• Title/Summary/Keyword: precise positioning

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Test Results of Dual-Use Wide-Area Differential GPS System for Extending the Operational Coverage

  • Kap Jin Kim;Jae Min Ahn
    • Journal of Positioning, Navigation, and Timing
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    • v.12 no.3
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    • pp.307-314
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    • 2023
  • Wide-Area Differential Global Positioning System (WADGPS) is a system that operates a number of reference stations to provide correction information to improve the accuracy of GPS users, and it is available to service users within the area where the wide-area reference stations are installed. Recently, as positioning information has been used in various applications, the need for WADGPS for precise navigation in long-distance spaced areas where the wide-area reference stations cannot be installed has been raised. This paper tested the user navigation performance outside the wide-area reference stations of the WADGPS system, which serves both GPS Precise Positioning Service (PPS) and Standard Positioning Service (SPS) users. Static and dynamic tests were conducted using vehicles, and as a result, position accuracy improvement through WADGPS was confirmed even at points hundreds of kilometers outside the network area of the wide-area reference stations. Through this, the performance of the PPS/SPS correction system and the possibility of expanding the service area were confirmed.

Precise Orbit Determination of GRACE-A Satellite with Kinematic GPS PPP

  • Choi, Byung-Kyu;Roh, Kyoung-Min;Yoo, Sung-Moon;Jo, Jung-Hyun;Lee, Sang-Jeong
    • Journal of Positioning, Navigation, and Timing
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    • v.1 no.1
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    • pp.59-64
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    • 2012
  • Precise Point Positioning (PPP) has been widely used in navigation and orbit determination applications as we can obtain precise Global Positioning System (GPS) satellite orbit and clock products. Kinematic PPP, which is based on the GPS measurements only from the spaceborne GPS receiver, has some advantages for a simple precise orbit determination (POD). In this study, we developed kinematic PPP technique to estimate the orbits of GRACE-A satellite. The comparison of the mean position between the JPL's orbit product and our results showed the orbit differences 0.18 cm, 0.54 cm, and 0.98 cm in the Radial, in Along-track, and Cross-track direction respectively. In addition, we obtained the root mean square (rms) values of 4.06 cm, 3.90 cm, and 3.23 cm in the satellite coordinate components relative to the known coordinates.

A Short-Term Prediction Method of the IGS RTS Clock Correction by using LSTM Network

  • Kim, Mingyu;Kim, Jeongrae
    • Journal of Positioning, Navigation, and Timing
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    • v.8 no.4
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    • pp.209-214
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    • 2019
  • Precise point positioning (PPP) requires precise orbit and clock products. International GNSS service (IGS) real-time service (RTS) data can be used in real-time for PPP, but it may not be possible to receive these corrections for a short time due to internet or hardware failure. In addition, the time required for IGS to combine RTS data from each analysis center results in a delay of about 30 seconds for the RTS data. Short-term orbit prediction can be possible because it includes the rate of correction, but the clock correction only provides bias. Thus, a short-term prediction model is needed to preidict RTS clock corrections. In this paper, we used a long short-term memory (LSTM) network to predict RTS clock correction for three minutes. The prediction accuracy of the LSTM was compared with that of the polynomial model. After applying the predicted clock corrections to the broadcast ephemeris, we performed PPP and analyzed the positioning accuracy. The LSTM network predicted the clock correction within 2 cm error, and the PPP accuracy is almost the same as received RTS data.

Near-Real-Time Ship Tracking using GPS Precise Point Positioning (GPS 정밀단독측위 기법을 이용한 준실시간 선박 위치추적)

  • Ha, Ji-Hyun;Heo, Moon-Beom;Nam, Gi-Wook
    • Journal of Advanced Navigation Technology
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    • v.14 no.6
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    • pp.783-790
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    • 2010
  • For safety navigation of ships at sea, ships monitor their location obtained from Global Positioning Satellite System (GNSS). In this study, we computed near-real-time positions of a ship at sea using GPS Precise Point Positioning (PPP) technique and analyzed precision of the near-real-time positions. We conducted ship borne GPS observations in the south sea of Korea. To process the GPS data using PPP technique, GIPSY-OASIS (GPS Inferred Positioning System-Orbit Analysis and Simulation Software) developed by the Jet Propulsion Laboratory was used. Antenna phase center variations, ocean tidal loading displacements, and azimuthal gradients of the atmosphere were corrected or estimated as standard procedures of high-precision GIPSY-OASIS data processing. As a result, the precisions of near-real-time positions was ~1cm.

A Review on the Usage of RTKLIB for Precise Navigation of Unmanned Vehicles

  • Lim, Cheolsoon;Lee, Yongjun;Cho, Am;Park, Byungwoon
    • Journal of Positioning, Navigation, and Timing
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    • v.10 no.4
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    • pp.243-251
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    • 2021
  • Real-Time Kinematic (RTK) is a phase-based differential GNSS technique and uses additional observations from permanent reference stations to mitigate or eliminate effects like atmospheric delays or satellite clocks and orbit errors. In particular, as the position accuracy required in the fields of autonomous vehicles and drones is gradually increasing, the demand for RTK-based precise navigation that can provide cm-level position is increasing. Recently, with the rapid growth of the open-source software market, the use of open-source software for building navigation system of unmanned vehicles, which is difficult to mount an expensive GNSS receivers, is gradually increasing. RTKLIB is an open-source software package that can perform RTK positioning and is widely used for research and education purposes. However, since the performance and stability of RTK algorithm of RTKLIB is inevitably inferior to that of commercial GNSS receivers, users need to verify whether RTKLIB can satisfy the navigation performance requirements of unmanned vehicles. Therefore, in this paper, the performance evaluation of the RTK positioning algorithm of RTKLIB was performed using GNSS observation data acquired in a dynamic environment. Therefore, in this paper, the RTK positioning performance of RTKLIB was evaluated using GNSS observation data acquired in a dynamic environment. Our results show that the current RTK algorithm of RTKLIB is not suitable for precise navigation of unmanned vehicles.

Analysis about Seismic Displacements Based on GPS for Management of Natural Disaster (자연재난 관리를 위한 GPS 기반의 지진재해 분석)

  • Park, Joon-Kyu;Yun, Hee-Cheon
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.29 no.3
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    • pp.311-318
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    • 2011
  • On March 11, 2011, an 9.0-magnitude earthquake occurred near the northeastem coast Japanese. It was the largest earthquake that hit Japan since the beginning of modern seismometry. The earthquake occurred 179km east of the Sendai, Miyagi Prefecture, leaving about 27,000 of people confirmed dead, injured or missing due to the earthquake and tsunami. In this study, crustal Deformation in Mizusawa, Tsukuba and Usuda station were calculated based on GPS data in IGS station of Japan. The observation data were processed by precise point positioning and relative-positioning method using on-line GPS data processing services and a high precision scientific GPS/GLONASS data processing software. The coseismic displacements in IGS stations before and after the earthquake were analyzed using kinematic precise point positioning method, and the crustal deformation of the areas before and after the earthquake were precisely calculated using the relative-positioning method. The results of the study calculated precise coordination that the RMSE is maximum ${\pm}0.003m$, respectively and showed that Mizusawa station moved 2.6m southeast by the earthquake.

Development of Reference Epoch Adjustment Model for Correction of GPS Precise Point Positioning Results (GPS 정밀단독측위 성과의 보정을 위한 기준시점 조정모델 개발)

  • Sung, Woo-Jin;Yun, Hong-Sik;Hwang, Jin-Sang;Cho, Jae-Myoung
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.30 no.3
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    • pp.249-258
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    • 2012
  • In this study, the epoch adjustment model was developed to correct GPS precise point positioning result to be suitable for the current geodetic datum of Korea which is tied at past epoch statically. The model is based on the formula describing crustal movements, and the formula is composed of several parameters. To determine the parameters, the data gathered at 14 permanent GPS stations for 10 years, from 2000 to 2011, were processed using GIPSY-OASIS II. It was possible to determine the position of permanent GPS stations with an error range of 16mm and the position of check points with an error range of 12mm by appling the model to GPS precise point positioning result. It is considered that more precise model could be calculated by using GPS data of more permanent GPS stations.

Positional Accuracy Analysis of Permanent GPS Sites Using Precise Point Positioning (정밀절대측위를 이용한 상시관측소 위치정확도 분석)

  • Kang, Joon-Mook;Lee, Yong-Wook;Kim, Min-Gyu;Park, Joon-Kyu
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.26 no.5
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    • pp.529-536
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    • 2008
  • Researches about 3-D Positioning system using GPS were carried out many-sided by national organs, laboratories, the worlds of science. And most of researches were development of relative positioning algorithm and its applications. Relative positioning has a merit, which can eliminate error in received signals. But its error increase due to distance of baseline. GPS absolute positioning is a method that decides the position independently by the signals from the GPS satellites which are received by a receiver at a certain position. And it is necessary to correct various kinds of error(clock error, effect of ionosphere and troposphere, multi-path etc.). In this study, results of PPP(Precise Point Positioning) used Bernese GPS software was compared with notified coordinates by the NGII(National Geographic Information Institute) in order to analyze the positional accuracy of permanent GPS sites. And the results were compared with results of AUSPOS - Online GPS Processing Service for comparison with relative positioning.

A precise positioning by a fuzzy-neural controller (퍼지 신경망을 이용한 정밀위치 제어)

  • Pak, Seung-Chul;Yang, Sang-Sik
    • Proceedings of the KIEE Conference
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    • 1997.11a
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    • pp.89-91
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    • 1997
  • Conventional linear control schemes often fail to provide precise positioning of a control object under the influence of friction, deadzone, saturation, etc. This paper proposes a control scheme for a precise point-to-point positioning system, which behaves well even under the above influences. The proposed scheme is composed of a fuzzy-neural controller. The neural network is employed to improve the performance of the fuzzy logic. To illustrate the effectiveness of this scheme, experiments are carried out for the cases of a fuzzy controller, the proposed fuzzy-neural controller, and the results are compared with each other.

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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.