• Journal of Korean Society for Geospatial Information Science
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• v.22 no.3
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• pp.39-46
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• 2014

Network RTK positioning, one of GNSS positioning systems, is currently very popular due to its easy operation and low cost. However, the network RTK positioning unquestioningly accepts observation result acquired with an ambiguity fixed-solution regardless of different field conditions and situations, and then it is applied to the practice. This paper, therefore, has investigated the effects of field conditions obtained network RTK survey data for the area with obstacles on the variation of positioning accuracy. Being explained in detail, after conducting survey by GPS-only positioning and combined GPS/GLONASS observations giving changes to the distance from obstacles and elevation angles, and then accuracy results of each positioning method were compared each other. As a result, while GPS-only point positioning method showed more stable results than combined GPS/GLONASS method in the areas with no obstacles, combined method gave better result than GPS-only for the areas with presence of obstacles. Based on the results of this experiment, when the further study is conducted with a variety of different field conditions affecting the survey accuracy, it can be expected that the accuracy of network RTK survey method would become to more popular.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.1
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• pp.89-95
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• 2009

The accuracy and efficiency of RTK-GPS is proved through its measurement, but it is not used in cadastral detail surveying, due to low accuracy caused by the trouble of satellite reception in a built-up area and lack of detailed guidelines for practical application. Thus, this study tries to offer detailed directions for the practical use of RTK-GPS by analyzing the application problem of RTK-GPS measurement. As results of the study, for the practical use of RTK-GPS it suggests enactment of regulations, connection of practical RTK-GPS measurement with the existing detail surveying methods, introduction of a VRS method for increasing the arrangement density of reference stations, and integrated use of GPS, GLONASS and Galileo satellites for securing accuracy and stability.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.6
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• pp.659-667
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• 2009

In this study, an integrated GNSS Simulator called Inha GNSS Simulation System (IGSS) using 3D spatial information was developed and validated. Also positioning availability and accuracy improvement were evaluated under the integrated GNSS environment using IGSS. GPS and GLONASS satellite visibility predictions were compared with real observations, and their frequency of error were 6.4% and 7.5%, respectively. To evaluate positioning availability and accuracy improvement under the integrated GNSS environment, the Daejeon government complex area was selected to be the test site because the area has high-rise buildings and thus is susceptible to signal blockages. The test consists of three parts: the first is when only GPS was used; the second is when both GPS and GLONASS were simulated; and the last is when GPS, GLONASS, and Galileo were used all together. In each case, the number of visible satellites and Dilution Of Precision were calculated and compared.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.4
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• pp.205-211
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• 2015

The Global Navigation Satellite System (GNSS) is undergoing dramatic changes. Nowadays, much more satellites are transmitting navigation data at more frequencies. A multi-GNSS analysis is performed to improve the positioning accuracy by processing combined observations from different GNSS. The multi-GNSS technique can improve significantly the positioning accuracy. In this paper, we present a combined Global Positioning System (GPS), the GLObal NAvigation Satellite System (GLONASS), the China Satellite Navigation System (BeiDou), and the Quasi-Zenith Satellite System (QZSS) standard point positioning (SPP) method to exploit all currently available GNSS observations at Mokpo (MKPO) station in South Korea. We also investigate the multi-GNSS data recorded at MKPO reference station. The positioning accuracy is compared with several combinations of the satellite systems. Because of the different frequencies and signal structure of the different GNSS, intersystem biases (ISB) parameters for code observations have to be estimated together with receiver clocks in multi-GNSS SPP. We also present GPS/GLONASS and GPS/BeiDou ISB values estimated by the daily average.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.2 s.20
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• pp.29-37
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• 2002

Many of the traffic accidents on roads are a result of alignment defect of the roads. This alignment of the road needs to lie analyzed with accuracy for improving design of road, and it needs the design drawing of road, and coordinates of the main point. Accordingly, in this study the precision of location based on existing design drawing was compared with the data acquired by the combination of RTK GPS/GLONASS. The result of study is included within range 5cm, we would like to propose an effective and useful approach method to utilize the satellite for road alignment information system by evaluating the represented road alignment.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.10a
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• pp.91-96
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• 2003

In static relative surveying, the difference of between the known cadastral supplementary control station and that of the acquired is 0.000∼0.0006m in GPS alone, GPS/GLONASS, and In the RTK-GPS/TS, 0.010∼0.077m on the non-ambiguity fixed solutions in the urban area, 0.008∼0.078m in the open area. it proved to be valid because it is within the allowed connecting errors, i.e 12cm on the baseline of l00m in 1/1,200 cadastral map.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.2045-2049
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• 2011

In this paper, the DOP improvement was studied for the solution to an intentional jamming and the increase of position accuracy by selecting preferred satellites with hybrid satellite navigation system(both GPS and GLONASS). As a result of data analysis, the increases in 0.3 ~ 0.8 GDOP, 0.2 ~ 0.6 PDOP, and 0.1 ~0.3 TDOP were acquired by using hybrid satellite navigation system instead of GPS-only.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2002.10a
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• pp.35-38
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• 2002

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.2
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• pp.119-127
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• 2009

Even though there are next generation Global Navigation Systems in development, only GPS and GLONASS are currently available for satellite positioning. In this study, GLONASS orbits were predicted using Keplerian elements in almanac and the orbit equation. For accuracy validation, predicted orbits were compared with precise ephemeris. As a result, the 3-D maximum and RMS (Root Mean Square) errors were 155.4 km and 56.3 km for 7-day predictions. Also, the GLONASS satellite visibility predictions were compared with real observations, and they agree perfectly except for several epochs when the satellite signal was blocked nearby buildings.

• Journal of Astronomy and Space Sciences
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• v.26 no.2
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• pp.199-210
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• 2009

Even though there are several Global Navigation Satellite Systems under development, only GPS and GLONASS are currently available for satellite positioning. In this study, GLONASS orbits were predicted from broadcast ephemeris using the 4th-order Runge-Kutta numerical integration. For accuracy validation, predicted orbits were compared with precise ephemeris. The RMS(Root Mean Square) and maximum 3-D errors were 14.3 km and 17.4 km for one-day predictions. In case of 7-day predictions, the RMS and maximum 3-D errors were 15.7 and 40.1 km, respectively. Also, the GLONASS satellite visibility predictions were compared with real observations, and they agree perfectly except for several epochs when the satellite signal was blocked by nearby buildings.