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RISS 인기검색어
- 검색키워드
- 저자 : Nobuaki KUBO (검색결과 5 건)
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How multipath error influences modernized GNSS ambiguity resolution in urban areas
Nobuaki KUBO,Akio YASUDA 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-
Commercial uses of GPS have been growing rapidly with applications for aircraft, ship, and land vehicle navigation as well as for surveying and time keeping. The next generation GPS and Japanese QZS (Quasi Zenith Satellite) will provide three different civil signals. Galileo will also provide several types of civil signals. The availability of the third civil frequency has obvious advantages to instantaneous carrier phase accuracy and ambiguity resolution for centimeter level measurements. This paper discusses the effects of additional new civil signals for the high accuracy positioning in urban areas based on simulation using practical raw data. As for constellation, only GPS and GPS+QZS are considered. For positioning, a short distance baseline is assumed in order to disregard atmosphere effects. In this simulation, mask angle and signal conditions were fixed and ambiguity success rates were compared between different triple frequency combination scenarios. The coefficient of reflection was set randomly from 0.05 to 0.5 and the multipath delay was also set randomly from 5-100 m. Visible satellites and signal strength were determined by raw data collected in Tokyo by car. These simulation results have confirmed that the availability of high accuracy positioning will increase in all scenarios if we use GPS+QZS with triple frequencies.
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How QZSS contributes to Positioning Performance in Large Asian Cities ?
Nobuaki Kubo 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
The US GPS and the planed Quasi Zenith Satellite System (QZSS) will enhance the capability of positioning performance. The paper describes numerical analysis of the positioning performance of combined GPS-QZSS system.The performance of general stand-alone positioning in Tokyo is analyzed for different scenarios of the present GPS and combined future GPS-QZSS system. It is also analyzed in the Asian cities of Seoul, Beijing, Shanghai, Singapore and Sydney. The software-based simulator was used for this analysis. This simulator generates everything needed to compute navigation solutions. In order to model the impact of ephemeris errors and atmospheric errors, the realobservation data was used. The results indicate that increasing the number of satellites has a benefit on the capability of getting position with high availability.
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Evaluation of Ambiguity Estimator between Reference Stations
Yasuto Gomi,Reiji Tominaga,Nobuaki Kubo,Akio Yasuda 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-
In order to apply the network adjustment, the correct ambiguities between each of reference stations must be calculated. This paper focused on the comparison of ambiguity resolution between the reference stations. Three hours test data with different baseline length from 20 km to 60 km have been analyzed. The results show that the time-to-fix between 20 km and 40 km is typically under 1 minute. However, over 60km baseline, the time-to-fix performance degrades.
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Shun-Ichiro Kondo,Nobuaki Kubo,Akio Yasuda 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-
Ionospheric scintillation induces a rapid change in the amplitude and phase of radio wave signals. This is due to irregularities of electron density in the F-region of the ionosphere. It reduces the accuracy of both pseudorange and carrier phase measurements in GPS/satellite based Augmentation system (SBAS) receivers, and can cause loss of lock on the satellite signal. Scintillation is not as strong at mid-latitude regions such that positioning is not affected as much. Serve effects of scintillation occur mainly in a band approximately 20 degrees on either side of the magnetic equator and sometimes in the polar and auroral regions. Most scintillation occurs for a few hours after sunset during the peak years of the solar cycle. This paper focuses on estimation of the effects of ionospheric scintillation on GPS and SBAS signals using a software receiver. Software receivers have the advantage of flexibility over conventional receivers in examining performance. PC based receivers are especially effective in studying errors such as multipath and ionospheric scintillation. This is because it is possible to analyze IF signal data stored in host PC by the various processing algorithms. A LI C/A software GPS receivers was developed consisting of a RF front-end module and a signal processing program on the PC. The RF program written in MATLAB implements signal acquisition, tracking, and pseudorange measurements. The receiver achieves standalone positioning with accuracy between 5 and 10 meters in 2drms. Typical phase locked loop (PLL) designs of GPS/SBAS receivers enable them to handle moderate amounts of scintillation. So the effects of ionospheric scintillation was estimated on the performance of GPS LI C/A and SBAS receivers in terms of degradation of PLL accuracy considering the effect of various noise sources such as thermal noise jitter, ionospheric phase jitter and dynamic stress error.
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The Benefit of Ambiguity Resolution Using Triple Frequency
Reiji Tominaga,Yasuto Gomi,Yun Zhang,Nobuaki Kubo,Akio Yasuda 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-
Modernized GPS will have three frequencies modulated with three signals, which will be accessible to all users in the near future. This new frequency provides an opportunity to resolve the double differenced (DD) integer ambiguity very fast and with almost no baseline constraints. In order to study the performance of triple frequency system for Ambiguity Resolution (AR) over the medium baseline under different ionospheric levels, the Klobuchar Model was implemented and used in our triple simulation to generate the ionospheric delay. Furthermore, the White-Gaussian noise applying to distance-dependent parameters was added to the DD ionospheric delay. For medium baseline (defined as here 20 to 40kms), success rates of AR has been pretty improved. In this paper, the medium baseline AR strategies that take advantage of carrier phase measurement on the third frequency will be discussed.
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