• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.31-31
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• 2015

토양수분은 일반적으로 시료를 채취하거나 현장에 설치된 다양한 센서를 통해 추정하지만 이는 시간과 비용이 많이 소모되기 ?문에 유역내의 공간적인 토양수분 분포를 추정하는데 상당한 어려움이 따른다. 토양수분뿐만 아니라 공간적인 대기현상, 토양수분, 식생현황 등을 관측하는데 대중적으로 사용되는 것이 위성 관측이며, 기본적으로는 위성에 탑재된 센서가 각 주파수대역에 따라 영상을 생성하면 이를 특정 알고리듬을 적용하여 원하는 값을 도출하게 된다. 토양수분 산정에 사용되는 대표적인 위성영상으로는 SMOS (Soil Moisture and Ocean Salinity), ARMS-E(Advanced Microwave Scanning Radiometer - Earth Observing System), ARMS2 (ARMS ver.2) 영상 등이 있으며, 이러한 위성은 해상도가 약 10 km ~ 40 km로 상당이 낮기 때문에 우리나라와 같이 면적이 좁고 지형이 복잡하며 다양한 토지피복이 밀집되어있는 곳에서는 기존 수문 연구에 응용할 수 있는 토양수분 공간지도 산정을 위해 상세화(Downscaling)과정이 필요하다고 판단된다. 따라서 본 연구에서는 ARMS2 토양수분 영상을 MODIS 영상의 식생지수(NDVI, Normalized Difference Vegetation Index), 알베도 및 온도를 활용하여 공간적으로 상세화된 토양 수분 지도를 작성하였고, 유역 내에서 실제 측정되고 있는 토양수분 관측값을 활용하여 상세화기법의 적용성을 검토하였다.

• 한국토양비료학회지
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• 제48권6호
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• pp.571-581
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• 2015

Soil moisture content is generally accepted as an important factor to understand the process of crop growth and is the basis of earth system models for analysis and prediction of the crop condition. To continuously monitor soil moisture changes at kilometer scale, it is demanded to create high resolution data from the current, several tens of kilometers. In this paper we described a downscaling method for Advanced Microwave Scanning Radiometer 2 (AMSR2) Soil Moisture Content (SMC) from 10 km to 30 m resolution using a soil texture and field measurements that have a high correlation with the SMC. As a result, the soil moisture variations of both data (before and after downscaling) were identical, and the Root Mean Square Error (RMSE) of SMC exhibited the low values. Also, time series analyses showed that three kinds of SMC data (field measurement, original AMSR2, and downscaled AMSR2) had very similar temporal variations. Our method can be applied to downscaling of other soil variables and can contribute to monitoring small-scale changes of soil moisture by providing high resolution data.

• 한국토양비료학회지
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• 제48권6호
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• pp.658-665
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• 2015

Temporal and spatial variation of soil moisture is important for understanding patterns of climate change, for developing and evaluating land surface models, for designing surface soil moisture observation networks, and for determining the appropriate resolution for satellite-based remote sensing instruments for soil moisture. In this study, we measured several soil moistures in upland soil using Advanced Microwave Scanning Radiometer 2 (AMSR2) Soil Moisture Content (SMC) during eight-month period in Chungbuk province. The upland soil moisture properties were expressed by simple statistical methods (average, standard deviation and coefficient of variation) from the monthly context. Supplementary studies were also performed about the effect of top soil texture on the soil moisture responses. If the results from this study were utilized well in specific cities and counties in Korea, it would be helpful to establish the countermeasures and action plans for preventing disasters because it was possible to compare with the relationship between soil moisture and top soil texture of each region. And it would be the fundamental data for estimating the effect of future agricultural plan.

• 대한원격탐사학회지
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• 제37권1호
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• pp.69-84
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• 2021

Awareness of boats is a main issue in areas of fishery management, illegal fishing, and maritime traffic, etc. For the awareness, Automatic Identification System (AIS) and Vessel-Pass System (V-PASS) have been widely used to collect the boat-related information. However, only using these systems makes it difficult to collect the accurate information. Recently, satellite-based data has been increasingly used as a cooperative system. In 2015, U.S. National Oceanic and Atmospheric Administration (NOAA) developed a boat detection algorithm using Visible Infrared Imaging Radiometer Suite (VIIRS) Day & Night Band (DNB) data. Although the detections have been widely utilized in many publications, it is difficult to estimate the night-time fishing boats immediately. Particularly, it is difficult to estimate the threshold due to the lunar irradiation effect. This effect must be corrected to apply a single specific threshold. In this study, the moon phase was considered as the main frequency of this effect. Considering the moon phase, relational expressions are derived and then used as offsets for relative correction. After the correction, it shows a significant reduction in the standard deviation of the threshold compared to the threshold of NOAA. Through the correction, this study can set a constant threshold every day without determination of different thresholds. In conclusion, this study can achieve the detection applying the single specific threshold regardless of the moon phase.

• 한국농공학회논문집
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• 제64권4호
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• pp.31-43
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• 2022

In this study, we estimated the monthly FDSI (Flash Drought Stress Index) for assessing flash drought on South Korea using AMSR2(Advanced Microwave Scanning Radiometer 2) satellite-based soil moisture footprints. We collected the AMSR2 soil moisture and climate-land surface data from April to November 2018 for analyzing the monthly FDSI values. We confirmed that the FDSI values were high at the regions with the high temperature/evapotranspiration while the precipitation is relatively low. Especially, the regions which satisfied an onset of flash drought (FDSI≧0.71) were increased from June. Then, the most of regions suffered by flash drought during the periods (July to August) with the high temperature and evapotranspiration. Additionally, the impacts of landuse and slope degree were evaluated on the monthly FDSI changes. The forest regions that have the steep slope degree showed the relatively higher FDSI values than the others. Thus, our results indicated that the the slope degree has the relatively higher impact on the onset and increasing of flash drought compared to the others.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.156-156
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• 2022

Explicitly spatially distributed and reliable data on industrial water demand is very much important for both policy makers and researchers in order to carry a region-specific analysis of water resources management. However, such type of data remains scarce particularly in underdeveloped and developing countries. Current research is limited in using different spatially available socio-economic, climate data and geographical data from different sources in accordance to predict industrial water demand at finer resolution. This study proposes a random forest regression (RFR) model to predict the industrial water demand at 0.50× 0.50 spatial resolution by combining various features extracted from multiple data sources. The dataset used here include National Polar-orbiting Partnership (NPP)/Visible Infrared Imaging Radiometer Suite (VIIRS) night-time light (NTL), Global Power Plant database, AQUASTAT country-wise industrial water use data, Elevation data, Gross Domestic Product (GDP), Road density, Crop land, Population, Precipitation, Temperature, and Aridity. Compared with traditional regression algorithms, RF shows the advantages of high prediction accuracy, not requiring assumptions of a prior probability distribution, and the capacity to analyses variable importance. The final RF model was fitted using the parameter settings of ntree = 300 and mtry = 2. As a result, determinate coefficients value of 0.547 is achieved. The variable importance of the independent variables e.g. night light data, elevation data, GDP and population data used in the training purpose of RF model plays the major role in predicting the industrial water demand.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2022년도 춘계학술대회
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• pp.211-212
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• 2022

지구온난화에 따른 우리나라 주변 환경의 변화와 최근 중국 불법어선의 연근해 어업자원의 고갈 등으로 인해 우리나라 연근해 어족자원을 보호할 필요성이 증대되고 있으며, 지속 가능한 어업을 위해서는 어획물의 종류와 양을 정확히 파악하고 불법 어업에 대한 철저한 감시 및 관리가 필요하다. 시공간적으로 다양하게 변하는 생태 및 어장 환경 정보와 선박에 대한 정보를 통해 해양관측과 위성 원격탐사를 동시에 이용함으로써 근해와 원양 생물자원 실태를 관측하는 것이 가능하다. 본 연구에서는 야간 불빛 위성 Suomi-NPP (Suomi National Polar-orbiting Partnership) 및 후속위성인 NOAA-20의 VIIRS (Visible Infrared Imaging Radiometer Suite) DNB (Day & Night Band) 영상을 이용하여 야간 불빛을 활용하고자 한다. 이 불빛 위성 자료를 이용하여 야간에 조업하는 어선 선단의 공간 분포를 분석할 수 있다. 또한 이 불빛 위성 자료와 AIS 자료를 상호 비교하여, 불빛 위성 자료를 통해 실제 선박의 위치 정보를 검색하는 것이 가능함을 검증하고자 한다.

• 대기
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• 제17권2호
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• pp.159-169
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• 2007

A comparison of the three land cover data sets (United States Geological Survey: USGS, International Geosphere Biosphere Programme: IGBP, and University of Maryland: UMd), derived from 1992-1993 Advanced Very High Resolution Radiometer(AVHRR) data sets, was performed over the Asian continent. Preprocesses such as the unification of map projection and land cover definition, were applied for the comparison of the three different land cover data sets. Overall, the agreement among the three land cover data sets was relatively high for the land covers which have a distinct phenology, such as urban, open shrubland, mixed forest, and bare ground (>45%). The ratios of triple agreement (TA), couple agreement (CA) and total disagreement (TD) among the three land cover data sets are 30.99%, 57.89% and 8.91%, respectively. The agreement ratio between USGS and IGBP is much greater (about 80%) than that (about 32%) between USGS and UMd (or IGBP and UMd). The main reasons for the relatively low agreement among the three land cover data sets are differences in 1) the number of land cover categories, 2) the basic input data sets used for the classification, 3) classification (or clustering) methodologies, and 4) level of preprocessing. The number of categories for the USGS, IGBP and UMd are 24, 17 and 14, respectively. USGS and IGBP used only the 12 monthly normalized difference vegetation index (NDVI), whereas UMd used the 12 monthly NDVI and other 29 auxiliary data derived from AVHRR 5 channels. USGS and IGBP used unsupervised clustering method, whereas UMd used the supervised technique, decision tree using the ground truth data derived from the high resolution Landsat data. The insufficient preprocessing in USGS and IGBP compared to the UMd resulted in the spatial discontinuity and misclassification.

• 한국전자파학회논문지
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• 제23권3호
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• pp.410-413
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• 2012

2차원 레이다 간섭계에서 표적의 공간 도달 각도를 추정하는 방법 중에서 1차원 알고리즘과 디지털 빔 포밍알고리즘, 위상차의 최소 자승 오차 알고리즘들의 각도 모호성 해소 성능을 비교한다. 위상 비교 모노 펄스 알고리즘의 경우, 2차원 레이다 간섭계에 적용하기 위해 방위각 방향과 고각 방향으로 각각 적용하였다. 성능 비교를 위해 Monte carlo 시뮬레이션 방법을 이용하여 2차원 레이다 간섭계에서 각도 추정 알고리즘 별 각도 모호성 해소 확률과 수행 시간을 비교하였다. 각도 모호성 해소 확률과 수행 시간을 고려할 때 위 여러 방법 중에서 위상 비교 모노 펄스 알고리즘이 실시간 신호 처리 분야에 가장 효율적임을 보여준다.

• 해양환경안전학회지
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• 제17권4호
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• pp.331-337
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• 2011

본 연구에서는 동북아시아 NOAA AVHRR 위성관측 16년간(1990-2005) 해양표면 수온영상을 이용하여 에러 값 제거와 결측 자료 보완을 위하여 마르코프 계수를 결정하였고, 이 값에서 현재 수온평년 값을 더하여 구름 없는 해양표면수온 생성 기법을 제시하였다. 마르코프 연쇄 모델의 결과에 의하면, 마르코프 계수는 해류가 강한 쿠로시오 해역 등이 해류가 약한 동해 북서부의 대부분 해역과 동중국해보다 그 계수가 상대적으로 낮게 나타났다. 평균 수온의 변동은 봄과 가을이 겨울과 여름에 비하여 분산이 크게 나타났고, 계절별 일간 수온 차이도 수온의 계절적 변동이 큰 봄과 가을이 여름과 겨울에 비하여 큰 지역적인 차이를 보였다. 그 지역적인 분포는 봄과 가을의 경우 전 해역의 대륙 인접부에서 대부분 크게 나타났고, 동해 극전선 남부해역과 쿠로시오해역에서는 난류에 의한 열수송으로 일간 수온의 차이가 작았다.