• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.1
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• pp.139-147
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• 2023

As heavy precipitation rates have increased due to climate change, the risk of landslides has also become greater. Studies in the field of disaster risk assessment predominantly focus on evaluating intrinsic importance represented by the use or role of facilities. This work, however, focused on evaluating risks according to the external conditions of facilities, which were presented via debris flow simulation. A random walk model (RWM) was partially improved and used for the debris flow simulation. The existing RWM algorithm contained the problem of the simulation results being overly concentrated on the maximum slope line. To improve the model, the center cell height was adjusted and the inertia application method was modified. Facility information was collected from a digital topographic map layer. The risk level of each object was evaluated by combining the simulation result and the digital topographic map layer. A risk assessment technique suitable for the polygon and polyline layers was applied, respectively. Finally, by combining the evaluated risk with the attribute table of the layer, a system was prepared that could create a list of objects expected to be damaged, derive various statistics, and express the risk of each facility on a map. In short, we used an easy-to-understand simulation algorithm and proposed a technique to express detailed risk information on a map. This work will aid in the user-friendly development of a debris flow risk assessment system.

• Spatial Information Research
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• v.17 no.2
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• pp.191-200
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• 2009

Aerial digital camera was used in outside since 2000 because of technical development & improvement of it. In korea, line type or frame type digital camera introduced since 2006 was used in manufacture and Correction of National base map appling the number and distribution of control point of analogue aerial triangulation from 2008. The main objective of the study is to compare and analyze the effects of the number and distribution of control points in accuracy of results, when we execute aerial triangulation with images from ADS40, line type sensored aerial digital camera available in korea. The result of RMSE can be concluded that accuracy of all the case are meet the aerial photograph surveying work regulation of NGI as to horizontal of control point ${\pm}0.068m$, ${\pm}0.073m$, ${\pm}0.071m$, height ${\pm}0.041m$, ${\pm}0.055m$, ${\pm}0.055m$, ${\pm}0.041m$, as to horizontal of check point ${\pm}0.167m$, ${\pm}0.113m$, ${\pm}0.110m$, height ${\pm}0.128m$, ${\pm}0.086m$, ${\pm}0.081m$. We have confirmed that it is possible to make out large scale digital topographic map.

• The Journal of the Korea Contents Association
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• v.12 no.2
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• pp.78-85
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• 2012

This paper proposes an efficient algorithm to develop a 3D terrain tools which is essential in the development of 3D computer games. In particular, this paper proposes a cross detection technique to improve picking speed. In other words, this paper proposes a more efficient cross detection technique consisting of a ray and a parallelogram than a cross detection technique consisting of a ray and a triangle. So, we can confirm the faster picking speed. This paper uses a picking example among DirectX SDK samples to test it. In addition, this paper compares the number of function calls for cross detection using the existing techniques and the proposed technique. As a result, in this paper the proposed technique has fallen off to about a 50 percent than the existing techniques. And if it is calculated by times, in this paper the proposed technique was reduced to 1 to 2 seconds than the existing techniques. Additionally, in this paper 3D terrain tools are provide more improved algorithms for features such as texture splatting, height map control, object arrangement and realistic water effect. So, 3D terrain tools is available efficient in the development of real 3d computer games.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.2
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• pp.33-40
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• 2014

At present, Cadastral map of 2 dimensional is in the stream of changing it to 3 dimensional type supported by GPS and laser techniques. In addition, this steam can be explained at the same time with improvement of equipment of storing much information, support of equipment for imaginative 3D spatial information, and support of equipment of expressing land in 3D Cadastral. This study suggest to apply airborne lidar survey technique on cadastral map to acquire comparably and quickly detailed height of ground. For doing this, this study checked out credibility regarding accuracy of airborne lider survey. After choosing research area, this study has done the airborne lidar survey and acquire the result after surveying Cadastral Comparison Point to check out the accuracy of acquired results. In addition, this study check out the result of Cadastral Comparison Point and airborne lidar survey applied by paired sample t-test based on actual results. The result is that test statistics is 0.322 which is 5 % similar level and null hypothesis cannot be rejected, so this study found out that result of both survey ways are the same. Therefore, the result of airborne lidar survey can be utilized to build up 3D Cadastral information hereafter.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.384-389
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• 2021

This study was conducted on October 23, 2020 at the Cheongpyeong Reservoir located in Seorakmyeon, Gapyeong-gun, Gyeonggi-do, and analyzed the horizontal and vertical distribution patterns of fish based on data obtained using fishfinder. The total surface area of fishfinder survey conducted was 782,853 m², and where the water depth (WD) ranges from 10 m to 12 m is widest which 31.7% of total surface area. As a result of the heat map analysis, fish density was highest at right bank under the Gapyeong-bridge, but there was no specific pattern in horizontal distribution of fish. As a result of vertical distribution of fish analysis, 86.6% of fishes are observed at below 6 m of the fish depth (FD, distance from water surface to fish). As a result of the relative height (RH, water depth-distance from bottom to fish ratio) analysis, there was a tendency that fishes are distributed in near surface area more as the WD increased. This tendency could have various reasons such as water temperature gradient along the water depth, and further studies are required for detailed explanation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2D
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• pp.311-318
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• 2009

Interactive terrain visualization is an important research area with applications in GIS, games, virtual reality, scientific visualization and flight simulators, besides having military use. This is a complex and challenging problem considering that some applications require precise visualizations of huge data sets at real-time rates. In general, the size of data sets makes rendering at real-time difficult since the terrain data cannot fit entirely in memory. In this paper, we suggest the effective Real-time LOD(level-of-detail) algorithm for displaying the huge terrain data and processing mass geometry. We used a hierarchy structure with $4{\times}4$ and $2{\times}2$ tiles for real-time rendering of mass volume DEM which acquired from Digital map, LiDAR, DTM and DSM. Moreover, texture mapping is performed to visualize realistically while displaying height data of normalized Giga Byte level with user oriented terrain information and creating hill shade map using height data to hierarchy tile structure of file type. Large volume of terrain data was transformed to LOD data for real time visualization. This paper show the new LOD algorithm for seamless visualization, high quality, minimize the data loss and maximize the frame speed.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.94-110
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• 2003

This study utilizes the dataset of Topex/Poseidon(T/P) altimeter sea surface height (1992-2000 yr., 286 cycles)to investigate the tempore-spatial variability in the East (Japan) Sea. Optimal interpolation (Ol) technique was applied to the pre-processed T/P dataset (level 2) to produce sea surface height anomaly (SSHA) map on regular grids. Spectral analyses of the timeseries of the SSHA at chosen stations and empirical orthogonal function (EOF) analysis of the SSHA in the entire East Sea were made. Distribution of the SSHA can be divided by the southern and northern regions sharply by the polar front situated in the middle of the East Sea. The southern region under the direct influence of the Tsushima Current exhibits higher amplitude of the SSHA fluctuation, while the northern region does relatively smaller one. The spatio-temporal variability of the SSHA in the East Sea can be characterized by the five modes of the EOFs accounting for more than 85% of the total variance. The first mode dominates the SSHA variation in the entire domain with strong seasonal and inter-annual periods accounting for the 72.3% of the total variance. The other modes (up to 5th account for 14%) are responsible for the SSHA variation associated with the local current system, meandering of the polar frontal axis, and mesoscale eddies. Spectral peaks with significant confluence level show semi-annual, annual and interannual (2, 3-4 years) periods.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.2
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• pp.165-175
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• 2007

Nowadays, architecture in urban areas is dominated by the goal of spanning wide spaces and creating openings large enough to distribute daylight to building interiors. Daylight availability of building in city strongly depends not only on the building's height but also on spaces between buildings. Recently numbers of disputes over the daylight availability are increasing in high density developed areas because residents' demand for pleasant residential environment is getting stronger. Therefore in this study we constructed the three-dimensional information of buildings using LiDAR data connected with digital map and then suggested conclusions by applying it to daylight availability analysis. This study presents an approach to judge accurately the violation of a right to enjoy sunshine by using altitude and azimuths of the sun, simulating three-dimensional urban space precisely, and classifying the total duration of sunshine and the continuous duration of sunshine each householder. We expect that local government performs precisely the confirmation and permission business about urban planning and design by advising this approach.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.11 no.2
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• pp.7-15
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• 1993

In order to generate database, we need to obtain speedy and corret topographic information according to requisite purpose. Generally methods to an acquisition of topographic information are available by the use of maps, satellite images, stereo models of aerophoto and so forth. But we must choose a optimal method in consideration of area of object region, spatial solution of image, required accuracy and economic. Therefore, this study aims at providing the establish method of efficient topographic data base of small object region by means of spatial layer techniques of geo-spatial information system and using acquisition of geo-information and production method of base map with photoballoon system to obtain topographic information for reasonable plan and design of object region which select a zone preparation of a collective village with small region. As a result of this study, we decided an f-stop and a shutter speed of camera to obtain accurate stereo model and were able to obtain stereo photography and topography for small region by using of photoballoon system through accuracy analysis according to change flight height and air base speedly and economically. We can establish the data base useable to efficient plan and design as existence map with overlay plan drawing.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.2
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• pp.175-182
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• 2006

The efficient management for minimum losses and demage precautions of fragile region against coastal disasters such as seismic waves and seawater overflows is proceeding continually. This study is to analyze inundation trace and extract expected damage areas with historic records of tsunami using Geographic Information System. Creating a digital elevation model of the Mangsang and the Nobong region in the east coast, we marked inundation record of tsunami and forecasted the flood area with a seismic wave height between 3 m and 5 m. The inundation trace layers and the expected damage areas on the cadastral map layer were superimposed individually. Consequently, the range and lot numbers of inundation expected area were calculated and inundation areas of 5 m tsunami were increased by 2.8 times than 3 m tsunami in case of subject regions. Analyzed results are expected to use evacuation work in case of seismic waves and to predict the compensation of the damaged area. And this study is expected to use suitable countermeasure for prevention from natural disasters.