• Korean Journal of Remote Sensing
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• v.38 no.5_3
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• pp.953-966
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• 2022

Since aerosols adversely affect human health, such as deteriorating air quality, quantitative observation of the distribution and characteristics of aerosols is essential. Recently, satellite-based Aerosol Optical Depth (AOD) data is used in various studies as periodic and quantitative information acquisition means on the global scale, but optical sensor-based satellite AOD images are missing in some areas with cloud conditions. In this study, we produced gap-free GeoKompsat 2A (GK-2A) Advanced Meteorological Imager (AMI) AOD hourly images after generating a Random Forest based gap-filling model using grid meteorological and geographic elements as input variables. The accuracy of the model is Mean Bias Error (MBE) of -0.002 and Root Mean Square Error (RMSE) of 0.145, which is higher than the target accuracy of the original data and considering that the target object is an atmospheric variable with Correlation Coefficient (CC) of 0.714, it is a model with sufficient explanatory power. The high temporal resolution of geostationary satellites is suitable for diurnal variation observation and is an important model for other research such as input for atmospheric correction, estimation of ground PM, analysis of small fires or pollutants.

• Journal of the Korean Association of Geographic Information Studies
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• v.27 no.3
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• pp.1-13
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• 2024

This paper proposes a cost-effective system design and user-friendly approach for the key technological elements necessary to configure an autonomous mobile robot. To implement a high-precision positioning system using an autonomous mobile robot, we established a Linux-based VRS (virtual reference station)-RTK (real-time kinematic) GNSS (global navigation satellite system) system with NTRIP (Network Transport of RTCM via Internet Protocol) client functionality. Notably, we reduced the construction cost of the GNSS positioning system by performing dynamic location analysis of the established system, without utilizing an RTK replay system. Dynamic location analysis involves sampling each point during the trajectory following of the autonomous mobile robot and comparing the location precision with ground-truth points. The proposed system ensures high positioning performance with fast sampling times and suggests a GPS waypoint system for user convenience. The centimeter-level precision GNSS information is provided at a 30Hz sampling rate, and the dead reckoning function ensures valid information even when passing through tall buildings and dense forests. The horizontal position error measured through the proposed system is 6.7cm, demonstrating a highly precise dynamic location measurement error within 10cm. The VRS network-RTK Linux system, which provides precise dynamic location information at a high sampling rate, supports a GPS waypoint planner function for user convenience, enabling easy destination setting based on GPS information.

• Ocean and Polar Research
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• v.42 no.3
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• pp.179-194
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• 2020

The present study aims to evaluate the effects of satellite-based SST (OSTIA) assimilation on a regional ocean circulation model for the Yellow and East China Seas (YECS), using three different assimilation methods: the Ensemble Optimal Interpolation (EnOI), Ensemble Kalman Filter (EnKF), and 4-Dimensional Variational (4DVAR) techniques, which are widely used in the ocean modeling communities. The model experiments show that an improved initial condition by assimilating the SST affects the seasonal water temperature and water mass distributions of the YECS. In particular, the SST data assimilation influences the temperature structures horizontally and vertically in winter, thereby improving the behavior of the YS warm current water. This is due to the fact that during wintertime the water column is well mixed, which is directly updated by the SST assimilation. The model comparisons indicate that the SST assimilation can improve the model performance in resolving the subsurface structures in wintertime, but has a relatively small impact in summertime due to the strong stratification. The differences among the different assimilation experiments are obvious when the SST was sharply changed due to a typhoon passage. Overall, the EnKF and 4DVAR show better agreement with the observations than the EnOI. The relatively low performance of EnOI under storm conditions may be related with a limitation of EnOI method whereby an analysis is obtained from a number of climatological fields, and thus the typhoon-induced SST changes in short-time scales may not be adequately reflected in the data assimilation.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.3
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• pp.229-236
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• 2001

One of the basic tasks in hydrological analysis is to delineate drainage basins and channel networks. Characteristics of channel networks and drainage basin parameters have been used widely in hydrologic calculation and modeling. DEMs(Digital Elevation Models) are generally used to automatically map the channel networks and to delineate drainage basins. This paper presents an effort to analyze basin characteristics using various DEMs. The quantitative analysis of channel networks begins with Horton's method of classifying stream according to Horton orders in hydro-geomorphy. HGSIS(Hydro-Geo-Spatial Information System) is possible to extract parameters. Usually, hydrologists. surveyors and GSIS researchers have some difficulties in accessing satellite images and in extracting DEMs from them. Therefore, the extracted DEMs from contours of digital map is widely used to have the basic works of hydrological analysis. This study presents proper DEMs to calculate Horton's orders, width function, drainage area, main channel length, total channel length, basin elevation and basin slope at digital map of 1:25,000 scale.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.315-328
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• 2004

In this paper, we present a good example of extreme solar and geomagnetic activities from October to November, 2003. These activities are characterized by very large sunspot groups, X-class solar flares, strong particle events, and huge geomagnetic storms. We discuss ground-based and space-based data in terms of space weather scales. Especially, we present several solar and geomagnetic disturbance data produced in Korea : sunspots, geo-magnetograms, aurora, Ionogram, and Total Electron Content (TEC) map by GPS data. Finally, we introduce some examples of the satellite orbit and communication effects caused by these activities; e.g., the disturbances of the KOMPSAT-1 operational orbit and HF communication.

• Proceedings of the Korea Contents Association Conference
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• 2003.05a
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• pp.255-259
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• 2003

The technique of birdeye image generation of terrain through the use of satellite digital images and digital maps are very important elements and have applications in planning establishment as well as the actual design of several construction work in complex fields. This paper studies stereo perspective image generation as a possibility through 3-dimensional analysis combined with digital elevation data and remotely sensed images. For this, first of all, ortho-images generated by very accurate GCP and DEM from contour file makes 3-dimensional terrain analysis possible and allows stereo-viewing at the highway construction planning sites. So, we developed the technical methods for the 3-dimensional approach on the planning sites of highways by use of perspective orthoimages. From this research diverse terrain analysis is possible through stereo perspective image generation, and can leads to various application in road construction through gain study results from access to realtime virtual spatial on the objects area in korea.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.216-219
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• 2004

In this study, the concept and techniques to generate the level lA, lB and 2A image products have been reviewed. In particular, radiometric and geometric corrections and bands registration used to generate level lA, lB and 2A products have been focused in this study. Radiometric correction is performed to take into account radiometric gain and offset calculated by compensating the detector response non-uniformity. And, in order to compensate satellite altitude, attitude, skew effects, earth rotation and earth curvature, some geometric parameters for geometric corrections are computed and applied. Bands registration process using the matching function between a geometry, which is called 'reference geometry', and another one which is corresponds to the image to be registered is applied to images in case of multi-spectral imaging mode. In order to generate level-lA image products, a simple radiometric processing is applied to a level-0 image. Level-lB image has the same radiometry correction as a level-lA image, but is also issued from some geometric corrections in order to compensate skew effects, Earth rotation effects and spectral misregistration. Level-2A image is generated using some geo-referencing parameters computed by ephemeris data, orbit attitudes and sensor angles. Level lA image is tested by visual analysis. The difference between distances calculated level 1 B image and distances of real coordinate is tested. Level 2A image is tested Using checking points.

• Proceedings of the KSRS Conference
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• 2007.03a
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• pp.92-96
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• 2007

전라남도 국민참여형 위성영상 블로그 시스템은 2006년도 행정자치부 자치단체정보화지원사업의 일환으로 구축된 것으로서， 사용자가 고해상도 위성영상 위에 직접 자신의 글，사진， 동영상을 올리고，이를 다른 사용자나 시스템과 공유할 수 있도록 구축된 시스템이다. 본 시스템이 궁극적으로 구현하고자 했던 과제는 다음과 같다. (1)지리정보 혹은 기타 정보의 고정성을 탈피하고，(2)지리정보와 멀티미디어 자료의 효율적 통합을 통해 geoUCC를 구축하며，(3)사용자의 참여를 통한 지리정보 제공 방식의 쌍방향성을 구현하여，(4) 사용자를 일방적 자료 활용자에서 자료 생성자로 발전시키고 궁극적으로는 자치단체와 국민 간 새로운 방식의 소통 방식을 생성하는 것이다. 본 시스템 구축의 결과로서 본 시스템에서 일반 국민에게 서비스되는 내용은 다음과 같다. (1) 전라남도 전역의 1m급 고해상도 위성영상의 대국민 서비스，(2)전라남도 전역에 대한 지번 단위까지의 주소 검색 서비스，(3)웹 상에서의 실시간 3차원 GIS 서비스，(4)Web2.0의 철학을 반영한 RSS, Trackback 및 Tag 검색 기능，(5)사용자가 직접 고해상도 위성영상 위에 자신의 글， 사진，동영상，홈페이지 등을 올릴 수 있는 "위성영상 블로그 쓰기 기능"，(6)국내 거의 모든 포털 사이트의 블로그와 홈페이지를 지원하는 시스템 연계(퍼가기) 기능 등이다. 결론적으로 본 시스템의 사용자는 고해상도 위성영상 기반의 지도 위에 자신의 여행기，사진， 동영상을 올림으로써 자신만의 사용자제작콘텐츠(UCC)를 생성할 수 있을 뿐만 아니라， 이를 다른 사용자와 공유， 활용함으로써 실질적인 쌍방향，참여형 지리정보시스템을 이용하게 된 것이다.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.4
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• pp.211-221
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• 2017

Ellipsodially referenced survey (ERS) is considered as one of the challenging issues in the hydrographic surveys due to the fact that the bathymetric data collected by this technique can be readily transformed either to the geodetic or the chart datum by application of some geoscientific models. Global Navigation Satellite Systems (GNSS) is a preferred technique to determine the ellipsoidal height of a vessel reference point (RP) because it provides cost-effective and unprecedentedly accurate positioning solutions. Especially, the GNSS-derived heights include heave and dynamic draft of a vessel, so as for the reduced bathymetric solutions to be potentially free from these corrections. Although over the last few decades, differential GNSS (DGNSS) has been widely adopted in the bathymetric surveys, it only provides limited accuracy of the vertical component. This technical barrier can be effectively overcome by adopting the so-called GNSS carrier phase (CPH) based techniques, enhancing accuracy of the height solution up to few centimeters. From the positioning algorithm standpoint, the CPH-based techniques are categorized under absolute and relative positioning in post-processing mode; the former is precise point positioning (PPP) correcting errors by the global or regional models, the latter is post-processed kinematic positioning (PPK) that uses the differencing technique to common error sources between two receivers. This study has focused on assessment of achievable accuracy of the ellipsoidal heights obtained from these CPH-based techniques with a view to their applications to hydrographic surveys where project area is, especially, few tens to hundreds kilometers away from the shore. Some field trials have been designed and performed so as to collect GNSS observables on static and kinematic mode. In this paper, details of these tests and processed results are presented and discussed.

• Spatial Information Research
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• v.17 no.2
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• pp.171-181
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• 2009

In Web2.0 environment, with advanced platform technologies, global vendors such as Google, Microsoft and Yahoo provide competitive geospatial services based on global map and satellite image. But the relatively low level of platform technologies has not rapidly increased the land information and geospatial service markets in Korea. For the ubiquitous next generation Internet, as a one of the R&D projects by Korean Land Spatialization Group, the project for platform technologies has being made to provide customized land information and geospatial service. The platform technologies can be categorized for streamming, mashup and geosearch. More specifically, the 2D/3D Hybird streamming engine, mashup engine for u-GIS service and next generation search engine for land information have being developed. In this context, the strategies for efficient development and use of geoweb platform technologies are required. This study surveys the present geospatial products and services using of platform technologies to propose the strategies for efficient development and use of platform technologies. The strategies for efficient development and use of platform technologies can be proposed focusing on target market and each of platform technologies.