• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.1
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• pp.683-692
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• 2009

On-site remote sensing technique by using single lens reflex(SLR) digital camera will be expected as the useful tool for the vegetation measurement field such as a crop growth management, the monitoring of revegetation slope and the evaluation of environment. We reviewed the availability of the vegetation measurement using a digital camera which is sailed for general-purpose. As a result, we could analysis relationship with the illuminance of image plane and incidence energy of multitemporal observation images by doing gamma correction and exposure compensation. And also, we proposed the model formulas for the correction of influences of capturing angle and illuminance. In addition, we obtained high correlation of normalized difference vegetation index(NDVI) between digital camera and spectral photometer.

• Korean Journal of Remote Sensing
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• v.29 no.1
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• pp.137-149
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• 2013

Solar insolation is essential to understand the interaction between the earth and solar system, and it is a significant parameter that is utilized in various research fields including earth science, agriculture, and energy engineering. Although solar insolation is broadly measured in the ground-based observation station, it is difficult to identify the spatial distribution of solar insolation accurately. The remote sensing approach is known to have several benefits because it can provide continuous data sets for large area. In this study, we conducted the validation of solar insolation from COMS in the South Korea by comparing with flux tower observation. The results showed that the correlations between COMS and observation were high in both 30 minutes interval data and daily average data. Thus, we can identify that COMS can provide a reasonable estimate of solar insolation.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.471-479
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• 2011

Evapotranspiration (ET) including evaporation from a land surface and transpiration from photosynthesis of vegetation is a hydrological factor that has an important role in water cycle. However, there is a limitation to understand it due to heterogeneity of land cover and vegetation. In this study, Mapping EvapoTRanspiration with Internalized Calibration (METRIC) model, one of the energy balance models, and MODerate resolution Imaging Spectroradiometer (MODIS) satellite based well-known Penman-Monteith algorithm were compared. Two ET maps were categorized and compared by land cover classification. The results represented overall applicability of the two models with the highest correlation coefficients in needleleaf and broadleaf forests. This study will be useful to estimate remote sensing based ET maps with high resolution and to figure out spatio-temporal variability and seasonal changes.

• The Journal of the Korea Contents Association
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• v.11 no.2
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• pp.487-494
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• 2011

This paper is to investigate the efficacy of cyber education by self-assessment strategy. Self-assessment strategy contains self-monitoring function and self-control function. 202 students of online university attended and analyzed with frequency, correlation, t-test, Paired t-test. The major findings were as follows. The learners who experienced self-assessment in the initial stage of class had higher changes in social distance to the mentally disabled people positively than the learners who didn't experienced that. This self-assessment strategy can be assumed that it is effective strategy to improve e-learning efficacy and it will contribute to self-directed education for enhancement of on-line education.

• Korean Journal of Remote Sensing
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• v.15 no.3
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• pp.195-208
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• 1999

In the classification of satellite images, the representative of training of classes is very important factor that affects the classification accuracy. Hence, in order to improve the classification accuracy, it is required to optimize pre-classification stage which determines classification parameters rather than to develop classifiers alone. In this study, the normality of training are calculated at the preclassification stage using SPOT XS and LANDSAT TM. A correlation coefficient of multivariate Q-Q plot with 5% significance level and a variance of initial training are considered as an object function of genetic algorithm in the training normalization process. As a result of normalization of training using the genetic algorithm, it was proved that, for the study area, the mean and variance of each class shifted to the population, and the result showed the possibility of prediction of the distribution of each class.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.390-390
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• 2021

본 연구에서는 통계적 방법에 의해 예측된 미래기간의 기온정보와 기온기반의 기준증발산량 산정방법을 연계하여 한강권역을 대상으로 최대 12개월의 미래기간에 대한 기준증발산량을 전망하였다. 기온정보는 Kim et al. (2020)의 연구와 같이 글로벌 기후지수와의 원격상관성을 기반으로 개발된 다중회귀모형을 이용하여 미래기간(예측시점 기준 1~12개월)에 대해 월 평균기온을 예측하고 이를 상세화하여 한강권역 내 주요 ASOS 지점별로 최고/최저기온을 도출하였다. 기준증발산량은 Hamon 방법(Hamon, 1960, 1963)을 기반으로 각 지점별로 상세화된 최고/최저기온을 이용하여 동일한 미래기간(1~12개월)에 대해 산정하였다. 한강권역 전체에 대해 2015년 1월~2020년 12월의 월별 평균기온과 각 지점별 산정한 기준증발산량을 활용하여 기온 및 기준증발산량에 대한 예측성을 분석하였다. 한강권역 전체에 대해 예측된 월별 평균기온의 경우 실제 관측값과 비교하였을 때, PBIAS 4.2~6.4%, R² 0.97~0.98, NSE 0.97~0.98 등으로 매우 높은 예측성을 보였다. 지점별로 상세화된 기온정보를 이용하여 산정한 기준증발산량을 실제 기온으로부터 산정한 기준증발산량과 비교한 결과는 PBIAS 5.0~6.8%, R² 0.97~0.98, NSE 0.96~0.97로 기온에 대한 예측성과 유사하게 나타났다. 기온과 기준증발산량 모두 일부 월이나 일부 지점에서 관측값과 비교했을 때 다소 차이를 보이는 경우도 있었으나, 대상유역 전반적으로는 매우 안정적인 예측결과를 확인할 수 있었다. 기준증발산량에 대한 예측결과(미래 1~12개월)는 계절 및 월 단위의 유역 수자원 전망에 유용하게 활용될 수 있을 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.329-329
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• 2023

가뭄은 수개월에서 수년에 걸쳐 평년보다 낮은 강수량을 특징으로 하는 극심한 기후 현상으로 크게 기상학적 가뭄과 식생 가뭄 또는 농업 가뭄, 수문학적 가뭄, 사회경제적 가뭄으로 구분할 수 있다. 본 연구에 사용된 기상학적 가뭄지수는 표준강수지수 (Standardized Precipitation Index), 증발수요가뭄지수 (Evaporative Demand Drought Index), 표준강수증발산지수 (Standardized Precipitation Evapotranspiration Index), Copula 기반 결합가뭄지수 (Copula-based Joint Drought Index)이다. 식생지수는 0부터 1까지 0.05 간격으로 가중치를 적용하여 21개의 식생건강지수(Vegetation Health Index)를 사용하였다. VHI는 널리 사용되고 있는 원격탐사자료 기반의 가뭄지수이며, 이는 식생상태지수 (Vegetation Condition Index)와 열상태지수 (Thermal condition index)의 선형 결합으로 이루어진다. 기상학적 가뭄지수와 식생지수 사이의 상호의존도 및 민감도를 분석하기 위해 상관성 분석을 수행하였으며, 이를 토지피복 유형 (시가화 건조지역, 농업지역, 초지, 산림지역)에 따른 분석도 수행하고자 하였다.

• Journal of Internet Computing and Services
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• v.19 no.1
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• pp.105-111
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• 2018

This paper presents the analysis of image quality with FHD(Full HD) resolution camera equipped DIC(Digital Image Correlation) platform for the measurement of the architectural structure's relative displacement. DIC platform was designed based on i.MX6 of Freescale. Displacement measurement based on DIC method, the error is affected by image quality factors as pixel number, brightness, contrast, and SNR[dB](Signal to Noise Ratio). The effect were analyzed. The displacement of ROI(Region Of Interest) area within the image was measured by sub-pixel units based on DIC method. The non-contact telemetry property of DIC method, it can be used to long distance non-contact measurement. The various displacement results was measured and analyzed with the image quality factor adjustment according to the distance(25m, 35m, 50m).

• Korean Journal of Remote Sensing
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• v.35 no.6_3
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• pp.1285-1298
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• 2019

Drought is one of the factors that can cause wildfires. Drought is related to not only the occurrence of wildfires but also their frequency, extent and severity. In South Korea, most wildfires occur in dry seasons (i.e. spring and autumn), which are highly correlated to drought events. In this study, we examined the relationship between wildfire occurrence and drought factors, and developed satellite-based new drought indices for assessing wildfire risk over South Korea. Drought factors used in this study were high-resolution downscaled soil moisture, Normalized Different Water Index (NDWI), Normalized Multi-band Drought Index (NMDI), Normalized Different Drought Index (NDDI), Temperature Condition Index (TCI), Precipitation Condition Index (PCI) and Vegetation Condition Index (VCI). Drought indices were then proposed through weighted linear combination and one-class support vector machine (One-class SVM) using the drought factors. We found that most drought factors, in particular, soil moisture, NDWI, and PCI were linked well to wildfire occurrence. The validation results using wildfire cases in 2018 showed that all five linear combinations produced consistently good performance (> 88% in occurrence match). In particular, the combination of soil moisture and NDWI, and the combination of soil moisture, NDWI, and precipitation were found to be appropriate for representing wildfire risk.

• Korean Journal of Remote Sensing
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• v.32 no.6
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• pp.741-746
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• 2016

Albedo is one of the climate variables that modulate absorption of solar energy, and its retrieval is important process for climate change study. High spatial resolution and long-term consistent periods are important considerations in order to efficiently use the retrieved albedo data. This study retrieved surface broadband albedo based on Landsat 8 as high resolution which is consistent with Landsat 7. First of all, we analyzed consistency of Landsat 7 channel and Landsat 8 channel. As a result, correlation coefficient(R) on all channels is average 0.96. Based on this analysis, we used multiple linear regression model using Landsat 7 albedo, which is being used in many studies, and Landsat 8 reflectance channel data. The regression coefficients of each channel calculated by regression analysis were used to derive a formula for converting the Landsat 8 reflectance channel data to broadband albedo. After Landsat 8 albedo calculated using the derived formula is compared with Landsat 7 albedo data, we confirmed consistency of two satellite using Root Mean Square Error (RMSE), R-square ($R^2$) and bias. As a result, $R^2$ is 0.89 and RMSE is 0.003 between Landsat 7 albedo and Landsat 8 albedo.