• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.3
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• pp.375-384
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• 2009

The GRACE satellite, Launched in March 2002, is applied to research on glacial melt of polar regions, glacial isostatic adjustment(GIA), sea level change, terrestrial water storage(TWS) variation of river basin and large-scale earthquake etc. In this research, the TWS variation of Yangtze river basin from August, 2002 to January, 2009 is analyzed using Level-2 GRACE monthly gravity field model. Particularly, gravity changes of the Three Gorges Dam during the impoundment process in 2003, 2006 and 2008 is observed by estimating equivalent water thickness(EWT). The research results show the distinct annual and seasonal changes of Yangtze river basin, and its amplitude of annual variation is 2.3cm. In addition, we compare the results with water resource statistics and hydrologic observation data to confirm the possibility of research of TWS variation of river basin using GRACE observation data, and also the satellite gravity data is of great help for the research on the movement and periodic changes of river basin.

• Journal of Korea Water Resources Association
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• v.45 no.8
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• pp.805-814
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• 2012

Most hydrologic data are obtained by ground observations. New observation methods are needed for some regions to overcome difficulties in accessibility and durability of long-term observation. In 2002, NASA launched twin satellites named GRACE which were designed to measure the gravitational field of the earth. Using the GRACE monthly gravity level-2 data, we calculated terrestrial water storage change (TWSC) of the Korean peninsula in various spatial smoothing radii (0 km, 300 km, 500 km). For the validation of GRACE-based TWSC, we compared it with land-based TWSC which was obtained using the ground observation data: precipitation and evaporation from WAMIS, and runoff from GLDAS. According to the mean square-error test, GRACE-based TWSC best fits the land-based one at 500 km smoothing radius. The variation of the terrestrial water storage in the Korean peninsula turned out to be 0.986 cm/month, which means that appropriate measures should be prepared for sustainable water resources management.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.5
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• pp.513-518
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• 2008

The research of global-scale mass redistribution and it changed by Earth gravity filed variation observations, including Earth's oblateness $J_2$(also called low degree spherical harmonic coefficient $C_{20}$), is in continuous progress. Recently, the comparative analysis of geodetic observation SLR can be made by the development of GRACE and other time-variable gravity measurements. In this study, $C_{20}$ time series changes in the value of comparative analysis was got by GRACE monthly Gravity filed model (CSR RL04) for the period April 2002 to May 2008. And comparative analysis the harmonic coefficients of $C_{20}$ was obtained from SLR observations. Signal analysis for two time-series data was made by wavelet transform, CWT(continuous wavelet transform), XWT(cross wavelet transform) and WTC(wavelet coherence) methods. The results indicate that GRACE and SLR values for $C_{20}$ had both decreasing trend, as well as SLR data represent the annual frequencies, and GRACE was semiannual variations. In addition, the results of GRACE and SLR had a strong correlation with the XWT and WTC in an annual cycle.