Browsing by Author "Lee, Bang Yong"

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Bathymetry enhancement by altimetry-derived gravity anomalies in the East Sea (Sea of Japan)
(2010-12-01)
Kim, Kwang Bae
;
Hsiao, Yu-Shen
;
Kim, Jeong Woo
;
Lee, Bang Yong
;
Kwon, Yi Kyun
The gravity-geologic method (GGM) was used to enhance the bathymetry of the East Sea (Sea of Japan) with satellite altimetry-derived free-air gravity anomalies and shipborne depth measurements. By comparison with the bathymetry model of Smith and Sandwell's (SAS) approach (1994), GGM was found to have an advantage with short wavelength (<= 12 km) components, while SAS better predicts longer wavelength (>= 25 km) components, despite its dependency on density contrast. To mitigate this limitation, a tuning density contrast of 10.25 g/cm(3) between seawater and the seafloor was primarily estimated by the downward continuation method and then validated by the check points method with GGM. Similarly, SAS is limited by the "A" value in low-pass part of the Wiener filter, which defines the effective range of the wavelength components on bathymetry. As a final result, we present an enhanced GGM bathymetry model by integrating all available data.
Bathymetry Estimation Using the Gravity-Geologic Method: An Investigation of Density Contrast Predicted by the Downward Continuation Method
(2011-06-01)
Hsiao, Yu-Shen
;
Kim, Jeong Woo
;
Kim, Kwang Bae
;
Lee, Bang Yong
;
Hwang, Cheinway
The downward continuation (DWC) method was used to determine the density contrast between the seawater and the ocean bottom topographic mass to estimate accurate bathymetry using the gravity-geologic method (GGM) in two study areas, which are located south of Greenland (Test Area #1: 40 - 50 degrees W and 50 - 60 degrees N) and south of Alaska (Test Area #2: 140 - 150 degrees W and 45 - 55 degrees N). The data used in this study include altimetry-derived gravity anomalies, shipborne depths and gravity anomalies. Density contrasts of 1.47 and 1.30 g cm(-1) were estimated by DWC for the two test areas. The considerations of predicted density contrasts can enhance the accuracy of 3 similar to 4 m for GGM. The GGM model provided results closer to the NGDC (National Geophysical Data Center) model than the ETOPO1 (Earth topographical database I) model. The differences along the shipborne tracks between the GGM and NGDC models for Test Areas #1 and #2 were 35.8 and 50.4 m in standard deviation, respectively. Furthermore, these differences were more strongly correlated with gravity anomalies than bathymetry in the test areas. It is shown that an accuracy of under 40 m can be obtained with comparisons to shipborne depths only in Test Area #1.