• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2573-2575
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• 2005

본 논문에서는 원자 시계를 이용한 위성 시계 고장 판단 기법을 제안한다. GPS 측정치 중 위성 시계 오차 성분을 제외한 위성 궤도 오차, 이온층 지연 오차, 대류층 지연 오차, 수신기 시계 오차를 제거하여 위성 시계 오차에 의한 영향만을 검사하도록 한다. 특히 TCXO와 같은 일반적인 수신기 시계를 사용할 경우 정확한 수신기 시계 오차 크기를 추정하기 어렵기 때문에 원자 시계와 같은 정밀 신호 발생기를 이용하여 수신기 시계 오차에 의한 영향을 제거하는 방법을 제시한다. 제시한 방법은 실제 위성 시계에 이상이 발생 했을 때 수집한 데이터를 이용한 실험을 통하여 검증하도록 한다.

• Journal of IKEEE
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• v.20 no.2
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• pp.143-151
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• 2016

Smart care surveillance system can take the position information of the user and monitor by controlling neighbor CCTVs using GPS receiver built into smart device. But because the position information contains a significant error, in general smart device, it is necessary to be corrected for precise monitoring. In previous smart care system, this error is corrected by using a plurality of CCTV. But it has disadvantage that two or more CCTVs pointed toward the same point at the same time. In this paper, we propose the method to correct error of the GPS location information by using only one CCTV. With experiment result, we find that the accuracy of GPS location information corrected with only one CCTV is as improved as two CCTVs.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.04a
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• pp.433-441
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• 2003

최근 SA(Selective Availability)의 해제에 따른 GPS의 활용이 증대되면서 차량운행에 있어서도 저가 GPS 수신기의 활용이 활발하게 이루어지고 있으며, 일반 차량 운행자를 위한 상용화가 급속도로 이루어지고 있다. 하지만 저가 GPS수신기를 통한 실시간 위치정보의 제공은 실질적으로 상당한 오차를 포함하고 있다. 이는 저가 수신기가 가지고 있는 문제라 할 수 있다. 이에 본 연구에서는 저가 수신기와 정밀 측위용 이주파 수신기를 이용하여 측지분야에서 검증된 GPS측량방법을 통해 오차를 비교ㆍ분석하고 저가 수신기의 정확도 향상을 위한 방법을 제시하고자 하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.4
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• pp.337-345
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• 2007

National Geographic Information Institute has installed the first permanent Global Positioning System (GPS) station SUWN in 1995 and, as of today, the number of sites is 14. In this study, we visited all the 14 stations and determined if the site mount and antenna configuration conforms to the international site guidelines published by International GNSS Service and National Geodetic Survey. The environment around each station was also checked for the possibility of causing positioning errors. In addition, the GPS data quality was evaluated using the quality-checking program called TEQC. As a result of site visits, we found that low stations (TABK, CHJU, KWNJ, and WNJU) have unfavorable environment and TEQC results validated it. TEQC results also showed that the GPS receiver change during years 2005-2006 reduced the multipath errors and the number of cycle slips at every station.

• Journal of Astronomy and Space Sciences
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• v.22 no.4
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• pp.491-500
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• 2005

Every time laboratory in the world follows an international standard time scale and GPS (Global Positioning System) is playing an important role. Korea Research Institute of Standards and Science is also operating a permanent GPS station for time transfer. To improve the accuracy and precision of the clock offsets derived from GPS we used carrier phase measurements. In addition, we tested four different kinds of GPS satellite orbits and compared the results. The precision of the time offsets using rapid and ultra-rapid orbits was about 0.5 nanoseconds (ns). Tn the case of broadcast orbits, the precision was better than 2 ns.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.1
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• pp.37-42
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• 2009

The accuracy of RTK GPS is limited by the distance dependent errors from orbit, ionosphere and troposphere, as the distance between the rover and the base station increases in the Real Time Kinematic surveying. To solve this problem, VRS system has installed. This study would estimated the accuracy of cadastral detail surveying, which is used on the VRS RTK instead of Total Station and RTK GPS demand for various equipments and time. As a result of study, the positioning accuracy of the VRS RTK and RTK GPS surveying make no greate difference, as RMSE of VRS RTK surveying is 0.144m and that of RTK GPS surveying is 0.146m and the new method would be more efficient.

• Spatial Information Research
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• v.13 no.1 s.32
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• pp.31-41
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• 2005

In order to carry out aerial photogrammetry using GPS/INS, it is necessary to apply exterior orientation parameters, obtained while making a photo, to the editing process. It should be noted that the verification process of aerial mapping result is the most crucial process at the GPS/INS based digital photogrammetry. To this end, this study has compared the mapping result by the ways of AT results, plotter, and orientation, which is from basis of the Analytical raw map produced by the existing AT results. When comparing the horizontal and vertical accuracy of the analytical mapping with that of digital restitution, it could be found that the latter is more accurate than that of the former. In addition, it was reveled that the horizontal error was bigger than that of vertical one. Even though the accuracy of the GPS/INS based AT Direct orientation was three times poorer than the of indirect one, it was recognized that the photogrammetry process was effectively performed in the application of scale 1:5000 mapping with satisfying the allowance errors.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.1
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• pp.47-54
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• 2014

Precise Point Positioning (PPP) algorithms using GPS code pseudo-range measurements were developed and their accuracy was validated for the purpose of implementing them on a portable device. The group delay, relativistic effect, and satellite-antenna phase center offset models were applied as fundamental corrections for PPP. GPS satellite orbit and clock offsets were taken from the International GNSS Service official products which were interpolated using the best available algorithms. Tropospheric and ionospheric delays were obtained by applying mapping functions to the outputs from scientific GPS data processing software and Global Ionosphere Maps, respectively. When the developed algorithms were tested for four days of data, the horizontal and vertical positioning accuracies were 0.8-1.6 and 1.6-2.2 meters, respectively. This level of performance is comparable to that of Differential GPS, and further improvements and fine-tuning of this suite of PPP algorithms and its implementation at a portable device should be utilized in a variety of surveying and Location-Based Service applications.

• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.536-542
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• 2011

This paper considers the performance of tightly-coupled GPS/INS integration using total-state UKF (Unscented Kalman Filter) for multipath error. In the city canyon there exists large multipath error and it may happen that GPS satellites are seen only three or less. For these situations simulations show that the performance of total-state UKF is better than that of EKF in the presence of multipath error. The total-state UKF shows robust performance for multipath error.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1043-1044
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• 2009

본 논문에서는 GPS 편차 정보를 이용하여 도로 네트워크 지도 제작시 불가피하게 발생하는 오차를 탐지하는 기법을 제안한다. 제안된 기법은 수십에서 수백 킬로미터 범위에 위치한 노드들이 공통적인 GPS오차를 겪는다는 점에 착안하고 있으며 각 도로 네트워크의 차량들이 동시간에 보고하는 위치 좌표를 이용하여 맵 매칭을 수행한 후 해당 시간스탬프의 오차를 계산한다. 이 오차를 이용하여 각 위치 좌표들를 보정한 후 다시 맵 매칭을 수행하여 맵 매칭의 오류가 한계치 이하라면 보고된 위치에 해당하는 도로들은 정확하게 플롯되어 있음을 알 수 있다. 이와 같은 통계들이 오랜 시간동안 쌓인다면 별도의 장비나 통신채널을 사용하지 않고 소프트웨어만으로 도로망 지도의 정확성을 검증할 수 있다.