• 한국측량학회:학술대회논문집
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• 한국측량학회 2003년도 춘계학술발표회 논문집
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• pp.55-60
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• 2003

As the distance between GPS rover station and GPS base station increases, more decorrelated positioning errors limit the ability for PDGPS(Precise Differential GPS). The objective of this paper is to present the improvement of using VRS(virtual reference station) based on multiple GPS reference station network to single reference station for static positioning in post-processing mode. For this, the VRS observations from GPS observations of real reference stations are derived by using Web service in post-mode. The coordinates of check point post-processed by 27 kind of VRS observations compared with the known ones.

• 한국측량학회지
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• 제34권4호
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• pp.425-430
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• 2016

Currently, start of the operation US GPS, the Russian Glonass, European Galileo, the Chinese Compass satellites for positioning are celebrating a true GNSS (Global Navigation Satellite System) generation. Korea is building advanced infrastructure such as a national network consisting of CORS (Continuously Operating Reference Station), VRS service for real-time precise positioning and perform continuous upgrading. However, the acquisition of geospatial information using the national infrastructure requires many steps and high dependence on foreign software part in this process. This study contributes to advanced construction technology of geospatial information by design of realtime GNSS surveying system. As a results, it has designed the surveying software that can effectively positioning realtime. Designed realtime surveying software can utilized in various fields.

• Journal of Positioning, Navigation, and Timing
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• 제11권4호
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• pp.239-244
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• 2022

R-Mode is terrestrial based Global Navigation Satellite System (GNSS) backup radio navigation technology which used existing maritime information service infrastructure. It has advantages on reduce the cost and reutilize the frequency resource. In this paper, we propose a method to develop a medium-frequency (MF) band R-Mode transmitting station by utilizing the currently operating Differential GNSS (DGNSS) reference station infrastructure. To this end, the considerations for co-operating the DGNSS reference station and the MF R-Mode transmitting station are analyzed. In this process, we also analyze what is necessary to configure the communication system as a navigation system for range measurement. Based on the analysis result, MF R-Mode transmitting station system is designed and architecture is proposed. The developed system is installed in the field, and the performance evaluation results is presented.

• Journal of Positioning, Navigation, and Timing
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• 제10권4호
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• pp.371-377
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• 2021

This research proposes the best combination of tropospheric delay models for Korean Positioning System (KPS). The overall results are based on real observation data of Japanese Quasi-Zenith satellite system (QZSS), whose constellation is similar to the proposed constellation of KPS. The tropospheric delay models are constructed as the combinations of three types of zenith path delay (ZPD) models and four types of mapping functions (MFs). Two sets of International GNSS Service (IGS) stations with the same receiver are considered. Comparison of observation residuals reveals that the ZPD models are more influential to the measurement model rather than MFs, and that the best tropospheric delay model is the combination of GPT3 with 5 degrees grid and Vienna Mapping Function 1 (VMF1). While the bias of observation residual depends on the receivers, it still remains to be further analyzed.

• Journal of Positioning, Navigation, and Timing
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• 제3권4호
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• pp.131-141
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• 2014

Over the last decade, the Global Navigation Satellite System (GNSS) has been increasingly utilized as a meteorological research tool. The Korea Astronomy and Space Science Institute (KASI) has also been developing a near real-time GNSS precipitable water vapor (PWV) information management system that can produce a precise PWV for the Korean Peninsula region using GNSS data processing and meteorological measurements. The goal of this paper is to evaluate whether the precise point positioning (PPP) strategy will be used as the new data processing strategy of the GNSS-PWV information management system. For this purpose, quality assessment has been performed by means of a comparative analysis of the troposphere zenith total delay (ZTD) estimates from KASI PPP solutions (KPS), KASI network solutions (KNS), and International GNSS Service (IGS) final troposphere products (IFTP) for ten permanent GNSS stations in the Korean Peninsula. The assessment consists largely of two steps: First, the troposphere ZTD of the KNS are compared to those of the IFTP for only DAEJ and SUWN, in which the IFTP are used as the reference. Second, the KPS are compared to the KNS for all ten GNSS stations. In this step, the KNS are used as a new reference rather than the IFTP, because it was proved in the previous step that the KNS can be a suitable reference. As a result, it was found that the ZTD values from both the KPS and the KNS followed the same overall pattern, with an RMS of 5.36 mm. When the average RMS was converted into an error of GNSS-PWV by considering the typical ratio of zenith wet delay and PWV, the GNSS-PWV error met the requirement for PWV accuracy in this application. Therefore, the PPP strategy can be used as a new data processing strategy in the near real-time GNSS-PWV information management system.

• 제어로봇시스템학회논문지
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• 제12권9호
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• pp.883-890
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• 2006

Nowadays, CPS is used widely, especially in cases which need more precise position information, such as car navigation systems and even in the mobile robot for position measuring in the outdoor environment. RTK (Real-Time Kinematics) and DGPS (Differential Global Positioning System) have more precise accuracy than the general-purposed GPS. However can't easily use them because of high prices and large size of equipments. In order fur the mobile robot to obtain precise position information it is important that CPS receiver has portability and low price. In this study, we introduce a new GPS data acquisition system that offers the precise position data using the DGPS mechanism and satisfying low cost and portability. In addition to this, we propose an improved data compensation algorithm that offers more accurate position information to the outdoor mobile robot by compensating the error rate of CPS data measured from the three points with geometrical rotation and distance formula. Proposed method is verified by comparing with the precise real position data obtained by RTK. Proposed method has more than 70% performance enhancement.

• 한국항행학회논문지
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• 제15권6호
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• pp.953-961
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• 2011

IGS(Internation GNSS Service) 초신속궤도력에 포함된 예측궤도력은 실시간 혹은 준실시간 정밀 항법에 적합한 궤도력이다. 이 논문에서는 예측궤도력에서 발생할 수 있는 궤도 이상 발생 현황을 점검하고, NANU(Current Notice Advisories to NAVSTAR Users)와 IGS 방송궤도력(BRDC, Broadcast Ephemerides)를 이용하여 예측궤도력의 이상 검출 성능을 분석하였다. 그 결과 예측궤도력은 2010년 1년간 93회의 궤도 이상이 나타났으며, NANU를 이용할 경우 88%, NANU와 BRDC를 함께 사용할 경우 95%의 이상 검출이 가능함을 확인할 수 있었다.

• 한국위성정보통신학회논문지
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• 제8권2호
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• pp.22-28
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• 2013

In this paper, new LBS (location based service) are proposed using conventional DMB (digital multimedia/mobile broadcasting) system. LBS applications are proposed that can be suitable for the subway and ground transportation based on S-DMB (satellite-DMB) and T-DMB (terrestrial-DMB) respectively. In the shaded area such as subway, the broadcasting signal transmitted from the satellite of S-DMB system should be retransmitted by the earth repeater called the gap filler and each gap filler has its own identification value called the gap filler ID which introduces the area in which the gap filler was installed. Therefore, the LBS can be implemented by using the gap filler ID of S-DMB on the subway in which the GPS (global positioning system) can't be received. Unlike the LBS on the subway, the combination of T-DMB and DGPS (differential GPS) will be introduced as a way for ground transportation. Generally, DGPS has been designed to compensate the position value calculated from the GPS signal so that positioning error of about 1 meter can be obtained by using DGPS information. T-DMB system transmitting DGPS signal will be expected to be commercial in Korea and, if using DGPS information transmitted through T-DMB network, LBS with more precise positioning than GPS alone can be implemented in the ground vehicles.

• 한국측량학회지
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• 제28권1호
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• pp.13-20
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• 2010

현재 GPS 자료처리에 사용되고 있는 소프트웨어들은 사용자의 숙련도에 따라 그 성과가 다르게 나타난다. 또한 전문가가 아닌 일반사용자가 GPS 자료처리 소프트웨어를 정상적으로 사용하는 데에는 많은 시간과 노력이 필요하다. 반면 온라인 GPS 자료처리 서비스의 경우 기술적인 노력과 시간이 필요 없이 인터넷만 연결이 되어 있다면 손쉽게 자료처리를 수행할 수 있다는 장점이 있다. 본 연구에서는 온라인 GPS 자료처리 서비스를 이용하여 국토지리정보원의 GPS 상시관측소 관측자료를 처리하고 이틀 국토지리정보원의 상시관측소 고시성과와 비교하여 위치정확도를 분석하여 온라인 GPS 자료처리 서비스를 이용한 위치결정의 활용성을 평가 하였다.

• 한국항행학회논문지
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• 제13권2호
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• pp.178-186
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• 2009

SBAS(Satellite Based Augmentation System) 시스템에서는 GNSS 사용자들의 위치 정확도 향상을 위해 위성궤도 및 시계보정정보를 제공하고 있는데, 본 논문에서는 이러한 보정정보의 정확도에 대해 분석하였다. IGS(International GNSS Service)에서 제공하는 GPS 위성의 정밀궤도력을 참값으로 가정하고, 그에 대한 오차를 이용하여 정확도를 분석/수행하였다. 이때 IGS 정밀궤도력과의 정확한 비교를 위해 GPS 위성에 대한 안테나 위상중심 편차와 P1-C1 편이를 고려하였다. SBAS 위성궤도 및 시계보정 정보로는 미국의 WAAS와 일본의 MSAS 보정정보를 이용하였다. 정확도 분석을 통해 SBAS에서 제공하는 위성궤도 보정정보와 위성시계 보정정보가 상당한 상관관계를 가지고 있음을 확인하였다. 또한 보정정보의 정확도는 SBAS 시스템의 지상 네트워크 크기와 위성의 궤적에 영향을 받는 것을 확인하였다.