• Journal of Fisheries and Marine Sciences Education
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• v.3 no.2
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• pp.19-28
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• 1991

The United States has been developing a GPS(Global Positoning System), and now we can make use of it everywhere in the world. The author measured the usable time and took position fixes from three fixed stations in Japan in order to evaluate the positioning accuracy of GPS, firstly by the difference in the time of the year and, secondly by the difference in location between the stations in 1988. I was able to receive positioning signals from only 6 or 7 satellites, but in July 1991, 14 GPS satellites became available. The results obtained are summerized as follows: 1) The usable time was 7~9 hours from only 6~7 satellites. 2) In the case of the former, the time zone of position fixes varied with the time of the year and there were a little differences of the accuracy of position fixes except 3H(three dimensiomal high level positioning). In the case of the latter, there were not obvious locality differences in 3D(three dimensional positioning). But the positioning errors and number of data varied on each level in 2D(two dimensiomal positioning), although the positioning errors were smaller than 0.1 nautical mile. 3) Th standard deviations of Dep(departure) were larger than tat of D.lat(difference of latitude), and varied widely to the east and west. But the standard deviations were smaller than 100 meters.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.216-216
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• 2011

목포는 지형 특성상 도시기반이 낮게 조성되어 있어 폭풍해일에 의한 영향이 그리 크지 않더라도 조위가 크게 상승하는 대조기에 해안 저지대에서는 침수범람이 빈번하게 발생하는 지역이다. 특히 1997년 8월 태풍 WINNIE(9713)와 2004년 7월 태풍 MINDULLE(0407)의 간접영향시기가 대조기 고조와 중첩됨에 따라 목포 내항 및 북항 일대에 해수범람 피해가 발생한 바 있으며, 이러한 피해에 대응하여 목포 해안시설물 표고는 1997년 이전의 D.L.(+)480~500cm(목포지방해양수산청, 1998)를 D.L.(+)550cm로 증고한 상태이다. 태풍이 발생하여 내습하는 시기에 해당하는 2010년 7월~9월까지 목포지역 조석예보표(www.khoa.go.kr)에 따르면 거의 매달 500cm 이상의 조위가 예측(최고 511cm, 2010년 8월 11일)되었고, 2004년 범람이 발생한 7월과 8월에는 5.2m 이상의 조위가 3회 이상 예측된 바 있다. 또한 2000년 이후 목포지역의 태풍에 의한 해일고가 매년 50cm 내외로 기록(최고 59 cm, 태풍 RUSA(0215)됨을 고려할 때 D.L.(+)550cm의 목포 해안시설물 표고는 범람피해로부터 안전을 확보하기에는 어려움이 있을 것으로 우려된다. 특히, 최근 2년 동안은 우리나라에 직접 영향을 미친 태풍이 없었으나, 올해 8월 중순에는 대조기에 태풍 DIANMU(1004)가 내습하여 남해안 일대에 피해가 발생하였고, 올해 9월 초에 서해안으로 상륙한 태풍 KOMPASU(1007)는 강한 세력을 유지하면서 북상하여 서해안 일대 및 수도권에 큰 피해가 발생하였다. 만약 태풍 KOMPASU(1007)가 태풍 DIANMU(1004)가 내습했던 대조기 또는 9월 중순의 대조기에 내습했다고 가정한다면, 목포와 같은 서남해안의 저지대는 물론 많은 해안지역에 엄청난 피해가 발생했을 것으로 사료된다. 이에 본 연구에서는 관련연구와 자료분석을 통해 목포해역의 침수범람 위험성을 파악하고, 올해 발생한 태풍의 수치모의 적용을 통해 위험성을 검토하고자 한다.

• Geophysics and Geophysical Exploration
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• v.22 no.1
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• pp.21-28
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• 2019

We perform a 3D tomographic inversion using surface wave dispersion curves to obtain S-velocity model and radial anisotropy beneath Saudi Arabia. The Arabian Peninsula is geologically and topographically divided into a shield and a platform. We used event data with magnitudes larger than 5.5 and epicentral distances shorter than $40^{\circ}$ during 2008 ~ 2014 from the Saudi Geological Survey. We obtained dispersion curves by using the multiple filtering technique after preprocessing the event data. We constructed SH- and SV-velocity models and consequently radial anisotropy model at 10 ~ 60 km depths by inverting Love and Rayleigh group velocity dispersion curves with period ranges of 5 ~ 140 s, respectively. We observe high-velocity anomalies beneath the Arabian shield at 10 ~ 30 km depths and low-velocity anomalies beneath the Arabian platform at 10 km depth in the SV-velocity model. This discrepancy may be caused by the difference between the Arabian shield and the Arabian platform, that is, the Arabian shield was formed in Proterozoic thereby old and cold, while the Arabian platform is covered by predominant Paleozoic, Mesozoic, and Cenozoic sedimentary layers. Also we obtained radial anisotropy by estimating the differences between SH- and SV-velocity models. Positive anisotropy is observed, which may be generated by lateral tension due to the slab pull of subducting slabs along the Zagros belt.

• Journal of Korean Society for Geospatial Information Science
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• v.24 no.3
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• pp.59-66
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• 2016

The 2011 debris flow in Mt. Umyeonsan in Seoul, South Korea caused significant damages to the surrounding urban area, unlike other similar incidents reported to have occurred in the past in the country's mountainous regions. Accordingly, landslides and debris flows cause damage in various surroundings, regardless of mountainous area and urban area, at a great speed and with enormous impact. Hence, many researchers attempted to forecast the extent of impact of debris flows to help minimize the damage. The most fundamental part in forecasting the impact extent of debris flow is to understand the debris flow behavior and sedimentation mechanism in complex three-dimensional topography. To understand sedimentation mechanism, in particular, it is necessary to calculate the amount of energy and erosion according to debris flow behavior. The previously developed debris flow models, however, are limited in their ability to calculate the erosion amount of debris flow. This study calculated the extent of damage caused by a massive debris flow that occurred in 2011 in Seoul's urban area adjacent to Mt. Umyeonsan by using DEM, created from aerial photography and airborne LiDAR data, for both before and after the damage; and developed and compared a debris flow behavioral analysis model that can assess the amount of erosion based on energy theory. In addition, simulations using the existing debris flow model (RWM, Debris 2D) and a comprehensive comparison of debris flow-stricken areas were performed in the same study area.

• Journal of the Korean Association of Geographic Information Studies
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• v.21 no.3
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• pp.127-137
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• 2018

Recently, UAVs and Drones have been used for various applications. In particular, in the field of surveying, there are studies on the technology for monitoring the terrain based on the high resolution image data obtained by using the UAV-equipped digital camera or various sensors, or for generating high resolution orthoimage, DSM, and DEM. In this study, we analyzed the accuracy of GCP(Ground control point) matching using UAV and VRS-GPS. First, we used VRS-GPS to pre-empt the ground reference point, and then imaged at a base altitude of 150m using UAV. To obtain DSM and orthographic images of 646 images, RMSE was analyzed using pix4d mapper version As a result, even if the number of GCP matches is more than five, the error range of the national basic map(scale : 1/5,000) production work regulations is observed, and it is judged that the digital map revision and gauging work can be utilized sufficiently.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.408-417
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• 2016

The frequent regional torrential or heavy rain and typhoon mostly caused by climate change has resulted in sediment disasters particularly in mountainous or hilly areas. More than 65% of South Korea is mountainous and development and rapid urbanization has brought lots of steep sloping industrial complexes, which are adjacent to cities. Such continuous urbanization and industrialization can result in an increase in serious damage to those places. Korea has very high population density so sediment disaster could result in a tremendous loss of property and life. A recent 10-year (2001~2010) study of the average annual loss shows 68 casualties and property loss of 1.7044 trillion Won(?), which indicates a 20% and 25% decrease for both life and property, respectively, but urban areas are experiencing increasing damage. In this paper, a comprehensive simulator composed by references, analyses, and the recent technologies was applied to visualize the scale of the damaged Woomyeon-san (Mt.) and verify the performance of the simulator.

• Korean Journal of Remote Sensing
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• v.25 no.4
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• pp.383-389
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• 2009

The main objective of the research is a feasibility study on the intertidal zone using a X-band radar satellite, TerraSAR-X. The TerraSAR-X data have been acquired in the west coast of Korea where large tidal flats, Ganghwa and Yeongjong tidal flats, are developed. Investigations include: 1) waterline and backscattering characteristics of the high resolution X-band images in tidal flats; 2) polarimetric signature of halophytes (or salt marsh plants), specifically Suaeda japonica; and 3) phase and coherence of interferometric pairs. Waterlines from TerraSAR-X data satisfy the requirement of horizontal accuracy of 60 m that corresponds to 20 cm in average height difference while current other spaceborne SAR systems could not meet the requirement. HH-polarization was the best for extraction of waterline, and its geometric position is reliable due to the short wavelength and accurate orbit control of the TerraSAR-X. A halophyte or salt marsh plant, Suaeda japonica, is an indicator of local sea level change. From X-band ground radar measurements, a dual polarization of VV/VH-pol. is anticipated to be the best for detection of the plant with about 9 dB difference at 35 degree incidence angle. However, TerraSAR-X HH/TV dual polarization was turned to be more effective for salt marsh monitoring. The HH-HV value was the maximum of about 7.9 dB at 31.6 degree incidence angle, which is fairly consistent with the results of X-band ground radar measurement. The boundary of salt marsh is effectively traceable specifically by TerraSAR-X cross-polarization data. While interferometric phase is not coherent within normal tidal flat, areas of salt marsh where the landization is preceded show coherent interferometric phases regardless of seasons or tide conditions. Although TerraSAR-X interferometry may not be effective to directly measure height or changes in tidal flat surface, TanDEM-X or other future X-band SAR tandem missions within one-day interval would be useful for mapping tidal flat topography.

• Spatial Information Research
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• v.23 no.4
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• pp.13-22
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• 2015

There has been much interest in the VWorld open platform with the addition of a variety of contents or services such as 2D map, 3D terrain, 3D buildings, and thematic map since 2012. However, the VWorld system architecture was not stable for the system overload. For example, the system was stopped due to the rapidly increasing user accesses when the 3D terrain service of the North Korea and the Baekdu mountain was launched at September 2012 and September 2013, respectively. It was because the system architect has just extended the server system and the network bandwidth whenever the rapid increase of user accesses occurs or new service starts. Therefore, this study proposes a new VWorld system architecture that can reliably serve the huge volume of National Spatial Data by applying the new technologies such as CDN, visualization and clustering. Finally, it is expected that the results of this study can be used as a basis for the next VWorld system architecture being capable of a huge volume of spatial data and users.

• Journal of the Korean Association of Geographic Information Studies
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• v.7 no.1
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• pp.75-83
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• 2004

In Korea the number of forest fire occurrence and its damaged area have increased drastically and the plans for afforestation such as sound erosion control restoration and forestation have performed to restore for forest fire damaged area. In this study fire resistant forest was developed by selecting fire resistance tree species and applying GIS analysis, considering the characteristic of forest fire and location environment in forest fire damaged area along the east coast. Moreover, it showed the possibility of how spatial information technology such as virtual GIS could be applied during restoring forest fire damaged area and approaching landscape ecology researches. Especially the fire resistant forest was established by using GIS analysis against large scaled forest fires then the best forest arrangement was performed through this fire resistant forest species and 3D modeling in study area. In addition, the forest landscape was established through site index on passing years and then 3D topography and tracking simulation, which is very similar to real world, were constructed by using virtual GIS.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.2
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• pp.117-131
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• 2007

Representation of building internal space is an active research area as the need for more geometrically accurate and visually realistic increases. 3 dimensional representation is common ground of research for disciplines such as computer graphics, architectural design and engineering and Geographic Information System (GIS). In many cases CAD plans are the starting point of reconstruction of 3D building models. The main objectives of building reconstruction in GIS applications are visualization and spatial analysis. Hence, CAD plans need to be preprocessed and edited to adapt to the data models of GIS SW and then georeferenced to enable spatial analysis. This study automated the preprocessing of CAD data using AutoCAD VBA (Visual Basic Application), and the processed data was topologically restructured for further analysis in GIS environment. Accuracy of georeferencing CAD data was also examined by comparing the results of coordinate transformation by using digital maps and GPS measurements as the sources of ground control points. The reconstructed buildings were then applied to visualization and network modeling.