• Spatial Information Research
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• v.19 no.2
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• pp.19-28
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• 2011

Three dimensional modeling for seafloor topography is essential to monitoring displacements in underwater structures as well as all sorts of disasters along the shore. MBES is a system that is capable of high-density water depth measurement for seafloor topography and is in broad uses for gathering 3D data and detecting displacements. MBES data, however, contain random errors that take place in the equipment offset and surveying process and require systematic researches on the correction of wrong depth measurements. Thus this study set out to propose a post-processing technique to eliminate an array of random errors taking place after equipment offset correction and basic noise correction in the MBES system and analyze its applicability to seafloor topography modeling by applying it to the subject area.

• Geophysics and Geophysical Exploration
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• v.11 no.2
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• pp.93-98
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• 2008

Abstract: Surface topography has a significant influence on seismic wave propagation in a reflection seismic exploration. Effects of surface topography on two-dimensional elastic wave propagation are investigated through modeling using a weighted-averaging (WA) finite-element method (FEM), which is computationally more efficient than conventional FEM. Effects of air layer on wave propagation are also investigated using flat surface models with and without air. To validate our scheme in modeling including topography, we compare WA FEM results for irregular topographic models against those derived from conventional FEM using one set of rectangular elements. For the irregular surface topography models, elastic wave propagation is simulated to show that breaks in slope act as a new source for diffracted waves, and that Rayleigh waves are more seriously distorted by surface topography than P-waves.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.868-878
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• 1998

There are recently increasing needs for precision XYZ-stage in the fields of nanotechnology, specially in AFMs(Atomic Force Microscope) and STMs(Scanning Tunneling Microscope). Force measurements are made in the AFM by monitoring the deflection of a flexible element (usually a cantilever) in response to the interaction force between the probe tip and the sample and controlling the force neasyred constant topography can be obtained. The power of the STM is based on the strong distance dependence of the tunneling current in the vacuum chamber and the current is a feedback for the tip to trace the surface topography. Therefore, it is required for XYZ-stage to position samples with nanometer resolution, without any crosscouples and any parasitic motion and with fast response. Nanometer resolution is essential to investigate topography with reasonable shape. No crosscouples and parasitic motion is essential to investigate topography without any shape distortion. Fast response is essential to investigate topography without any undesirable interaction between the probe tip and sample surface ; sample scratch. To satisfy these requirements, this paper presents a novel XYZ-stage concept, it is actuated by PZT and has a monolithic flexible body that is made symmetric as possible to guide the motion of the moving body linearly. PZT actuators have a very fast response and infinite resolution. Due to the monolithic structure, this XYZ-stage has no crosscouples and by symmetry it has no parasitic motion. Analytical modeling of this XYZ-stage and its verification by FEM modeling are performed and optimal design that is to maximize 1st natural frequencies of the stage is also presented and with that design values stage is manufactured.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.6
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• pp.649-661
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• 2008

The impact of the detailed surface data on regional meteorological fields in complex coastal area is studied using RAMS. Resolutions of topography and land use data are very important to numerical modeling, because high resolution data can reflect correct terrain height and detail characteristics of the surface. Especially, in complex coastal region such as Gwangyang area, southern area in Korean Peninsula, high resolution topography and land use data are indispensable for accurate modeling results. This study investigated the effect of resolutions of terrain data using SRTM with 3 second resolution topography and KLU with 1 second resolution land use data. Case HR was the experiment using high resolution data, whereas Case LR used low resolution data. In Case HR, computed surface temperature was higher than Case LR along the coastline and wind speed was $1{\sim}2m/s$ weaker than Case LR. Time series of temperature and wind speed indicated great agreement with the observation data. Moreover, Case HR indicated outstanding results on statistical analysis such as regression, root mean square error, index of agreement.

• Geophysics and Geophysical Exploration
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• v.5 no.4
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• pp.291-298
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• 2002

We have developed a two-dimensional (2-D) magnetotelluric (MT) inversion algorithm, which can include topographic effects in inversion. We use the finite element method (FEM) to incorporate topography into forward calculation. Topography is implemented simply by moving nodes of rectangular elements in z-direction according to the elevation of air-earth interface. In the inversion process, we adopt a spatially variable Lagrangian multiplier algorithm in the smoothness-constrained least-squares inversion. The inversion algorithm developed in this study reconstructs subsurface resistivity structure quite well when topography variation exists. Also, it turns out to be effective in both resolution and stability from a model study and field data application.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.5207-5215
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• 2010

Selecting proper location for complex facility with special purpose need comprehensive consideration on the condition and surrounding environment. Especially, in case of living space for human, lighting, ventilation, efficiency in land use, etc. are important elements. Diverse 3D analysis through 3D topography modeling and virtual simulation is necessary for this. Now, it can be processed with relatively inexpensive cost since high resolution satellite image essential in topography modeling is provided with domestic technology through Arirang No. 2 satellite (KOMPSAT2). In this study, several candidate sites is selected for complex planning with special purpose and analysis on proper location was performed using the 3D topography modeling and land information. For this, land analysis, land price calculation, slope analysis and aspect analysis have been carried out. As a result of arranging the evaluation index for each candidate site and attempting the quantitative evaluation, proper location could be selected efficiently and reasonably.

• Journal of Conservation Science
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• v.38 no.4
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• pp.347-359
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• 2022

Gongsanseong Fortress was registered of a World Heritage Site in 2015 as a representative cultural heritage from the Woongjin Baekje period, and it has been used throughout the entire period from Baekje Kingdom to the Joseon Dynasty. Within Gongsanseong Fortress, the area around Ssangsujeong is presumed the site of royal palace of the Woongjin Baekje. Also, the excavated culture layers of the Baekje Kingdom, the Unified Silla period, and the Joseon Dynasty were confirmed. In this study, paleotopography was modeled by digitally converting the elevation data obtained through surveying the excavation process, and the use of the topography in the Ssangsujeong area was considered by examining the variations in the topography according to the periods. As a result, the topography of the slope around the peak changed by periods, and the topography did not change on the flat land. The topography between the Baekje Kingdom and the Unified Silla period appeared to be almost identical, and it seems that the space of the Baekje period was maintained as it is. Also, during the Joseon Dynasty, it is confirmed that flat surfaces in the previous period were used. However, sediments on the slopes flowed down, reducing the area of the flatland, and architectural techniques that could utilize the natural topography of the changed slope were applied to interpret it as having a different topography from the previous period. In order to model and interpret the paleotopography, excavation data, geological and topographic analysis, and digital data must be secured. It is expected that location conditions and ancient human life can be identified if the analysis technique in the study is applied to other archaeological sites in the future.

• Journal of Korean Society for Geospatial Information Science
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• v.24 no.3
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• pp.67-73
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• 2016

The present study evaluated the blocking effect of natural and artificial topography on sunshine duration in the southern coastal area of Haui-do. The geospatial data for the target area was constructed by geographic information system(GIS) data. Three-dimensional modeling based on solar azimuth and altitude angles was conducted for the assessment of sunshine environment. The sunshine area was evaluated over 80~90% of the target area in the daytime, especially in summer. The blocking effect of mountainous terrain on sunshine duration was presented at the northern residential area in the late afternoon. There was also the effect of artificial topography by construction of fill-up bank on sunshine environment at the southern residential area early in the morning and the south-western part of salt field in the late afternoon.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.275-284
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• 2007

For precise interpretation of magnetotelluric (MT) data distorted by irregular surface terrain, topography effects are investigated by computing apparent resistivities, phases, tippers and induction vectors for a three-dimensional (3D) hill-and-valley model. To compute MT responses for the 3D surface topography model, we use a 3D MT modeling algorithm based on an edge finite-element method which is free from vector parasites. Distortions on the apparent resistivity and phase are mainly caused by distorted currents that flow along surface topography. The distribution of tipper amplitudes over both hill and valley are the same, while the tipper points toward the center of hill and the base of the valley. The real part of induction vector also points in the same direction as that of tipper, while the imaginary part in the opposite direction.

• Geophysics and Geophysical Exploration
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• v.4 no.2
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• pp.34-44
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• 2001

Forward modeling by construction of synthetic data is usually practiced in a horizontal surface and a few subsurface structures. However, in-situ surveys often take place in such topographic changes that the corrupted field data always make it difficult to interpret the right signals. To examine the propagation characteristic of elastic waves on the irregular surface, a general mesh generation code for finite element method was modified to consider the topography. By implementing this algorithm, the time domain modeling was practiced in some models with surface topography such as mound, channel, etc. The synthetic data obtained by receivers placed on surface also agreed with the analytic solution. The snapshots showing the total wave-field revealed the propagation characteristic of the elastic waves through complex subsurface structures and helped to identify the signals on the time traces. The transmission of Rayleigh waves along the surface, compressive waves, and sheer waves was observed. Moreover, it turned out that the Rayleigh waves behave like a new source at the edge.