• Journal of Astronomy and Space Sciences
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• v.21 no.2
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• pp.129-140
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• 2004

KAO(Korea Astronomy Observatory) GPS group has developed an iRTK system as a near-real time positioning system using GPS carrier phase data. We focused on improving the accuracy of positioning through the updated capability of data processing of KAO's iRTK system using low-cost L1 carrier phase receiver. The accuracy of a positioning was demonstrated by Extended Kalman filter. Experiments were accomplished using from 30m to 20km baselines. Within 10km, the positioning accuracy was improved by approximately 50-70% to the previous study using one minute observable data. However, it took two minutes to obtain 1m level positioning accuracy at 20km point. We expect that the developed iRTK system can be applied to the various fields of GPS in near-real time positioning.

• The KIPS Transactions:PartC
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• v.13C no.1 s.104
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• pp.95-102
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• 2006

Nowadays, GPS is used widely, especially in case which needs precise position information, such as car navigation systems and various kinds of position measuring instruments in an outdoor environment. According to their applications, there are many kinds of GPS receivers with different costs and error rates. The maximum error range of the general-purpose GPS receiver is within 30m, though the error rate depends on receiving rate of signal and weather condition. RTK(Real-Time Kinematic) and DGPS(Differential Global Positioning System) have more precise accuracy than the general-purpose GPS. However end users can't afford use them because of their high price and large size of equipments. In order for the end user to obtain precise position information, it is important that GPS receivers has portability and low price. In this study, we introduce a new system that offers precise position information using the DGPS mechanism satisfying low cost and portability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1207-1214
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• 2014

Recently it has become easier to figure out cargo positional information by using GPS(Global Positioning System) and wireless communication technology. The acceleration of globalization in the shipping logistics is ever more increasing the need to provide visibility, traceability and real time informations of entry, departure of vessel including cargo and status of logistic vehicle entry into each logistic base. Providing such positional information to logistics party by using wireless communication technology can bring effective operation of supply chain and reduction in logistics costs. In the previous paper, I suggested a global location tracking system based on GPS data in global shipping logistics by means of software using GPS data. However, the previous system had a problem of being inadequate to figure out a real time location movement information and was unsatisfactory on quickly searching and checking the location of global logistics hubs according to the longitude and latitude coordinates. Hence, in this paper, I suggest a real-time location tracking system that provided real-time location of the container cargos and logistics hubs can be searched quickly according to the GPS coordinates in global shipping logistics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6D
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• pp.1033-1041
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• 2006

In this study, we calculated a space-time variation of GPS precipitable water vapor using GPS meteorology technique during a progress of the typhoon EWINIAR had made an effect on Korean peninsular at 10 July, 2006. We estimated tropospheric dry delay and wet delay for one hourly using 22 GPS permanent stations and precipitable water vapor was conversed by using surface meteorological data. The Korean weighted mean temperature and air-pressure of versa-reduction to the mean sea level have been used for an accuracy improvement of GPS precipitable water vapor estimation. Finally, we compared MTSAT water vapor image, radar image and precipitable water vapor map during a passage of the typhoon EWINIAR.

• Journal of Industrial Technology
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• v.36
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• pp.65-69
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• 2016

Deflection of the vertical is used in geodetic surveying associated with geoid network construction for geoid modeling and ellipsoid decision and obtained by gravity survey, astronomic survey etc. Technique of astronomic survey and gravity survey is very complex and requires a significant amount of time until gathering data. So this study is to determined a various method which evaluates deflection of the vertical and components about deflection of the vertical using GPS results and orthometric height value decided by leveling. Results of components about deflection of the vertical using GPS/leveling is that ${\xi}$ conponent is distributed $-2.11^{{\prime}{\prime}}{\pm}0.62$, ${\eta}$ component is distributed $1.75^{{\prime}{\prime}}{\pm}0.71$. Decision of component about deflection of the vertical using GPS is less complex than existing astronomic survey. Decision of component about deflection of vertical line using GPS is not complicated than astronomic surveying and can determine in a very short time. So it will be important means to determine the exact orthometric height, topographic study and diastrophism if can periodically calculate.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.6_2
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• pp.673-680
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• 2012

Long-term GPS data analysis was performed in order to analyze the seasonal variation of tropospheric delay and the success rate of the ambiguity resolution. For this analysis, a total of 57 stations including 10 IGS stations in East Asia were processed together with double-differenced observables using Bernese GPS Software V5.0. The time span for this study ranges from 2002.0 to 2012.5 (10.5 years). The average baseline length is 339.0 km and the maximum reaches up to 2,000 km. The analysis is focused on two things: the annual variation of the tropospheric delay and the ambiguity resolution rate. The tropospheric delay is closely related to the weather condition, especially relative humidity, therefore it was estimated that the maximum would be in summer, while reaching its minimum in winter with the apparent seasonal variations. On the contrary, however, the success rate of the ambiguity resolution shows the opposite pattern: its maximum was in winter and minimum in summer. The fact seems to be induced by the surrounding conditions; that is, the trees thick with leaves near the GPS antenna interfere with GPS signals in summer. This seems to confirm partly that there is a distinct trend in the decreasing success rate since 2006 because the trees are growing every year. It is necessary to eliminate the factors that degrade the GPS quality and the tropospheric modeling for Korea needs to be studied further.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.10a
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• pp.75-80
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• 2003

Most of the control point surveying use a triangulation point and a bench mark with Total Station and Level. nowadays, the research is being accomplished for practical use of GPS. but In this study the optimum time and the optimum occupation time are analyzed, so as to examine possibility of the control point surveying that use GPS continuous station data of National Geography Institute. Also, The efficient surveying methods that compare the result of data that processed using broadcast ephemeris with the result of data that processed using precise ephemeris. As a result of that, Error feature analysis of the control point surveying in connection with GPS continuous observation will provide us estimation of errors and efficient topography information acquisition

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.27.2-27.2
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• 2011

The Total Electron Content (TEC) measured from Global Positioning System (GPS) can be continuously or peculiarly increased (positive ionospheric storm) or decreased (negative ionospheric storm) with solar and geomagnetic activities as well as the chemical and dynamic processes with thermosphere in the mid-latitudes. The ionospheric storm is not easy to predict owing to its difficult mechanism, and the real-time GPS TEC monitoring may be useful to follow ionospheric response to solar and geomagnetic storms. Korea Astronomy & Space Science Institute has continuously monitor GPS TEC over Korea Peninsula in near real-time of 10 minutes to watch activities. In this presentation, we will report the variation of GPS TEC over Daejeon and JeJu in Korea during the period of solar flare eruption and geomagnetic storm events in 2011. These events in 2011 will be compared with the event in October 2003 and November 2004.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.22-25
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• 2016

해상에서의 선박 항해에 있어서 GPS와 같은 위성항법시스템에 대한 의존도가 매우 높다. 하지만 전파 교란 등과 같은 열악한 환경이 선박 주위에 가해질 경우 선박에 탑재된 GPS 수신기에서 위치를 추정할 수 없기 때문에 정상적인 항해가 어렵게 된다. 본 논문에서는 위와 같은 약한 전파 교란 환경을 가정하여 열악한 환경 내에서 GPS 수신기가 위치 추정 정확도는 열화되더라도 자신의 위치를 처음 파악하는 데 걸리는 시간인 TTFF(Time To First Fix)를 감소시켜 선박의 신속한 위치 계산을 위한 개략 위치 추정 기법을 설계하였다. 또한 열악한 신호 환경을 가정하여 진행된 실험에서 기존 GPS TTFF와의 비교를 통해 설계된 기법을 검증하였다.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.948-950
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• 1999

In this paper, a monitoring system is desigend for a GPS/INS integration system. The function of the monitoring system is to acquire real-time data from system and displayed them. The monitoring system supervises the operation of navigation system. Visual C++ was used in the implementation. The performance of the monitoring system was verified through a real-time test for a GPS/INS Integration system which is composed of a GPS Receiver. IMU(Inertial Measurement Unit), NCU (Navigation Computer Unit)