, it became the biggest advantages in Visibility Graph Analysis of room to room typed museum. Visibility Graph Analysis derived detailed results in exhibit arrangement so it will be the useful method not only for architecture but also for planning of exhibit arrangement in open typed museum. Through this study, various possibilities on Quantitative Analysis Method of Museum Architecture could be verified. However, the analysis still has limitation of second dimension. Therefore, diverse and liberal following study will be expected to accomplish.

• Atmosphere
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• v.30 no.4
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• pp.391-404
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• 2020

To understand the characteristics of the relationship between visibility and particulate matter (PM) in different meteorological conditions, we investigated the contributions of PM and relative humidity (RH) to visibility in Seoul, South Korea. For the period from 2001 to 2018, both PM and RH show descending trends, resulting in a visibility increase. PM has little impact on the hourly variation of visibility, which could be explained more by the RH variability. Meanwhile, the daily change of PM accounts for daily visibility variation. For the monthly variation of visibility, both PM and RH showed similar influence. The correlation coefficients of PM10, PM2.5, and RH with visibility was -0.486, -0.644, and -0.556, respectively, which became higher during the high PM seasons of spring and winter. The correlation coefficient between PM2.5 and visibility was -0.454 for RH higher than 80%, and -0.780 for RH between 40% and 60%. From 2017 to 2018, there were 10 cases of extreme visibility impairment, among which five cases were incurred by high PM pollution, and two cases were by high humidity. Further analysis with PM chemical composition measurements is required to better understand the characteristics of visibility in Seoul.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4419-4441
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• 2016

A cause of vehicle accidents is the reduced visibility due to bad weather conditions such as fog. Therefore, an onboard vision system should take visibility detection into account. In this paper, we propose a simple and effective approach for measuring the visibility distance using a single camera placed onboard a moving vehicle. The proposed algorithm is controlled by a few parameters and mainly includes camera parameter estimation, region of interest (ROI) estimation and visibility computation. Thanks to the ROI extraction, the position of the inflection point may be measured in practice. Thus, combined with the estimated camera parameters, the visibility distance of the input foggy image can be computed with a single camera and just the presence of road and sky in the scene. To assess the accuracy of the proposed approach, a reference target based visibility detection method is also introduced. The comparative study and quantitative evaluation show that the proposed method can obtain good visibility detection results with relatively fast speed.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.6
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• pp.503-514
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• 2002

During the past two decades, primary pollutants in the ambient air have been substantially reduced in Korea by aggressive government efforts such as the switchover to clean fuels and equipment of automobiles with a three-way catalytic converter. However, visibility impairment in Seoul and major metropolitan areas has been a stubborn problem. It is apparent that both directly emitted fine particles mainly from vehicles and secondary fine particles from photochemical reactions could contribute to this visibility impairment. In addition, Korea is located downwind of the prevailing westerlies from China and is influenced by the emissions of air pollutants in China. In order to assess this complicated problem of visibility impairment, the visibility trends for the past 17 years observed at more than 60 stations throughout the country were analyzed. The results showed that visibilities were generally the lowest in the winter morning in comparison with those in the summer afternoon as well as the annual average values. It was believed that primary pollution was principally responsible for visibility impairment in most areas. The visibility in the summer afternoon was lower in clean coastal areas along with a high level of relative humidity due to the inflow of moist air accompanied by sea breeze. Although contributions of secondary particles from photochemical reactions and long-range transport of fine particles to the visibility impairment were probable, their certain evidences were not found.

• Korean Journal of Human Ecology
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• v.19 no.6
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• pp.1053-1062
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• 2010

To assist the further development of hight-visibility clothing this study compared the visibility and subjective wear sensation of commercial protective vests with retro-reflecting materials or LEDs. Nine subjects compared high-visibility vests to evaluate how easy they were to see when exposed to the headlight of a car at night, and the subjects assessed the wear sensation of the vests also. The intensity and visibility of five different colored LEDs assembled on the five substrates separately were also evaluated to select the suitable LED color for night protective clothing. The intensity of illumination was measured by an illuminometer, and the visibility was evaluated by 11 participants both in a dark room and in front of a car outdoors at night. Results showed, the most effective LEDs were high intensity LEDs which shift blinking red and white were most effective. However, excessively high intensity of illumination could decrease the working efficiency. In subjective wear evaluation, the most favorable vest had a front opening, were adjustable at the sides, and had an electric power switch on the front of the vest.

• Journal of Environmental Science International
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• v.8 no.6
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• pp.639-643
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• 1999

After analyzing the correlation between air pollution and visibility, TSP and $NO_2$ is responsible for poor visibility in Pusan. After analyzing the correlation between meteorological factors and visibility, general pattern of humidity has clear negative correlation. The variation of wind speed has a positive correlation. In order to investigate the cause of poor visibility in Pusan area, the Andersen sampler and PM-2.5 are used to collect and analyze aerosol. This study was carried out to monitor the visibility using Forward scattering meter and to find out the characteristics and the cause of good visibility case and poor visibility case by measuring and analyzing a variety of parameters, such as particle size distributions, chemical compositions, and meteorological conditions in Pusan. According to the analysis of intensive sampling, $NO_3^-,NH_4^+$ ion concentration increased together with the mass concentration around $0.5\~2.5{\mu}m$ approximately during the case of poor visibility. $NH_4NO_3,\;NH_4Cl,\;and\;NaCl$ were thought to be the major components of fine particles.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.3
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• pp.35-45
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• 2008

Realtime visibility measurement using camera is a new method which can collect some realtime visibility data similar to those of the human eyes, and can replace the existing methods using the expensive optical equipment. There have been a few attempts to measure visibility by extracting depth and three-dimensional structure under bad weather conditions. However, if there are many movements of objects in the image, these approaches seem to be inappropriate. In addition, the realtime visibility measurement will require a relatively simple and fast processing. Typically the contrast degrades exponentially in the bad weather. Therefore, in this paper we propose an easy and quick method that extract contrast from images using a moving area filter and measure visibility by mathematically modelling of the relationship between image contrast and visibility. The moving area filter is used for removing the area of the sky and moving objects that affect visibility measurement on images. The method proposed here can make possible not only realtime visibility measurement from images taken by CCD cameras, but also steady visibility measurement by using the moving area filter in case of much traffic on the road.

• Journal of Astronomy and Space Sciences
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• v.27 no.3
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• pp.195-204
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• 2010

The optimal Earth-Moon transfer trajectory considering spacecraft's visibility from the Daejeon ground station visibility at both the trans lunar injection (TLI) and lunar orbit insertion (LOI) maneuvers is designed. Both the TLI and LOI maneuvers are assumed to be impulsive thrust. As the successful execution of the TLI and LOI maneuvers are crucial factors among the various lunar mission parameters, it is necessary to design an optimal lunar transfer trajectory which guarantees the visibility from a specified ground station while executing these maneuvers. The optimal Earth-Moon transfer trajectory is simulated by modifying the Korean Lunar Mission Design Software using Impulsive high Thrust Engine (KLMDS-ITE) which is developed in previous studies. Four different mission scenarios are established and simulated to analyze the effects of the spacecraft's visibility considerations at the TLI and LOI maneuvers. As a result, it is found that the optimal Earth-Moon transfer trajectory, guaranteeing the spacecraft's visibility from Daejeon ground station at both the TLI and LOI maneuvers, can be designed with slight changes in total amount of delta-Vs. About 1% difference is observed with the optimal trajectory when none of the visibility condition is guaranteed, and about 0.04% with the visibility condition is only guaranteed at the time of TLI maneuver. The spacecraft's mass which can delivered to the Moon, when both visibility conditions are secured is shown to be about 534 kg with assumptions of KSLV-2's on-orbit mass about 2.6 tons. To minimize total mission delta-Vs, it is strongly recommended that visibility conditions at both the TLI and LOI maneuvers should be simultaneously implemented to the trajectory optimization algorithm.