• Journal of KIISE:Computing Practices and Letters
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• v.14 no.9
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• pp.841-849
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• 2008

Natural disaster such as inundation due to the typhoon induced storm-surge has inflicted severe losses on the coastal area. The problem of global warming and sea surface rising has issued and thus influences the increase of frequency and potential power of storm-surge. What we can do is to make intelligent effort to predict and prevent the losses through the early warning and prevention activity from the accurate prediction and forecasting about the time-varying storm-surge height and its arriving time resulted from the numerical simulation with sea observations. In this paper, we developed the web service based GIS-Enabled storm-surge visualization system to predict and prevent the storm-surge disasters. Moreover. for more accurate topography around coastal area and fine-grid storm-surge numerical model, we have accomplished GIS-based coastal mapping through LiDAR measurement.

• Korean Journal of Remote Sensing
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• v.13 no.1
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• pp.57-73
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• 1997

This paper is related to the correction of radiometric distortions induced by topographic relief. RADARSAT SAR image data were obtained over the mountainous area near southern part of Seoul. Initially, the SAR data was geometrically corrected and registered to plane rectangular coordinates so that each pixel of the SAR image has known topographic parameters. The topographic parameters (slope and aspect) at each pixel position were calculated from the digital elevation model (DEM) data having a comparable spatial resolution with the SAR data. Local incidence angle between the incoming microwave and the surface normal to terrain slope was selected as a primary geometric factor to analyze and to correct the radiometric distortions. Using digital maps of forest stands, several fields of rather homogeneous forest stands were delineated over the SAR image. Once the effects of local incidence angle on the radar backscatter were defined, the radiometric correction was performed by an empirical fuction that was derived from the relationship between the geometric parameters and mean radar backscatter. The correction effects were examined by ground truth data.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.430-430
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• 2017

본 연구에서는 유역모델링 시 오염원 산정의 공간적 범위를 합리적으로 고려하기 위해서, 유역모델링을 위한 소유역 구분간의 공간해상도를 유역의 오염부하량 산정을 위한 공간단위 수준으로 설정하여 새만금호 유역수질모델링을 실시하였다. 모형 구축은 HSPF (Hydrological Simulation Program - Fortran)를 이용하였으며, 오염부하량 산정단위인 리 동의 행정경계, 수치표고모델(DEM), 농경지 배수로 등 구조물들을 고려하여 새만금 유역을 대상으로 804개의 소유역을 구분 적용하였다. 소유역 세분화에 따른 계산량을 고려하여 효과적인 모델 구동을 위해 만경유역 7개, 동진유역 7개, 연안유역 3개 (총 17개)의 서브모델로 모의시스템을 구성하여 상류에서 하류로 서브모델을 순차적으로 보 검정 및 모의하도록 구현하였다. 유량 보 검정은 14개소 수문측정자료(2009~2013)와 자동보정기법을 적용하여 수행하였다. 유량보 검정결과 NSE (Nash-Sutcliffe coefficient)가 0.66~0.97, PBIAS가 -31~16.5%, $R^2$는 0.75~0.98의 범위를 보여 모형의 적용성을 확인할 수 있었다. 한편, 수질 보 검정의 경우 29개소 수질측점을 대상으로 온도, DO, BOD, TN, TP의 항목에 대해 유량보정과 같은 기간에 대해 수동보정을 실시하였다. 수질결과는 일부 상류유역에서 갈수기시 모의값이 다소 불안정한 부분이 발견되나 대체로 각 측점의 수질에 대한 시간적 변동 패턴과 평균적 수질은 합리적으로 모의하는 것으로 나타났다. 공간세분화에 따른 모델링결과를 선행연구들과 비교한 결과, 유량부문에서 우수성을 보였으나 수질부문은 비슷한 수준으로 나타났다. 본 연구는 향후 유역 오염원, 수자원 운영 등에 관한 정밀 자료 확보 시 이를 고려하는 고도화된 수문 수질 모델링 개발 및 구축에 적용될 수 있는 시스템으로 활용성이 높을 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.468-468
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• 2017

최근 기후변화로 인해 수자원 위험요소인 가뭄 및 홍수피해가 증가하고 있으며, 인구증가에 따른 수량감소로 수자원관리가 더욱 어려워지고 있는 실정이다. 효율적인 수자원관리 및 기후변화 대응을 위해 세계 물시장은 점점 증가하고 있으며, 이에 따라 국내기업 또한 해외사업 진출을 추진하고 있으나, 사업에 필수적인 기상, 수문 등 기초자료의 부재로 어려움을 겪고 있다. 본 연구에서는 국내기업의 해외사업 진출 시 필요한 기상, 지형, 수문, 인문 사회 등 기초자료를 제공하는 글로벌 수자원정보제공시스템(Global Water Bank, GWB)을 설계 및 개발하고자 한다. 국내 외 예비타당성보고서 및 국내에서 수집 가능한 국외 정보현황을 분석하여 자료 제공인자를 도출하였으며, 이를 토대로 시스템 내 제공항목을 기상, 지형, 수문해석, 인문 사회, 기후변화 자료로 구분하였다. 해외시장 진출범위를 고려하여 자료의 공간적인 범위를 전지구로 설정하였으며, 전지구 자료의 가용성을 검토하여 제공자료를 구축하였다. 기상자료는 NCDC (National Climate Data Center)의 관측 지점자료와 APHRODITE (Asian Precipitation - Highly-Resolved Observational Data Integration Towards Evaluation) 격자자료를 수집하였으며, 오 결측 자료는 품질검토를 수행하여 보정하였다. 지형자료의 경우 USGS (U.S. Geological Survey)의 DEM, FAO (Food and Agriculture Organization of the United Nations)의 토양도, UMD (University of Maryland)의 토지피복도를 구축하였다. 수문자료는 GRDC(Global Runoff Data Centre)의 관측 지점자료를 수집하였으며, 미계측 지역의 수문자료 구축을 위해 VIC(Variable Infiltration Capacity) 수문모형을 활용하여 $0.5^{\circ}$ 공간해상도의 격자 유출량 자료를 생산하였다. 인문 사회자료로 World Bank의 국가별 통계자료를 수집하였으며, 구축된 각 자료는 GWB 시스템을 통해 제공된다. 시스템의 시범운영을 위해 아시아 지역을 대상으로 GWB- 버전을 개발하였으며, 시범지역 내 관측자료와 비교분석하여 자료의 활용성을 검증하였다. 추후 GWB 시스템은 해외진출 사업 우선지역 선정 근거로 활용될 수 있는 가상수 및 물산업지수 등의 추가정보를 제공하고 타 지역으로 확대적용 예정이다.

• Journal of Environmental Science International
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• v.16 no.4
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• pp.523-532
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• 2007

This study utilized the 1/25,000 topographic map of the upper area from the Geum-ho watermark located at the middle of Geum-ho river from the National Geographic Information Institute. For the analysis, first, the influence of the size of critical area to the hydro topographic factors was examined changing grid size to $10m{\times}10m,\;30m{\times}30m\;and\;50m{\times}50m$, and the critical area for the formation of a river to $0.01km^2{\sim}0.50km^2$. It is known from the examination result of watershed morphology according to the grid size that the smaller grid size, the better resolution and accuracy. And it is found, from the analysis result of the degree of the river according to the minimum critical area for each grid size, that the grid size does not affect on the degree of the river, and the number of rivers with 2nd and higher degree does not show remarkable difference while there is big difference in the number of 1st degree rivers. From the results above, it is thought that the critical area of $0.15km^2{\sim}0.20km^2$ is appropriate for formation of a river being irrelevant to the grid size in extraction of hydro topographic parameters that are used in the runoff analysis model using topographic maps. Therefore, the GIUH model applied analysis results by use of the river level difference law proposed in this study for the explanation on the outflow response-changing characters according to the decision of a critical value of a minimum level difference river, showed that, since an ogival occurrence time and an ogival flow volume are very significant in a flood occurrence in case of not undertow facilities, the researcher could obtain a good result for the forecast of river outflow when considering a convenient application of the model and an easy acquisition of data, so it's judged that this model is proper as an algorism for the decision of a critical value of a river basin.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.208-220
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• 2016

Automatic Mountain Meteorology Observation System (AMOS) is an important ingredient for several climatological and forest disaster prediction studies. In this study, we select the optimal sites for AMOS in the mountain areas of Honam and Jeju in order to prevent forest disasters such as forest fires and landslides. So, this study used spatial dataset such as national forest map, forest roads, hiking trails and 30m DEM(Digital Elevation Model) as well as forest risk map(forest fire and landslide), national AWS information to extract optimal site selection of AMOS. Technical methods for optimal site selection of the AMOS was the firstly used multifractal model, IDW interpolation, spatial redundancy for 2.5km AWS buffering analysis, and 200m buffering analysis by using ArcGIS. Secondly, optimal sites selected by spatial analysis were estimated site accessibility, observatory environment of solar power and wireless communication through field survey. The threshold score for the final selection of the sites have to be higher than 70 points in the field assessment. In the result, a total of 159 polygons in national forest map were extracted by the spatial analysis and a total of 64 secondary candidate sites were selected for the ridge and the top of the area using Google Earth. Finally, a total of 26 optimal sites were selected by quantitative assessment based on field survey. Our selection criteria will serve for the establishment of the AMOS network for the best observations of weather conditions in the national forests. The effective observation network may enhance the mountain weather observations, which leads to accurate prediction of forest disasters.

• Journal of the Korean Association of Geographic Information Studies
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• v.19 no.4
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• pp.76-91
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• 2016

The purpose of this study is to analyze the effects of spatial characteristics, such as land cover and topography, on heat wave days from the city of Milyang, which has recently drawn attention for its heat wave problems. The number of heat wave days was calculated utilizing RCP-based South Korea climate data from 2000 to 2010. Land cover types were reclassified into urban area, agricultural area, forest area, water, and grassland using 2000, 2005, and 2010 land cover data constructed by the Ministry of Environment. Topographical features were analyzed by topographic position index (TPI) using a digital elevation model (DEM) with 30 m spatial resolution. The results show that the number of heat wave days was 31.4 days in 2000, which was the highest, followed by 26.9 days in 2008, 24.2 days in 2001, and 24.0 days in 2010. The heat wave distribution was relatively higher in agricultural areas, valleys, and rural areas. The topography of Milyang contains more mountainous slope (51.6%) than flat (19.7%), while large-scale valleys (12.2%) are distributed across some of the western region. Correlation analysis between heat wave and spatial characteristics showed that the correlation between forest area land cover and number of heat wave days was negative (-0.109), indicating that heat wave can be mitigated. Topographically, flat areas and heat wave showed a positive correlation (0.305). These results provide important insights for urban planning and environmental management for understanding the impact of land development and topographic change on heat wave.

• Korean Journal of Remote Sensing
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• v.29 no.4
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• pp.361-373
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• 2013

The monitoring of urban area, target detection and building reconstruction have been actively studied and investigated since high resolution X-band SAR images could be acquired by airborne and/or satellite SAR systems. This paper describes an efficient approach to reconstruct artificial structures (e.g. apartment, building and house) in urban area using high resolution X-band SAR images. Building footprint was first extracted from 1:25,000 digital topographic map and then a corner line of building was detected by an automatic detecting algorithm. With SAR amplitude images, an initial building height was calculated by the length of layover estimated using KS-test (Kolmogorov-Smirnov test) from the corner line. The interferometric SAR phases were simulated depending on SAR geometry and changable building heights ranging from -10 m to +10 m of the initial building height. With an interferogram from real SAR data set, the simulation results were compared using the method of the phase consistency. One of results can be finally defined as the reconstructed building height. The developed algorithm was applied to repeat-pass TerraSAR-X spotlight mode data set over an apartment complex in Daejeon city, Korea. The final building heights were validated against reference heights extracted from LiDAR DSM, with an RMSE (Root Mean Square Error) of about 1~2m.

• Korean Journal of Agricultural and Forest Meteorology
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• v.13 no.4
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• pp.176-184
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• 2011

Cold air on sloping surfaces flows down to the valley bottom in mountainous terrain at calm and clear nights. Based on the assumption that the cold air flow may be the same as the water flow, current models estimate temperature drop by regarding the cold air accumulation at a given location as the water-like free drainage. At a closed catchment whose outlet is blocked by man-made obstacles such as banks and roads, however, the water-like free drainage assumption is no longer valid because the cold air accumulates from the bottom first. We developed an empirical model to estimate quantitatively the effect of cold pool on nocturnal temperature in a closed catchment. In our model, a closed catchment is treated like a "vessel", and a digital elevation model (DEM) was used to calculate the maximum capacity of the cold pool formed in a closed catchment. We introduce a topographical variable named "shape factor", which is the ratio of the cold air accumulation potential across the whole catchment area to the maximum capacity of the cold pool to describe the relative size of temperature drop at a wider range of catchment shapes. The shape factor is then used to simulate the density profile of cold pool formed in a given catchment based on a hypsometric equation. The cold lake module was incorporated with the existing model (i.e., Chung et al., 2006), generating a new model and predicting distribution of minimum temperature over closed catchments. We applied this model to Akyang valley (i.e., a typical closed catchment of 53 $km^2$ area) in the southern skirt of Mt. Jiri National Park where 12 automated weather stations (AWS) are operational. The performance of the model was evaluated based on the feasibility of delineating the temperature pattern accurately at cold pool forming at night. Overall, the model's ability of simulating the spatial pattern of lower temperature were improved especially at the valley bottom, showing a similar pattern of the estimated temperature with that of thermal images obtained across the valley at dawn (0520 to 0600 local standard time) of 17 May 2011. Error in temperature estimation, calculated with the root mean square error using the 10 low-lying AWSs, was substantially decreased from $1.30^{\circ}C$ with the existing model to $0.71^{\circ}C$ with the new model. These results suggest the feasibility of the new method in predicting the site-specific freeze and frost warning at a closed catchment.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.233-241
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• 2016

Experiments were carried out to quantify the topographic effects on attenuation of sunshine in complex terrain and the results are expected to help convert the coarse resolution sunshine duration information provided by the Korea Meteorological Administration (KMA) into a detailed map reflecting the terrain characteristics of mountainous watershed. Hourly shaded relief images for one year, each pixel consisting of 0 to 255 brightness value, were constructed by applying techniques of shadow modeling and skyline analysis to the 3m resolution digital elevation model for an experimental watershed on the southern slope of Mt. Jiri in Korea. By using a bimetal sunshine recorder, sunshine duration was measured at three points with different terrain conditions in the watershed from May 15, 2015 to May 14, 2016. The brightness values of the 3 corresponding pixel points on the shaded relief map were extracted and regressed to the measured sunshine duration, resulting in a brightness-sunshine duration response curve for a clear day. We devised a method to calibrate this curve equation according to sky condition categorized by cloud amount and used it to derive an empirical model for estimating sunshine duration over a complex terrain. When the performance of this model was compared with a conventional scheme for estimating sunshine duration over a horizontal plane, the estimation bias was improved remarkably and the root mean square error for daily sunshine hour was 1.7hr, which is a reduction by 37% from the conventional method. In order to apply this model to a given area, the clear-sky sunshine duration of each pixel should be produced on hourly intervals first, by driving the curve equation with the hourly shaded relief image of the area. Next, the cloud effect is corrected by 3-hourly 'sky condition' of the KMA digital forecast products. Finally, daily sunshine hour can be obtained by accumulating the hourly sunshine duration. A detailed sunshine duration distribution of 3m horizontal resolution was obtained by applying this procedure to the experimental watershed.