• Title/Summary/Keyword: International GNSS Service

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Preliminary Analysis on the Effects of Tropospheric Delay Models on Geosynchronous and Inclined Geosynchronous Orbit Satellites

  • Lee, Jinah;Park, Chandeok;Joo, Jung-Min
    • Journal of Positioning, Navigation, and Timing
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    • v.10 no.4
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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.

Performance Analysis of GPS and QZSS Orbit Determination using Pseudo Ranges and Precise Dynamic Model (의사거리 관측값과 정밀동역학모델을 이용한 GPS와 QZSS 궤도결정 성능 분석)

  • Beomsoo Kim;Jeongrae Kim;Sungchun Bu;Chulsoo Lee
    • Journal of Advanced Navigation Technology
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    • v.26 no.6
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    • pp.404-411
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    • 2022
  • The main function in operating the satellite navigation system is to accurately determine the orbit of the navigation satellite and transmit it as a navigation message. In this study, we developed software to determine the orbit of a navigation satellite by combining an extended Kalman filter and an accurate dynamic model. Global positioning system (GPS) and quasi-zenith satellite system (QZSS) orbit determination was performed using international gnss system (IGS) ground station observations and user range error (URE), a key performance indicator of the navigation system, was calculated by comparison with IGS precise ephemeris. When estimating the clock error mounted on the navigation satellite, the radial orbital error and the clock error have a high inverse correlation, which cancel each other out, and the standard deviations of the URE of GPS and QZSS are small namely 1.99 m and 3.47 m, respectively. Instead of estimating the clock error of the navigation satellite, the orbit was determined by replacing the clock error of the navigation message with a modeled value, and the regional correlation with URE and the effect of the ground station arrangement were analyzed.

Development of Precise Point Positioning Method Using Global Positioning System Measurements

  • Choi, Byung-Kyu;Back, Jeong-Ho;Cho, Sung-Ki;Park, Jong-Uk;Park, Pil-Ho
    • Journal of Astronomy and Space Sciences
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    • v.28 no.3
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    • pp.217-223
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    • 2011
  • Precise point positioning (PPP) is increasingly used in several parts such as monitoring of crustal movement and maintaining an international terrestrial reference frame using global positioning system (GPS) measurements. An accuracy of PPP data processing has been increased due to the use of the more precise satellite orbit/clock products. In this study we developed PPP algorithm that utilizes data collected by a GPS receiver. The measurement error modelling including the tropospheric error and the tidal model in data processing was considered to improve the positioning accuracy. The extended Kalman filter has been also employed to estimate the state parameters such as positioning information and float ambiguities. For the verification, we compared our results to other of International GNSS Service analysis center. As a result, the mean errors of the estimated position on the East-West, North-South and Up-Down direction for the five days were 0.9 cm, 0.32 cm, and 1.14 cm in 95% confidence level.

Ionospheric TEC Monitoring over Jeju Island using the Chinese BeiDou Satellite Navigation System

  • Choi, Byung-Kyu;Lee, Woo Kyoung;Sohn, Dong-Hyo;Yoo, Sung-Moon;Roh, Kyoung-Min;Joo, Jung-Min;Heo, Moon Beom
    • Journal of Positioning, Navigation, and Timing
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    • v.9 no.1
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    • pp.1-6
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    • 2020
  • The Chinese BeiDou Satellite Navigation System consists of three kinds of constellations: the geostationary Earth orbit (GEO), the inclined geosynchronous satellite orbit (IGSO), and the medium Earth orbit (MEO). The BeiDou has expanded its service coverage from regional to global. Recently, the BeiDou has been widely used in ionospheric total electron content (TEC) research. In this study, we analyzed the BeiDou signals for ionospheric TEC monitoring over Jeju Island in South Korea. The BeiDou GEO TEC showed a clear pattern of diurnal variations. In addition, we compared the TEC values from the BeiDou GEO, the BeiDou IGSO, GPS, and International GNSS Service (IGS) Global Ionosphere Maps (GIM). There was a difference of about 5 TEC units between the BeiDou GEO and the IGS GIM. This may be due to the altitude difference between the different navigation satellites.

A Study on the Approval Process and Criteria for Operation of Ground-Based Augmentation System (GBAS) in Korea (GBAS 국내 운용을 위한 승인 절차 및 기준 연구)

  • Bae, Joong-Won;Yun, Young-Sun;Choi, Chul-Hee;Jeong, Myeong-Sook;Kim, Dong-Min;Jun, Hyang-Sig
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.22 no.4
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    • pp.115-125
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    • 2014
  • Ground-Based Augmentation System (GBAS) is providing precision approach and landing service with aircraft around airport. FAA granted System Design Approval (SDA) of SLS-4000 to Honeywell as the first GBAS category I system on September 2009. Since then, according to their own kind of approval process including System Design Approval, Facility Approval and Operational Approval, USA, Germany, Spain and Australia have approved GBAS category I system which are installed in some airports in order to provide commercial GBAS service. Recently, KARI has also installed GBAS category I system into Gimpo international airport to establish operational technology of GBAS domestically and to validate effectiveness of GBAS system in Korea. This paper introduces overseas trends and activities regarding approval process of GBAS system and presents approval process and criteria appropriate for future commercial operation of GBAS in Korea.

Accuracy Analysis of Online GPS Data Processing Service (온라인 GPS 자료처리 서비스의 정확도분석)

  • Kong, Joon-Mook;Park, Joon-Kyu;Lee, Choi-Gu;Lee, Young-Wook
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.28 no.1
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    • pp.13-20
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    • 2010
  • Currently, GPS data process software appears different results that according to user's skills or software. Also, lots of time and efforts are necessary for using GPS data process software to general user, not a specialist On the other band, on-line GPS data process service have a merit that can cony out GPS data process without technical efforts and time. In this study, permanent GPS site's observation data of NGII(National Geographic Information Institute) was processed by on-line GPS data process service, and utilization assessment of on-line GPS data process service was performed by comparing this result with notified coordinates by the NGII in order to analyze positional accuracy. 10 permanent GPS sites of NGII including Suwon which is registered in IGS(International GNSS Service) were selected and these GPS observation data was processed by AUSPOS and CSRS-PPP.

An Analysis on the Real-Time Performance of the IGS RTS and Ultra-Rapid Products (IGS RTS와 Ultra Rapid 실시간 성능 분석)

  • Kim, Mingyu;Kim, Jeongrae
    • Journal of Advanced Navigation Technology
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    • v.19 no.3
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    • pp.199-206
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    • 2015
  • For real-time precise positioning, IGS provides ephemeris predictions (IGS ultra-rapid, IGU) and real-time ephemeris estimates (real-time service, RTS). Due to the RTS data latency, which ranges from 5 s to 30 s, a short-term prediction process is necessary before applying the RTS corrections. In this paper, the real-time performance of the RTS correction and IGU prediction are compared. The RTS correction availability for the GPS satellites observed in Korea is computed as 99.3%. The RTS correction is applied to broadcast ephemeris to verify the accuracy of the RTS correction. The 3D orbit RMS error of the RTS correction is 0.043 m. Prediction of the RTS correction is modeled as a polynomial, and then the predicted value is compared with the IGU prediction value. The RTS orbit prediction accuracy is nearly equivalent to the IGU prediction, but RTS clock prediction performance is 0.13 m better than the IGU prediction.

THE EFFECT OF SURFACE METEOROLOGICAL MEASUREMENTS ON PRECISION GPS HEIGHT DETERMINATION

  • Wang Chuan-Sheng;Liou Yuei-An;Wang Cheng-Gi
    • Proceedings of the KSRS Conference
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    • 2005.10a
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    • pp.178-181
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    • 2005
  • The positioning accuracy of the Global Positioning System (GPS) has been improved considerably during the past two decades. The main error sources such as ionospheric refraction, orbital uncertainty, antenna phase center variation, signal multipath, and tropospheric delay have been reduced substantially, if not eliminated. In this study, the GPS data collected by the GPS receivers that were established as continuously operating reference stations by International GNSS Service (IGS), Ministry of the Interior (MOl), Central Weather Bureau (CWB), and Industrial Technology Research Institute (ITRI) Of Taiwan are utilized to investigate the impact of atmospheric water vapor on GPS positioning determination. The surface meteorological measurements that were concurrently acquired by instruments co-located with the GPS receivers include temperature, pressure and humidity data. To obtain the influence of the GPS height on the proposed impact study. A hydrodynamic ocean tide model (GOTOO.2 model) and solid earth tide were used to improve the GPS height. The surface meteorological data (pressure, temperature and humidity) were introduced to the data processing with 24 troposphere parameters. The results from the studies associated with different GPS height were compared for the cases with and without a priori knowledge of surface meteorological measurements. The finding based on the measurements in 2003 is that the surface meteorological measurements have an impact on the GPS height. The associated daily maximum of the differences is 1.07 cm for the KDNM station. The impact is reduced due to smoothing when the average of the GPS height for the whole year is considered.

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다중기준국을 이용한 육상교통 환경에서 항법위성 궤도력에 따른 위치결정 성능향상 분석 연구

  • Park, Jae-Ik;Lee, Eun-Seong;Gang, U-Yong;Han, Ji-Ae;Kim, Hyeon-Su;Heo, Mun-Beom
    • Bulletin of the Korean Space Science Society
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    • 2011.04a
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    • pp.25.5-26
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    • 2011
  • 이 연구에서는 네트워크 기반의 다중기준국을 이용하여 육상교통환경에서 항법위성의 궤도력에 따른 위치결정 성능향상의 정도를 분석하였다. 위성항법보정시스템(Differential Global Positioning System)을 활용하였을 경우 항법위성의 궤도력 오차정보가 소거되지 않는다는 가정 하에 방송궤도력이 아닌 International GNSS Service(IGS) 정밀궤도력중 신속궤도력(Ultra-Rapid)을 이용하여 궤도력 오차에 따라 위치결정 정확도가 향상됨을 확인하였다. 일반적으로 사용하는 위성항법보정시스템을 활용한 위치결정 방법은 기준국과 사용자의 거리에 따라서 그 성능이 달라진다. 이는 궤도 오차, 대류층 및 전리층 오차 등이 거리에 의존적이기 때문이다. 다중기준국을 활용하는 방법은 거리가 멀어짐에 따라 소거되지 않는 오차등을 극복하기 위한 기술이며 사용자 주변을 둘러싼 기준국들의 측정값을 조합하여 보상을 하거나 정확하게 모델링하여 사용자에게 오차정보를 보정정보로 전송하여 위치결정의 성능을 향상시키는 방법이다. 분석된 결과는 네트워크 기반의 다중기준국 환경에서 사용자와 기준국간의 거리에 따른 공간이격 오차정보 보정정보 생성 연구에 활용하며 이를 통해 육상교통 사용자의 위치결정 정확도 성능을 향상하는데 기여할 것으로 기대된다.

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Generation of Klobuchar Coefficients for Ionospheric Error Simulation

  • Lee, Chang-Moon;Park, Kwan-Dong;Ha, Ji-Hyun;Lee, Sang-Uk
    • Journal of Astronomy and Space Sciences
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    • v.27 no.2
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    • pp.117-122
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    • 2010
  • An ionospheric error simulation is needed for creating precise Global Positioning System (GPS) signal using GPS simulator. In this paper we developed Klobuchar coefficients n ${\alpha}_n$ and ${\beta}_n$ (n = 1, 2, 3, 4) generation algorithms for simulator and verified accuracy of the algorithm. The algorithm extract those Klobuchar coefficients from broadcast (BRDC) messages provided by International GNSS Service during three years from 2006 through 2008 and curve-fit them with sinusoidal and linear functions or constant. The generated coefficients from our developed algorithms are referred to as MODL coefficients, while those coefficients from BRDC messages are named as BRDC coefficients. The maximum correlation coefficient between MODL and BRDC coefficients was found for ${\alpha}_2$ and the value was 0.94. On the other hand, the minimum correlation was 0.64 for the case of ${\alpha}_1$. We estimated vertical total electron content using the Klobuchar model with MODL coefficients, and compared the result with those from the BRDC model and global ionosphere maps. As a result, the maximum RMS was 3.92 and 7.90 TECU, respectively.