• Journal of the Korean Association of Geographic Information Studies
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• v.25 no.4
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• pp.200-209
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• 2022

Providing real-time location information is emerging as a major goal of the national industry. In order to provide such real-time location information (3D spatial information), it is essential to develop a technology for a satellite positioning method. Therefore, the country continues to make efforts to increase satisfaction with the needs of consumers by introducing the Network RTK GNSS method. In this study, among the Network RKT GNSS(Global Navigation Satellite System) methods provided by the National Geographic Information Service, continuous observation and single observation were measured at the integrated reference point using VRS(Virtual Reference Station) and FKP(Flӓachen-Korrektur Parameter) to evaluate accuracy. In addition, we aim to maximize efficiency by presenting accuracy on the rapidly increasing Network RTK GNSS method in the field.

• Spatial Information Research
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• v.18 no.5
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• pp.1-11
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• 2010

Since January 2009, Seoul Metro Government(SMG) is operating own Network RTK Systems connecting four(4) GNSS Reference Stations which are installed inside Seoul Metro City area. SMG is currently providing VRS data service via wireless internet for Network-RTK and RINEX data observed from GNSS Reference Stations. This paper will discuss utilization of data available from SMG Network-RTK System for various applications, and present the test results on practicalities of Virtual RINEX data. For the utilization of data available from SMG Network- RTK system, 1)NTRIP data delivery of GNSS realtime observables streaming and converting to RINEX at receiving side, 2) monitoring deformation of bulky structures using GNSS observation were discussed. In addition to those discussion, 3) broadcasting VRS correction data for job site via radio modem after acquiring such correction data on-line using NTRIP based GNSS Internet Radio from SMG Network-RTK System were introduced. For the test results on practicalities of Virtual RINEX data, 1) the post-processing results of the GNSS observation data on a certain point with GNSS Reference Station data have been compared to the post-processing results of Virtual RINEX data on the same point generated from SMG Network-RTK System, and 2) VRS RTK positioning results for a certain point and post-processing results of Virtual RINEX data for the point were compared. The results showed only a few mm difference, and the high possibility for using Virtual RINEX data for post-processing applications.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.171-174
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• 2006

A large number of service providers in countries all over the world have established GNSS reference station networks in the last years and are using network software today to provide a correction stream to the user as a routine service. In current GNSS network processing, all the geometric related information such as ionospheric free carrier phase ambiguities from all stations and satellites, tropospheric effects, orbit errors, receiver and satellite clock errors are estimated in one centralized Kalman filter. Although this approach provides an optimal solution to the estimation problem, however, the processing time increases cubically with the number of reference stations in the network. Until now one single Personal Computer with Pentium 3.06 GHz CPU can only process data from a network consisting of no more than 50 stations in real time. In order to process data for larger networks in real time and to lower the computational load, a federated filter approach can be considered. The main benefit of this approach is that each local filter runs with reduced number of states and the computation time for the whole system increases only linearly with the number of local sensors, thus significantly reduces the computational load compared to the centralized filter approach. This paper presents the technical aspect and performance analysis of the federated filter approach. Test results show that for a network of 100 reference stations, with the centralized approach, the network processing including ionospheric modeling and network ambiguity fixing needs approximately 60 hours to process 24 hours network data in a 3.06 GHz computer, which means it is impossible to run this network in real time. With the federated filter approach, only less than 1 hour is needed, 66 times faster than the centralized filter approach. The availability and reliability of network processing remain at the same high level.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.269-277
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• 2022

In this paper, we overview the system development status of the national maritime precise point positioning-real-time kinematic (PPP-RTK) service in Korea, also known as the Precise POsitioning and INTegrity monitoring (POINT) system. The development of the POINT service began in 2020, and the open service is scheduled to start in 2025. The architecture of the POINT system is composed of three provider-side facilities-a reference station, monitoring station, and central control station-and one user-side receiver platform. Here, we propose the detailed functionality of each component considering unidirectional broadcasting of augmentation data. To meet the centimeter-level user positioning accuracy in maritime coverage, new reference stations were installed. Each reference station operates with a dual receiver and dual antenna to reduce the risk of malfunctioning, which can deteriorate the availability of the POINT service. The initial experimental results of a testbed from corrections generated from the testbed network, including newly installed reference stations, are presented. The results show that the horizontal and vertical accuracies satisfy 2.63 cm and 5.77 cm, respectively. For the purpose of (near) real-time broadcasting of POINT correction data, we designed a correction message format including satellite orbit, satellite clock, satellite signal bias, ionospheric delay, tropospheric delay, and coordinate transformation parameters. The (near) real-time experimental setup utilizing (near) real-time processing of testbed network data and the designed message format are proposed for future testing and verification of the system.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.2
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• pp.199-210
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• 2012

This paper is designed to put forth a proposal for configuration of an optimized observation network based on GNSS CORS with a view to continued monitoring of crustal deformation in the East-Asian region. For this purpose, a comprehensive analysis of the results of the testing of various forms of GNSS CORS observation network tentatively constructed based on the Asia-Pacific IGS station has confirmed that geometrically arranged minimum five and ten or more reference points and an EAREF, constructed with a baseline length no longer than 2,500km, can produce an optimum outcome. And an EAREF-applied analysis on the effects of the Great Eastern Japan Earthquake of March 2011 shows that there were conspicuous positional movements in Japan and Korea while there was no significant movement in other regions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4D
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• pp.579-586
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• 2008

In this study, it was evaluated that the 3D tracking accuracy of basketball zone track line by real time GNSS satellite positioning methods which are VRS (Virtual Reference System), DGPS (Marine Differential GPS) and PP (Point Positioning) methods. The results of comparison between three methods over horizontal track of basketball zone, VRS, DGPS and PP methods showed ${\pm}$ several cm, ${\pm}$ m, and ${\pm}$ 2m horizontal position accuracy compared with real size respectively. And also, the grade and height deviation of the checking points on basketball zone by VRS method is very similar to the real grade and height, but results by DGPS and PP methods showed big variation and deviation in each case. We expected that VRS method using GNSS reference network will be a very useful tool compared with single based RTK method in real time accurate positioning such as precision construction fields, especially.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.411-415
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• 2006

In recent years there has been considerable interest in the network GPS RTK surveying. Single RTK has some limit in long distance and it has an accuracy problem depend on the baseline length. The significant improvement of GPS network technology, RTCM V3.0 correction format and telecommunication technology can eliminate the weakness of single GPS RTK. This paper is the practical field result of GPS network RTK.

• Journal of Positioning, Navigation, and Timing
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• v.3 no.4
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• pp.131-141
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• 2014

Over the last decade, the Global Navigation Satellite System (GNSS) has been increasingly utilized as a meteorological research tool. The Korea Astronomy and Space Science Institute (KASI) has also been developing a near real-time GNSS precipitable water vapor (PWV) information management system that can produce a precise PWV for the Korean Peninsula region using GNSS data processing and meteorological measurements. The goal of this paper is to evaluate whether the precise point positioning (PPP) strategy will be used as the new data processing strategy of the GNSS-PWV information management system. For this purpose, quality assessment has been performed by means of a comparative analysis of the troposphere zenith total delay (ZTD) estimates from KASI PPP solutions (KPS), KASI network solutions (KNS), and International GNSS Service (IGS) final troposphere products (IFTP) for ten permanent GNSS stations in the Korean Peninsula. The assessment consists largely of two steps: First, the troposphere ZTD of the KNS are compared to those of the IFTP for only DAEJ and SUWN, in which the IFTP are used as the reference. Second, the KPS are compared to the KNS for all ten GNSS stations. In this step, the KNS are used as a new reference rather than the IFTP, because it was proved in the previous step that the KNS can be a suitable reference. As a result, it was found that the ZTD values from both the KPS and the KNS followed the same overall pattern, with an RMS of 5.36 mm. When the average RMS was converted into an error of GNSS-PWV by considering the typical ratio of zenith wet delay and PWV, the GNSS-PWV error met the requirement for PWV accuracy in this application. Therefore, the PPP strategy can be used as a new data processing strategy in the near real-time GNSS-PWV information management system.

• 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.615-622
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• 2012

Since the accuracy of precipitable/integrated water vapor estimates from GNSS measurements is proportional to the accuracy of water vapor Weighted Mean Temperature Model (WMTM), the WMTM is a significant formulation in the retrieval of precipitable water vapor from zenith wet delay of GNSS signal. The purpose of this paper is to develop available the WMTM to apply for GNSS meteorology in the region of Algeria, by using the Algerian radiosonde network in the World Meteorological Organization (WMO). It can be concluded that the available GNSS precipitable water vapor which is retrieved by the developed Algerian Weighted Mean Temperature Equation (AWMTE) can be useful technique for sensing of water vapor in the Algeria, after Algerian Continuously Operating Reference System (CORS) will be constructed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.3
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• pp.145-152
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• 2017

In this paper, GNSS(global navigation satellite system) to monitoring the fine for the construction of structure displacement based on satellite communications signals of GNSS. At the same time on USN(ubiquitous sensor network) and proposed a new approach to precise positioning by analyzing the results. A major construction structure for the safety diagnosis and prevent disaster from the risk of collapse. Precision measurement methods to mm level GNSS in that case and experiments in the application of new technologies that can most commonly used to replace the current through the permanent. The way a GNSS baseline and tested it on to prove. As a result, at our country at precise positioning and fine displacement monitoring application virtual reference station(VRS) in a GNSS mm of a margin of error of horizontal and vertical directions can be found.