• 한국환경과학회지
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• 제4권2호
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• pp.159-168
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• 1995

To predict reasonably the movement and the concentration of the pollutants in the coastal area. A simulation model should be prepared considering detail topography with land-sea and the urban effects, and the resolution near the source. The explicit method can not be applied due to the instability of the numerical calculation in high horizontal-grid resolution, while the ADI scheme satisfied with the high horizontal grid resolution and can be used in the fine mesh system which shows the detail topography, atmospheric flow The ADI method which studied the high horizontal grid resolution was excellent. The two dimensional model used in the study using ADI method is proved as a reasonable model to predict the wind field in any small scale area including mountainous coastal urban area.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.115-118
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• 2004

Images with high resolution are desired and often required in many visual applications. When resolution can not be improved by replacing sensors, either because of cost or hardware physical limits, super resolution image reconstruction method is what can be resorted to. Super resolution image reconstruction method refers to image processing algorithms that produce high quality and high resolution images from a set of low quality and low resolution images. The method is proved to be useful in many practical cases where multiple frames of the same scene can be obtained, including satellite imaging, video surveillance, video enhancement and restoration, digital mosaicking, and medical imaging. The method can be either the frequency domain approach or the spatial domain approach. Much of the earlier works concentrated on the frequency domain formulation, but as more general degradation models were considered, later researches had been almost exclusively on spatial domain formulations. The method in spatial domains has three stages: i) motion estimate or image registration, ii) interpolation onto high resolution grid and iii) deblurring process. The super resolution grid construction in the second stage was discussed in this paper. We applied the Maximum A­Posteriori(MAP) reconstruction method that is one of the major methods in the super resolution grid construction. Based on this method, we reconstructed high resolution images from a set of low resolution images and compared the results with those from other known interpolation methods.

• 한국안전학회지
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• 제39권1호
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• pp.70-81
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• 2024

With heavy rainfall due to extreme weather causing increasing damage, the importance of urban flood forecasting continues to grow. To forecast urban flooding accurately and promptly, a sewer network and surface grid with appropriate detail are necessary. However, for urban areas with complex storm sewer networks and terrain structures, high-resolution grids and detailed networks can significantly prolong the analysis. Therefore, determining an appropriate level of network simplification and a suitable surface grid resolution is essential to secure the golden time for urban flood forecasting. In this study, InfoWorks ICM, a software program capable of 1D-2D coupled simulation, was used to examine urban flood forecasting performance for storm sewer networks with various levels of simplification and different surface grid resolutions. The inundation depth, inundation area, and simulation time were analyzed for each simplification level. Based on the analysis, the simulation time was reduced by up to 65% upon simplifying the storm sewer networks and by up to 96% depending on the surface grid resolution; further, the inundation area was overestimated as the grid resolution increased. This study provides insights into optimizing the simplification level and surface grid resolution for storm sewer networks to ensure efficient and accurate urban flood forecasting.

• 대한공간정보학회지
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• 제20권1호
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• pp.109-116
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• 2012

본 연구에서는 CCHE2D와 EFDC모형을 이용한 모의를 통하여 격자의 횡단해상도에 따른 물리적 지형의 재현성과 모의결과에 대한 영향을 검토하고자 하였다. 낙동강 금호강 유입구간을 대상으로 2006년 강우사상에 대한 부정류모의를 통하여 면적고도곡선과 대상구간내 수위관측소 지점에서의 실측치와 모의치간의 비교를 통하여 구성격자망의 적정성 및 모의결과에 대한 영향을 각각 검토하였다. 일반적으로 격자 해상도의 증가는 계산시간의 증가를 야기하므로 수행 내용과 목적, 계산의 효율성 측면에서 적절한 격자해상도의 선택이 필요하다. 정밀한 모의를 위해서는 고해상도 격자를 이용한 모의를 수행해야 하나, 빠른 의사결정이 요구되는 홍수기와 같이 모형수행의 효율성을 고려해야 하는 경우에 적용 가능한 물리적 지형의 재현성과 결과에 대한 신뢰성을 보장할 수 있는 적정 격자 해상도가 존재함을 확인할 수 있었다.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2003년도 추계학술발표회 논문집
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• pp.379-384
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• 2003

In this paper, we introduce a change detection system that can extract and analyze change elements from high-resolution satellite imagery as well as low- or middle-resolution satellite imagery. The developed system provides not only 7 pixel-based methods that can be used to detect change from low- or middle-resolution satellite images but also a float window concept that can be used in manual change detection from high-resolution satellite images. This system enables fast process of the very large image, because it is constituted by OGC grid coverage components. Also new change detection algorithms can be easily added into this system if once they are made into grid coverage components.

• 대한원격탐사학회지
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• 제36권4호
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• pp.557-571
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• 2020

High-resolution flows around a steep mountainous island (Ulleungdo) in Korea were simulated by a computational fluid dynamics (CFD) model. To cover entire Ulleungdo and to resolve the topography around the Ulleungdo automatic synoptic observing system (ASOS) with high resolution, one-way nested grid system with large (60 m), and small (20 m) grid sizes was applied in the CFD model simulations. We conducted the numerical simulations for 16 inflow directions, and, for each inflow direction, we considered six different wind velocities(5, 10, 15, 20, 25, and 30 m s^-1) at the reference height (1,000 m). The effects of topography on surface wind observations were well reflected in the observed wind roses for the period of January 01, 2012 ~ December 31, 2016 at the Ulleungdo ASOS and marine buoy. Wind roses at the Ulleungdo ASOS was reproduced based on the CFD simulations. The changes in surface winds at the Ulleungdo ASOS caused by surrounding topography were relatively well simulated by the CFD model. The simulated wind-rose indicated that south-southwesterly and northeasterly were the dominant wind directions, which were also observed at the Ulleungdo ASOS. We investigated the flow characteristics around the Ulleungdo ASOS for northwesterly, south-southwesterly, and northeasterly winds in detail.

• 대한기계학회논문집B
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• 제22권7호
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• pp.1030-1040
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• 1998

One of the main unresolved issues in large-eddy simulation(LES) of wall-bounded turbulent flows is the requirement of high spatial resolution in the near-wall region, especially in the spanwise direction. Such high resolution required in the near-wall region is generally used throughout the computational domain, making simulations of high Reynolds number, complex-geometry flows prohibitive. A grid-embedding strategy using a nonconforming spectral domain-decomposition method is proposed to address this limitation. This method provides an efficient way of clustering grid points in the near-wall region with spectral accuracy. LES of transitional and turbulent channel flow has been performed to evaluate the proposed grid-embedding technique. The computational domain is divided into three subdomains to resolve the near-wall regions in the spanwise direction. Spectral patching collocation methods are used for the grid-embedding and appropriate conditions are suggested for the interface matching. Results of LES using the grid-embedding strategy are promising compared to LES of global spectral method and direct numerical simulation. Overall, the results show that the spectral domain-decomposition grid-embedding technique provides an efficient method for resolving the near-wall region in LES of complex flows of engineering interest, allowing significant savings in the computational CPU and memory.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1099-1101
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• 2003

Change detection technology, which discovers the change information on the surface of the earth by comparing and analyzing multi-temporal satellite images, can be usefully applied to the various fields, such as environmental inspection, urban planning, forest policy, updating of geographical information and the military usage. In this paper, we introduce a change detection system that can extract and analyze change elements from high-resolution satellite imagery as well as low- or middle-resolution satellite imagery. The developed system provides not only 7 pixelbased methods that can be used to detect change from low- or middle-resolution satellite images but also a float window concept that can be used in manual change detection from highresolution satellite images. This system enables fast access to the very large image, because it is constituted by OGC grid coverage components. Also new change detection algorithms can be easily added into this system if once they are made into grid coverage components.

• 대기
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• 제26권4호
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• pp.697-709
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• 2016

This study estimates and evaluates the extreme value of 30 m-resolution daily maximum and minimum temperatures over South Korea, using inverse distance weighting (IDW), parameter-elevation regression on independent slopes model (PRISM) and generalized extreme value (GEV) method. The three experiments are designed and performed to find the optimal estimation strategy to obtain extreme value. First experiment (EXP1) applies GEV firstly to automated surface observing system (ASOS) to estimate extreme value and then applies IDW to produce high-resolution extreme values. Second experiment (EXP2) is same as EXP1, but using PRISM to make the high-resolution extreme value instead of IDW. Third experiment (EXP3) firstly applies PRISM to ASOS to produce the high-resolution temperature field, and then applies GEV method to make high resolution extreme value data. By comparing these 3 experiments with extreme values obtained from observation data, we find that EXP3 shows the best performance to estimate extreme values of maximum and minimum temperatures, followed by EXP1 and EXP2. It is revealed that EXP1 and EXP2 have a limitation to estimate the extreme value at each grid point correctly because the extreme values of these experiments with 30 m-resolution are calculated from only 60 extreme values obtained from ASOS. On the other hand, the extreme value of EXP3 is similar to observation compared to others, since EXP3 produces 30m-resolution daily temperature through PRISM, and then applies GEV to that result at each grid point. This result indicates that the quality of statistically produced high-resolution extreme values which are estimated from observation data is different depending on the combination and procedure order of statistical methods.

• 대한전자공학회논문지SP
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• 제48권3호
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• pp.30-41
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• 2011

산란선을 흡수하여 보다 선명한 x선 영상을 얻기 위하여 산란방지 그리드를 사용하여 투사영상을 얻는데, 이때 그리드로 인한 왜곡이 발생한다. 본 논문에서는 회전된 그리드를 사용하여 그리드 왜곡의 제거가 용이하도록 x선 디지털 영상을 얻는 방법에 있어서 기존의 왜곡 성분의 중심주파수를 가장자리로 보내는 경우를 보다 심도 있게 분석하여 확장된 결과를 도출하였으며, min-max 개념에서 주어진 그리드 밀도에 대하여 최적화하는 방법을 제시하였다. 또한 실질적으로 사용가능한 그리드 밀도에 대하여 적절한 그리드 각도를 제시하고 그러한 그리드를 사용하여 획득한 x선 디지털 영상에서 그리드 왜곡이 용이한 알고리듬을 제안하고 그 성능을 비교해보았는데, 원영상의 해상도를 어느 정도 유지하면서 그리드 왜곡을 줄일 수 있었다.