• Journal of Institute of Control, Robotics and Systems
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• v.14 no.1
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• pp.7-12
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• 2008

A GNSS(Global Navigation Satellite System) using GPS provides us with very useful information concerning the positioning of users in many sectors such as transportation, social services, the justice system and customs services, public works, search and rescue systems and leisure. A GNSS using the Galileo satellite is due to work in 2008 and expected to be used in various fields such as aviation, marine transportation, land surveying, resources development precise agriculture, telemetics, and so on. In this paper, we discuss the implementation and testing of a combined GPS/Galileo receiver which we named KSTAR V1.0. Each tracking module of GPS/Galileo dual mode correlator has the five track arms which consist of Very Early code, Early code, Prompt code, late code, and Very late code. Each of 24 tracking modules can be assigned to GPS and/or Galileo signal by changing mode selection register. The basic correlator integration dump period is set to 1ms for GPS C/A code and fast Galileo signal tracking. The performance of the developed combined GPS/Galileo receiver was tested and evaluated using the IF (Intermediated Frequency)-level GPS/Galileo signal generator.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.5
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• pp.615-621
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• 2009

Since GPS receivers and INS algorithms do not work properly in the spinning vehicles due to change of the GPS signal and excess of the measurement limitation of the gyroscope, conventional GPS/INS integrated navigation systems do not provide accurate navigation outputs. This paper proposes a design method for GPS/INS integrated navigation systems of spinning vehicles. A special GPS receiver with a signal tracking loop for changed GPS signal caused by spinning and an INS with a roll estimation method are configured and the conventional integration filter is combined. The proposed method was verified through comparison of the navigation results. The result of the proposed method for the spinning vehicle was similar to that of the conventional navigation system without spinning.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.12
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• pp.1065-1072
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• 2014

We developed a GPS digital signal processing FPGA IP, SIGP-1001 to replace the obsolete GP2021 device, which has been used for many space-borne GPS receivers. From a series of tests, we verified that SIGP-1001 has equivalent performance to the GP2021 device under the same operating condition and concluded that SIGP-1001 can replace the GP2021 device. The reliability of a GPS receiver can be improved by using a space-grade FPGA with SIGP-1001 instead of the GP2021 device and its performance is expected to be improved by increasing the number of search channels.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.12 no.2
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• pp.155-161
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• 1994

Accurate positioning method using low cost GPS modules is proposed, which use the technique of differential GPS. DGPS experiments have been made using two coarse-acquisition (C/A) code GPS modules. Position accuracy of better than 5 m was obtained for position dilution of precision (PDOP) of 2-3 and that of better than 10 m after filtering was obtained for PDOP of about 9 in a local area. Static DGPS experiments were performed at Kookmin university with the DGPS correction data of KRISS reference station at Taejon. The distance between two stations is about 140 km. The results show that precision of the position is about 10 m (2 drms), which is ten times better than the results with the GPS module alone. Accuracy of about 10 meters can be obtained in near real time by the DGPS service with a reference station in our country.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.3
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• pp.385-392
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• 2009

This study aims to methodology a system which is able to monitor and configuration management 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.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.3
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• pp.213-221
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• 2005

In order to get more accurate GPS position with the changes of the inner configuration setting of GPS receiver, the authors carried out measurements of the position at known it with one antenna and two GPS receivers manufactured by same company. We have investigated the accuracies of positions according to the change of the maskangle and receiving mode of output data in inner configuration of GPS receivers, and analyzed the relationships between numbers of satellites visibility and maskangles, and values of HDOP and maskangles. When the maskangles in inner configuration were set below 20 degree, the accuracies of positions were high. But if they were became bigger than 25 degree, standard deviations ot position errors and HDOPS of positions were became bigger. Numbers of satellites visibility(y) and maskangles(x) have relations with a formula, y = -0.1662x+9.9225, and values of HDOP(y) and maskangles(x) have relations with a formula, y = 0.6035 $e^{0.0517x}$. The results of position accuracies observed by two GPS receivers to the known position at same time were that average errors of position fixs by GPS receiver configured with NMEA0183 mode were 6.7m and standard deviations were 1.5m, and them by GPS receiver configured with binary mode were 5.0m and standard deviations were 1.1m respectively.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.1
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• pp.1-8
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• 2001

The aim of this study is to know the GPS absolute positioning accuracy after discontinuing of Selective Availability (SA). The GPS satellite clock errors and the observation station coordinates were calculated using GPS C/A code pseudorange and compared with the JPL precise ephemerides and the previous known coordinates. As the results, the correction or the GPS clock errors in SA-on is about $\pm$40m but in SA-off $\pm$2m. The 95% probable errors for the measurements in SA-on are about $\pm$65m but in SA-off $\pm$10m in X, Y and SA-off $\pm$15m in Z.

• Journal of Korean Society for Geospatial Information Science
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• v.16 no.1
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• pp.43-48
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• 2008

In this study, it was estimated efficiency of GPS/INS photogrammetry by comparison of accuracy and economical efficiency between conventional aerial triangulation and GPS/INS aerial triangulation at the base of large scale digital mapping using GPS/INS aerial survey. The results of aerial triangulation with GPS/INS showed that 40% of working amount was reduced in the process of ground control point survey compared to conventional aerial triangulation. In case of 1/5000 scale aerial triangulation, the results showed that 55% GCP work was reduced in 10 and 20 block size, and 60% GCP work was reduced in 30 block size, under the assumption of keeping the same accuracy.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.41.3-41.3
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• 2009

우주측지 정밀도 향상을 위해 대류층 지연오차의 정확한 산출은 필수적이다. 한국천문연구원은 GPS 자료를 이용하여 대류층 지연오차 요인인 대기 중의 수증기량을 정확히 산출하는 연구를 수행하고 있다. 또한, 1999년부터 GPS 관측을 시작한 이래로 10년 이상의 연속 관측자료를 보유하고 있다. 이 연구에서는2000년부터 2008년까지 한국천문연구원의 GPS 상시관측소 5곳(서울, 대전, 목포, 밀양, 속초)의 GPS 가강수량을 산출하고 이들의 다년간 변화경향을 분석하였다. 산출된 GPS 가강수량을 라디오존데 관측값과 비교하여 신뢰도 검증하였다. 선형회귀방법을 통하여 GPS 가강수량에 대한 경향을 분석하면 관측 지역마다 기울기의 차는 있으나 전체적으로 시간이 지날수록 GPS 가강수량이 증가하는 경향을 보였다. 해당 기간동안 GPS 가강수량의 연간 변화량은 평균 0.20mm 증가하였고 목포의 경우 0.25mm로 가장 큰 변화량을 보였으며 서울이 0.16mm로 가장 작은 변화량을 보였다. 여름철 연간 변화량은 평균 0.32mm 증가하였고 겨울철은 평균 0.08mm 감소하였다. 일반적으로 기온이 상승하면 상대습도가 내려가 수증기의 증발이 활발해져 대기중의 수증기량이 증가한다. 최근 10년간 기상청의 기온은 매해 평균 $0.16^{\circ}C$씩 증가하였으며 대기 중의 수증기량과 직접적으로 연관되어 있는 GPS 가강수량의 변화 경향과 유사함을 확인하였다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.2
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• pp.72-79
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• 2001

In the GPS/DR integrated system, the GPS position(or velocity) is used to compensate the DR output and to calibrate errors of the DR sensor. This synergistic relationship ensures that the calibrated DR accuracy can be maintained even when the GPS signal is blocked. Because of the observability problem, however, the DR sensors are not sufficiently calibrated when the vehicle speed is low. This problem can be solved if we use a multi-antenna GPS receiver for attitude determination instead of conventional one. This paper designs a two-antenna GP receiver integrated with DR sensors. The proposed integration system has three remarkable features. First, the DR sensor can be calibrated regardless of the vehicle speed with the aid of two-antenna GPS receiver. Secondly, the search space of integer ambiguities in GPS carrier-phase measurements is reduced to a part of the surface of the sphere using DR heading. Thirdly, the detection resolution of cycle-slips in GPS carrier-phase measurements is improved with the aid of DR heading. From the experimental result, it is shown that the search space is drastically reduced to about 3/20 of the non-aided case and the cycle-slips of 1 or half cycle can be detected.