• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.3
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• pp.145-152
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• 2017

In this paper, GNSS(global navigation satellite system) to monitoring the fine for the construction of structure displacement based on satellite communications signals of GNSS. At the same time on USN(ubiquitous sensor network) and proposed a new approach to precise positioning by analyzing the results. A major construction structure for the safety diagnosis and prevent disaster from the risk of collapse. Precision measurement methods to mm level GNSS in that case and experiments in the application of new technologies that can most commonly used to replace the current through the permanent. The way a GNSS baseline and tested it on to prove. As a result, at our country at precise positioning and fine displacement monitoring application virtual reference station(VRS) in a GNSS mm of a margin of error of horizontal and vertical directions can be found.

• Journal of Korean Society for Geospatial Information Science
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• v.21 no.1
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• pp.11-18
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• 2013

Eulsukdo located in the Nakdong Estuary plays important role in ecosystem and coastal wetland. There have been various changes in Eulsukdo up to now. Recently, we expect a great change of the western part of shoreline in Eulsukdo due to the floodgate construction but there is few databases. In this study, shorelines were digitized after we had produced the ortho-images by using aerial photos taken for 30 years(8 times). SCE, NSM and EPR were analysed by DSAS 4.2 program using vector data. In addition, the changes of shoreline were analysed in October 2011 from before Eulsukdo water gate construction to now by adding field surveying with VRS. The amount of years shoreline change is -0.34m/yr in 2009(before water gate construction) and -0.50m/yr in 2011(during the water gate construction), and the change trend shows an accumulation aspect.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.11a
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• pp.61-64
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• 2004

현재 GPS를 이용한 위성측위시스템은 기존의 DGPS에 의한 정밀도 향상 차원을 넘어 상시관측소를 활용한 기준국의 활용 증대 및 다양한 동시 사용자의 욕구를 충족시키기 위해 여러 가지 연구들이 진행되고 있다 현재 국내 연구동향으로 VRS-RTK (Virtual Reference Station Real Time Kinematic)에 대한 기초 연구가 진행 중에 있으며 해양수산부의 전파를 이용한 비콘 방식과 표준과학연구원 천문대에서는 MBC와 연계한 FM-DARC(Data Radio Channel)방식 등이 활용 방안으로 준비중에 있으며, 여러 기관과 대학 연구 기관에서 기초 연구가 진행 중에 있다. 따라서 이미 독일, 싱가폴, 일본 등에서 활용하고 있는 VRS의 연구를 보다 심화하여 현재 각기 다른 기관에서 보유하고 있는 70여개의 GPS 상시관측소의 효율적인 활용과 대 국민 서비스를 제공할 수 있는 시스템이 절실히 필요한 시기이다. 따라서 본 논문에서는 이런 가상관측의 결과를 산출할 수 있는 통계학적 모델링을 통한 가상관측 보정값을 산출할 수 있는 보정값을 제시할 수 있는 알고리즘 개발에 그 목적이 있다. 향후 알고리즘 개발이 완료되면 통계학적 모델링을 통해 단일 기준점에 의한 GPS 측량에서 불가능한 위치 결정 네트웍의 가상 관측을 가능하게 할 것이며, 신뢰성 있는 미지정수 해를 만들 수 있을 것이다.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.1
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• pp.75-82
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• 2009

In this parer, we propose a new way of improving DGNSS service using combination of multiple SBAS information. Because SBAS uses Geostationary Earth Orbit (GEO) satellites, it has very large coverage but it can be unavailable in urban canyon because of visibility problem. R. Chen solved this problem by creating Virtual Reference Stations (VRS) using the SBAS signal [1]. VRS converts SBAS signal to RTCM signals corresponding its location, and broadcast the converted RTCM signals over the wireless internet. This method can solve the visibility problem cost effectively. Furthermore it can solve DGNSS coverage problem by creating just a transmitter instead of a reference station. Developing above method, this paper proposes the methods that integrate two or more SEAS signals into one RTCM signal and broadcast it. In Korea, MSAS signal is available even though it is not officially certified for Korean users. As a Korean own SBAS-like system, there is the internet-based KWTB (Korean WADGPS Test Bed) which we developed and released at ION GNSS 2006. As a result, virtually two different SBAS corrections are available in Korea. In this paper, we propose the integration methods for these two independent SBAS corrections and present the test results using the actual measurements from the two systems. We present the detailed algorithm for these two methods and analyze the features and performances of them. To verify the proposed methods, we conduct the experiment using the logged SBAS corrections from the two systems and the RINEX data logged at Dokdo monitoring station in Korea. The preliminary test results showed the improved performance compared to the results from two independent systems, which shows the potential of our proposed methods. In the future, the newly developed SBASs will be available and the places which can access the multiple SBAS signals will increase. At that time, the integration or combination methods of two or more SBASs will become more important. Our proposed methods can be one of the useful solutions for that. As an additional research, we need to extend this research to the system level integration such as the concept of the decentralized W ADGPS.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.3
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• pp.117-126
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• 2018

Due to intelligent transport systems, location-based applications, and augmented reality, demand for image maps and 3D (Three-Dimensional) maps is increasing. As a result, data acquisition using UAV (Unmanned Aerial Vehicles) has flourished in recent years. However, even though orthophoto map production and research using UAVs are flourishing, few studies on 3D modeling have been conducted. In this study, orthophoto and 3D modeling research was performed using various angle images acquired by a UAV. For orthophotos, accuracy was evaluated using a GPS (Global Positioning System) survey that employed VRS (Virtual Reference Station) acquired checkpoints. 3D modeling was evaluated by calculating the RMSE (Root Mean Square Error) of the difference between the outline height values of buildings obtained from the GPS survey to the corresponding 3D modeling height values. The orthophotos satisfied the acceptable accuracy of NGII (National Geographic Information Institute) for a 1/500 scale map from all angles. In the case of 3D modeling, models based on images taken at 45 degrees revealed better accuracy of building outlines than models based on images taken at 30, 60, or 75 degrees. To summarize, it was shown that for orthophotos, the accuracy for 1/500 maps was satisfied at all angles; for 3D modeling, images taken at 45 degrees produced the most accurate models.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.5
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• pp.379-388
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• 2019

Recently, a technique for acquiring spatial information data using UAV (Unmanned Aerial Vehicle) has been greatly developed. It is a very crucial issue of the GIS (Geographic Information System) mapping system that passes way point in the unmanned airframe and finally measures the accurate image and stable localization to the desired destination. Though positioning using DGPS (Differential Global Navigation System) or RTK-GPS (Real Time Kinematic-GPS) guarantee highly accurate, they are more expensive than the construction of a single positioning system using a single GPS. In the case of a low-priced single GPS system, the stability of the positioning data deteriorates. Therefore, it is necessary to supplement the uncertainty of the absolute position data of the UAV and to improve the accuracy of the current position data economically in the operating state of the UAV. The aim of this study was to present an algorithm enhancing the stability of position data in a single GPS mode of UAV with multiple GPS. First, the arrangement of multiple GPS receivers through the center of gravity of the UAV were examined. Next, MD (Mahalanobis Distance) is applied to detect instantaneous errors of GPS data in advance and eliminate outliers to increase the accuracy of previously collected multiple GPS data. Processing procedure for multiple GPS reception data by applying the center of the triangular method were presented to improve the position accuracy. Second, UAV navigation systems integrated multiple GPS through configuration of the UAV specifications were implemented. Using the unmanned airframe equipped with multiple GPS receivers, GPS data is measured with the TCM (Triangular Center Method). In addition, UAV equipped with multiple GPS were operated in study area and locational accuracy of multiple GPS of UAV with VRS (Virtual Reference Station) GNSS surveying were compared. The result showed that the error factors are compensated, and the error range are reduced, resulting in the reliability of the corrected value. In conclusion, the result in this paper is expected to realize high-precision position estimation at low cost in UAV using multiple low-cost GPS receivers.