• Journal of Positioning, Navigation, and Timing
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• 제8권1호
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• pp.31-40
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• 2019

In recent years, Intelligent Transport Systems (ITS) and Autonomous Vehicle Technology have actively studied around the world. In order to achieve the purpose of Advanced Driver Assistance System (ADAS) and Autonomous Vehicle Technology, it must be obtained accurate and reliable positioning. However, the problem of positioning in the urban area is a low position accuracy caused by the reduction of the number of visible satellites due to high buildings. In this paper, we analyzed the availability of precise positioning system in urban area are using GPS/BDS integrated system. For this study, GPS and BDS satellite signals were collected using two low-cost receivers in the open sky and a designed software based platform for precise positioning performance analysis. And we analyzed the precise positioning performance by changing the mask angle considering the urban area. From the results, it can be confirmed that the performance of precise positioning of GPS only and BDS only decrease in the environment where mask angle is $40^{\circ}$ to $45^{\circ}$, however, GPS/BDS integrated system maintains high performance of precise positioning.

• Journal of Positioning, Navigation, and Timing
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• 제3권1호
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• pp.31-36
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• 2014

Precise Point Positioning (PPP) is a stand-alone precise positioning approach. As the quality of satellite orbit and clock products from analysis centers has been improved, PPP can provide more precise positioning accuracy and reliability. A combined use of Global Positioning System (GPS) and Global Orbiting Navigation Satellite System (GLONASS) in PPP is now available. In this paper, we explained about an approach for combined GPS and GLONASS PPP measurement processing, and validated the performance through the comparison with GPS-only PPP results. We also used the measurement obtained from the GRAS reference station for the performance validation. As a result, we found that the combined GPS/GLONASS PPP can yield a more precise positioning than the GPS-only PPP.

• Journal of Astronomy and Space Sciences
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• 제28권1호
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• pp.55-62
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• 2011

The precise orbit determination (POD) of low earth orbiter (LEO) has complied with its required positioning accuracy by the double-differencing of observations between International GNSS Service (IGS) and LEO to eliminate the common clock error of the global positioning system (GPS) satellites and receiver. Using this method, we also have achieved the 1 m positioning accuracy of Korea Multi-Purpose Satellite (KOMPSAT)-2. However double-differencing POD has huge load of processing the global network of lots of ground stations because LEO turns around the Earth with rapid velocity. And both the centimeter accuracy and the near real time (NRT) processing have been needed in the LEO POD applications--atmospheric sounding or urgent image processing--as well as the surveying. An alternative to differential GPS for high accuracy NRT POD is precise point positioning (PPP) to use measurements from one satellite receiver only, to replace the broadcast navigation message with precise post processed values from IGS, and to have phase measurements of dual frequency GPS receiver. PPP can obtain positioning accuracy comparable to that of differential positioning. KOMPSAT-5 has a precise dual frequency GPS flight receiver (integrated GPS and occultation receiver, IGOR) to satisfy the accuracy requirements of 20 cm positioning accuracy for highly precise synthetic aperture radar image processing and to collect GPS radio occultation measurements for atmospheric sounding. In this paper we obtained about 3-5 cm positioning accuracies using the real GPS data of the Gravity Recover and Climate Experiment (GRACE) satellites loaded the Blackjack receiver, a predecessor of IGOR. And it is important to reduce the latency of orbit determination processing in the NRT POD. This latency is determined as the volume of GPS measurements. Thus changing the sampling intervals, we show their latency to able to reduce without the precision degradation as the assessment of their precision.

• Journal of Positioning, Navigation, and Timing
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• 제4권2호
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• pp.73-77
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• 2015

Global Positioning System (GPS) Precise Point Positioning (PPP) has been extensively used for geodetic applications. Since December 2012, BeiDou navigation satellite system has provided regional positioning, navigation and timing (PNT) services over the Asia-Pacific region. Recently, many studies on BeiDou system have been conducted, particularly in the area of precise orbit determination and precise positioning. In this paper PPP method based on BeiDou observations are presented. GPS and BeiDou data obtained from Mokpo (MKPO) station are processed using the Korea Astronomy and Space Science Institute Global Navigation Satellite System (GNSS) PPP software. The positions are derived from the GPS PPP, BeiDou B₁/B₂ PPP and BeiDou B₁/B₃ PPP, respectively. The position errors on BeiDou PPP show a mean bias < 2 cm in the east and north components and approximately 3 cm in the vertical component. It indicates that BeiDou PPP is ready for the precise positioning applications in the Asia-Pacific region. In addition, BeiDou tropospheric zenith total delay (ZTD) is compared to GPS ZTD at MKPO station. The mean value of their difference is approximately 0.52 cm.

• 한국측량학회지
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• 제17권2호
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• pp.145-152
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• 1999

제트추진연구소(JPL : Jet Propulsion Laboratory)에서는 매일 전세계에 분포된 정밀 측지용 GPS수신기의 광역망으로 부터 관측자료를 수집하고 분석하여 정밀한 GPS transmitter parameters (위성의 위치력 및 시계 보정값)를 산정하고 있으며 이를 이용한 자동화된 GPS 자료 해석 서비스를 제공하고 있다. 본 연구에서는 한측점의 2주파 GPS수신기로부터 획득한 위성관측자료를 E-mail 및 ftp(file transfer protocol)로 JPL의 주컴퓨터에 연결시켜 JPL의 정밀 GPS transmitter parameters 및 Gipsy/Oasis-II (GOA-II) s/w를 활용한 정밀절대측위(PPP : Precise Point Positioning)기법의 정밀도를 분석하고 PPP에 의한 GPS기준점 좌표의 산정 방안을 검토한 것이다. 검토결과, X, Y, Z 직교좌표계에서 수 cm급의 위치결정이 가능하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.146-146
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• 2000

This paper presents field test results of the GPS precise positioning using carrier phase observable. The Least-squares AMBiguity Decorrelation Adjustment(LAMBDA) method is implemented to resolve integer ambiguity problem for two epoch Ll carrier phase measurement data. Field test results show that the GPS precise positioning of cm-level accuracy is obtainable with conventional low cost, single frequency C/A code GPS receivers.

• 한국측량학회지
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• 제31권6_2호
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• pp.539-547
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• 2013

This research is suggesting the most effective positioning method for GPS based positioning when no GPS reference point is available in the neighborhood. For this purpose, we carried out positioning of the IGS realtime observatories in Australia in various conditions. According to the research, we were certainly assured the one reference point with a short baseline length is more effective for differential positioning than multiple reference points with a long baseline distance beyond 1,000km and suggested the precise point positioning based positioning method can be an excellent substitute when no reference point is available around an unknown point. The research result may be used as the basic data for accurate positioning in poor reference point environments, especially in Antarctica.

• 한국측량학회지
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• 제30권3호
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• pp.249-258
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• 2012

본 연구에서는 정적 측지기준계를 채택하고 있는 우리나라에서 GPS 정밀단독측위 해석 결과에 정적 측지기준계의 기준시점으로부터 지진이나 지각변동에 의해 발생한 위치의 변동량을 보정함으로써 위치정확도를 향상시키기 위한 기준시점 조정모델을 개발하였다. 이를 위하여 우리나라 GPS상시관측소 중 14개소를 선정하여 2000년부터 2011년까지 약 10년간의 일별 GPS데이터에 대하여 GIPSY-OASIS II를 이용한 정밀단독측위 해석을 실시하고 이로부터 GPS상시관측소의 지각변동량을 결정하였다. 이로부터 SOPAC에서 채택하고 있는 지각변동모델식의 파라미터를 계산함으로써 기준시점 조정모델을 구하였다. 본 연구에서 구하여진 기준시점 조정모델을 적용한 결과 GPS상시관측소의 위치는 약 12mm의 정확도로 결정할 수 있었으며, 일반 측량점의 위치는 약 16mm의 정확도로 결정할 수 있다. 향후 보다 많은 GPS상시관측소의 데이터 처리를 통하여 기준시점 조정모델을 결정할 경우 지진이나 지각변동에 의하여 변동된 측량점의 위치를 실용적인 정확도 범위 내에서 GPS 정밀단독측위에 의하여 정적 측지계 기준의 좌표로 추정할 수 있을 것이다.

• Journal of Positioning, Navigation, and Timing
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• 제6권1호
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• pp.35-41
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• 2017

Precise Point Positioning (PPP) method is based on dual-frequency data of Global Navigation Satellite Systems (GNSS). The recent multi-constellations GNSS (multi-GNSS) enable us to bring great opportunities for enhanced precise positioning, navigation, and timing. In the paper, the multi-GNSS PPP with a combination of four systems (GPS, GLONASS, Galileo, and BeiDou) is analyzed to evaluate the improvement on positioning accuracy and convergence time. GNSS observations obtained from DAEJ reference station in South Korea are processed with both the multi-GNSS PPP and the GPS-only PPP. The performance of multi-GNSS PPP is not dramatically improved when compared to that of GPS only PPP. Its performance could be affected by the orbit errors of BeiDou geostationary satellites. However, multi-GNSS PPP can significantly improve the convergence speed of GPS-only PPP in terms of position accuracy.

• 한국측량학회지
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• 제26권5호
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• pp.529-536
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• 2008

상대측위는 좌표가 정확히 알려진 측점을 기준으로 다른 측점의 좌표를 상대적으로 결정하는 방법으로 측지분야 및 정밀측위 분야에 활용되고 있다. DGPS(Differential GPS) 기법은 일정한 거리 내에서 위성과 수신기의 공통오차를 소거할 수 있다는 장점이 있지만 기선의 길이가 증가할수록 오차가 증가하는 단점을 가지고 있다. GPS 절대측위는 상대측위와는 달리, 원하는 측점의 수신기에서 수신한 GPS 위성들의 신호를 이용하여 독립적으로 측점의 위치를 결정하는 방식이다.이때 관측된GPS 신호에는 위성시계 오차, 전리층 및 대류권 통과에 따른 오차, 다중경로 오차 등 위치 결정에 영향을 주는 여러 오차 요인들이 포함되어 있어 이를 보정해 주어야 한다. 본 연구에서는 Bernese GPS Software 5.0을 이용한 정밀절대측위 방법과 AUSPOS - Online GPS Processing Service를 이용한 상대측위 방법으로 국토지리정보원의 GPS 상시관측소 관측자료를 처리하고 이를 국토지리정보원의 고시성과와 비교.분석하여 정밀절대측위를 이용한 정밀위치결정의 정확도를 분석하고 그 효용성을 제시 하고자 한다.