• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1039-1041
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• 2003

Ocean color products derived from remote sensing satellite data are useful for monitoring the sea water quality such as the concentrations of chlorophyll, sediments and dissolved organic matter. Currently, ocean color products derived from MODIS data can be requested from NASA over the internet. However, due to the bandwidth limitation of most users in this region, and the time delay in data delivery, the products cannot be use for near-real time monitoring of sea water chlorophyll. CRISP operates a MODIS data receiving station for environmental monitoring purposes. MODIS data have been routinely received and processed to level 1B. We have adapted the higher level processing algorithms from the Institutional Algorithms provided by NASA to run in a standalone environment. The implemented algorithms include the MODIS ocean color algorithms. Seasonal chlorophyll concentration composite can be compiled for the region. By comparing the near-real time chlorophyll product with the seasonal composite, anomaly in chlorophyll concentration can be detected.

• Journal of Korea Water Resources Association
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• v.48 no.10
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• pp.831-843
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• 2015

This study estimates MODIS-derived evapotranspiration data quality by revised RS-PM algorithm in Seolmacheon test basin. We used latent flux with eddy covariance method to evaluate MODIS-derived spatial evapotranspiration and gap-filled these data by three methods (FAO-PM, MDV and Kalman Filter) and to quantify daily evapotranspiration. Gap-filled daily evapotranspiration data was used to evaluate evapotranspiration computed by revised RS-PM algorithm derived MODIS satellite images. For the water budget analysis, we used soil moisture content that is quantified to average individual soil moisture rate observed by TDR (Time Domain Reflectometry) sensor at soil depth. The soil moisture variation is calculated in consideration from initial to final soil moisture content. According to the result of this study, evapotranspiration computed by revised RS-PM algorithm is very larger than eddy covariance data gap-filled by three methods. Also, water budget characteristics is not closed. We could analysis that MODIS-derived spatial evapotranspiration does not represent actual evapotranspiration in Seolmacheon.

• Journal of the Korean earth science society
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• v.32 no.1
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• pp.21-32
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• 2011

Using six-year (2004-2009) SKYNET measurements, MODIS-derived AOTs were validated at five SKYNET sites (Seoul, Chiba, Etchujima, Fukuejima, and Hedomisaki), in addition to climatological analysis of MODIS-derived optical properties over the East Asian domain ($20-50^{\circ}N$, $90-150^{\circ}E$). In so doing MODIS-SKYNET collocated AOT data were constructed if two measurements are taken within 25 km distance and within 30 minute time difference. From the comparison of two measurements, it is demonstrated that aerosol type insignificantly affects the accuracy of MODIS AOT. It is because the aerosol model combining predefined fine aerosol model and coarse aerosol model is used for the retrieval. However, positive bias between MODIS and SKYNET increases as fraction of the coarse aerosol model increases. In addition, MODIS AOT appears to be overestimated in case of lower aerosol loading while the overestimation tends to decrease with increased aerosol loading. Regression analysis between MODIS AOT and SKYNET AOT for 550 nm band yields 0.86, 0.16, and 0.61 of regression slope, intercept, and coefficient of determination, respectively. Those statistical results may draw a conclusion that MODIS AOTs over East Asia carry a reasonable accuracy compared to ground-based SKYNET measurements.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.2
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• pp.141-151
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• 2013

This study presents a modeling of aerosol extinction vertical profiles in Korea by using the Moderate Resolution Imaging Spectro-radiometer(MODIS) derived aerosol optical thickness(AOT) and ground based visibility observation data. The method uses a series of physical equations for the derivation of aerosol scale height and vertical profiles from MODIS AOT and surface visibility data. The modelled results under the standard atmospheric condition showed small differences with the standard aerosol vertical profile used in the radiative transfer model. Model derived aerosol scale heights for two cases of clean(${\tau}_{MODIS}=0.12{\pm}0.07$, visibility=$21.13{\pm}3.31km$) and hazy atmosphere(${\tau}_{MODIS}=1.71{\pm}0.85$, visibility=$13.33{\pm}5.66km$) are $0.63{\pm}0.33km$ and $1.71{\pm}0.84km$. Based on these results, aerosol extinction profiles can be estimated and the results are transformed into the KML code for visualization of dataset. This has implications for atmospheric environmental monitoring and environmental policies for the future.

• Korean Journal of Remote Sensing
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• v.19 no.1
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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.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.301-304
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• 2008

Since longer wavelength microwave radiation can penetrate clouds, satellite passive microwave sensors can observe sea ice of the entire polar region on a daily basis. Thus, it is becoming popular to derive sea ice motion vectors from a pair of satellite passive microwave sensor images observed at one or few day interval. Usually, the accuracies of derived vectors are validated by comparing with the position data of drifting buoys. However, the number of buoys for validation is always quite limited compared to a large number of vectors derived from satellite images. In this study, the sea ice motion vectors automatically derived from pairs of AMSR-E 89GHz images (IFOV = 3.5 ${\times}$ 5.9km) by an image-to-image cross correlation were validated by comparing with sea ice motion vectors manually derived from pairs of cloudless MODIS images (IFOV=250 ${\times}$ 250m). Since AMSR-E and MODIS are both on the same Aqua satellite of NASA, the observation time of both sensors are the same. The relative errors of AMSR-E vectors against MODIS vectors were calculated. The accuracy validation has been conducted for 5 scenes. If we accept relative error of less than 30% as correct vectors, 75% to 92% of AMSR-E vectors derived from one scene were correct. On the other hand, the percentage of correct sea ice vectors derived from a pair of SSM/I 85GHz images (IFOV = 15 ${\times}$ 13km) observed nearly simultaneously with one of the AMSR-E images was 46%. The difference of the accuracy between AMSR-E and SSM/I is reflecting the difference of IFOV. The accuracies of H and V polarization were different from scene to scene, which may reflect the difference of sea ice distributions and their snow cover of each scene.

• Journal of Astronomy and Space Sciences
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• v.29 no.4
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• pp.407-411
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• 2012

Space-borne remote sensing is an effective and inexpensive way to identify crop fields and detect the crop condition. We examined the multi-temporal spectral characteristics of rice fields in South Korea to detect their phenological development and condition. These rice fields are compact, small-scale parcels of land. For the analysis, moderate resolution imaging spectroradiometer (MODIS) and RapidEye images acquired in 2011 were used. The annual spectral tendencies of different crop types could be detected using MODIS data because of its high temporal resolution, despite its relatively low spatial resolution. A comparison between MODIS and RapidEye showed that the spectral characteristics changed with the spatial resolution. The vegetation index (VI) derived from MODIS revealed more moderate values among different land-cover types than the index derived from RapidEye. Additionally, an analysis of various VIs using RapidEye satellite data showed that the VI adopting the red edge band reflected crop conditions better than the traditionally used normalized difference VI.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.1
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• pp.19-24
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• 2010

The purpose of this study is to estimate monthly Morton evapotranspiration (ET) using normalized difference vegetation index (NDVI) from MODIS satellite images. Morton ET for land surface conditions was evaluated by using daily meteorological data, and the monthly averaged Morton ETs for each land cover were compared with the monthly NDVIs of three years (2000-2002) at Chungjudam Watershed. There was a high correlation between monthly NDVI and Morton ET for the watershed with average coefficient of determination, 0.80. By comparing the MODIS NDVI ET with SLURP Morton ET, the SLURP ET was smaller than the MODIS NDVI ET. This was estimated from the consideration of soil moisture condition for the ET occurrence in the SLURP model, the limited information from the monthly NDVI values, and the errors from the derived regression equations.

• Proceedings of the KSRS Conference
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• 2002.10a
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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.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.101-103
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• 2005

Vicarious calibration method using MODIS-derived surface reflectivity data as inputs to a radiative transfer model have been developed for the planned COMS solar channel. Pilot test was conduced over the Simpson Desert targets in Australia. Results suggested that calibration can be achieved within $5\%$ error range.