• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.61-69
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• 2012

This paper shows results of the precise time comparison technique based on GPS code transfer in order to determine the UTC(Universal Time Coordinated) and generate TAI(International Atomic Time). CGGTTS(CCTF Group on GNSS Time Transfer Standards) which is generated by GPS timing receivers is used as the international standard format. For geodetic receivers which provide RINEX formats as GPS time transfer results, ROB(Royal Observatory of Belgium) developed a conversion program, r2cggtts, and have distributed the program to timing laboratories participating in TAI link all over the world. Timing laboratories generate the time comparison results of GPS code transfer by the program and send them to BIPM(Bureau International des Poids et Mesures) periodically. In this paper, we introduce the delay features generated while GPS code is transferred and the calibration methods of them. Then, we introduce the tropospheric delay and analyze the results of Saastamoinen model and NATO(North Atlantic Treaty organization) model. Saastamoinen model is the representative tropospheric zenith path delay model and NATO model is applied to the legacy r2cggtts program.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.351-353
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• 2006

In this paper, we present the traditional GPS Position- Velocity (PV) model to apply for both Discrete-Time Kalman Filter and Discrete-Time $H_{\infty}$ Filter. The positioning algorithms of both filters are proposed for a stand-alone low-cost GPS module to increase its accuracy. For disturbance cancellation, the Kalman Filter requires the statistical information about process and measurement noises while the $H_{\infty}$ Filter only requires that these noises are bounded. Experiments show that with the same measurement data, $H_{\infty}$ Filter gives us better positioning results compared with Least-Squared method and Kalman Filter.

• Journal of Industrial Technology
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• v.21 no.A
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• pp.105-110
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• 2001

A continuous and reliable electrical energy supply is the objective of any power system operation. A transmission line is the part of the power system where faults are most likely to happen. This paler describes the use of wavelet transform for analyzing power system fault transients in order to determine the fault location. Synchronized sampling was made possible by precise time receivers based on GPS time reference, and the sampled data were analyzed using wavelet transform. This paper describes a fault location monitoring system and fault locating algorithm with GPS, DSP processor, and data acquisition board, and presents some experimental results and error analysis.

• Structural Engineering and Mechanics
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• v.66 no.2
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• pp.185-193
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• 2018

In this study, low- and high-frequency structure behaviors were identified and a systematic analysis procedure was proposed using noisy GPS data from a 165-m-high tower in ${\dot{I}}stanbul$, Turkey. The raw GPS data contained long- and short-periodic position changes and noisy signals at different frequencies. To extract the significant results from this complex dataset, the general structure and components of the GPS signal were modeled and analyzed in the time and frequency domains. Uncontrolled jumps and deviations involving the signal in the time domain were pre-filtered. Then, the signal was converted to the frequency domain after applying low- and high-pass filters, and the frequency and periodic component values were calculated. The spectrum of the tower motion obtained from the filtered GPS data had dominant peaks at a low frequency of $1.15572{\times}10-4Hz$ and a high frequency of 0.16624 Hz, consistent with two equivalent GPS datasets. Then, the signal was reconstructed using inverse Fourier transform with the dominant low frequency values to obtain filtered and interpretable clean signals. With the proposed sequence, processing of noisy data collected from the GPS receivers mounted very close to the structure is effective in revealing the basic behaviors and features of buildings.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.1984-1986
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• 2001

In order to provided continuous solutions, latest developing navigation systems tend to integrate GPS receiver with INS or DR. Using the GPS carrier-phase measurements, an attitude GPS receiver with three antennas obtain the 3-dimensional attitude such as roll, pitch, and heading as well as position and velocity. With these angle measurements, in the attitude GPS/INS integrated system, attitude or gyro errors can be directly compensated. In this paper, we develop an integrated navigation system that combines attitude GPS receiver with INS. The performance of real-time integrated navigation system is determined by not only the implements of integration filter but also the synchronization of measurements. To meet these real-time requirements, the navigation software is implemented in multi-tasking structure in this paper. We also employ time-synchronization technique in the multi-sensor fusion. Experimental results show that the performance of the attitude GPS/INS integrated system is consistent even when cycle-slip occurs in carrier-phase measurements.

• Journal of Korean Society for Geospatial Information Science
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• v.13 no.1 s.31
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• pp.37-43
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• 2005

GPS has been increasingly used in high precision positioning thanks to rapid advances of GPS technology. In order to acquire precise coordinates from GPS, it is important to solve accurately integer ambiguity inherent in GPS signals. The previous methods to solve this ambiguity were mostly based on multi-epoch data but recently a method based on single-epoch data has been developed. In this study, we selected three sets of software based on these methods, applied them to GPS baseline processing, and analyzed the experimental results. From these analyses, we have also verified the potential of their uses in real time precision positioning.

• Aerospace Engineering and Technology
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• v.2 no.1
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• pp.98-107
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• 2003

In this study, a survey of time synchronization methods between the remote places. Generally, there are many kinds of time synchronization methods for distant places and they can be grouped three categories according to the type of time transfer methods. The three methods are ground based network, GPS/NAVSTAR and geostationary satellite. Especially, the relay base stations for wireless digital communication are operated based on the timing signal service of the GPS/NAVSTAR satellite network. And as the back-up of the timing signal service of the GPS/NAVSTAR, the geostationary satellite based time synchronization method have researched. In this short paper, the brief explanations about each category were presented.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.3
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• pp.377-383
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• 2010

This study aims to develop the system which is able to monitor long span bridge behavior in real time using GPS. Through measuring displacement of long span bridge by GPS in real time, over all 3D behavior of bridge could be analyzed and managed. Monitoring system of long span bridge which is developed in this study is able to manage in real time the safety of bridge by transmitting horizontal and vertical displacement of bridge, and danger signals to an integrated operations center. Also it is able to monitor the absolute behavior of long span bridge by GPS, and to construct a national bridge safety management networks.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.1
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• pp.46-55
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• 2006

The purpose of this study is a development of an automatic mosaicing for applying to large number of airborne multispectral images, which reduces manual operation by human. 2436 airborne multispectral images were acquired from DuncanTech MS4100 camera with three bands; green, red and near infrared. LIDAR(LIght Detection And Ranging) data and GPS/INS(global positioning system/inertial navigation system) data were collected with the multispectral images. First, the multispectral images were converted to image patterns by unsupervised classification. Their patterns were compared with those of adjacent images to derive relative spatial position between images. Relative spatial positions were derived for 80% of the whole images. Second, it accomplished an automatic mosaicing using GPS/INS data and unsupervised classification. Since the time of GPS/INS data did not synchronized the time of readout images, synchronized GPS/INS data with the time of readout image were selected in consecutive data by comparing unsupervised classified images. This method realized mosaicing automatically for 96% images and RMSE (root mean square error) for the spatial precision of mosaiced images was only 1.44 m by validation with LIDAR data.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.22 no.1
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• pp.11-19
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• 2004

Such social structures as bridges,, buildings, dams and towers have been transformed by their own load or fundamental ground. They have been behaved by other external causes. These regular or irregular behaviors threaten to do their users safety. Therefore, to monitor the load of the structures or reaction shown by them could help to verify their behaviors. RTK GPS allows the use of a static base station and remote rover unit to allow f3r data collection within several seconds and in real time. It is useful for monitoring the behaviors of massive structures like bridges. In this Study, Among GPS methods, we used RTK GPS to analyze the precision of monitoring and then on the basis of it, we developed a monitoring system using RTK GPS when measured the behavior of main tower of a suspension bridge by using RTK GPS. Comparing a deviation between observation values, X axis was Imm, Y axis was 1mm and Z axis 2.2mm. It turned out that it was possible to monitor and measure structures by RTK GPS.