• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.6
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• pp.151-158
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• 2015

This paper presents the real-time experiments of WA-DGNSS transmission system using a pseudolite and shows the performance of WA-DGNSS. We implement a server/client program to receive the WA-DGNSS data from the master station, and fabricate a pseudolite to transmit the WA-DGNSS data to users. The performance of the WA-DGNSS transmission system is tested by software and hardware GPS receivers, respectively. The experiments show that the WA-DGNSS data is well transmitted to GPS receivers without errors and thus WA-DGNSS works well.

• Journal of Advanced Navigation Technology
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• v.19 no.1
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• pp.15-21
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• 2015

WA-DGNSS is a system to service for users using a satellite which received correction data from ground station that calculates the relative errors of the tracked GNSS signals and sends to a satellite. Users are guaranteed the reliability of the GNSS signal and the accuracy of positioning. ICAO recommends the application of WA-DGNSS for the airplane taking off and landing process. In this paper, we suggests methods to verify of the pre-developed WA-DGNSS reference software constituting modules and an integration test process refer to the RTCA DO-278 which is a document for the development process of an aeronautics software. Also, we statistically verified the reference software test through our methods. And then, we confirmed to performance the function of the reference software properly.

• Journal of Navigation and Port Research
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• v.37 no.1
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• pp.49-54
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• 2013

This paper describes the progress and results of 'Wide Area Differetial GNSS (WA-DGNSS) Development' project which is supported by Korea Ministry of Land, Transport and Maritime Affairs. This project develops the main algorithm of the WA-DGNSS which can guarantee the improved accuracy, availability and integrity all over the Korean peninsula. After the establishment of WA-DGNSS ground system, a real time demonstration using pseudolite will be conducted. Product of this project will be directly utilized in Korean Satellite Based Augmentation System(SBAS) development project which is planned to be started from 2014.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.390-392
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• 2013

In the paper, design and implementation results of the reference station software are described for the WA-DGNSS that is currently developed in pseudo-realtime concept. The reference software is designed and implemented by applying the object oriented methodology.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.260-267
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• 2014

For the purpose of improving the accuracy of Wide Area Differential GNSS (WA-DGNSS), estimation performance of ionospheric delay error which has a great impact on GPS error sources should be enhanced. This paper applied multi-constellation GNSS which represents GPS in USA, GLONASS in Russia, and Galileo in Europe to WA-DGNSS algorithm in order to improve performance of ionospheric delay estimation. Furthermore, we conducted simulation to analyze ionospheric delay estimation performance in Korean region by increasing the number of reference stations. Consequently, using multi-constellation GNSS to improve performance of ionospheric delay estimation is more effective than increasing the number of reference stations in spite of similar number of measurements which are in use for estimation. We expect this result can contribute to improvement for ionospheric delay estimation performance of single-frequency SBAS (Satellite Based Augmentation System) user.

• Journal of Navigation and Port Research
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• v.37 no.4
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• pp.367-373
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• 2013

Wide area differential GNSS(WA-DGNSS) collects GPS measurements from the several reference stations and estimates 3-D satellite orbit error, satellite clock error, ionospheric delay. These correction messages are broadcasted to user, then user can have more accurate and reliable position estimates. The performance of WA-DGPS can be changed depending on the position of reference stations. To select proper reference stations, performance analysis with the change of reference stations is necessary. In this paper, changing the geographical location of reference stations, we carried out simulation based test and show the performance of WA-DGNSS in Korea.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.10a
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• pp.343-344
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• 2012

본 논문에서는 국토해양부 해양교통시설과의 연구개발과제인 '광역보정시스템(WA-DGNSS) 구축기술개발' 과제의 현재까지 진행사항과 주요 연구결과에 대하여 설명한다. 본 연구개발과제에서는 전국토에 균일한 정확도, 가용성 및 무결성 성능을 보장할 수 있는 광역보정시스템의 핵심알고리듬을 개발하고 지상기반 데모시스템 구축을 완료하여 최종 년도에는 의사위성을 통한 실시간 데모를 실시할 예정이다. 또한 미래 다중 GNSS에 대비하여 GLONASS 및 Galileo를 포함하는 광역보정시스템의 성능을 시뮬레이션을 통해 예측하였다. 본 과제에서 개발된 연구 결과들은 알고리즘 설명서 및 핵심기술권고사항으로 문서화되어 2014년부터 진행될 위성기반 광역보정시스템(SBAS)의 개발에 직접적으로 활용될 예정이다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.103-104
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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 Korea, WA-DGNSS development project, which aims to develop core algorithms and verify the performance using pseudolite-based demo system, is currently in progress. In this paper, overall structure of developed system and experimental methods which enables the post-processing test with commercial receiver will be described. In this system, pseudolite is used to broadcast augmenting signal and RF signal logger and broadcaster were used to test the performance. Performance test was conducted broadcasting the logged RF signal and pseudolite signal to commercial receiver and those results will be described.

• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.523-535
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• 2011

The precipitable water vapor (PW) was estimated using Global Navigation Satellite System (GNSS) from several GNSS stations within the Korean Peninsula. Nearby radiosonde sites covering the GNSS stations were used for the comparison and validation of test results. GNSS data recorded under typical and severe weather conditions were used to generalize our approach. Based on the analysis, we have confirmed that the derived PW values from the GNSS observables were well agreed on the estimates from the radiosonde observables within 10 mm level. Assuming that the GNSS observables could be a good weather monitoring tool, we further tested the performance of the current WAAS tropospheric delay model, UNB3, in the Korean Peninsula. Especially, the wet zenith delays estimated from the GNSS observables and from UNB3 delay model were compared. Test results showed that the modelled approach for the troposphere (i.e., UNB3) did not perform well especially under the wet weather conditions in the Korean Peninsula. It was suggested that a new model or a near real-time model (e.g., based on regional model from GNSS or numerical weather model) would be highly desirable for the Korean WA-DGNSS to minimize the effects of the tropospheric delay and hence to achieve high precision vertical navigation solutions.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.323-325
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• 2011

광역보정시스템은 기존의 NDGPS 방식과 달리 GPS 측정치 오차를 기준국을 기준으로 스칼라량으로 계산하지 않고, 전리층 지연 오차의 경우 전리층 분포 맵을 생성하고 위성관련오차의 경우 4차원(x, y, z, t) 보정정보를 생성하게 된다. 이러한 특성으로 인해 광역보정시스템은 기존의 NDGPS 방식보다 적은 수의 기준국으로 보다 넓은 지역을 커버할 수 있고 광역보정사용자는 기준국과의 거리와 관계 없이 균일하고 우수한 수준의 보정정보 및 무결성 정보를 제공받을 수 있게 된다. 본 논문에서는 광역보정시스템 구축에 필요한 핵심 기술 중 하나인 전리층 지연 오차 추정 알고리듬에 대해 설명하였다. 기준국 측정치를 이용해 전리층 분포 맵을 생성하기 위해 핵심적인 단계인 위성 및 기준국 수신기 IFB(Inter-Frequency Bias) 제거 방법에 대해서 설명하고 격자 알고리듬을 활용한 전리층 맵 생성방법에 대해서 설명하고 그 결과를 시뮬레이션을 통해 확인하였다.