• Journal of Navigation and Port Research
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• v.37 no.1
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• pp.35-40
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• 2013

In the eLoran navigation system, the dominant deterioration factors of navigation accuracy are the TOA measurement errors on user receiver and the GDOP between the receiver and the transmitters. But if the ASF data measured at dLoran reference station are provided for users through the Loran data channel, it will be possible to correct the TOA measurement errors. The position accuracy can be determined by the DOP depending on the geometry of receiver-transmitters, and their optimal placement improves the navigation accuracy. In this study we determined the geometric placement in case of up to six stations, and evaluated the performance of position accuracy for the receiver-transmitter geometry set of eLoran stations. The proposed geometry of eLoran stations can be referred for the construction of eLoran infrastructure meeting the capability of HEA for maritime, and time/frequency users in Korea.

• Journal of Navigation and Port Research
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• v.38 no.4
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• pp.391-397
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• 2014

Wide Area Differential GNSS(WA-DGNSS) was developed in order to improve the accuracy and integrity performance of GNSS. In this paper, overall structure of Pseudolite-Based Augmentation System(PBAS) and experimental methods which enables the post-processing test with commercial receiver will be described. For generating augmenting message, GPS measurement collected from five NDGPS reference stations were processed by reference station S/W and master station S/W. The accuracy of augmenting message was tested by comparing SP3, IONEX data. In the test, RF signal of user was collected and correction data were generated. After that, RF signal was broadcasted with pseudolite signal. Test was conducted using three commercial receiver and the performance was compared with MSAS and standalone user. From the position output of each receiver, it was shown that improved position was obtained by applying augmenting message.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.3 s.21
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• pp.107-114
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• 2002

The cadastral surveying is essential for the effective management of a country, the D/B building of NGIS. Many of GPS applications require a positioning accuracy of several centimeters for rover in real-times. But, to achieve higher positioning accuracies in real-time, the double differencing technique should be implemented using carrier phase data. Corrected observations at the reference station can be transmitted and used to form double difference observations at the rover using a data link. In this study, the area accuracy of cadastral survey using the RTK GPS will be assessed, and will produce area of parcel of land. As the result of comparison among area by TS, planer surveying and RTK GPS. parcels-register for site is analyzed by this data. The results show that mean error of area calculated min. $2.42m^{2}{\sim}\;max.\;13.69m^{2}$ and RMSE calculated min. $0.00329\;{\sim}\;max.\;0.01846$.

• Journal of Navigation and Port Research
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• v.36 no.8
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• pp.625-630
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• 2012

The DGNSS Central Office operates 17 DGNSS reference stations. Compared to the other DGNSS sites, the TEQC data quality of some sites is poorer. In this study, we tried to find out the causes that degrade the quality of GPS data for the purpose of improving the signal quality of the DGNSS stations. We selected the Chungju station that is the one of those stations with bad data quality. Through the on-site visit, we found that there is no signal-blocking obstacles. In addition to site surveys, we conducted two experiments; simultaneous observation considering environmental factors and comparison test through equipment replacements to check the malfunctioning of GPS equipments. In the simultaneous test results, we realized that environmental factors do not induce any bad effects on the data quality. In equipment replacement experiments, we confirmed that the data quality is of excellent quality when the test receiver was used instead of the original one installed at the site. When we replaced the antenna instead of the receiver, the data quality was bad. Through those two experiments, we concluded that the receiver is the main factor that degrades the signal quality.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.10a
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• pp.280-282
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• 2014

DMB 기반 DGPS 시스템은 기존 중파 DGPS의 음영구역 해소 및 내륙에서의 DGPS 이용자 활성화를 목적으로 개발된 전달매체이다. 본 연구는 향후 유동인구와 교통량이 많아 이용 수요가 크게 예상되며, 멀티패스 등의 영향으로 측위 오차가 큰 도심에서 저가형 수신기를 이용하여 실제 기준국 및 가상 기준국의 DGPS 보정정보를 DMB 기반으로 수신하여 수신환경 수신기별 정지측량과 이동측위를 측정한 결과를 분석하였다.

• Journal of Advanced Navigation Technology
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• v.14 no.2
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• pp.151-160
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• 2010

For the realization of future intelligent transportation systems, fine-grained lane-by-lane traffic monitoring and control functionalities are among the most important technology barriers to overcome. To satisfy the accuracy requirement for traffic monitoring, a GNSS receiver network is designed. The designed receiver network consists of three different types of entities; reference server, broadcaster, and client. For deployment flexibility, all the entities utilize the international message standard RTCM SC-104 version 3.0. For fine-grained traffic monitoring, the client is designed to utilize position-domain carrier-smoothed-code filters to provide accurate vehicle coordinates in spite of frequent addages and outages of visible satellites. An experiment result is presented to evaluate the positioning accuracy of the proposed method.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.25-26
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• 2011

사용자 의사거리 보정 잔차(UDRE)는 위성항법보정정보의 측위성능을 예측하는데 이용하는 매우 중요한 무결성 감시정보이다. 위성항법보정정보 사용자는 위성별로 제공되는 사용자 의사거리 보정 잔차 정보를 이용하여 목표로 하는 측위성능을 보장할 수 있는지 여부를 계산하고, 이 결과를 반영하여 위성항법보강시스템의 보정정보를 사용할지 아니면, 무시할지를 판단한다. 즉, 사용자 의사거리 보정 잔차는 위성별로 제공되는 보정정보를 이용하여 보정을 한 후에도 제거되지 않고 남는 위성과 사용자 수신기 간의 통계학적 거리 오차로서 가우시안 분포를 갖는다고 본다. 따라서 동일한 위성항법신호 환경이라도 위성항법보강시스템의 종류와 응용분야별로 다르게 설정되는 측위성능의 보장 수준에 따라 사용자 의사거리 보정 잔차는 다른 값을 갖게 된다. 본 논문은 위성항법보강시스템의 무결성 감시성능에 영향을 미치는 사용자 의사거리 보정 잔차 추정기법의 성능해석을 목적으로 다중 기준국 원시정보를 이용한 사용자 의사거리 보정 잔차 추정기법 구조분석과 영향력을 소개하고, 성능에 영향을 미치는 인자와 사용자 의사거리 보정 잔차 추정성능의 지표에 대해 정의한다. 그리고 마지막으로 성능해석의 방법을 제안하고, 타당성을 검증한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.29-30
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• 2011

GNSS 시스템의 다원화에 따른 DGPS RSIM 기능도 DGNSS 체제로 기능적, 시스템적 고도화가 필요한 시점이 도래하고 있다. 이와 관련하여 차세대 DGNSS RSIM 아키텍처를 미국 해양경비대(USCG) NAVCEN에서 제안하였는데, 이 차세대 DGPS RSIM 아키텍처의 기본 요구조건은 PC 플랫폼 기반의 신규 신호 및 기술에 대한 충분한 유연성을 확보할 수 있고, 기존 사용자 수신기와 기존 기준국 시스템과의 충분한 호환이 가능해야 한다는 것이다. 그러나 위의 제시된 아키텍처는 DGPS RSIM 시스템의 소프트웨어 응용에 초점이 맞추어져 있어서 GNSS 다원화에 따른 DGNSS 기준국 기능 고도화에 한계가 있다. 그러므로 본 논문에서는 소프트웨어 DGNSS RSIM 개발을 위한 후속연구로서, 현재 운영 중인 GPS/GLONASS를 중심으로 보정정보 생성 및 그 측위정확도 성능분석에 중점을 두고자 한다. 기 설계된 DGNSS 소프트웨어 RSIM 아키텍처에 대해 설명하고, 설계된 아키텍처와 통합보정정보 생성 및 처리 기법이 적용된 GPS/GLONASS 통합보정시스템을 구현하여, 향후 소프트웨어 DGNSS RSIM을 위한 측위정확도 측면에서의 성능을 분석한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.135-143
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• 2009

Integrating the Global Positioning System (GPS) and Inertial Navigation System (INS) sensor technologies using the precise GPS Carrier phase measurements is a methodology that has been widely applied in those application fields requiring accurate and reliable positioning and attitude determination; ranging from 'kinematic geodesy', to mobile mapping and imaging, to precise navigation. However, such integrated system may not fulfil the demanding performance requirements when the baseline length between reference and mobil user GPS receiver is grater than a few tens of kilometers. This is because their positioning/attitude determination is still very dependent on the errors of the GPS observations, so-called "baseline dependent errors". This limitation can be remedied by the integration of GPS and INS sensors, using multiple reference stations. Hence, in order to derive the GPS distance dependent errors, this research proposes measurement processing algorithms for multiple reference stations, such as a reference station ambiguity resolution procedure using linear combination techniques, a error estimation based on Kalman filter and a error interpolation. In addition, all the algorithms are evaluated by processing real observations and results are summarized in this paper.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.3
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• pp.259-267
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• 2020

For real-time precise positioning, N-RTK (Network Real-Time Kinematic) technology is widely used these days. However, the currently operating N-RTK system has a limitation in terms of the number of users. Therefore, if reference points generate correction messages with no limit on the number of users are developed later, it is determined that an appropriate reference point installation interval is required, so that the accuracy of the N-RTK system according to the baseline distance was analyzed. This experiment utilized receivers with varying performance that estimated the rover position, and RTKLIB, an open-source software, is used for processing data. As a result, the rover position was estimated accurately with a high rate of fixed ambiguity for all the receivers. When the reference station with a baseline length of 40 km was used, the vertical RMSE (Root Mean Squared Error) was quite similar to the short baseline case, but only half of the ambiguity fixing rate was achieved. The outlier in the estimated rover position was not observed for the longer baselines in the case of a high-end receiver. It is necessary to analyze the ambiguity fixing and the accuracy of the kinematic positioning with scientific GNSS processing software.