• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1027-1029
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• 2003

The primary uses of SWIR bands of ASTER data are to analyze geological features. In this study, we are attempting to evaluate the effect of using the narrow band A STER data for extracting information related to biophysical information of forest vegetation. ASTER and ETM+ data have been obtained simultaneously over the study area in Kyongan-River basin on May 8, 2003. Two data sets were initially processed to reduce atmospheric effects and converted to percent reflectance values, which make them comparable each other. ASTER and ETM+ reflectance were then analyzed by using the field survey data that include forest leaf area index (LAI), cover types, species composition, and stand density. Preliminary results show that ASTER reflectance were not much different to ETM+ reflectance to explain LAI.

• 대한원격탐사학회지
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• 제33권4호
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• pp.411-422
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• 2017

This research aims to analyze spectral reflectance of intertidal zone and its changes under various environmental conditions. We sampled sand of Mongsanpo tidal flat, Korea, and measured its spectral reflectance by using a spectroradiometer under various water contents, compositions and granularity. We also simulated the reflectance of Landsat 7 ETM+ and compared it with an actual satellite data. Five locations were selected for sampling from the coastline towards the ocean. Grain size diminished stepwise from the coastline to ocean direction, while spectral reflectance differed with wavelength. Water contents lowered the overall reflectance especially at the water absorption bands. Spectral reflectance data were then converted into the simulated one by using Landsat 7 ETM+ spectral reflectance function to be compared with the actual Landsat 7 ETM+ images. It showed the decrease of the spectral reflectance due to the increase of moisture contents from seashore towards the ocean. It is shown that Landsat 7 ETM+ imagery can be efficient to extract moisture contents in the tidal flat while compositional analysis needs satellite sensors with much higher spectral resolution.

• 대한원격탐사학회지
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• 제22권5호
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• pp.305-311
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• 2006

Although there have been several attempts to estimate forest LAI using optical remote sensor data, there are still not enough evidences whether the NDVI is effective to estimate forest LAI, particularly in fully closed canopy situation. In this study, we have conducted a simple correlation analysis between LAI and spectral reflectance at two different settings: 1) laboratory spectral measurements on the multiple-layers of leaf samples and 2) Landsat ETM+ reflectance in the close canopy forest stands with fieldmeasured LAI. In both cases, the correlation coefficients between LAI and spectral reflectance were higher in short-wave infrared (SWIR) and visible wavelength regions. Although the near-IR reflectance showed positive correlations with LAI, the correlations strength is weaker than in SWIR and visible region. The higher correlations were found with the spectral reflectance data measured on the simulated vegetation samples than with the ETM+ reflectance on the actual forests. In addition, there was no significant correlation between the forest.LAI and NDVI, in particular when the LAI values were larger than three. The SWIR reflectance may be important factor to improve the potential of optical remote sensor data to estimate forest LAI in close canopy situation.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.378-381
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• 2002

We retrieved the aerosol optical thickness $\tau$$_{a}$ over land from Landsat-7/ETM+ image data using the correlation between the visible reflectance and middle IR reflectance. This band correlation method for aerosol retrieval was originally proposed fur MODIS data analysis by Kaufman et al.(1977). The results of retrieved aerosol optical thickness $\tau$$_{a}$ from Landsat-7/ETM+ data were compared with the simultaneous sky observation data at our study site. We found a good agreement between the retrieved and observed values. We presented the distribution maps of the aerosol optical thickness over land, retrieved from Landsat-7/ETM+ image data. Then, the surface reflectance map was also presented. The aerosol optical thickness over sea was retrieved assuming no reflected contribution from sea in the near IR band. In addition, we discussed some limitations when we apply the band correlation method.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.679-684
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• 2002

MODIS LAI has been one of key products for analyzing the quantitative aspects ofterrestrial ecology. This study was designed to validate MODIS LAS product by using the reference LAI map that was derived from both ground measurements and ETM＋ surface reflectance. The study area, the Kwangneung Experiment Forest in Korea, covers mixed species of deciduous and conifers of temperate forest. Throughout the growing season of 2002, we have measured LAS at the 30 sample plots using an optical device. Ground measured LAS data were then correlated to the ETM＋ reflectance to produce a continuous map of LAS over the study area. Preliminary comparison between MODIS LAI and the reference LAI map showed the lower LAI values from the MODIS product.

• 대한원격탐사학회지
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• 제19권1호
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• pp.1-9
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• 2003

MODIS LAI product has been one of key variable for analyzing the quantitative aspects of terrestrial ecology at global scale. This study was designed to validate MODIS global LAI product for regional application. To examine the quality of MODIS LAI data, we developed a reference LAI surface that was derived by relating the ground LAI measurements to Landsat ETM+ reflectance. The study area, the Kwangneung Experiment Forest in Korea, covers mixed deciduous and coniferous species of temperate forest. Ground measurements of LAI were conducted at 30 sample plots by using a photo-optical instrument during the growing season of 2002. Ground measured LAI data were then related to the ETM+ reflectance to produce a continuous map of LAI surface over the study area. From the comparison between the MODIS LAI and the reference LAI, it was found that the MODIS LAI values were slightly higher at the forestland. Considering the limitations of producing the reference LAI surface and the uncertainty of the input variable for the MODIS LAI algorithm, such small discrepancy mal not be significant.

• 대한원격탐사학회지
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• 제19권5호
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• pp.371-380
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• 2003

The primary objective of this study is to develop a suitable methodology to generate forest leaf area index (LAI) map at regional and local scales. To build empirical models, we collected the LAI values at 30 sample plots over the forest within the kyongan watershed area by the field measurements using an optical instrument. Landsat-7 ETM＋ multispectral data obtained at the same growing season with the field LAI measurement were used. Three datasets of remote sensing signal were prepared for analyzing the relationship with the field measured LAI value and they include raw DN, atmospherically corrected reflectance, and topographically corrected reflectance. From the correlation analysis and regression model development, we found that the radiometric correction of topographic effects was very critical step to increase the sensitivity of the multispectral reflectance to LAI. In addition, the empirical model to generate forest LAI map should be separately developed for each of coniferous and deciduous forest.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.425-427
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• 2004

Motivation of this study is based on these two aspects: geologic uses of ASTER and application scheme of Spectral Mixture Analysis. This study aims at geologic mapping for mineral exploration using ASTER and LANDSAT 7 ETM+ at Mongolian plateau region by SMA. After basic pre-processing such as the normalization, geometric corrections and calibration of reflectance, related to endmembers selection and spectral signature deviation, both methods using spectral library and using PPI(Pixel Purity Index) are performed and compared on a given task. Based on these schemes, SMA is performed using LANDSAT 7 ETM+ and ASTER image. As the results, fraction map showing geologic rock types are enough to meet purposes such as geologic mapping and mineral potential mapping in the case of both uses of these different types of remotely sensed images. It concluded that this approach based on SMA with LANDSAT and ASTER is regarded as one of effective schemes for geologic remote sensing.

• 대한원격탐사학회지
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• 제19권2호
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• pp.117-133
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• 2003

이 연구에서는 곰소만 조간대에서 현장 시료채취와 동시에 얻어진 Landsat ETM+ 자료를 이용하여 조간대 환경요인들이 ETM+에 의해 관측된 반사도와 어떤 관계를 가지고 있는 지 밝히고, 광학위성영상을 이용한 조간대 표층퇴적물의 분류의 적용 가능한 기준입도를 제시하고자 하였다. 일반적인 퇴적학적 분류 기준이 되는 4 $\Phi$ 입도를 기준으로 했을 때 입도와 영상의 반사도 간의 상관관계는 매우 낮은 것으로 나타났으나, 2 $\Phi$ 이상의 입자를 기준으로 하였을 때는 상부조간대의 천주변에 작은 입자로 구성된 지역의 자료들을 제외하면 ETM+ 밴드 4번과 0.699의 높은 상관계수를 보인다. 즉, 입도 2 $\Phi$ 곰소만 조간대에서의 광학위성 자료에 의한 표층퇴적물 분류를 위한 기준입도로 사용하는 것이 타당하다. 입도와 함수율은 비교적 높은 음의 상관관계를 보이며 특히 입도 2 $\Phi$ 기준과는 -0.811로서 뚜렷하게 음의 상관관계를 보인다 위성자료의 Factor analysis 결과는 지형요소에 의해 크게 영향을 받는 독일의 조간대와는 다른 특성을 보이며, 이는 곰소만의 경우는 입자가 세립하여 지형보다는 함수율에 더 큰 영향을 받는 것으로 나타났다. 결국 조간대 원격탐사에서는 입도뿐만 아니라 함수율과 지형 등의 환경요소가 함께 고려하여야만 한다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.852-855
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• 2006

There is an increasing need to use data from different sensors in order to maximize the chances of obtaining a cloud-free image and to meet timely requirements for information. However, the use of data from multiple sensor systems is depending on comprehensive relationships between sensors of different types. Indeed, a study of inter-sensor relationships is well advanced in the effective use of remotely sensed data from multiple sensors. This paper was concerned with relationships between sensors of different types for vegetation indices (VI). The study was conducted using IKONOS and Landsat-7 ETM+ images. IKONOS and Landsat-7 ETM+ image of the same or about the same dates were acquired. The Landsat-7 ETM+ images were resampled in order to make them coincide with the pixel sizes of IKONOS. Inter-relationships of vegetation indices between images were performed using at-satellite reflectance obtained by converting image digital number (DN). All images were applied to topographic normalization method in order to reduce topographic effect in digital imagery. Also, Inter-sensor model equations between two sensors were developed and applied to other study region. In the result, the relational equations can be used to compute or interpret VI of one sensor using the VI of another sensor.