• Journal of Positioning, Navigation, and Timing
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• v.8 no.1
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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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• v.3 no.1
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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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• v.28 no.1
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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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• v.4 no.2
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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.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.17 no.2
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• pp.145-152
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• 1999

JPL(Jet Propulsion Laboratory) has been routinely produced the precise GPS ephemeris and clock's correction parameter using data collected from globally distributed permanent GPS tracking stations, and has been offering the automated GPS data analysis(Precise Point Positioning： PPP) service by using them. In this study, after investigating the potential capacity of JPL's PPP service, the coordinates computation of the GPS base station by this service were investigated. For this, the dual frequency P codes data of 24 hours were observed from continuously operating four reference stations in USA. sent to the JPL's main computer through E-mail and/or ftp, and then were processed by Gipsy/Oasis-II (GOA-II) software with the precise GPS transmitter parameters. Centimeter-level positioning results were available to obtain in X, Y, Z geocentric rectangular coordinate system.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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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.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.6_2
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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.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.3
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• pp.249-258
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• 2012

In this study, the epoch adjustment model was developed to correct GPS precise point positioning result to be suitable for the current geodetic datum of Korea which is tied at past epoch statically. The model is based on the formula describing crustal movements, and the formula is composed of several parameters. To determine the parameters, the data gathered at 14 permanent GPS stations for 10 years, from 2000 to 2011, were processed using GIPSY-OASIS II. It was possible to determine the position of permanent GPS stations with an error range of 16mm and the position of check points with an error range of 12mm by appling the model to GPS precise point positioning result. It is considered that more precise model could be calculated by using GPS data of more permanent GPS stations.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.1
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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.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.5
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• pp.529-536
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• 2008

Researches about 3-D Positioning system using GPS were carried out many-sided by national organs, laboratories, the worlds of science. And most of researches were development of relative positioning algorithm and its applications. Relative positioning has a merit, which can eliminate error in received signals. But its error increase due to distance of baseline. GPS absolute positioning is a method that decides the position independently by the signals from the GPS satellites which are received by a receiver at a certain position. And it is necessary to correct various kinds of error(clock error, effect of ionosphere and troposphere, multi-path etc.). In this study, results of PPP(Precise Point Positioning) used Bernese GPS software was compared with notified coordinates by the NGII(National Geographic Information Institute) in order to analyze the positional accuracy of permanent GPS sites. And the results were compared with results of AUSPOS - Online GPS Processing Service for comparison with relative positioning.