• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.14 no.2
• /
• pp.116-127
• /
• 2002

Most of finite difference numerical models for the simulation of tsunami propagation developed so for are based on the shallow-water equations which are frequently solved by the leap-frog scheme. If the grid size is properly selected, this numerical scheme gives a correct dispersion effect fur constant water depth. However, if the water depth changes, the dispersion effect of tsunamis can not be accurately considered at every grid point in the whole computational domain. In this study we improved the existing two-dimensional dispersion-correction finite difference numerical scheme. The present scheme satisfies the local dispersion relationships of tsunamis propagating over a slowly varying topography while using uniform grid size and time step. To verify the applicability of the improved numerical model, a tsunami due to 1983 East Sea central earthquake is simulated for Korean harbors with the tide gage records such as Sokcho, Mukho, Pohang and Ulsan in the East Sea. Numerical results of the 1983 tsunami are compared with the measured data and the accuracy of the present numerical model is evaluated.

• Journal of Korean Society for Geospatial Information Science
• /
• v.17 no.1
• /
• pp.13-19
• /
• 2009

The Gwangalli Beach, one of beaches representative of Busan together with the Haeundae Beach, is a tourist attraction, having increased tourists since the completion of Gwangandaero Bridge in 2003 and recording more than 10 million tourists in 2006. Although the competent local government office has conducted artificial beach nourishment/gravel removal projects every year to manage it, systematic monitoring and studies of erosion are insufficient. This study analyzed the changes in the coastline of Gwangalli Beach using aerial photos, tidal data, GPS survey data for the last sixty years, and examined how the Gwangandaero Bridge, which had been constructed on the Gwanganlli sea, has affected the changes. The results show that the area of Gwangalli Beach has increased 40% for the last sixty years, and that the effects of Gwangandaero Bridge on the coastline are insignificant.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.6 no.3
• /
• pp.290-297
• /
• 1994

As satellite altimetry is being progressed to apply with higher precision to marginal seas, it is necessary to improve correction procedures fer tidal signals in altimetry with more accurate tidal model than the well-known model of Schwiderski. The Bay of Bengal renders many conspicuous coastal oceanographic issues including tide and storm surge interactions along the upper Bangladesh coast. As a first step. tidal regime of semidiurmal tides (M$_2$, S$_2$, $N_2$, $K_2$) and diurnal tides (K$_1$, $O_1$, P$_1$) are computed with a model having a mesh resolution of 1/4 degree over the whole Bay of Bengal. Computed results are discussed with observation and previous Schwideski's tidal map of the region.

• Economic and Environmental Geology
• /
• v.40 no.4
• /
• pp.445-459
• /
• 2007

Superconducting Gravimeter(SG) was installed and has been successfully operated at MunGyung, Kyungsang province in Korea in March 2005. It was registered as the 21st observatory of the Global Geodynamics Project. Since SG can precisely measure the gravity variations below the 1mHz frequency band, it has the outstanding capability to sense and resolve many different periodic gravity components from each other. From the raw data collected between 18 March 2005 and 21 February 2006 diurnal and semi-diurnal tidal band's residual gravity components were analyzed. During this process, the instrumental noises, air pressure, and ground water corrections were carried out. Values of $-3.18nm/s^2/hPa\;and\;17nm/s^2/m$ were used respectively in the air pressure and groundwater corrections. Hartmann-Wenzel and Whar-Dehant Earth tide models were adopted to compute the residual gravity for Q1, O1, P1, K1, M2, N2, S2, K2 tidal bands. For the ocean loading correction, SCW80, FES952, and FES02 models were used and compared. As a result, FES02 ocean loading model has shown the best match for the data processing at MunGyung SG MunGyung SG gravity was compared with GRACE satellite gravity. The correlation coefficient between the two gravity after groundwater correction was 0.628, which is higher than before ground water correction. To evaluate sensitivity at MunGyung SG gravity statition, the gravity data measured during 2005 Indodesian earthquake was compared with STS-2 broad band seismometer data. The result clearly revealed that the SG could recorded the same period of earthquake with seismometer event and a few after-shock events those were detected by seismometer.

• Ocean and Polar Research
• /
• v.41 no.4
• /
• pp.213-232
• /
• 2019

This study evaluates the accuracy of four satellite-composite (OSTIA, AVHRR, G1SST, FNMONC-S) and three model-reanalysis (HYCOM, JCOPE2, FNMOC-M) daily sea surface temperature (SST) data around the Korean Peninsula (KP) using ocean buoy data from 2011-2016. The results reveal that OSTIA has the lowest root mean square error (RMSE; 0.68℃) and FNMOC-S/M has the highest correction coefficients (r = 0.993) compared with observations, while G1SST, JCOPE2, and AVHRR have relatively larger RMSEs and smaller correlations. The large RMSEs were found in the western coastal regions of the KP where water depth is shallow and tides are strong, such as Chilbaldo and Deokjeokdo, while low RMSEs were found in the East Sea and open oceans where water depth is relatively deep such as Donghae, Ulleungdo, and Marado. We found that the main sources of the large RMSEs, sometimes reaching up to 5℃, in SST data around the KP, can be attributed to rapid SST changes during events of strong tidal mixing, upwelling, and typhoon-induced mixing. The errors in the background SST fields which are used in data assimilations and satellite composites and the missing in-situ observations are also potential sources of large SST errors. These results suggest that both satellite and reanalysis SST data, which are believed to be true observation-based data, sometimes, can have significant inherent errors in specific regions around the KP and thus the use of such SST products should proceed with caution particularly when the aforementioned events occur.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.26 no.1
• /
• pp.51-61
• /
• 2008

The determination of precise geoid model for the Jeju island is needed to minimize the effect of different vertical datums. This study describes the development of gravimetric geoid model referred to GRS80 reference surface for the area of Jeju island. We used ECM96 up to degree and order 360 as a reference model and added the terrain and the residual gravity effects to the reference model. After then 17 GPS/Levelling data were used to correct the difference between the GPS/Levelling-derived geoid heights and gravimetric geoid heights. The least square collocation was applied to derive the correction and the grid values. The final precise geoid model(Jeju_GEOID07) that consist of $0.75'{\times}1'$(about $1.4km{\times}1.5km)$ grid interval was obtained in the region of $33^{\circ}{\sim}33.8^{\circ}N$ and $125.8^{\circ}{\sim}127.2^{\circ}E$. Concerning this works, the precise geoid for the Korean peninsula should be determined by integrating the different geoid developed for the peninsula and Jeju island. It is also need to integrate the vertical datum using long-term tide and GPS observations.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.40 no.3
• /
• pp.187-193
• /
• 2022

In the Yeongdong region of Gangwon-do, coastal areas are important resources in terms of cultural, social and economic aspects. However, the coast of Gangwon-do is experiencing severe erosion, and it is concerned that its adverse effects will gradually increase. In this study, coastline changes of Yangyang and Gangneung in Gangwon-do were tracked and analyzed over a long period of time. In order to build time series image data, aerial photos from the 1940s to the present were mainly used, and data from CORONA satellite, which operated from the 1960s to the early 1970s, were collected and used together. Using 51cm resolution ortho image and 2m resolution Digital Elevation Model(DEM) as reference, ground control points were selected to perform geometric correction on the aerial photos and CORONA images. Subsequently, Canny edge detector applied to these images to extract the coastlines. As a result of analyzing the extracted and vectorized coastlines by overlaying them in chronological order, erosion and deposition occurring around the artificial structures and on the nearby beaches were observed. In this study, the effect of seasonal variation, tide, and various coastal management including the beach filling were not considered. Because coastal erosion is greatly affected by geographic factors, each local government must find its own solution. Continuous research and local data accumulation are required.