• Proceedings of the KSRS Conference
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• 2007.03a
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• pp.271-276
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• 2007

지표면의 파장별 방출율을 알고 있다는 가정하에 대기의 흡수효과가 상이한 두 파장역을 이용하여 대기효과를 보정해주는 일반적인 분리대기창(Generalized Split-Window) 방법으로 MTSAT-1R 자료로부터 지표면 온도(LST) 산출 알고리즘을 개발하였다. 지표면온도 산출 회귀식은 대기복사전달모델 MODTRAN4.0으로 위성으로부터 LST를 산출하는데 영향을 주는 여러 가지 요소(주/야간，수증기, 방출율，위성관측각 등)들을 고려하여 모의된 자료로부터 도출하였다. 개발한 LST 산출알고리즘의 수준을 분석하기 위해 MSGl SEVIRI 센서에 적합하도록 개 발된 Sobrino and Romaguera(2004)의 알고리즘과 GMS-5 VISSR 센서에 적합하도록 개발된 Prata and Cechet(1999)의 알고리즘과 비교하였다. 3 알고리즘을 MTSAT-1R 자료에 적용하여 LST를 산출한 결과 LST의 공간분포는 정성적으로 서로 유사하게 나타났으나，정량적으로는 지리적 위치，계절 및 주간/야간에 따라서 LST가 다르게 나타났다.

• Proceedings of the KSRS Conference
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• 2009.03a
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• pp.87-92
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• 2009

현재 미국 NASA에서는 전 지구에서 일별 발생하는 산불 탐지 영상(MOD14 product)을 제작, 배포하고 있다. 그러나, 이러한 MOD14 영상은 MODIS 자체의 낮은 공간해상도로 인하여 우리나라와 같이 소규모 산불이 발생하는 지역에서는 산불 탐지 정확도가 매우 낮게 나타났다. 본 연구에서는 기존의 MODIS 산불 지도에서 탐지되지 못한 소규모 산불을 대상으로 혼합화소분석기법(spectral mixed analysis)을 적용한 새로운 산불 탐지 알고리즘을 제시하였다. 새로운 산불 탐지 알고리즘은 진행산불 탐지 알고리즘과 연소지 탐지 알고리즘으로 구성된다. 소규모 산불이 170건 이상 발생한 2004년과 2005년 4월 남한지역을 대상으로 적용한 결과 1ha 규모의 연소지 탐지가 가능하게 되었으며, 연구 결과 소규모 진행산불과 연소지에 대해 70%이상의 탐지율을 확보하였으며, 40% 이하의 오탐지율(false alarm ratio)을 산출하였다.

• Proceedings of the KSEEG Conference
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• 2000.04a
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• pp.107-108
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• 2000

• Proceedings of the KSRS Conference
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• 2008.03a
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• pp.125-130
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• 2008

Mid-Infrared (MIR) 영상은 화산 활동 및 산불로 인한 재난관측, 지표물질 관측, 해수 온도 측정과 같은 분야들에서 사용되고 있다. 그러나 MIR영역은 지표의 복사율과 대기의 영향으로 인한 변화가 매우 심하고, 낮 영상의 경우 태양 복사량에 의한 영향도 고려해야 하는 어려움이 있다. 따라서 단일밴드인 MIR영상을 이용하여 표면온도를 얻기 위해서는 영상이 취득된 시간과 장소에서 관측된 태양 복사량 및 여러 가지 대기 변수가 필요하다. 본 연구의 목적은 기존의 MIR 영상 연구가 다중밴드를 기반으로 한 것과 달리 단일 밴드의 영상을 이용하여 표면온도를 측정하는데 있다. 이를 위하여 MODIS MIR 영상을 대상으로 MODTRAN을 사용하여 MIR 영역의 대기보정 기법을 적용 한 뒤 복사전달 모델을 이용하여 지표의 복사량을 측정하였다. 획득된 지표온도 영상의 정밀도를 측정하기 위해서 기존의 온도 알고리즘인 split-window algorithm에 의해 얻어진 해수온도 영상과의 비교를 통하여 오차 원인에 대해 분석을 실시하였다. 그 결과 낮 영상의 경우 -4.19${\pm}$1.19$^{\circ}C$ 정도의 온도 차가 났으며, 밤 영상의 경우 0.5$^{\pm}C$0.39$^{\circ}C$ 정도로 비교적 좋은 결과를 보였다. 이는 낮 영상의 경우 지표의 복사율에 대한 온도의 민감도가 매우 높기 때문에 높은 오차가 발생하지만, 밤 영상의 경우 태양빛에 의한 영향이 없으므로 좋은 결과를 나타내기 때문이다. 따라서 단일밴드 MIR영상을 이용한 지표온도 추정 시 대기에 의한 영향보다 지표 복사율에 의한 영향이 높다고 추정할 수 있다.

• Korean Journal of Remote Sensing
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• v.35 no.6_3
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• pp.1299-1312
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• 2019

As land remote sensing applications are expanding to the extraction of quantitative information, the importance of atmospheric correction is increasing. Considering the difficulty of atmospheric correction for land images, it should be applied when it is necessary. The quantitative information extraction and time-series analysis on biophysical variables in land surfaces are two major applications that need atmospheric correction. Atmospheric aerosol content and column water vapor, which are very dynamic in spatial and temporal domain, are the most influential elements and obstacles in retrieving accurate surface reflectance. It is difficult to obtain aerosol and water vapor data that have suitable spatio-temporal scale for high- and medium-resolution multispectral imagery. Selection of atmospheric correction method should be based on the availability of appropriate aerosol and water vapor data. Most atmospheric correction of land imagery assumes the Lambertian surface, which is not the case for most natural surfaces. Further BRDF correction should be considered to remove or reduce the anisotropic effects caused by different sun and viewing angles. The atmospheric correction methods of optical imagery over land will be enhanced to meet the need of quantitative remote sensing. Further, imaging sensor system may include pertinent spectral bands that can help to extract atmospheric data simultaneously.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2003.03a
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• pp.113-120
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• 2003

The estimation of the coeff. of permeability is a major process that influenced in very large portion to the changing of gound water movement and estimation of the outflow’s quantity in the ground water movement modelling. To overcome the error caused by difficulty of the ground investigation for the hydraulic parameter’s estimation, in this paper, we study of correlation between electric resistivity and coeff. of permeability, and analyse of coeff. of permeability from electric resistivity. To accomplish this purpose, we carry out electrical logging, AMT survey as an in-situ test, and measure electric resistivity, porosity, permeability for the intact rock as a laboratory test. Based on the results of this research, it can be applied that estimation of the coeff. of permeability using electrical logging and AMT survey is a effective method for the impossible area of the ground investigation caused by geographical condition and petition.

• Geophysics and Geophysical Exploration
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• v.20 no.2
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• pp.100-113
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• 2017

Induced polarization (IP) method is based on the measurement of a polarization effect known as overvoltage of the ground. IP techniques have been usually used to find mineral deposits, however, nowadays widely applied to hydrogeological investigations, surveys of groundwater pollution and foundation studies on construction sites. IP surveys can be classified by its source type, i.e., time-domain IP estimating chargeability, frequency-domain IP measuring frequency effect (FE), and complex resistivity (CR) and spectral IP (SIP) measuring complex resistivity. Recently, electromagnetic-based IP has been studied to avoid the requirement for spike electrodes to be placed in the ground. In order to understand IP methods in this study, we: 1) classify IP surveys by source type and measured data and illustrate their basic theories, 2) describe historical development of each IP forward modeling and inversion algorithm, and finally 3) introduce various case studies of IP measurements.

• Korean Journal of Remote Sensing
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• v.30 no.1
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• pp.47-59
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• 2014

Volcanic ash (VA) can be estimated by remote sensing sensors through their spectral signatures determined by the inherent optical property (IOP) including complex refractive index and the scattering properties. Until now, a very limited range of VA refractive indices has been reported and the VA from each volcanic eruption has a different composition. To improve the robustness of VA remote sensing, there is a need to understanding of VA - radiation interactions. In this study, we calculated extinction coefficient, scattering phase function, asymmetry factor, and single scattering albedo which show different values between andesite and pumice. Then, IOPs were used to analyze the relationship between theoretical remote sensed radiation calculated by radiative transfer model under various aerosol optical thickness (${\tau}$) and sun-sensor geometries and characteristics of VA. It was found that the mean rate of change of radiance at top of atmosphere versus ${\tau}$ is six times larger than in radiance values at 0.55 ${\mu}m$. At the surface, positive correlation dominates when ${\tau}$ <1, but negative correlation dominates when ${\tau}$ >1. However, radiance differences between andesite and pumice at 11 ${\mu}m$ are very small. These differences between two VA types are expressed as the polynomial regression functions and that increase as VA optical thickness increases. Finally, these results would allow VA to be better characterized by remote sensing sensors.

• Geophysics and Geophysical Exploration
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• v.26 no.1
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• pp.1-7
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• 2023

This study derives the expressions of vector gravity and gravity gradient tensor due to an elliptical cylinder. The vector gravity for an arbitrary three-dimensional (3D) body is obtained by differentiating the gravitational potential, including the triple integral, according to the shape of the body in each axis direction. The vector gravity of the 3D body with axial symmetry is integrated along the axial direction and reduced to a double integral. The complex Green's theorem using complex conjugates subsequently converts the double integral into a one-dimensional (1D) closed-line integral. Finally, the vector gravity due to the elliptical cylinder is derived using 1D numerical integration by parameterizing a boundary of the elliptical cross-section as a closed line. Similarly, the gravity gradient tensor due to the elliptical cylinder is second-order differentiated from the gravitational potential, including the triple integral, and integrated along the vertical axis direction reducing it to a double integral. Consequently, all the components of the gravity gradient tensor due to an elliptical cylinder are derived using complex Green's theorem as used in the case of vector gravity.

• Korean Journal of Remote Sensing
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• v.14 no.1
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• pp.83-94
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• 1998

To have a basic idea on the spectral reflectance signature in paddy rice canopy, we measured spectral reflectance from paddy rice canopy(Ilpumbyeo) using spectroradiometer (GER Inc. SFOV : 0.35~2.50 ${\mu}{\textrm}{m}$) in situ weekly or biweekly from transplanting to ripening stage. Spectral reflectance of the visible range (0.4~0.7 ${\mu}{\textrm}{m}$) was decreased to below 5% and then slightly increased again after heading stage in rice canopy. Meanwhile spectral reflectance of the near-infrared range (0.7~1.1 ${\mu}{\textrm}{m}$) was increased to 40~50% and then decreased a great deal after panicle initiation stage in rice canopy. Landsat TM equivalent band set ($\bar{p}$$_{TMi}$) was created by averaging spectral reflectance values to the real TM bands. Correlation analysis between the rice crop variables (LAI, total dry matter) and TM equivalent band set ($\bar{p}$$_{TMi}$) showed that LAI and total dry matter of rice were highly correlated with visible bands such as $\bar{p}$$_{TM1}$, $\bar{p}$$_{TM2}$, and $\bar{p}$$_{TM3}$. Ratio values ($\bar{p}$$_{TMi}$/$\bar{p}$$_{TMi}$) such as $\bar{p}$$_{TM4}$/$\bar{p}$$_{TM2}$ were also highly correlated with rice crop variables such as LAI and total dry matter.