• Title/Summary/Keyword: GPS time

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Estimation of Errors in Inertial Navigation Systems with GPS

  • Chang, Yu-Shin;Ha, Seong-Ki;Kim, Eun-Joo;Hong, Sin-Pyo;Lee, Man-Hyung
    • 제어로봇시스템학회:학술대회논문집
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    • 2001.10a
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    • pp.69.1-69
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    • 2001
  • In this paper, observability properties of a multiantenna GPS measurement system for the estimation of errors in INS are presented. It is shown that time-invariant INS error models are observable with measurements from at least three GPS antennas on the vehicle. There is at least one unobservable mode with two antennas. There are three unobservable modes with one antenna. It is also shown that time-varying INS error models are instantaneously observable with measurements from three GPS antennas. A numerical simulation results are given to verify the effectiveness of the multiantenna measurement system on the INS error estimation. In the simulation, a GPS measurement system is considered in which a trade-off between computational load and accuracy of estimation is achieved.

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Study of Monitering and Analysis Technology for Long Span Bridge Using Multi-GPS (멀티GPS에 의한 장대교량 모니터링 및 분석기술)

  • Choi, Byoung-Gil;Na, Young-Woo;Kim, Young-Gon;Kim, Tae-Hoon
    • Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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    • 2010.04a
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    • pp.195-196
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    • 2010
  • This study aims to methodology a system which is able to monitoring and analysis of long span bridge in real time using multi GPS. Through setting up many GPS at the important points of long span bridge and measuring displacement in real time, over all 3D configuration of bridge could be analyzed. Behavior analyzing system developed in this study is able to digitize and visualize the overall and points displacement of bridge and deal with events actively. Also it is able to calculate statistical data related to analyze behavior through the constricting database of measuring data.

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A Novel GPS Initial Synchronization Scheme with Decomposed Differential Matched Filter (분해형 차분 정합필터를 갖는 새로운 GPS 초기동기 방식)

  • Park, Sang-Hyun;Lee, Sang-Jeong
    • Journal of Institute of Control, Robotics and Systems
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    • v.8 no.2
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    • pp.185-192
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    • 2002
  • A novel GPS initial synchronization scheme with low hardware complexity is proposed. The proposed method has the decomposed differential matched filter, which consists of 25% multiplier and adder of the conventional matched filter. This paper presents the generalized mean acquisition time of initial synchronization scheme with multiple correlator. It is shown that the proposed method, in spite of its low hardware complexity, has the equal performance to the conventional method. The performance of the proposed method is verified through the simulation test by the GPS simulator. It is shown that the proposed method prevents the squaring loss of non-coherent integration.

Precision Assessment of Near Real Time Precise Orbit Determination for Low Earth Orbiter

  • Choi, Jong-Yeoun;Lee, Sang-Jeong
    • Journal of Astronomy and Space Sciences
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    • v.28 no.1
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    • pp.55-62
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    • 2011
  • The precise orbit determination (POD) of low earth orbiter (LEO) has complied with its required positioning accuracy by the double-differencing of observations between International GNSS Service (IGS) and LEO to eliminate the common clock error of the global positioning system (GPS) satellites and receiver. Using this method, we also have achieved the 1 m positioning accuracy of Korea Multi-Purpose Satellite (KOMPSAT)-2. However double-differencing POD has huge load of processing the global network of lots of ground stations because LEO turns around the Earth with rapid velocity. And both the centimeter accuracy and the near real time (NRT) processing have been needed in the LEO POD applications--atmospheric sounding or urgent image processing--as well as the surveying. An alternative to differential GPS for high accuracy NRT POD is precise point positioning (PPP) to use measurements from one satellite receiver only, to replace the broadcast navigation message with precise post processed values from IGS, and to have phase measurements of dual frequency GPS receiver. PPP can obtain positioning accuracy comparable to that of differential positioning. KOMPSAT-5 has a precise dual frequency GPS flight receiver (integrated GPS and occultation receiver, IGOR) to satisfy the accuracy requirements of 20 cm positioning accuracy for highly precise synthetic aperture radar image processing and to collect GPS radio occultation measurements for atmospheric sounding. In this paper we obtained about 3-5 cm positioning accuracies using the real GPS data of the Gravity Recover and Climate Experiment (GRACE) satellites loaded the Blackjack receiver, a predecessor of IGOR. And it is important to reduce the latency of orbit determination processing in the NRT POD. This latency is determined as the volume of GPS measurements. Thus changing the sampling intervals, we show their latency to able to reduce without the precision degradation as the assessment of their precision.

A Study on the Accuracy of GPS Received Data in Travel Vehicle (통행차량에 대한 GPS수신자료의 정확도에 관한 연구)

  • Kim, Jae-Seok;Lee, Seung Jun;Woo, Yong-Han
    • Journal of the Korean Association of Geographic Information Studies
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    • v.5 no.4
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    • pp.75-85
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    • 2002
  • The introduction of GPS technique in transportation study make real time tracking of driving vehicle's position possible. Position information data gauged with three dimension(X, Y, Z) can be achieved with time-continuity and from more than two driving vehicles. For this field of study, in past day, there were many difficulties in collecting real time data, but now, it becomes easy thanks to this. But for the resonable result analysis, fully understanding of GPS data-accuracy must be proceeded. Because accompanied magnitude of error depends on the study's accuracy. For this reason, this study surveyed the GPS data's error and suggest calibrate technique. This study's result will be helpful for following studies using DGPS data. For this, this study takes two types study in road, and set triangulation coordinates, and compare it with GPS data. DGPS data contains less than 0.6m's error.

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A Study of GPS Precise Ephemeris Interpolation for Maritime Precise Positioning Applications (해양 정밀측위 활용을 위한 GPS 정밀위성궤도 보간 연구)

  • Cho, Deuk-Jae;Park, Sang-Hyun
    • Journal of Navigation and Port Research
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    • v.33 no.10
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    • pp.699-702
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    • 2009
  • Currently many vessels determine an overhead obstruction by a rule of thumb based on their draft for maritime navigation. Therefore they doesn't have a good overhead obstruction clearance because vertical position of vessels varies on time by tidal. As a result, it is occurred maritime accidents that the mainmast of vessels is bumped against overhead facilities. And disaster by global warming and rising sea levels have increased casualties. So we feel keenly the necessity of warning system for not an earthquake but disaster wave such a tsunami. This paper analyzes a precise GPS ephemeris for maritime precise positioning to solve these problems. The precise GPS ephemeris provided by International GNSS service gives a difficulty to real-time application because of its sample interval. This paper proposes an effective interpolation method for real-time application, and it analyzes an accuracy of precise GPS ephemeris through an interpolation method.

Methodology of Calibration for Falling Objects Accident-Risk-Zone Approach Detection Algorithm at Port Considering GPS Errors (GPS 오차를 고려한 항만 내 낙하물 사고위험 알고리즘 보정 방법론 개발)

  • Son, Seung-Oh;Kim, Hyeonseo;Park, Juneyoung
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.19 no.6
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    • pp.61-73
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    • 2020
  • Real-time location-sensing technology using location information collected from IoT devices is being applied for safety management purposes in many industries, such as ports. On the other hand, positional error is always present owing to the characteristics of GPS. Therefore, accident-risk detection algorithms must consider positional error. This paper proposes an methodology of calibration for falling object accident-risk-zone approach detection algorithm considering GPS errors. A probability density function was estimated, with positional error data collected from IoT devices as a probability variable. As a result of the verification, the algorithm showed a detection accuracy of 93% and 77%. Overall, the analysis results derived according to the GPS error level will be an important criterion for upgrading algorithms and real-time risk managements in the future.

Elimination of Clock Jump Effects in Low-Quality Differential GPS Measurements

  • Kim, Hee-Sung;Lee, Hyung-Keun
    • Journal of Electrical Engineering and Technology
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    • v.7 no.4
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    • pp.626-635
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    • 2012
  • Most of single frequency GPS receivers utilize low-quality crystal oscillators. If a lowquality crystal oscillator is utilized as the time reference of a GPS receiver, the receiver's clock bias grows very fast due to its inherent low precision and poor stability. To prevent the clock bias becoming too large, large clock jumps are intentionally injected to the clock bias and the time offset for clock steering purpose. The abrupt changes in the clock bias and the time offset, if not properly considered, induce serious accuracy degradation in relative differential positioning. To prevent the accuracy degradation, this paper proposes an efficient and systematic method to eliminate the undesirable clock jump effects. Experiment results based on real measurements verify the effectiveness of the propose method.

Times Series Analysis of GPS Receiver Clock Errors to Improve the Absolute Positioning Accuracy

  • Bae, Tae-Suk;Kwon, Jay-Hyoun
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.25 no.6_1
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    • pp.537-543
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    • 2007
  • Since the GPS absolute positioning with pseudorange measurements can significantly be affected by the observation error, the time series analysis of the GPS receiver clock errors was performed in this study. From the estimated receiver clock errors, the time series model is generated, and constrained back in the absolute positioning process. One of the CORS (Continuously Operating Reference Stations) network is used to analyze the behavior of the receiver clock. The dominant part of the model is the linear trend during 24 hours, and the seasonal component is also estimated. After constraining the modeled receiver clock errors, the estimated position error compared to the published coordinates is improved from ${\pm}11.4\;m\;to\;{\pm}9.5\;m$ in 3D RMS.

Real-time Precision GPS Positioning Algorithm Based on Reconfiguration Kalman Filter (재구성기법을 이용한 칼만필터 기반의 실시간 정밀 GPS 측위기법)

  • Won, Jong-Hoon;Ko, Sun-Jun;Lee, Ja-Sung
    • Proceedings of the KIEE Conference
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    • 2000.07d
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    • pp.2439-2442
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    • 2000
  • This paper presents a practical On-The-Fly(OTF) integer ambiguity resolution algorithm for real-time precise positioning with low cost, $L_1$ single frequency, conventional C/A code GPS receiver. A state reconfiguration scheme is adopted in the Kalman filter to deal with the variation of ambiguity states caused by varying sets of visible GPS satellites. The proposed algorithm reduces the ambiguity search space from the coarse m-level C/A code pseudorange measurements of the conventional C/A code reciever, thereby reducing the computational time. Simulation results are presented to show that the algorithm achieves a cm-level accuracy.

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