• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.6
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• pp.651-657
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• 2011

There exists a high correlation between the ionospheric delays and the integer ambiguity in GPS observation equation, so that the sufficient time span is required to revolve the integer ambiguity. This means that the ambiguity resolution plays a key role especially in rapid-static positioning mode. To analyze the effect of ionospheric disturbances on the positioning accuracy, 02/19/2011 day of dataset was selected processed in rapid-static positioning mode. The total of 141 30-minute sessions were processed, i.e., the estimation procedure started every 10 minutes, and the time-to-fix information of each data interval is obtained. In this study, the analysis is performed by comparing the time-to-fix with the magnitudes of ionospheric delays. The computed correlation coefficient between the time-to-fix and the magnitudes of ionospheric delays is 0.31, which indicates the ionospheric disturbances affect the positioning accuracy in rapid-static positioning mode. Therefore, it is required to collect and process sufficient data when the GPS surveying is performed in unfavorable ionospheric conditions.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.1
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• pp.43-52
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• 2018

In recent years, the need of high accuracy navigation for vehicles has increased due to the development of autonomous driving vehicles and increase in land transportation convenience. This study is performed for vehicle users to achieve a performance of centimeter-level positioning accuracy by utilizing Compact Network Real-time Kinematic (RTK) that is applicable as a national-level infrastructure. To this end, medium-baseline RTK was implemented in real time to estimate accurate integer ambiguities between reference stations for reliable generation of Network RTK correction using the linear combination of carrier-phase observations and L1/L2 pseudo-range measurements. The residual tropospheric error was estimated in real time to improve the accuracy of double-differenced integer ambiguity resolution between network configuration reference stations that have at least 30 km or longer baseline distance. In addition, C++ based software was developed to enable real-time generation and broadcasting of Compact Network RTK correction information by utilizing an accurately estimated double-differenced integer ambiguity values. As a result, the horizontal and vertical 95% accuracy was 2.5cm and 5.2cm, respectively, without performance degradation due to user's position change within the network.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.3
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• pp.159-168
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• 2021

Precise Point Positioning-Real Time Kinematic (PPP-RTK) is an improved PPP method that provides the user receiver with satellite code and phase bias correction information in addition to the satellite orbit and clock, thus enabling single-receiver ambiguity resolution. Single station PPP-RTK concept is special case of PPP-RTK in that corrections are computed, instead of a network, by only one single GNSS receiver. This study is performed to experimentally verify the positioning accuracy performance of single baseline RTK level by a user who utilizes correction for a single station PPP-RTK using dual frequencies. As an experimental result, the horizontal and vertical 95% accuracy was 2.2 cm, 4.4 cm, respectively, which verify the same performance as the single baseline RTK.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.705-713
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• 2011

In this paper, we introduce two techniques for resolving integer ambiguities between reference stations, which is one of the most important processes in Network RTK correction generation process. Each techniques uses Hatch filter and combination of L1/L2 measurements and we used simulation data and real data to evaluate performance of the techniques. For evaluating performance of each technique, we compared corrections generated from user site and Network RTK. As a result, Network RTK with the technique which uses Hatch filter improves user performance much more than single baseline RTK does. Residual of user is smaller than a half size of wavelength so it does not affect user integer ambiguity resolution, however, it contains significant bias error. On the other hand, when we used the technique which uses combination of L1/L2 measurements, residual error of user is largely reduced compared to the technique using Hatch filter.

• 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.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.04a
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• pp.115-118
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• 2003

높은 정밀도를 갖는 상대위치결정은 매우 정밀한 반송파 측정값을 이용하며, 단기간에 높은 정밀도를 얻기 위해서는 미지정수가 결정되어야 한다. 본 논문에서는 LAMBDA 방법을 이용하여 이중차 미지정수를 해결하는 알고리즘을 정립하고, L1 반송파를 이용하여 상대위치를 결정하는 프로그램을 개발하였다.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.3
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• pp.222-227
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• 2005

Resolving the integer ambiguity of GPS carrier phase measurements is the most important routine in precise positioning. In this paper, success rate is analyzed when using baseline information in the process of determining attitude. The result is verified through the simulation. Determining the initial position for the ambiguity resolution is estimated by using code measurement and baseline constraint. Success rate is estimated using covariance of the formed initial position. UKF has been used to overcome the nonlinear baseline condition during the process so that the higher success rate has been obtained compared with the general attitude determination.

• Journal of Advanced Navigation Technology
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• v.2 no.1
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• pp.3-10
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• 1998

GPS is one of the main navigation systems. In these days, the application scope of GPS is extended to attitude determination using Differential GPS(DGPS) technique and Cycle Ambiguity resolution technique. In this paper, we propose an attitude determination algorithm using Kalman filter through double differenced measurement equation which is not for users with GPS patch antennas, but for users with low-priced GPS receivers. This paper also shows the simulation results and the effectiveness of proposed algorithm.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.1
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• pp.49-58
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• 2003

Compared with generic GPS receiver, post-processing software GPS receiver has many advantages for high dynamic vehicle tracking. It has the advantage of the application of various tracking algorithms and aiding schemes. The post-processing system observes the carrier phase measurement data from the recorded GPS signals, detects and isolates the cycle slip. The observed carrier phase data and the raw data of the reference station are processed by carrier phase DGPS scheme. And the integer ambiguity resolution algorithm is used for resolving single frequency carrier phase ambiguity. The results of static and real flight test are presented and show that the proposed GPS translator processing system satisfies submeter accuracy.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.74-83
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• 2004

The carrier phase measurements from GPS and GLONASS have different characteristics and therefore, have to be processed with different methods to provide precise positions or attitudes. In this contribution, at first, a measurement model is derived which can be used to not only GLONASS only applications but also both GPS and GLONASS applications. And then an error analysis of the proposed method performed using the derived model to derive analytic relationships between GDOP, PDOP and RGDOP. Finally, an integer ambiguity resolution method which was used in GPS is expanded to GPS and GLONASS. The proposed results can be directly applied to the design and analysis of GLONASS receiver and application programs. Furthermore, it is expected that the suggested method can also be effectively applied to combine the characteristically different measurements from the future satellite navigation systems such as GPS modernization, Galileo and QZSS.