• Title/Summary/Keyword: CDGPS

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Improving the Performance of CDGPS using the Shaping Filter on Multipath (다중경로 환경에서 형상필터를 이용한 CDGPS 성능 향상 기법)

  • Cho, Sung-Lyong;Han, Young-Hoon;Choi, Heon-Ho;Heo, Moon-Beom;Park, Chan-Sik;Lee, Sang-Jeong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.12
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    • pp.2318-2325
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    • 2011
  • The quality of float solution deeply influences the performance of CDGPS because the theories being used in the integer ambiguity resolution method are derived under the assumption of AWGN. But in real world, the properties of noises are far from AWGN, especially when multipath are concerned. It results in the bias in float solution which affects the success rate of integer ambiguity and the precision of position in CDGPS. This paper designs an augmented Kalman filter using shaping filter and Kalman filter for the performance improvement of CDGPS on multipath. The experimental results with real measurements show that the correct integer ambiguity is always found while the success rates of WLSQ and ordinary Kalman filter are 5% and 18%, respectively. Eventually, the position accuracy is also improved by using the proposed algorithm.

A Development of Carrier Phase DGPS Aided with INS

  • Lee, Ki-Won;Lee, Jae-Ho;Seo, Hung-Serk;Sung, Tae-Kyung
    • 제어로봇시스템학회:학술대회논문집
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    • 2001.10a
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    • pp.133.1-133
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    • 2001
  • When the signals from satellite vehicles are blocked, it is impossible to provide positioning information. Integrating CDGPS with INS, the performances of output can be greatly improved. In the CDGPS/INS integrated system, the error growth in INS can be efficiently suppressed due to CDGPS. On the contrary, the search range of integer ambiguities can be reduced with the aids of INS. Furthermore, cycle slips in carrier phase measurements can be easily detected using INS. The paper presents a CDGPS/INS integrated system that utilizes CDGPS aided with INS. Using the outputs of CDGPS/INS integration filter, a method to reduce search range of integer ambiguities is proposed. A method to detect cycle slips in carrier phase measurements is ...

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A study on improving LSAST ambiguity resolution for CDGPS (CDGPS를 위한 LSAST 미지정수 추정기법 개선에 관한 연구)

  • Lee, Gi-Hun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.5
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    • pp.74-80
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    • 2006
  • GPS, which has been opened to the public since the 1980's, uses the C/A code time of arrival to estimate the position, and measures the carrier doppler frequency to estimate the velocity. In development from the 1990's, DGPS has improved position accuracy by eliminating common errors and CDGPS has achieved cm-level position accuracy using carrier phase. In this paper, a modified LSAST ambiguity resolution method for CDGPS is proposed to improve reliability and computational efficiency. Also the test results of cm level relative positioning of a moving vehicle using single frequency GPS receivers are compared to INS position. This research result can be widely used for the development of high precision INS, unmanned autonomous driving, survey and mapping, etc.

A Development of CDGPS/INS integrated system with 3-dimensional attitude determination GPS Receiver (3차원 자세 결정용 GPS 수신기를 이용한 CDGPS/INS 통합 시스템 설계)

  • Lee, Ki-Won;Lee, Jae-Ho;Seo, Hung-Seok;Sung, Tae-Kyung
    • Proceedings of the KIEE Conference
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    • 2001.07d
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    • pp.2075-2077
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    • 2001
  • For precise positioning, GPS carrier measurements are often used. In this case, accurate position having mm${\sim}$cm error can be obtained. For 3D positioning, in CDGPS, more than five carrier phase measurements are required. When GPS signals are blocked or carrier phase measurements are insufficient, it cannot provide positioning solution. By integrating CDGPS with INS, continuity of positioning solution can be guaranteed. However, when a vehicle moves in low speed or in stationary, the CDGPS/INS integrated system is difficult to compensate INS attitude errors because GPS velocity error become relatively lange. In this paper, we used the 3D attitude GPS receiver to compensate the INS attitude error. By field experiments, it is shown that the proposed integration system maintains the navigation performance even when a vehicle is in low speed or GPS signal is blocked for a period of time.

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A Study on Spotlight SAR Image Formation by using Motion Measurement Results of CDGPS (CDGPS의 요동 측정 결과를 이용한 Spotlight SAR 영상 형성에 관한 연구)

  • Hwang, Jeonghun;Ko, Young-Chang;Kim, So-Yeon;Kwon, Kyoung-Il;Yoon, Sang-Ho;Kim, Hyung-Suk;Shin, Hyun-Ik
    • Journal of the Korea Institute of Military Science and Technology
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    • v.21 no.2
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    • pp.166-172
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    • 2018
  • To develop and evaluate the real-time SAR(Synthetic Aperture Radar) motion measurement system, true antenna phase center(APC) positions during SAT(Synthetic Aperture Time) are needed. In this paper, CDGPS(Carrier phase Differential Global Positioning System) post processing method is proposed to get the true APC position for spotlight SAR image formation. The CDGPS position is smoothed to remove high frequency noise which exists inherently in the carrier phase measurement. This paper shows smoothed CDGPS data is enough to provide the true APC for high-quality SAR image formation through motion measurement result, phase error estimation and IRF(Impulse Response Function) analysis.

Simulation of aircraft automatic landing using GPS (위성항법(GPS)을 이용한 항공기 자동착륙 시뮬레이션)

  • 윤두희;기창돈
    • 제어로봇시스템학회:학술대회논문집
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    • 1997.10a
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    • pp.1342-1347
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    • 1997
  • In this paper, we performed simulations of aircraft automatic landing using GPS, DGPS and CDGPS. Our purpose is examining the possibility of aircraft landing using GPS through the simulation results. The aircraft landing is composed of two stages, glide-slope and flare. Therefore, LQG controllers are designed separately. In simulations, measurement noise depends not only on UERE and UERRE(which have different values in GPS, DGPS, and CDGPS) but also on DOPs. DOPs are determined only by the geometry of GPS satellite constellation. For DOP calculation, we also made program for GPS satellites orbit simulatiion. Accordin to the simulation results, ICAO CAT III can be achieved of CDGPS is used.

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Precise Survey of Dokaebi Road Using CDGPS (CDGPS를 이용한 도깨비 도로의 정밀 측위)

  • Kee, Chang-Don;Kim, Jeong-Han
    • Journal of Advanced Navigation Technology
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    • v.3 no.1
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    • pp.13-19
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    • 1999
  • Using GPS carrier phase whose cycle ambiguities are resolved, it is possible to perform precise survey requiring centimeter-level positioning accuracy. Because of an optical illusion, we cannot recognize the exact slope of Dokaebi Road. In this paper, we performed kinematic survey experiments in order to calculate the exact slope of Dokaebi Road with high positioning accuracy of CDGPS. By post-processing experimental data using CDGPS, it was possible to generate the exact vertical trajectory of Dokaebi Road with centimeter-level accuracy.

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Field Test Results of CDGPS Precision Positioning Using Single Frequency, CA Code GPS Receivers (단일주파수 CA코드 GPS 수신기를 이용한 CDGPS 정밀측위실험)

  • Won, Jong-Hoon;Ko, Sun-Jun;Park, Heun-Jun;Lee, Ja-Sung
    • Proceedings of the KIEE Conference
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    • 2000.07d
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    • pp.2436-2438
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    • 2000
  • In this paper, field test results of a new efficient integer ambiguity resolution algorithm for precision Carrier Differential GPS(CDGPS) positioning are presented. The new algorithm is based on a reconfiguration Kalman filter which is designed to be used for the real-time precise positioning with low cost, single frequency, conventional C/A code GPS receivers. The tests were performed both in static and kinematic environment

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Performance Improvement of a Floating Solution Using a Recursive Filter

  • Cho, Sung Lyong;Lee, Sang Jeong;Park, Chansik
    • Journal of Positioning, Navigation, and Timing
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    • v.3 no.3
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    • pp.117-122
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    • 2014
  • In CDGPS, ambiguity resolution is determined by the performance of a floating solution, and thus, the performance needs to be improved. In the case of precise positioning at a stationary position, the batch method using multiple measurements is used for the accuracy improvement of a position. The position accuracy performance of a floating solution is outstanding, but it has a problem of high computation cost because all measurements are used. In this study, to improve the floating solution performance of the initial static user in CDGPS, a floating solution method using a recursive filter was implemented. A recursive filter estimates the position solution of the current epoch using the position solution of up to the previous epoch and the pseudorange measurement of the current epoch. The computation cost of the floating solution method using a recursive filter was found to be similar to that of the epoch-by-epoch method. Also, based on actual GPS signals, the floating solution performance was found to be similar to that of the batch method. The floating solution using a recursive filter could significantly improve the performance of the prompt initial position and ambiguity resolution of the initial static user.

A Study on Pseudolite-augmented Positioning Method for Automatic Docking (자동접안을 위한 의사위성 보강 측위기법에 관한 연구)

  • Park, Sang-Hyun;Cho, Deuk-Jae;Oh, Se-Woong
    • Journal of Navigation and Port Research
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    • v.30 no.10 s.116
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    • pp.839-845
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    • 2006
  • A laser docking system provides a centimeter-level accuracy distance from jetty mounted laser sensors in order to help a vessel to approach to a pier. It is very accurate & useful, whereas there are too many considerable problems. Laser sensors of the laser docking system need to be correctly positioned and installed on a jetty to allow for full range of vessels to be berthed and to consider loading condition and tidal variations. Above all, the laser docking system is expensive and its service coverage is limited. In order to solve these problems, CDGPS positioning method using GPS satellites has been proposed. This paper presents that, through RHDOP simulation, the previous CDGPS positioning method using only GPS satellites is not able to provide the continuous service with centimeter-level positioning accuracy. And this paper proposes a pseudolite-augmented positioning method for vessel docking in order to solve the problem of the continuous service on the previous CDGPS positioning method. In this paper, pseudolite is used to aid in CDGPS positioning. This paper shows that the proposed method can provides the continuous service through comparison analysis of RHDOP simulation results between the GPS satellite constellation and the pseudolite-augmented GPS satellite constellation. Furthermore, it is shown that the proposed positioning method satisfies the positioning performance required for vessel automatic docking at a test bed designed for performance evaluation.