• 제목/요약/키워드: International GNSS Service

검색결과 76건 처리시간 0.02초

Regional Ionosphere Modeling using GPS, Galileo, and QZSS (GPS, Galileo, QZSS를 이용한 지역 전리층 모델링)

  • Byung-Kyu Choi;Dong-Hyo Sohn;Junseok Hong;Jong-Kyun Chung
    • Journal of Positioning, Navigation, and Timing
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    • 제13권2호
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    • pp.159-165
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    • 2024
  • The Global Navigation Satellite System (GNSS) has been used as a tool to accurately extract the Total Electron Content (TEC) in the ionosphere. The multi-GNSS (GPS, GLONASS, BeiDou, Galileo, and QZSS) constellations bring new opportunities for ionospheric research. In this study, we develop a regional ionospheric TEC model using GPS, Galileo, and QZSS measurements. To develop an ionospheric model covering the Asia-Oceania region, we select 13 International GNSS Service (IGS) stations. The ionospheric model applies the spherical harmonic expansion method and has a spatial resolution of 2.5°×2.5° and a temporal resolution of one hour. GPS TEC, Galileo TEC, and QZSS TEC are investigated from January 1 to January 31, 2024. Different TEC values are in good agreement with each other. In addition, we compare the QZSS(J07) TEC and the Center for Orbit Determination in Europe (CODE) Global Ionosphere Map (GIM) TEC. The results show that the QZSS TEC estimated in the study coincides closely with the CODE GIM TEC.

Long-term Analysis of Availability and Accuracy Variation of GPS Ionospheric Delay Model (GPS 전리층 모델의 장기간 가용성 및 정확도 변화 분석)

  • Jeongrae Kim;Yongrae Kim
    • Journal of Advanced Navigation Technology
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    • 제27권6호
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    • pp.841-848
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    • 2023
  • The Klobuchar ionospheric model included in global positioning system (GPS) navigation messages provides ionospheric correction information to single-frequency users. This ionospheric model accuracy has a significant impact on the accuracy of navigation solutions. We examine the GPS navigation messages from 1993 to 2022 and analyze their accuracy, presence of coefficients and accuracy of the Klobuchar model. Early GPS navigation messages often did not include ionospheric data, and even when they did include ionospheric models, the accuracy was often quite low. From 2002, when the accuracy of the ionospheric model was stabilized, until 2022, the accuracy of the ionospheric model is analyzed by comparing it with the ionospheric model of the International GNSS Service (IGS). Changes in accuracy per day and per year and accuracy differences along geomagnetic latitude are analyzed.

Construction of Ionospheric TEC Retrieval System Using Korean GNSS Network (국내 GNSS 관측 자료를 이용한 전리권 총전자밀도 산출 시스템 구축)

  • Lee, Jeong-Deok;Shin, Daeyun;Kim, Dohyeong;Oh, Seung Jun
    • Journal of Satellite, Information and Communications
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    • 제7권3호
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    • pp.30-34
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    • 2012
  • National Meteorological Satellite Center(NMSC) of Korea Meteorological Administration(KMA) has launched to implement the application development to get prepared for the space weather operation since 2010. As a action of KMA's space weather work, NMSC constructed Global Navigation Satellite System(GNSS) application system for meteorology and space weather. We will introduce NMSC's space weather application system which derives regional TEC(Total Electron Content) in near real time using nation-wide GNSS network data. First, We constructed system for collecting GNSS data, which is currently collecting about 80 stations operated by agencies like NGII(National Geographic Information Institute), Central Office of DGPS(Differential GPS), and KASI(Korea Astronomy and Space Science) including KMA's own data of 2 stations. In order to retreive regional TEC over Korean peninsular, we build up the automatic processes running every 1-hour. In these processes, firstly, GNSS data of every stations with 24 hours time window are processed to derive DCBs(Differential Code Biases) of each GNSS station and TEC values on every ionosphere piercing point(IPP). Then we made gridded regional TEC map with resolution of 0.25 degree from 31N, 121E to 41N, 135E by combination of all station results within 30 minutes window with assumption that TEC of a given point during a given 30 minutes window would have a constant value. The grid points without TEC value are interpolated using Barnes objective analysis. We presentour regional TEC maps, which can describe better on the status of ionosphere over Korean peninsular compared to IGS TEC maps.

Quality Assessment of Tropospheric Delay Estimated by Precise Point Positioning in the Korean Peninsula

  • Park, Han-Earl;Roh, Kyoung Min;Yoo, Sung-Moon;Choi, Byung-Kyu;Chung, Jong-Kyun;Cho, Jungho
    • 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.

A Study of Effects on GPS and GLONASS Time offset according to leap seconds in GNSSS time transfer (GNSS 시각 전송에서 윤초 적용 여부에 따른 GPS 시각과 GLONASS 시각의 오프셋 영향 연구)

  • Yu, Dong-Hui;Lee, Young-Kyu;Yang, Sung-Hoon;Lee, Chang-Bok
    • Journal of the Korea Institute of Information and Communication Engineering
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    • 제18권11호
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    • pp.2628-2633
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    • 2014
  • BIPM(International Bureau of Weights and Measures) uses GPS Time Transfer technique for UTC(Universal Time Coordinated). Recently, since GLONASS constellation started the service, studies on GLONASS time transfer and combination of GPS and GLONASS time transfer have been conducted. This paper introduces GNSS time, UTC and leap seconds and proposes the time offset results for applicability of leap seconds in GLONASS time transfer.

Accuracy Verification of the SBAS Tropospheric Delay Correction Model for the Korean Region (한반도 지역 SBAS 대류층 지연 보정 모델의 정확도 검증)

  • Kim, Dong-uk;Han, Deok-hwa;Kee, Chang-don;Lee, Chul-soo;Lee, Choong-hee
    • Journal of Advanced Navigation Technology
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    • 제20권1호
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    • pp.23-28
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    • 2016
  • In this paper, we verified accuracy of the satellite based augmentation system (SBAS) tropospheric delay correction model for the Korean region. We employed the precise data of the tropospheric zenith path delay (ZPD) which is provided by the international GNSS service (IGS). In addition, we compared the verification results with that of the Saastamoinen model and the Hopfield model. Consequently, the bias residual error of the SBAS tropospheric delay correction model is about 50 mm, whereas the Saastamoinen model and the Hopfield model are more accurate. This residual error by the tropospheric delay model can affect the SBAS user position accuracy, but there is no problem in SBAS accuracy requirement. If we modified the meteorological parameters for SBAS tropospheric model to appropriate in Korean weather environment, we can provide better SBAS service to the Korean user.

Anomaly Detection of IGS Predicted Orbits for Near-Real-Time Positioning Using GPS (GPS기반 준실시간 위치추적을 위한 IGS 예측궤도력 이상 검출)

  • Ha, Ji-Hyun;Heo, Moon-Beom;Nam, Gi-Wook
    • Journal of Advanced Navigation Technology
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    • 제15권6호
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    • pp.953-961
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    • 2011
  • IGS (International GNSS Service) predicted orbits contained in IGS ultra-rapid orbits is suitable for real-time or near-real-time precise positioning. In this paper, we analyzed orbit anomalies of the IGS predicted orbits and detected the anomalies NANU (Current Notice Advisories to NAVSTAR Users) messages and IGS BRDC (Broadcast Ephemerides). As a results, the orbit anomalies of the predicted orbits were observed 93 times in 2010. In case of using the NANUs, we could get detection performance of 88% about the IGS predicted orbits's anomalies. And we could achieve 95% detection performance when the NANUs and BRDCs were used together.

Assessment on the Performance of Search And Rescue Service of KPS

  • Lee, Jung-Hoon;Lee, Sanguk;Won, Jong-Hoon
    • Journal of Positioning, Navigation, and Timing
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    • 제8권3호
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    • pp.119-127
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    • 2019
  • COsmicheskaya Sisteyama Poiska Avariynich Sudov Search and Rescue Satellite-Aided Tracking (COSPAS-SARSAT) is an international communication support program to perform search and rescue (SAR) operations in emergency situations by using satellite signals relayed from a beacon. The legacy COSPAS-SARSAT was originally composed of low altitude and geostationary Earth orbit satellites; thus, a limited number of directional dish antennas was sufficient to cover the limited number of visible satellites at the local user terminal. However, the second generation COSPAS-SARSAT newly added the medium Earth orbit satellites, e.g., Global Navigation Satellite Systems (GNSS) to the existing system, so that the number of visible satellites increase dramatically, and the system upgrade to cover all the visible satellites is foreseen. The additional use of planned Korea Positioning System (KPS) to existing GNSS is envisaged to provide a better performance of their SAR service. This paper presents the benefits of the additional use of KPS together with the phased array antennas at the local user terminal of the COSPAS-SARSAT. This is to effectively response to the increase of the number of visible satellites. Numerical simulation is included to evaluate the performance improvement of COSPAS-SARSAT in terms of the number of visible satellites, geometry between satellites and user, and position estimation accuracy.

VLBI TRF Combination Using GNSS Software

  • Kwak, Younghee;Cho, Jungho
    • Journal of Astronomy and Space Sciences
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    • 제30권4호
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    • pp.315-320
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    • 2013
  • Space geodetic techniques can be used to obtain precise shape and rotation information of the Earth. To achieve this, the representative combination solution of each space geodetic technique has to be produced, and then those solutions need to be combined. In this study, the representative combination solution of very long baseline interferometry (VLBI), which is one of the space geodetic techniques, was produced, and the variations in the position coordinate of each station during 7 years were analyzed. Products from five analysis centers of the International VLBI Service for Geodesy and Astrometry (IVS) were used as the input data, and Bernese 5.0, which is the global navigation satellite system (GNSS) data processing software, was used. The analysis of the coordinate time series for the 43 VLBI stations indicated that the latitude component error was about 15.6 mm, the longitude component error was about 37.7 mm, and the height component error was about 30.9 mm, with respect to the reference frame, International Terrestrial Reference Frame 2008 (ITRF2008). The velocity vector of the 42 stations excluding the YEBES station showed a magnitude difference of 7.3 mm/yr (30.2%) and a direction difference of $13.8^{\circ}$ (3.8%), with respect to ITRF2008. Among these, the 10 stations in Europe showed a magnitude difference of 7.8 mm/yr (30.3%) and a direction difference of $3.7^{\circ}$ (1.0%), while the 14 stations in North America showed a magnitude difference of 2.7 mm/yr (15.8%) and a direction difference of $10.3^{\circ}$ (2.9%).

A Preliminary Study of Near Real-time Precision Satellite Orbit Determination (준 실시간 정밀 위성궤도결정을 위한 이론적 고찰)

  • Bae, Tae-Suk
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • 제27권1호
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    • pp.693-700
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    • 2009
  • For real-time precise GPS data processing such as a long baseline network RTK (Real-Time Kinematic) survey, PPP (Precise Point Positioning) and monitoring of ionospheric/tropospheric delays, it is necessary to guarantee accuracy comparable to IGS (International GNSS Service) precise orbit with no latency. As a preliminary study for determining near real-time satellite orbits, the general procedures of satellite orbit determination, especially the dynamic approach, were studied. In addition, the transformation between terrestrial and inertial reference frames was tested to integrate acceleration. The IAU 1976/1980 precession/nutation model showed a consistency of 0.05 mas with IAU 2000A model. Since the IAU 2000A model has a large number of nutation components, it took more time to compute the transformation matrix. The classical method with IAU 2000A model was two times faster than the NRO (non-rotating origin) approach, while there is no practical difference between two transformation matrices.